Biomaterials, 2004 Aug, 25(18), 4117 - 25 Search for the insertion element IS256 within the ica locus of Staphylococcus epidermidis clinical isolates collected from biomaterial-associated infections; Arciola CR et al.; Staphylococcus epidermidis biofilm-forming strains produce a polysaccharide intercellular adhesin (PIA), which mediates bacterial cell aggregation and favours the colonisation on prosthetic implants . PIA synthesis is regulated by the icaADBC locus . In vitro, by repeated subcultures of a biofilm-producing strain, the loss of the ability to produce biofilm appears associated with the insertion of the IS256 element into the ica locus . This study was aimed (i) to investigate if the five genes of ica locus are always all present in different strains of S . epidermidis, and (ii) to search if IS256 insertion naturally occurs in ica locus without making recourse to the experimental procedure of repeated subcultures of strains . 120 S . epidermidis clinical isolates from peri-prosthesis infections were investigated both by an original multiplex PCR analysis of the ica genes and by PCR amplification of the IS256 element . Also two reference strains (the biofilm-negative S . epidermidis ATCC 12228 and the biofilm-forming ATCC 35984 {RP62A}) and two biofilm-negative RP62A-derived acriflavin mutants (D9 and HAM892) were analysed . D9 e HAM892 were for the first time shown to contain in ica locus, at the base 3319, a 1300-bp insertion with a DNA sequence corresponding to IS256 . Among the 120 clinical isolates, 51 (43%) turned out completely ica-positive, 69 completely ica-negative (57%) . The genes of the ica locus appear, in all cases of the present collection, strictly linked each other, so they are either all present or all absent . In this collection, IS256 was present in eight out of the 69 ica-negative strains and in 34 out of the 51 ica-positive strains . IS256, also when present in bacterial genomic DNA, was never found inside the ica locus, thus suggesting that insertion/excision of this element is not a natural occurring mechanism for off/on switching of biofilm production. Biochem Soc Trans, 2004 Apr, 32(Pt 2), 188 - 92 Functional genomics-based studies of the microbial ecology of hyperthermophilic micro-organisms; Johnson MR et al.; Although much attention has been paid to the genetic, biochemical and physiological aspects of individual hyperthermophiles, how these unique micro-organisms relate to each other and to their natural habitats must be addressed in order to develop a comprehensive understanding of life at high temperatures . Phylogenetic 16 S rRNA-based profiling of samples from various geothermal sites has provided insights into community structure, but this must be complemented with efforts to relate metabolic strategies to biotic and abiotic characteristics in high-temperature habitats . Described here are functional genomics-based approaches, using cDNA microarrays, to gain insight into how ecological features such as biofilm formation, species interaction, and possibly even gene transfer may occur in native environments, as well as to determine what genes or sets of genes may be tied to environmental functionality. Am J Gastroenterol, 2004 Feb, 99(2), 383 - 9 Enteroaggregative Escherichia coli: an emerging enteric pathogen; Huang DB et al.; Enteroaggregative Escherichia coli (EAEC) represents an emerging pathogen that causes enteric and food-borne infectious diseases . Subgroups in many populations throughout the world are susceptible to EAEC infection . EAEC pathogenesis involves adherence to the intestinal mucosa; increased production and deposition of a mucus biofilm; and mucosal toxicity due to inflammation and cytokine release . Due to the heterogeneity of EAEC strains and differing host immune responses, not all EAEC infections are symptomatic . Recent data suggest that individuals with a homozygous genotype -251 AA single nucleotide polymorphism (SNP), in the IL-8 promoter region, are more susceptible to EAEC diarrhea . The HEp-2 cell adherent assay allows identification of EAEC's characteristic aggregative or "stacked brick" adherence pattern . Antimicrobial treatment of individuals who develop EAEC diarrhea should be individually based . Ciprofloxacin and rifaximin, compared to placebo, have been shown to significantly shorten the course of diarrhea in patients who developed EAEC infection . The objective of this review is to increase awareness of this important emerging pathogen and to discuss the epidemiology, pathogenesis, and host-pathogen factors associated with EAEC infection. Microb Pathog, 2004 May, 36(5), 237 - 45 The ability of biofilm formation does not influence virulence of Staphylococcus aureus and host response in a mouse tissue cage infection model; Kristian SA et al.; The virulence of Staphylococcus aureus Sa113 (SA113) and an isogenic ica deletion mutant (ica-), deficient in the production of polysaccharide intercellular adhesin (PIA), which is crucial for biofilm formation, was compared in a mouse tissue cage infection model . The minimal infective doses for the induction of persistent tissue infections in C57BL/6 mice were 10(3) CFU for both SA113 and the ica- mutant . Bacterial growth, initial adherence to surfaces within the implants and the course of inflammation including growth-dependent host TNF and MIP-2 release, influx of phagocytes and an accumulation of dead leukocytes were similar as well . Since SA113 expressed PIA in vivo, we could demonstrate that PIA and the lack of biofilm formation did not influence the capacity of S . aureus to induce persistent infections and did not modulate host responses in the mouse tissue cage model. Curr Opin Investig Drugs, 2004 Feb, 5(2), 186 - 97 Candida biofilms: antifungal resistance and emerging therapeutic options; Kuhn DM et al.; Intravascular catheter infections are a major cause of morbidity and mortality in hospitalized patients, accounting for the majority of the 200,000 nosocomial bloodstream infections occurring in the US annually . Of the intravenous lines that are culture-positive for Candida, 40% actually represent fungemia, which generally necessitates systemic treatment and line removal to affect cure . Until recently, the reason for the need for device removal was unclear . However, our research group and others have demonstrated a near-total resistance to antifungals by biofilm-associated Candida . Similar to bacterial species, Candida biofilm formation proceeds through early, intermediate and maturation phases . This process is associated with the generation of a polysaccharide extracellular matrix (ECM) . Mature C . albicans biofilms have a heterogeneous architecture, in terms of distribution of fungal cells and ECM, and exhibit broad antimicrobial resistance . The mechanisms causing such profound antifungal resistance are beginning to be understood . Recent data indicate that resistance is phase-specific and multifactorial, involving efflux pumps and sterol synthesis (at early and mature biofilm phases, respectively) . Neither metabolic quiescence nor the ECM appear to contribute substantially . Susceptibility testing and confocal scanning laser microscopy demonstrated that azoles failed to exert activity against mature Candida biofilms . However, sub-inhibitory concentrations of voriconazole impaired biofilm formation and caused cell morphological aberrations . In contrast, lipid-formulation amphotericins and the echinocandins uniquely exhibited activity against mature biofilms . The mechanisms underlying this ability are unknown . The role of other pharmacological (eg, catheter coatings, antimicrobial peptides and antibiotic locks) and non-pharmacological methods in the prevention and treatment of device-related biofilms is discussed in this review. J Magn Reson, 2004 Apr, 167(2), 322 - 7 Magnetic resonance microscopy of biofilm structure and impact on transport in a capillary bioreactor; Seymour JD et al.; Microorganisms that colonize surfaces, biofilms, are of significant importance due to their role in medical infections, subsurface contaminant remediation, and industrial processing . Spatially resolved data on the distribution of biomass within a capillary bioreactor, the heterogeneity of the biofilm itself and the impact on transport dynamics for a Staphylococcus epidermidis biofilm in the natural growth state are presented . The data demonstrate the ability of magnetic resonance microscopy to study spatially resolved processes in bacterial biofilms, thus providing a basis for future studies of spatially resolved metabolism and in vivo clinical detection. Nat Rev Microbiol, 2004 Feb, 2(2), 95 - 108 Bacterial biofilms: from the natural environment to infectious diseases; Hall-Stoodley L et al.; Biofilms--matrix-enclosed microbial accretions that adhere to biological or non-biological surfaces--represent a significant and incompletely understood mode of growth for bacteria . Biofilm formation appears early in the fossil record (approximately 3.25 billion years ago) and is common throughout a diverse range of organisms in both the Archaea and Bacteria lineages, including the 'living fossils' in the most deeply dividing branches of the phylogenetic tree . It is evident that biofilm formation is an ancient and integral component of the prokaryotic life cycle, and is a key factor for survival in diverse environments . Recent advances show that biofilms are structurally complex, dynamic systems with attributes of both primordial multicellular organisms and multifaceted ecosystems . Biofilm formation represents a protected mode of growth that allows cells to survive in hostile environments and also disperse to colonize new niches . The implications of these survival and propagative mechanisms in the context of both the natural environment and infectious diseases are discussed in this review. Infect Immun, 2004 Apr, 72(4), 2177 - 85 Role of biofilm-associated protein bap in the pathogenesis of bovine Staphylococcus aureus; Cucarella C et al.; Staphylococcus aureus is a common cause of intramammary infections, which frequently become chronic, associated with the ability of the bacteria to produce biofilm . Here, we report a relationship between the ability to produce chronic bovine mastitis and biofilm formation . We have classified bovine mastitis S . aureus isolates into three groups based on the presence of particular genetic elements required for biofilm formation: group 1 (ica(+) bap(+)), group 2 (ica(+), bap negative), and group 3 (ica negative, bap negative) . Overall, animals naturally infected with group 1 and 2 isolates had a lower milk somatic cell count than those infected with isolates of group 3 . In addition, Bap-positive isolates were significantly more able to colonize and persist in the bovine mammary gland in vivo and were less susceptible to antibiotic treatments when forming biofilms in vitro . Analysis of the structural bap gene revealed the existence of alternate forms of expression of the Bap protein in S . aureus isolates obtained under field conditions throughout the animal's life . The presence of anti-Bap antibodies in serum samples taken from animals with confirmed S . aureus infections indicated the production of Bap during infection . Furthermore, disruption of the ica operon in a bap-positive strain had no effect on in vitro biofilm formation, a finding which strongly suggested that Bap could compensate for the deficiency of the PIA/PNAG product (a biofilm matrix polysaccharide) . Altogether, these results demonstrate that, in the bovine intramammary gland, the presence of Bap may facilitate a biofilm formation connected with the persistence of S . aureus. Infect Immun, 2004 Apr, 72(4), 1939 - 45 Aeromonas flagella (polar and lateral) are enterocyte adhesins that contribute to biofilm formation on surfaces; Kirov SM et al.; Aeromonas spp . (gram-negative, aquatic bacteria which include enteropathogenic strains) have two distinct flagellar systems, namely a polar flagellum for swimming in liquid and multiple lateral flagella for swarming over surfaces . Only approximately 60% of mesophilic strains can produce lateral flagella . To evaluate flagellar contributions to Aeromonas intestinal colonization, we compared polar and lateral flagellar mutant strains of a diarrheal isolate of Aeromonas caviae for the ability to adhere to the intestinal cell lines Henle 407 and Caco-2, which have the characteristic features of human intestinal enterocytes . Strains lacking polar flagella were virtually nonadherent to these cell lines, while loss of the lateral flagellum decreased adherence by approximately 60% in comparison to the wild-type level . Motility mutants (unable to swim or swarm in agar assays) had adhesion levels of approximately 50% of wild-type values, irrespective of their flagellar expression . Flagellar mutant strains were also evaluated for the ability to form biofilms in a borosilicate glass tube model which was optimized for Aeromonas spp . (broth inoculum, with a 16- to 20-h incubation at 37 degrees C) . All flagellar mutants showed a decreased ability to form biofilms (at least 30% lower than the wild type) . For the chemotactic motility mutant cheA, biofilm formation decreased >80% from the wild-type level . The complementation of flagellar phenotypes (polar flagellar mutants) restored biofilms to wild-type levels . We concluded that both flagellar types are enterocyte adhesins and need to be fully functional for optimal biofilm formation. Infect Immun, 2004 Apr, 72(4), 1929 - 38 Immunoglobulin-mediated agglutination of and biofilm formation by Escherichia coli K-12 require the type 1 pilus fiber; Orndorff PE et al.; The binding of human secretory immunoglobulin A (SIgA), the primary immunoglobulin in the gut, to Escherichia coli is thought to be dependent on type 1 pili . Type 1 pili are filamentous bacterial surface attachment organelles comprised principally of a single protein, the product of the fimA gene . A minor component of the pilus fiber (the product of the fimH gene, termed the adhesin) mediates attachment to a variety of host cell molecules in a mannose inhibitable interaction that has been extensively described . We found that the aggregation of E . coli K-12 by human secretory IgA (SIgA) was dependent on the presence of the pilus fiber, even in the absence of the mannose specific adhesin or in the presence of 25 mM alpha-CH(3)Man . The presence of pilus without adhesin also facilitated SIgA-mediated biofilm formation on polystyrene, although biofilm formation was stronger in the presence of the adhesin . IgM also mediated aggregation and biofilm formation in a manner dependent on pili with or without adhesin . These findings indicate that the pilus fiber, even in the absence of the adhesin, may play a role in biologically important processes . Under conditions in which E . coli was agglutinated by SIgA, the binding of SIgA to E . coli was not increased by the presence of the pili, with or without adhesin . This observation suggests that the pili, with or without adhesin, affect factors such as cell surface rigidity or electrostatic repulsion, which can affect agglutination but which do not necessarily determine the level of bound immunoglobulin. Int J Antimicrob Agents, 2004 Mar, 23 Suppl 1, S67 - 74 Bacterial biofilm formation on urologic devices and heparin coating as preventive strategy; Tenke P et al.; In the process of endourological development a variety of foreign bodies have been invented besides urinary catheters, on which biofilm can be formed . Bacteria in the biofilm are less susceptible to antibiotics . An additional problem of medical biomaterials in the urinary tract environment is the development of encrustation and consecutive obstruction . The most promising prevention strategy for bacterial biofilms is the production of materials with anti-adhesive surfaces such as heparin . Although heparin-coated ureteral stents are expensive, they justify their cost . Our studies show that such devices are protected against incrustation and biofilm formation for a longer period of time: 6-12 months, both in vitro and in vivo. Int J Antimicrob Agents, 2004 Mar, 23 Suppl 1, S24 - 9 Emergence of antibiotic resistance and prudent use of antibiotic therapy in nosocomially acquired urinary tract infections; Wagenlehner FM et al.; Nosocomially acquired urinary tract infections (NAUTI) are common . The reported rates, however, depend very much on the definitions used and the number of investigations requested . In a prospective study on a surgical intensive care unit and adhering closely to the CDC criteria, NAUTI was diagnosed in about 17% of the patients . The urinary catheter associated UTI rate per 1000 catheter days was 14.5 much higher than otherwise reported . Whereas the rates of symptomatic NAUTI and other nosocomially acquired infections were similar, the main difference was found for asymptomatic UTI which depends very much on the effort to search for it systematically . In a prospective study on a urological ward it could be demonstrated that cross-transmission probably plays a much greater role than so far suggested . Continuous surveillance of the bacterial spectrum and resistance is necessary not only on a global but also on a local level . Selection of an appropriate agent for empirical antibacterial therapy can be better tailored if not only the total bacterial spectrum is considered but if all information already available during the identification process is used, such as Gram stain and other simple and rapid tests for stratification of the pathogens . Since in NAUTI usually some kind of biofilm infection is involved, the fluoroquinolones can be considered agents of choice . Only those substances with high antibacterial activity, good bioavailability and those that are mainly excreted by the kidneys should be chosen and they have to be administered at sufficiently high doses. Appl Microbiol Biotechnol, 2004 Jun, 64(5), 718 - 25 Epub 2004 Mar 19. Membrane-aerated biofilm reactor for the removal of 1,2-dichloroethane by Pseudomonas sp . strain DCA1; Hage JC et al.; A membrane-aerated biofilm reactor (MBR) with a biofilm of Pseudomonas sp . strain DCA1 was studied for the removal of 1,2-dichloroethane (DCA) from water . A hydrophobic membrane was used to create a barrier between the liquid and the gas phase . Inoculation of the MBR with cells of strain DCA1 grown in a continuous culture resulted in the formation of a stable and active DCA-degrading biofilm on the membrane . The maximum removal rate of the MBR was reached at a DCA concentration of approximately 80 micro M . Simulation of the DCA fluxes into the biofilm showed that the MBR performance at lower concentrations was limited by the DCA diffusion rate rather than by kinetic constraints of strain DCA1 . Aerobic biodegradation of DCA present in anoxic water could be achieved by supplying oxygen solely from the gas phase to the biofilm grown on the liquid side of the membrane . As a result, direct aeration of the water, which leads to undesired coagulation of iron oxides, could be avoided. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub, 2003 Nov, 147(1), 27 - 35 Pathogenesis of prosthesis-related infection; Gallo J et al.; In spite of its incidence decreasing to 1% nowadays, prosthesis-related infection remains a research, diagnostic, therapeutic and cost-related problem . It can be defined as a presence of bacteria in the artificial joint space, which is significantly associated with evident laboratory and/or tissue markers, and clinical signs of running infection . We believe that the more precise understanding of pathogenesis, the more effective preventative and therapeutic measures, and the lower infection rate . The implants are colonized by airborne, skin-, and/ or surgeon-related bacteria during surgery despite being operated in closely respected operating regime . Some prosthetic characteristics are advantageous and may play important roles in the process of bacterial adherence . After successful attachment on the biomaterial surface bacteria multiply and physiologically transform into a "biofilm" community, making them much more resistant to antibiotic therapy and host immunity . Bacterial resistance is a complex phenomenon influenced by intrinsic and extrinsic factors, including the cell configuration in the biofilm community . So the cure of periprosthetic sepsis without removing of all foreign bodies and necrotic bone fragments is often ineffective . Acute hematogenous sepsis is suggestive of a distortion of a previously aseptic joint space by invasion of bacteria through the vessels. J Ind Microbiol Biotechnol, 2004 Mar, 31(3), 109 - 14 Epub 2004 Mar 16. Biodegradation of acid blue-15, a textile dye, by an up-flow immobilized cell bioreactor; Sharma DK et al.; Acid blue-15, a complex and resonance-stabilized triphenylmethane (TPM) textile dye, resistant to transformation, was decolorized/degraded in an up-flow immobilized cell bioreactor . A consortium comprised of isolates belonging to Bacillus sp., Alcaligenes sp . and Aeromonas sp . formed a multispecies biofilm on refractory brick pieces used as support material . The TPM dye was degraded to simple metabolic intermediates in the bioreactor with 94% decolorization at a flow rate of 4 ml h(-1). Arch Otolaryngol Head Neck Surg, 2004 Mar, 130(3), 339 - 43 Bacterial biofilm presence in pediatric tracheotomy tubes; Perkins J et al.; OBJECTIVE: To determine whether bacterial biofilms are present on pediatric tracheotomy tubes . DESIGN: Prospective observational series . INTERVENTIONS: Eleven tracheotomy tubes removed during routine tracheotomy tube changes were analyzed for biofilm and live bacteria presence using confocal microscopy and vital stains . The external and internal surfaces of the tracheotomy tubes were studied in 3 locations: distal tip, midtracheotomy tube, and proximal opening . These data were correlated with tracheotomy site cultures and the reason for tracheotomy dependence . MAIN OUTCOME MEASURES: Microscopic images were analyzed for the presence of a biofilm (its morphological features and the presence of live and dead bacteria within the biofilm) . RESULTS: Of 11 tracheotomy tubes, 10 had biofilm present on the internal surface of the distal tip . Externally, at the same location, 4 tubes had biofilms . On the internal surface of the midtracheotomy site, 8 had biofilm present, whereas only 1 had a biofilm on the internal surface of the proximal tracheotomy tube site . In the distal internal tracheotomy tube site, the biofilm was confluent in 5 tubes and patchy with evidence of microcolony formation in the remaining 5 tubes . Live bacteria were present in all biofilms . Control tracheotomy tubes did not have biofilms . All tracheotomy site cultures and disease states (chronic aspiration and bronchopulmonary dysplasia) were associated with tracheotomy tube biofilms . CONCLUSION: Bacterial biofilms containing live bacteria were demonstrated in most pediatric tracheotomy tubes, being most frequent and extensive on the internal surface of the distal tracheotomy tip. Curr Opin Infect Dis, 2004 Apr, 17(2), 91 - 6 Bacteria and wound healing; Edwards R et al.; PURPOSE OF REVIEW: Wound healing is a complex process with many potential factors that can delay healing . There is increasing interest in the effects of bacteria on the processes of wound healing . All chronic wounds are colonized by bacteria, with low levels of bacteria being beneficial to the wound healing process . Wound infection is detrimental to wound healing, but the diagnosis and management of wound infection is controversial, and varies between clinicians . RECENT FINDINGS: There is increasing recognition of the concept of critical colonization or local infection, when wound healing may be delayed in the absence of the typical clinical features of infection . The progression from wound colonization to infection depends not only on the bacterial count or the species present, but also on the host immune response, the number of different species present, the virulence of the organisms and synergistic interactions between the different species . There is increasing evidence that bacteria within chronic wounds live within biofilm communities, in which the bacteria are protected from host defences and develop resistance to antibiotic treatment . SUMMARY: An appreciation of the factors affecting the progression from colonization to infection can help clinicians with the interpretation of clinical findings and microbiological investigations in patients with chronic wounds . An understanding of the physiology and interactions within multi-species biofilms may aid the development of more effective methods of treating infected and poorly healing wounds . The emergence of consensus guidelines has helped to optimize clinical management. FEMS Microbiol Lett, 2004 Mar 12, 232(1), 39 - 43 Streptococcus mutans fructosyltransferase interactions with glucans; Rozen R et al.; Streptococcus mutans utilizes sucrose to synthesize glucans by glucosyltransferase and fructans by fructosyltransferase (FTF) . Antibodies raised against a recombinant FTF were used to study S . mutans FTF secretion . Low amounts of cell-free FTF were found in culture of S . mutans grown with sucrose, while an increase in bacteria displaying cell surface FTF was detected . FTF added to S . mutans cultures was adsorbed to bacteria grown with sucrose but not to bacteria grown with glucose or fructose or to a gtf inactivated mutant grown with sucrose . Recombinant FTF was found to have high affinity for glucans suggesting that fructans and glucans are an integral part of the polysaccharide matrix of oral biofilms. J Pharm Biomed Anal, 2004 Mar 1, 34(4), 803 - 10 Potential use of solid phase immunoassays in the diagnosis of coagulase-negative staphylococcal infections; Lamari FN et al.; Staphylococcus epidermidis is a major nosocomial pathogen, even though it is a member of the normal bacterial flora of skin and the mucous membranes . A major complication is the development of biofilms on implanted medical devices . Diagnosis of coagulase-negative staphylococcal infections relies on the presence of clinical manifestation of infections and on microbiologic evidence, usually obtained after the removal of the biomaterial . Solid-phase immunoassays have not yet been used for routine diagnosis of coagulase-negative staphylococcal infections and distinction between pathogenic and normal cocci . The enzyme immunoassays developed in the last decade are presented in this review article . Serodiagnosis has been attempted by determining antibodies against bacterial cells, mixtures of S . epidermidis slime antigens and discrete slime antigens . Detection or typing of staphylococcal cells has been performed by specific antibodies and lectins . There is still a long way until the application of such assays in the routine clinical laboratory and large clinical studies are necessary. Water Res, 2004 Mar, 38(6), 1626 - 32 Effect of O2 exposure on perchlorate reduction by Dechlorosoma sp . KJ; Song Y et al.; Anaerobic bioreactors have been developed to remove perchlorate from water, but backwashing and operational interruptions can expose biofilms to oxygen . While it is well known that oxygen is a preferential electron acceptor to perchlorate for perchlorate-respiring bacteria, little is known about the effect of oxygen exposure or redox potentials on perchlorate reduction . Four different dissolved oxygen scavengers were tested for their ability to quickly restore anaerobic conditions and allow perchlorate reduction by a facultative, perchlorate respiring bacterium Dechlorosoma sp . KJ . Of the four different oxygen scavengers tested (Oxyrase trade mark, L-cysteine, Na2S and FeS), only Oxyrase trade mark was able to rapidly (<30 min) scavenge dissolved oxygen and allow cell growth . There was no cell growth after addition of Na2S and FeS, and l-cysteine produced a long lag in cell growth . To investigate the effect of dissolved oxygen on perchlorate reduction, anaerobically grown cultures Dechlorosoma sp . KJ, were exposed to dissolved oxygen for various periods ranging from 1 to 32 h . Perchlorate reduction and redox potential were then measured for cells returned to an anaerobic environment containing an oxygen scavenger . It was determined that cells exposed to dissolved oxygen for more than 12h were incapable of reducing perchlorate . Cells exposed to dissolved oxygen for less than 12h quickly reduced the redox potential to negative values (-127 mV to -337 mV) and were able to reduce perchlorate or chlorite . Our results suggest that aeration during backwashing of biofilm reactors, or exposure of perchlorate-degrading cell suspensions to dissolve oxygen for less than 12h, will not be detrimental to the ability of perchlorate-degrading bacteria to use perchlorate as an electron acceptor. Water Res, 2004 Mar, 38(6), 1530 - 41 Overcoming oxygen limitations in membrane-attached biofilms--investigation of flux and diffusivity in an anoxic biofilm; Emanuelsson EA et al.; The possibility of overcoming oxygen limitations in membrane-attached biofilms has been investigated by using nitrate as an electron acceptor instead of oxygen in an extractive membrane bioreactor (EMB) degrading toluene . The effect of nitrate concentration on toluene flux, the effective diffusivity in the biofilm and the biofilm activity has been investigated . A counter-diffusion-reaction model is also presented, describing the pollutant flux versus biofilm thickness . The toluene flux decreased with increasing biofilm thickness under excess nitrate concentrations, similar to the experiment with low nitrate . Mathematical modelling indicated that this was either due to decreasing activity, and/or different diffusivities in the biofilm . The effective diffusivity was investigated by using an inert tracer molecule . It remained constant for biofilm thicknesses up to 1.8mm, with a value twice that in water . The biofilm activity was investigated by inactivating a mature biofilm using sodium azide . The toluene flux remained the same before and after the addition of sodium azide, suggesting that the activity in the biofilm is very low . We conclude that the decreasing toluene flux with increasing biofilm thickness is due to the diffusional resistance of the inactive biofilm. Water Res, 2004 Mar, 38(6), 1457 - 66 Survival of Mycobacterium avium in a model distribution system; Norton CD et al.; A pilot study was designed to examine the impact of nutrient levels, pipe materials, and disinfection on the survival of M . avium in model drinking water distribution system biofilms . Studies showed that the survival of the organism was dependant upon a complex interaction between pipe surface, nutrient levels, and disinfectants . The findings showed that when no disinfection was applied, M . avium could be recovered from biofilms at nutrient levels of 50microg/L assimilable organic carbon . M . avium concentrations were lower on copper pipe surfaces following disinfection with free chlorine as compared to monochloramine . However, due to the interference of corrosion products, chloramination of iron pipe surfaces controlled M . avium levels better than free chlorine . These data demonstrate the significance of pipe materials on the survival of M . avium complex in biofilms . Elimination of competitive heterotrophic bacteria on copper pipe surfaces by the application of disinfection resulted in a population of nearly 100% M . avium . Heat treatment of M . avium biofilms was affected by the pipe composition and organic content of the water . Effluent temperatures >53 degrees C were required to control the occurrence of M . avium in the pipeline system . Although additional studies are required using improved detection methods, the results of this investigation suggest that reducing the biodegradable organic material in drinking water, control of corrosion, maintenance of an effective disinfectant residual, and management of hot water temperatures can help limit the occurrence of M . avium complex in drinking water biofilms. Water Res, 2004 Mar, 38(6), 1390 - 404 The influence of substrate kinetics on the microbial community structure in granular anaerobic biomass; Batstone DJ et al.; The development of a strong, active granular sludge bed is necessary for optimal operation of upflow anaerobic sludge blanket reactors . The microbial and mechanical structure of the granules may have a strong influence on desirable properties such as growth rate, settling velocity and shear strength . Theories have been proposed for granule microbial structure based on the relative kinetics of substrate degradation, but contradict some observations from both modelling and microscopic studies . In this paper, the structures of four granule types were examined from full-scale UASB reactors, treating wastewater from a cannery, a slaughterhouse, and two breweries . Microbial structure was determined using fluorescence in situ hybridisation probing with 16S rRNA-directed oligonucleotide probes, and superficial structure and microbial density (volume occupied by cells and microbial debris) assessed using scanning electron microscopy (SEM), and transmission electron microscopy (TEM) . The granules were also modelled using a distributed parameter biofilm model, with a previously published biochemical model structure, biofilm modelling approach, and model parameters . The model results reflected the trophic structures observed, indicating that the structures were possibly determined by kinetics . Of particular interest were results from simulations of the protein grown granules, which were predicted to have slow growth rates, low microbial density, and no trophic layers, the last two of which were reflected by microscopic observations . The primary cause of this structure, as assessed by modelling, was the particulate nature of the wastewater, and the slow rate of particulate hydrolysis, rather than the presence of proteins in the wastewater . Because solids hydrolysis was rate limiting, soluble substrate concentrations were very low (below Monod half saturation concentration), which caused low growth rates. Water Res, 2004 Mar, 38(6), 1376 - 89 Anaerobic sludge granulation; Hulshoff Pol LW et al.; This paper reviews different theories on anaerobic sludge granulation in UASB-reactors that have been proposed during the past two decades . The initial stages of the formation of anaerobic granules follow the same principles as biofilm formation of bacteria on solid surfaces . There exist strong evidence that inert carriers play an important positive role in granulation . Most researchers conclude that Methanosaeta concilii is a key organism in granulation . Only the Cape Town Hypothesis presumes that an autotrophic hydrogenotrophic organism, i.e., Methanobacterium strain AZ, growing under conditions of high H(2)-pressures, is the key organism in granulation . Many authors focus on the initial stage of granulation, and only a few contributions discuss the latter stages in granulation: granule maturation and multiplication . Granule enhancing factors in the latter stages predominantly rely on manipulation of the selection pressure, through which selectively heavier sludge particles are retained in the UASB reactor. Water Res, 2004 Mar, 38(6), 1355 - 67 Retention and removal of pathogenic bacteria in wastewater percolating through porous media: a review; Stevik TK et al.; Properly designed biological filters or infiltration systems have the capacity to significantly reduce effluent concentrations of pathogenic microorganisms in wastewater . The retention and elimination of microbial cells in biological wastewater filter systems is influenced by several factors . In this review, these factors are discussed . Immobilization of microbial cells moving through a porous media is influenced by mechanisms such as physical straining as well as adsorption to porous media . The grain size of porous media and bacterial cell size are important factors affecting the straining of bacteria, as are the hydraulic loading rate or the extent of clogging layer development in the filter . Adsorption of cells to the porous media is influenced by the content of organic matter, degree of biofilm development, and electrostatic attraction due to ion strength of the solution or electrostatic charges of cell- and particle surfaces . The rate of inactivation of pathogenic microorganisms, in adsorbed or liquid phases, has been shown to be affected by abiotic and biotic factors such as moisture content, pH, temperature, organic matter, bacterial species, predation, and antagonistic symbiosis between microorganisms in the system. Clin Diagn Lab Immunol, 2004 Mar, 11(2), 379 - 86 Establishment of an animal model using recombinant NOD.B10.D2 mice to study initial adhesion of oral streptococci; Abdus Salam M et al.; An oral biofilm is a community of surface-attached microorganisms that coats the oral cavity, including the teeth, and provides a protective reservoir for oral microbial pathogens, which are the primary cause of persistent and chronic infectious diseases in patients with dry mouth or Sjogren's syndrome (SS) . The purpose of this study was to establish an animal model for studying the initial adhesion of oral streptococci that cause biofilm formation in patients with dry mouth and SS in an attempt to decrease the influence of cariogenic organisms and their substrates . In nonobese diabetogenic (NOD) mice that spontaneously develop insulin-dependent diabetes mellitus (IDDM) and SS, we replaced major histocompatibility complex (MHC) class II (A(g7) E(g7)) and class I D(b) with MHC class II (A(d) E(d)) and class I D(d) from nondiabetic B10.D2 mice to produce an animal model that inhibited IDDM without affecting SS . The adhesion of oral streptococci, including Streptococcus mutans, onto tooth surfaces was then investigated and quantified in homologous recombinant N5 (NOD.B10.D2) and N9 (NOD.B10.D2) mice . We found that a higher number of oral streptococci adhered to the tooth surfaces of N5 (NOD.B10.D2) and N9 (NOD.B10.D2) mice than to those of the control C57BL/6 and B10.D2 mice . On the basis of our observation, we concluded that these mouse models might be useful as animal models of dry mouth and SS for in vivo biological studies of oral biofilm formation on the tooth surfaces. Infect Dis Clin North Am, 2003 Dec, 17(4), 679 - 95 Hospital-acquired pneumonia: etiologic considerations; Alcon A et al.; The development of pneumonia requires the pathogen to reach the alveoli and the host defenses to be overwhelmed, either by microorganism virulence or by inoculums size . The endogenous sources of microorganisms are nasal carriers, sinusitis, mouth, oropharynx, gastric, or tracheal colonization, and hematogenous spread . The exogenous sources of microorganisms are biofilm of the tracheal tube, ventilator circuits, nebulizers, and humidifiers . Health care workers may also play a role in this setting . Different microorganisms can be found depending on the onset time of pneumonia and on the local pattern variation encountered between different institutions and countries . Healthy patients may be chronically colonized . A very important, unresolved issue is the definition of early and late-onset pneumonia; it still remains uncertain from the literature whether the given threshold refers to the number of days in hospital or to the number of days following intubation . Noninvasive ventilation is demonstrating that the term "ventilator-associated pneumonia" is perhaps inaccurate and should be referred to as "intubation-associated pneumonia." Appl Environ Microbiol, 2004 Mar, 70(3), 1698 - 707 Molecular evidence for the evolution of metal homeostasis genes by lateral gene transfer in bacteria from the deep terrestrial subsurface; Coombs JM et al.; Lateral gene transfer (LGT) plays a vital role in increasing the genetic diversity of microorganisms and promoting the spread of fitness-enhancing phenotypes throughout microbial communities . To date, LGT has been investigated in surface soils, natural waters, and biofilm communities but not in the deep terrestrial subsurface . Here we used a combination of molecular analyses to investigate the role of LGT in the evolution of metal homeostasis in lead-resistant subsurface bacteria . A nested PCR approach was employed to obtain DNA sequences encoding P(IB)-type ATPases, which are proteins that transport toxic or essential soft metals such as Zn(II), Cd(II), and Pb(II) through the cell wall . Phylogenetic incongruencies between a 16S rRNA gene tree and a tree based on 48 P(IB)-type ATPase amplicons and sequences available for complete bacterial genomes revealed an ancient transfer from a member of the beta subclass of the Proteobacteria (beta-proteobacterium) that may have predated the diversification of the genus PSEUDOMONAS: Four additional phylogenetic incongruencies indicate that LGT has occurred among groups of beta- and gamma-proteobacteria . Two of these transfers appeared to be recent, as indicated by an unusual G+C content of the P(IB)-type ATPase amplicons . This finding provides evidence that LGT plays a distinct role in the evolution of metal homeostasis in deep subsurface bacteria, and it shows that molecular evolutionary approaches may be used for investigation of this process in microbial communities in specific environments. Appl Environ Microbiol, 2004 Mar, 70(3), 1528 - 36 High diversity among environmental Escherichia coli isolates from a bovine feedlot; Yang HH et al.; Approximately 280 Escherichia coli isolates were isolated from a bovine feedlot at the University of Connecticut campus via enrichment in lauryl tryptose broth and random selection from MacConkey plates . The E . coli subspecies diversity was estimated by employing whole-cell BOX-PCR genomic fingerprints . A total of 89 distinct operational taxonomic units (OTUs) were identified by employing a criterion of 85% fingerprint similarity as a surrogate for an OTU, while the Chao1 index estimated the E . coli population richness at 128 OTUs . One genotype (at a similarity level of 60%) dominated the population at 66% regardless of sampling depth or location, while no significant vertical distribution pattern was observed in terms of genotype, mobility, antibiotic resistance profile, or biofilm-forming ability . Motility, measured by a soft agar assay, had a very broad range among the E . coli population and was positively correlated with biofilm-forming ability in minimal medium (Spearman's rank correlation coefficient r = 0.619, P < 10(-4)) but not in Luria broth . Only an estimated 48% of the population possessed gene agn43, which encodes Ag43, a phase-variable outer membrane protein that has been implicated in biofilm formation in minimal medium . We observed significantly more biofilm formation in both minimal medium and Luria broth for agn43(+) strains, with a larger effect in minimal medium . This study represents an exhaustive inventory of extant E . coli population diversity at a bovine feedlot and reveals significant subspecies heterogeneity in interfacial behavior. Appl Environ Microbiol, 2004 Mar, 70(3), 1321 - 7 Characterization of the arginine deiminase operon of Streptococcus rattus FA-1; Griswold A et al.; The arginine deiminase system (ADS) is of critical importance in oral biofilm pH homeostasis and microbial ecology . The ADS consists of three enzymes . Arginine is hydrolyzed by AD (ArcA) to generate citrulline and ammonia . Citrulline is then converted to ornithine and carbamoylphosphate via ornithine carbamoyltransferase (ArcB) . Finally, carbamate kinase (ArcC) transfers a phosphate from carbamoylphosphate to ADP, yielding ATP . Ammonia production from this pathway protects bacteria from lethal acidification, and ATP production provides a source of energy for the cells . The purpose of this study was to initiate a characterization of the arc operon of Streptococcus rattus, the least cariogenic and sole ADS-positive member of the mutans streptococci . Using an arcB gene fragment obtained by degenerate PCRs, the FA-1 arc operon was identified in subgenomic DNA libraries and sequence analysis was performed . Results showed that the genes encoding the AD pathway in S . rattus FA-1 are organized as an arcABCDT-adiR operon gene cluster, including the enzymes of the pathway, an arginine-ornithine antiporter (ArcD) and a putative regulatory protein (AdiR) . The arcA transcriptional start site was identified by primer extension, and a sigma(70)-like promoter was mapped 5' to arcA . Reverse transcriptase PCR was used to establish that arcABCDT could be cotranscribed . Reporter gene fusions and AD assays demonstrated that the operon is regulated by substrate induction and catabolite repression, the latter apparently through a CcpA-dependent pathway. J Microbiol Methods, 2004 Apr, 57(1), 95 - 106 Green and red fluorescent protein vectors for use in biofilm studies of the intrinsically resistant Burkholderia cepacia complex; Tomlin KL et al.; Cystic fibrosis isolates of the Burkholderia cepacia complex (BCC) have demonstrated a propensity to associate intimately with Pseudomonas aeruginosa in mixed community biofilms, which may impact on their overall pathogenicity during infection of the lungs in cystic fibrosis . Here, we describe the construction and use of novel green and red fluorescent protein expression vectors suitable for labeling biofilm cells of multi-resistant clinical isolates of the BCC for microscopic analysis of both single species biofilms and mixed community associations with P . aeruginosa . Antimicrobial susceptibility testing established that tetracycline and/or trimethoprim were suitable selective agents for widespread use in BCC . The green and red fluorescent protein genes, driven by constitutively active promoters, were cloned into two mobilizable plasmids pBBR1MCS-3 and pBBR1Tp, carrying tetracycline and trimethoprim resistance cassettes, respectively . The fluorescence of transformed BCC and P . aeruginosa planktonic cells was detectable using fluorescence microscopy and/or fluorometry . The plasmids were stable in the absence of selection for at least 3 days in planktonic and biofilm cultures, and fluorescence was still visible in a 4-day glass coverslip flow cell biofilm . The plasmids functioned well to distinguish the two species in a mixed community biofilm, with no indications of plasmid transfer between species or cross-talk of the fluorescent signals . These vectors represent the first green and red fluorescent vectors to be constructed and analyzed specifically for wide spread use in BCC and P . aeruginosa single and mixed biofilm cultures. J Microbiol Methods, 2004 Apr, 57(1), 55 - 64 Methods for in situ detection and characterization of extracellular polymers in biofilms by electron microscopy; Kamper M et al.; Electron microscopy of biofilms and the localization of extracellular polymers at high resolution require the adaptation of conventional electron microscopic preparation and imaging techniques . A method developed for in situ fixation and embedding of biofilms, imaging of unstained thick sections with electron spectroscopic imaging and the application of lectin or antibody-based marker systems allowed interpretation of extracellular polymer distribution at micrometer scale . By this way, it is possible to discriminate in situ between extracellular polymers produced by different organisms. Arch Oral Biol, 2004 Apr, 49(4), 295 - 304 Biofilm-specific surface properties and protein expression in oral Streptococcus sanguis; Black C et al.; OBJECTIVE: Oral streptococci are primary colonisers of the tooth surface and are abundant in dental plaque biofilms . Bacteria growing in these relatively dense, surface-associated communities are phenotypically quite distinct from their planktonic counterparts . The purpose of the present study was to develop a method to investigate biofilm-specific surface protein expression by Streptococcus sanguis to help provide a better understanding of the critical events in plaque development . DESIGN: Biofilm cells were grown on the surface of glass beads in a biofilm device fed with mucin-containing artificial saliva . Planktonic cells were grown in continuous culture at approximately the same growth rate . Surface hydrophobicity of biofilm and planktonic cells was determined by hexadecane partitioning, and expression of streptococcal fibronectin adhesin CshA was determined in ELISA using specific antiserum . Antisera raised to glutaraldehyde-fixed whole biofilm or planktonic grown cells were used to screen an expression library of S . sanguis genomic DNA, and isolated clones were sequenced . RESULTS: Phenotypic analysis of biofilm and planktonic cells confirmed that mode of growth affected surface properties of S . sanguis . Thus, hydrophobicity and CshA expression was significantly elevated in biofilm cells . Library screening with biofilm antiserum yielded 32 recombinant clones representing 21 different S . sanguis proteins involved in adhesion and colonisation, carbohydrate utilisation or bacterial metabolism . In differential analysis of four selected Escherichia coli clones, biofilm antiserum reacted five times stronger than planktonic antiserum with cell-free extracts of clones encoding homologues of CshA and Cna collagen adhesin of Staphylococcus aureus, suggesting that these surface proteins are up-regulated in biofilm cells . In contrast, both antisera reacted equally strongly with cell-free extracts of the remaining two clones (encoding dihydrofolate synthase and an unknown protein) . CONCLUSIONS: The method described represents a useful means for determining bacterial protein expression in biofilms based on a combination of molecular and immunological techniques . Surface expression of putative fibronectin and collagen adhesins was up-regulated in biofilm cells. J Proteome Res, 2004 Jan-Feb, 3(1), 132 - 6 Biofilm proteome: homogeneity or versatility? Vilain S, Cosette P, Zimmerlin I, Dupont JP, Junter GA, Jouenne T. The problems associated with biofilm infections in humans result from the distinct characteristics of biofilms, in particular their high level of resistance to antibiotics . One of the hypotheses that have been advanced to explain this resistance to antimicrobials is the phenotypic differentiation of biofilm cells . Although many studies on biofilms have highlighted physiological alterations following the attachment of bacteria to a surface, no studies have explicitly demonstrated a "biofilm" physiology . To contribute to this topical debate, we used principal component analysis to interpret spot quantity variations observed on electropherograms obtained by two-dimensional gel electrophoresis of crude protein extracts from planktonic and sessile Pseudomonas aeruginosa cells . These analyses showed that the proteome of attached P . aeruginosa cells differs from that of their planktonic counterparts . Furthermore, we found that the proteome of sessile P . aeruginosa is strongly dependent on the nature of the biofilm substratum. J Chemother, 2003 Dec, 15(6), 536 - 42 Device-related infections in critically ill patients . Part II: Prevention of ventilator-associated pneumonia and urinary tract infections; Di Filippo A et al.; Device utilization in critically ill patients is responsible for a high risk of complications such as catheter-related bloodstream infections (CRBSI), ventilator-associated pneumonia (VAP) and urinary tract infections (UTI) . In this article we will review the current status of data regarding the prevention of VAP and UTI . The results of the more recent (5 years) randomized controlled trials are reviewed and discussed . General recommendations include staff education and use of a surveillance program with a restrictive antibiotic policy . Adequate time must be allowed for hand washing and barrier precautions must always be used during device manipulation . Specific measures for VAP prevention are: 1) use of multi-use, closed-system suction catheters; 2) no routine change of the breathing circuit; 3) lubrication of the cuff of the endotracheal tube (ET) with a water-soluble gel; 4) maintenance of patient in semi-recumbent position to improve chest physiotherapy in intubated patients . Specific measures for UTI prevention include: 1) use of a catheter-valve instead of a standard drainage system; 2) use of a silver-alloy, hydro gel-coated latex urinary catheter instead of uncoated catheters . Biofilm represents a new variable: the capacity of bacteria to organize a biofilm on a device surface can explain the difficulty in preventing and eradicating an infection in a critically ill patient . More clinical trials are needed to verify the efficacy of prevention measures of ICU infections. Appl Microbiol Biotechnol, 2004 Jun, 64(5), 726 - 34 Epub 2004 Mar 02. High-diversity biofilm for the oxidation of sulfide-containing effluents; Ferrera I et al.; In the present work, we describe for the first time the utilization of a complex microbial biofilm for the treatment of sulfide-containing effluents . A non-aerated packed-column reactor was inoculated with anoxic lake sediment and exposed to light . A biofilm developed in the column and showed a stable oxidation performance for several weeks . Microbial species composition was analyzed by microscopy, pigment analysis and a bacterial 16S rRNA gene clone library . Colorless sulfur bacteria, green algae and purple sulfur bacteria were observed microscopically . Pigment composition confirmed the presence of algae and purple sulfur bacteria . The clone library was dominated by alpha-Proteobacteria (mostly Rhodobacter group), followed by gamma-Proteobacteria (Chromatiaceae-like and Thiothrix-like aerobic sulfur oxidizers) and the Cytophaga- Flavobacterium- Bacteroides group . Plastid signatures from algae were also present and a few clones belonged to both the beta- ( Rhodoferax sp., Thiobacillus sp.) and delta-Proteobacteria ( Desulfocapsa sp.) and to the low G+C Gram-positive bacteria (Firmicutes group) . The coexistence of aerobic, anaerobic, phototrophic and chemotrophic microorganisms in the biofilm, the species richness found within these metabolic groups (42 operational taxonomic units) and the microdiversity observed within some species could be very important for the long-term functioning and versatility of the reactor. Appl Microbiol Biotechnol, 2004 Jun, 64(5), 659 - 64 Epub 2004 Mar 02. A new non-aerated illuminated packed-column reactor for the development of sulfide-oxidizing biofilms; Ferrera I et al.; This paper describes an illuminated reactor that allows the spontaneous development of biofilms aimed at the treatment of sulfide-containing streams . The reactor operates as a sulfidostat and is composed of an illuminated packed-column, in which microorganisms are exposed to constant low substrate concentrations, thereby avoiding inhibition due to high sulfide concentrations . The control system allows highly polluted streams to be oxidized by the microbial biofilm while ensuring the quality of the effluent produced . Both monospecies and multispecies biofilms have been developed . Biofilms undergo changes in light irradiance and sulfide load while providing a consistent reduction of the sulfide levels, down to micromolar concentrations . Both types of biofilm developed differ from stirred reactors in that their specific activities are lower, constituting systems with a slow dynamic behavior and, therefore, they are less sensitive to sudden disturbances. J Bacteriol, 2004 Mar, 186(6), 1838 - 50 Quorum sensing in Staphylococcus aureus biofilms; Yarwood JM et al.; Several serious diseases are caused by biofilm-associated Staphylococcus aureus, infections in which the accessory gene regulator (agr) quorum-sensing system is thought to play an important role . We studied the contribution of agr to biofilm development, and we examined agr-dependent transcription in biofilms . Under some conditions, disruption of agr expression had no discernible influence on biofilm formation, while under others it either inhibited or enhanced biofilm formation . Under those conditions where agr expression enhanced biofilm formation, biofilms of an agr signaling mutant were particularly sensitive to rifampin but not to oxacillin . Time lapse confocal scanning laser microscopy showed that, similar to the expression of an agr-independent fluorescent reporter, biofilm expression of an agr-dependent reporter was in patches within cell clusters and oscillated with time . In some cases, loss of fluorescence appeared to coincide with detachment of cells from the biofilm . Our studies indicate that the role of agr expression in biofilm development and behavior depends on environmental conditions . We also suggest that detachment of cells expressing agr from biofilms may have important clinical implications. Oral Dis, 2004 Jan, 10(1), 5 - 12 Involvement of periodontopathic biofilm in vascular diseases; Okuda K et al.; Oral bacteria inhabit biofilms, which are firm clusters adhering in layers to surfaces and are not easily eliminated by immune responses and are resistant to antimicrobial agents . Dental plaque is one such biofilm . In the past 10 years, subgingival plaque bacteria forming biofilms have been increasingly reported to be involved in systemic diseases . A close relationship between microbial infections and vascular disease has also been reported in the past two decades . The present review discusses the significance of the ecologic characteristics of biofilms formed by periodontopathic bacteria in order to further clarify the associations between periodontal disease and systemic disease . We focus on the relationships between periodontal disease-associated bacteria forming biofilms and vascular diseases including atherosclerosis and carotid coronary stenotic artery disease, and we discuss the direct and indirect effects on vascular diseases of lipopolysaccharides as well as heat shock proteins produced by periodontopathic bacteria. Oral Dis, 2004 Mar, 10(2), 106 - 12 Candida yeasts in chronic periodontitis tissues and subgingival microbial biofilms in vivo; Jarvensivu A et al.; The frequency of Candida infection in periodontal tissues of chronic periodontitis (CP) patients and the extent of candidal penetration into gingival tissues was studied . Tissue specimens collected from 25 CP patients during periodontal flap operations of initial periodontal therapy were examined by immunohistochemistry using Candida albicans-specific antibodies . Sections were also stained with periodic acid-Schiff (PAS) and subgingival plaque samples from 17 patients were cultured . Immunoreactivity for Candida was present in four of the 25 CP specimens (16%) . Only one yeast-positive specimen was found when PAS-staining was used (4%) and two yeast-positive specimens were found with plaque culture (8%) . Hyphal formation seemed essential and candidal hyphae were found to extend into the periodontal connective tissue . The degree and type of inflammation adjacent to the hyphae varied from a site and a patient to another . The sensitivity of specific antibodies was superior to PAS-stain or plaque culture in detection of Candida in tissues. Microb Ecol, 2004 Apr, 47(3), 205 - 17 Epub 2004 Mar 04. Sulfate-reducing bacteria-dominated biofilms that precipitate ZnS in a subsurface circumneutral-pH mine drainage system; Labrenz M et al.; The microbial diversity of ZnS-forming biofilms in 8 degrees C, circumneutral-pH groundwater in tunnels within the abandoned Piquette Zn, Pb mine (Tennyson, Wisconsin, USA) has been investigated by molecular methods, fluorescence in situ hybridization (FISH), and cultivation techniques . These biofilms are growing on old mine timbers that generate locally anaerobic zones within the mine drainage system . Sulfate-reducing bacteria (SRB) exclusively of the family Desulfobacteriaceae comprise a significant fraction of the active microbiota . Desulfosporosinus strains were isolated, but could not be detected by molecular methods . Other important microbial clusters belonged to the beta-, gamma-, and epsilon-Proteobacteria, the Cytophaga/Flexibacter/Bacteroides-group (CFB), Planctomycetales, Spirochaetales, Clostridia, and green nonsulfur bacteria . Our investigations indicated a growth dependence of SRB on fermentative, cellulolytic, and organic acid-producing Clostridia . A few clones related to sulfur-oxidizing bacteria were detected, suggesting a sulfur cycle related to redox gradients within the biofilm . Sulfur oxidation prevents sulfide accumulation that would lead to precipitation of other sulfide phases . FISH analyses indicated that Desulfobacteriaceae populations were not early colonizers in freshly grown and ZnS-poor biofilms, whereas they were abundant in older, naturally established, and ZnS-rich biofilms . Gram-negative SRB have been detected in situ over a period of 6 months, supporting the important role of these organisms in selective ZnS precipitation in Tennyson mine . Results demonstrate the complex nature of biofilms responsible for in situ bioremediation of toxic metals in a subsurface mine drainage system. Microb Ecol, 2004 Apr, 47(3), 284 - 92 Epub 2004 Mar 04. Utilization of microbial biofilms as monitors of bioremediation; Peacock AD et al.; A down-well aquifer microbial sampling system was developed using glass wool or Bio-Sep beads as a solid-phase support matrix . Here we describe the use of these devices to monitor the groundwater microbial community dynamics during field bioremediation experiments at the U.S . Department of Energy Natural and Accelerated Bioremediation Research Program's Field Research Center at the Oak Ridge National Laboratory . During the 6-week deployment, microbial biofilms colonized glass wool and bead internal surfaces . Changes in viable biomass, community composition, metabolic status, and respiratory state were reflected in sampler composition, type of donor, and groundwater pH . Biofilms that formed on Bio-Sep beads had 2-13 times greater viable biomass; however, the bead communities were less metabolically active {higher cyclopropane/monoenoic phospholipid fatty acid (PLFA) ratios} and had a lower aerobic respiratory state (lower total respiratory quinone/ PLFA ratio and ubiquinone/menaquinone ratio) than the biofilms formed on glass wool . Anaerobic growth in these systems was characterized by plasmalogen phospholipids and was greater in the wells that received electron donor additions . Partial 16S rDNA sequences indicated that Geobacter and nitrate-reducing organisms were induced by the acetate, ethanol, or glucose additions . DNA and lipid biomarkers were extracted and recovered without the complications that commonly plague sediment samples due to the presence of clay or dissolved organic matter . Although microbial community composition in the groundwater or adjacent sediments may differ from those formed on down-well biofilm samplers, the metabolic activity responses of the biofilms to modifications in groundwater geochemistry record the responses of the microbial community to biostimulation while providing integrative sampling and ease of recovery for biomarker analysis. Microbiology, 2004 Mar, 150(Pt 3), 735 - 42 Effect of acid stress on the physiology of biofilm cells of Streptococcus mutans; McNeill K et al.; Streptococcus mutans is a component of the dental plaque biofilm and an important aetiological agent in dental caries . Although this organism growing in the suspended (planktonic) state has been well characterized, relatively little is known about its physiology in biofilms, particularly in the acidic environments associated with caries development . The authors determined the effect of biofilm age (1-5 days) and cell density on selected metabolic properties under conditions of glucose limitation in a biofilm-chemostat at pH 7.5 and compared these baseline values with those of 3 day biofilms subjected to acid stress . Biofilm cell biomass more than doubled over the 5 day experimental period under baseline conditions, with the glycolytic rate, glucose uptake, glucose-PTS (phosphotransferase system) activity and protein synthesis maximum at 1-2 days . DNA and RNA synthesis increased for the first 3 days before decreasing in the 5 day biofilms, while H(+)/ATPase activity was higher in 5 day biofilms than 1 day biofilms, with overall activity 5-13-fold higher per cell unit than in the associated planktonic cells . Glucose pulsing (50 mM final concentration) for three consecutive days without pH control for 5 h (pH 4.39+/-0.02) resulted in a progressive decrease in planktonic cell numbers; however, the rate of acid formation and glucose utilization in the chemostat by these cells increased per cell unit . Assays for carbohydrate metabolism in the latter cells showed increased activity, as did an assay for H(+)/ATPase (8-fold); however, DNA, RNA and protein synthesis were repressed (0.3-0.7-fold) . Although the 3 day biofilm viable cell counts declined by 51 % on glucose pulsing, all the physiological parameters measured by cell unit increased in activity, with notable increases in RNA and protein synthesis (4.6-7.6-fold) . The results indicate that the maintenance of intracellular pH homeostasis is the basis of the enhanced physiological status and acid tolerance of biofilm cells. Biotechnol Bioeng, 2004 Mar 30, 85(7), 697 - 705 High-rate ferric sulfate generation by a Leptospirillum ferriphilum-dominated biofilm and the role of jarosite in biomass retention in a fluidized-bed reactor; Kinnunen PH et al.; The aims of this work were to develop a high-rate fluidized-bed bioprocess for ferric sulfate production, to characterize biomass retention, and to determine the phylogeny of the enrichment culture . After 7 months of continuous enrichment and air aeration at 37 degrees C, the iron oxidation rate of 8.2 g Fe(2+) L(-1)h(-1) (4.5.10(-12) g Fe(2+) cell(-1) h(-1)) was obtained at a hydraulic retention time (HRT) of 0.6 h . However, oxygen supply became the rate-limiting factor . With gas mixture (99.5% O(2)/0.5% CO(2) (vol/vol)) aeration and HRT of 0.2 h, the iron oxidation rate was 26.4 g Fe(2+) L(-1)h(-1) (1.0.10(-11) g Fe(2+) cell(-1) h(-1)) . Leptospirillum sp . was predominant in the mesophilic fluidized-bed reactor (FBR) enrichment culture as determined by fluorescent in situ hybridization, while Acidithiobacillus ferrooxidans was not detected . Denaturing gradient gel electrophoresis (DGGE) of the amplified partial 16S rDNA showed only three bands, indicating a simple microbial community . DGGE fragment excision and sequencing showed that the populations were related to L . ferriphilum (100% similarity in sequence) and possibly to the genus Ferroplasma (96% similarity to F . acidiphilum) . Jarosite precipitates accumulated on the top of the activated carbon biomass carrier material, increasing the rate of iron oxidation . The activated carbon carrier material, jarosite precipitates, and reactor liquid contained 59% (or 3.71.10(9) cells g(-1)), 31% (or 3.12.10(10) cells g(-1)) and 10% (or 1.24.10(8) cells mL(-1)) of the total FBR microbes, respectively, demonstrating that the jarosite precipitates played an important role in the FBR biomass retention . Bioprocess Biosyst Eng, 2004 Apr, 26(3), 169 - 75 Epub 2004 Feb 19. Bioprocess kinetics in a horizontal rotating tubular bioreactor; Ivancic M et al.; A horizontal rotating tubular bioreactor (HRTB) is a plug flow bioreactor whose interior is provided with O-ring-shaped partition walls that serve as carriers for microbial biomass . During this investigation, microbial biomass was grown in suspension and on the bioreactor inner surface as a microbial biofilm with average mass that was considerably higher than suspended biomass . The dynamics of bioprocess in HRTB was studied by different combinations of process parameters (bioreactor rotation speed and mean residence time) and it was monitored by withdrawing the samples from five positions along the bioreactor . During this investigation it was also observed that mean residence time had a more pronounced effect on the bioprocess dynamics than bioreactor rotation speed . For the description of bioprocess kinetics in HRTB an unstructured kinetic model was established that defines biomass growth, product formations and substrate consumption rate by using a modified Monod (Levenspiel) model . This kinetic model defines changes in suspension and in microbial biofilm, and it shows relatively good agreement with experimental data. Clin Oral Investig, 2004 Jun, 8(2), 97 - 101 Epub 2004 Feb 19. Impact of the intraoral location on the rate of biofilm growth; Auschill TM et al.; The aims of the present study were: a) to assess the impact of the intraoral location on the rate of biofilm growth, and b) to establish an in vivo biofilm model to examine intraoral biofilm growth . Eight healthy volunteers wore acrylic splints with 15 glass slabs each in the upper and lower jaws to build up plaque . After 48 h, the specimens were removed and stained using the vital fluorescence technique . Biofilm thickness was evaluated by confocal laser scanning microscopy (CLSM) . The mean plaque thickness amounted to 77.6 +/- 29.1 microm on the buccal sites of the upper jaw and 71.9 +/- 26.3 microm on the buccal sites of lower jaw . On the palatal site a biofilm of 52.1 +/- 26.2 microm thickness was grown, which was significantly less compared with the other locations evaluated (p < 0.001) . The results demonstrate that the in situ biofilm thickness on the buccal sites was similar irrespective of the location in the oral cavity . The new splint system described may be a useful tool for further standardised experimental studies regarding influences on growth and structure of intraoral biofilms. Shanghai Kou Qiang Yi Xue, 2002 Mar, 11(1), 37 - 9 {The role of dead bacteria in streptococcus sanguis biofilm reformation}; Ma R et al.; OBJECTIVE: To investigate the role of dead bacteria in Streptococcus sanguis biofilm reformation . METHODS: Vital fluorescent staining technique and Confocal laser Scanning Microscopy (CLSM) were combined to observe Streptococcus sanguis biofilm on the saliva-coated glass (SCG) in an artificial mouth model, the thickness and bacterial density were compared between biofilm reformed on saliva covered slide with dead cells (test group) and biofilm reformed on saliva coated slide without dead cells (control group) at different times . RESULTS: At 30 min, the bacterial density rather than biofilm thickness of test group was significantly higher than that of control group (P<0.05), whereas at 60 min, 120min, 240min, the biofilms were significantly thicker in test group than that (P<0.05) . CONCLUSION: The dead cells may help biofilm reformation during the formation of biofilm. Antimicrob Agents Chemother, 2004 Mar, 48(3), 890 - 6 Killing by ampicillin and ofloxacin induces overlapping changes in Escherichia coli transcription profile; Kaldalu N et al.; The basis of bactericidal versus bacteriostatic action of antibiotics and the mechanism of bacterial cell death are largely unknown . Related to this important issue is the essential invulnerability to killing of persisters: cells forming a small subpopulation largely responsible for the recalcitrance of biofilms to chemotherapy . To learn whether death is accompanied by changes in expression of particular genes, we compared transcription profiles of log-phase Escherichia coli treated with bactericidal concentrations of two unrelated antibiotics: ampicillin and ofloxacin . Massive changes in transcription profile were observed in response to either agent, and there was a significant overlap in genes whose transcription was affected . A small group of mostly uncharacterized genes was induced and a much larger set was transcriptionally repressed by both antibiotics . Among the repressed genes were those required for flagellar synthesis, energy metabolism, transport of small molecules, and protein synthesis. Water Sci Technol, 2004, 49(2), 107 - 13 Impact of localised dissolved iron concentrations on the biofouling of environmental wells; Stuetz RM et al.; Iron biofouling of wells can significantly impact the performance of a groundwater extraction system . A subsurface drainage scheme (Wakool, Australia) designed to reduce waterlogging was used to identify some of the relationships between aquifer properties and well biofouling . Piezometers drilled radially one metre from two biofouled wells showed that during normal well operation the concentration of dissolved iron (Fe2+) entering the groundwater well was highly localised around the site and with depth . CCTV survey of the biofouling on the well screens supported these findings of localised iron concentrations . Dissolved oxygen (DO) measured during pumping and under non-pumping conditions (aquifer DO) showed that oxygen was not a limiting factor, whereas stalked bacteria (Gallionella sp.) were only found in the biofouled wells . The wellhead water therefore represents only a composite of all the waters entering the well and does not indicate the possibility of localised iron concentrations in a shallow aquifer . The degree of iron biofouling within a groundwater well is therefore related directly to the presence of dissolved iron in the groundwater, as well as various oxidative processes occurring as the groundwater enters the well screen and its subsequent extraction . The distribution of iron biofilms on the well screen reflects these processes; however, the presence of well biofouling cannot always be linked to a decrease in well screen performance, but can have an impact on the overall performance of the groundwater extraction system. Water Sci Technol, 2004, 49(2), 91 - 8 The physico-chemistry of biofilm-mediated pitting corrosion of copper pipe supplying potable water; Keevil CW; Copper is a generally robust material that has beneficial properties to reduce biofilm formation and pathogen colonisation of pipes supplying potable water . However, a rare pitting corrosion can occur in soft, poorly buffered waters that can lead to pipe failure . This has been shown to be mediated by a copper-tolerant biofilm whose physical and chemical heterogeneity can establish microenvironments for corrosion potentials, causing micro pits that eventually coalesce into large perforations through the pipe wall . Control of the biofilm, for example through reduced cold water or elevated hot water temperatures, can suppress this corrosion phenomenon. Infect Immun, 2004 Mar, 72(3), 1431 - 40 Effects of RelA on key virulence properties of planktonic and biofilm populations of Streptococcus mutans; Lemos JA et al.; Streptococcus mutans is a biofilm-forming bacterium that is adapted to tolerate rapid and dramatic fluctuations in nutrient availability, carbohydrate source, and pH in its natural environment, the human oral cavity . Dissecting the pathways used to form stable biofilms and to tolerate environmental stress is central to understanding the virulence of this organism . Here, we investigated the role of the S . mutans relA gene, which codes for a guanosine tetraphosphate and guanosine pentaphosphate {(p)ppGpp} synthetase/hydrolase, in biofilm formation and acid tolerance . Two mutants in which relA was insertionally inactivated or replaced by an antibiotic resistance determinant were constructed . Under normal growth and stress conditions, the mutants grew slower than the wild-type strain, although the final yields were similar . The mutants, which were still able to accumulate (p)ppGpp after the induction of a stringent response, showed significant reductions in biofilm formation on microtiter plates or hydroxylapatite disks . There was no difference in the sensitivities to acid killing of the parent and relA strains grown in planktonic cultures . However, when cells were grown in biofilms, the mutants became more acid resistant and could lower the pH through glycolysis faster and to a greater extent than the wild-type strain . Differences in acid resistance were not correlated with increases in F-ATPase activity, although bacterial sugar:phosphotransferase activity was elevated in the mutants . Expression of the luxS gene was increased as much as fivefold in the relA mutants, suggesting a link between AI-2 quorum sensing and the stringent response. Front Biosci, 2004 May 01, 9, 1267 - 77 Virulence properties of Streptococcus mutans; Banas JA; Streptococcus mutans is considered one of the primary causative agents of dental caries and can also be a source of infective endocarditis . The main virulence factors associated with cariogenicity include adhesion, acidogenicity, and acid tolerance . Each of these properties works coordinately to alter dental plaque ecology . The ecological changes are characterized by increased proportions of S . mutans and other species that are similarly acidogenic and aciduric . The selection for a cariogenic flora increases the magnitude of the drop in pH following the fermentation of available carbohydrate and increases the probability of enamel demineralization . This review focuses on the bacterial components that contribute to each of the major virulence properties . Further understanding of how these components work together in the development of dental caries will be aided by the recent completion of the sequence of the S . mutans genome and experimental designs that model the dental plaque biofilm. Water Res, 2004 Mar, 38(5), 1237 - 47 Quantification of oxygen fluxes in a long gravity sewer; Huisman JL et al.; Quantification of the oxygen fluxes in the sewer system is at present the optimal methodology to obtain information about the influence of sewers on transformations and mass balances in the urban drainage system . However, the relative and absolute values of these fluxes are practically unknown . In this work, the oxygen fluxes were quantified experimentally in a full-scale aerobic main sewer . The sewer biofilm respiration was determined with an in situ flow cell, a method that has not been used before in the sewer . The surface reaeration was determined with a gas tracer method based on the inert, non-radio-active and non-toxic gas tracer sulphur hexafluoride . In addition, the wastewater biomass respiration rate was measured . The validity of the applied methods was verified with redundant oxygen balances over a 2-km-long section . Measurement campaigns under different hydrodynamic conditions showed that the relative contribution of the biofilm, the wastewater, the reaeration and the in- and outflow with the water, all contributed significantly . However, the absolute contributions varied extensively and depended especially on the discharge . The COD conversion in the sewer could be estimated from the aerobic activity . The aerobic total degradation in the study reach was 3% . However, when extrapolated to the entire sewer net of the catchment area with 5000 PE, the COD conversion was estimated as high as 30% of the dissolved COD during the night . This indicates that the wastewater composition at the treatment plant will be strongly affected by the sewer system. Water Res, 2004 Mar, 38(5), 1197 - 206 Investigation of natural biofilms formed during the production of drinking water from surface water embankment filtration; Emtiazi F et al.; Populations of bacteria in biofilms from different sites of a drinking water production system were analysed . Polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) analyses revealed changing DNA band patterns, suggesting a population shift during bank filtration and processing at the waterworks . In addition, common DNA bands that were attributed to ubiquitous bacteria were found . Biofilms even developed directly after UV disinfection (1-2m distance) . Their DNA band patterns only partly agreed with those of the biofilms from the downstream distribution system . Opportunistic pathogenic bacteria in biofilms were analysed using PCR and Southern blot hybridisation (SBH) . Surface water appeared to have a direct influence on the composition of biofilms in the drinking water distribution system . In spite of preceding filtration and UV disinfection, opportunistic pathogens such as atypical mycobacteria and Legionella spp . were found in biofilms of drinking water, and Pseudomonas aeruginosa was detected sporadically . Enterococci were not found in any biofilm . Bacterial cell counts in the biofilms from surface water to drinking water dropped significantly, and esterase and alanine-aminopeptidase activity decreased . beta-glucosidase activity was not found in the biofilms . Contrary to the results for planktonic bacteria, inhibitory effects were not observed in biofilms . This suggested an increased tolerance of biofilm bacteria against toxic compounds. Water Res, 2004 Mar, 38(5), 1189 - 96 Investigation of biocide efficacy by photoacoustic biofilm monitoring; Schmid T et al.; The undesired growth of biofilms on solid surfaces is often termed biofouling . Biofilms consist mainly of water and microbial cells which are embedded in a biopolymer matrix . Biofouling lowers the water quality and increases the frictional resistance in tubes . Further, biofilms increase the pressure differences in membrane processes and can clog filtration membranes, valves, and nozzles . For investigation and improvement of biocide efficacy and anti-fouling strategies, on-line and in situ monitoring of the biofilm is necessary . In this study, photoacoustic spectroscopy (PAS) was employed for biofilm monitoring . PAS allows the depth-resolved investigation of growth and detachment processes of biofilms . Strategies based on the oxidant hydrogen peroxide were compared to popular isothiazolinone biocides . Hydrogen peroxide allowed a very fast and efficient removal of attached biofilms, whereas no effect on the biofilm matrix was observed in most cases when isothiazolinone biocides were used. Recenti Prog Med, 2003 Dec, 94(12), 537 - 9 {Biofilms in infectious diseases}; Rossi G; Microorganisms attack and grow upon living as well inorganic surfaces, forming a "biofilm" . Biofilms are a serious problem of public health, because biofilm-associated microorganisms exhibit increased resistance to antibiotics . The mechanisms of biofilm formation, the mechanisms of resistance and the possibilities of therapy are briefly summarized. J Bacteriol, 2004 Mar, 186(5), 1574 - 8 VpsT is a transcriptional regulator required for expression of vps biosynthesis genes and the development of rugose colonial morphology in Vibrio cholerae O1 El Tor; Casper-Lindley C et al.; Vibrio cholerae switches between smooth and rugose colonial variants . The rugose variant produces more vibrio polysaccharides (VPS(El Tor)) and forms well-developed biofilms . Both phenotypes depend on expression of vps biosynthesis genes . We identified a positive transcriptional regulator of vps gene expression, VpsT, which is homologous to response regulators of two-component regulatory systems . Disruption of vpsT in the rugose variant yields smooth colonies, prevents formation of mature biofilms, and decreases vps gene expression . The interaction between VpsT and VpsR, a previously identified positive regulator of vps genes, was also investigated. J Bacteriol, 2004 Mar, 186(5), 1249 - 57 Capsule shields the function of short bacterial adhesins; Schembri MA et al.; Bacterial surface structures such as capsules and adhesins are generally regarded as important virulence factors . Here we demonstrate that capsules block the function of the self-recognizing protein antigen 43 through physical shielding . The phenomenon is not restricted to Escherichia coli but can occur in other gram-negative bacteria . Likewise, we show that other short adhesins exemplified by the AIDA-I protein are blocked by the presence of a capsule . The results support the notion that capsule polysaccharides sterically prevent receptor-target recognition of short bacterial adhesins . This negative interference has important biological consequences, such as affecting the ability of bacteria to form biofilms. J Colloid Interface Sci, 2004 Mar 15, 271(2), 351 - 8 The measurement temperature: an important factor relating physicochemical and adhesive properties of yeast cells to biomaterials; Gallardo-Moreno AM et al.; Flow chambers applied to the study of the initial adhesion process of Candida parapsilosis are rarely found in the literature . The ability of these microorganisms to proliferate and form biofilms in environments at temperatures around 22 or 37 degrees C is reflected in the contamination of laboratory instruments and material or in human implant infections, respectively . The initial interaction between yeasts and substrata is mediated by physicochemical forces, which in turn originate from the physicochemical surface properties of both interacting phases . In this context, this work aims to relate the initial rates of adhesion rates to glass and silicone of Candida parapsilosis, strains 294 and 289, grown at 22 and 37 degrees C with the theoretical predictions of the adhesion process, expressed by the interaction free energies and calculated through the physicochemical parameters, which are also measured at 22 and 37 degrees C . The results indicate that physicochemical parameters of yeasts are changed not only by the culture temperature but also by the measurement temperature; only when the measurement temperature is equal to the growth temperature a coherent relation between in vitro adhesion data and interaction free energies can be established . In this sense, the adhesion to glass is mediated by long-range forces or, what amounts to the same thing, by Lifshitz-van der Waals interaction free energy . On the other hand, the adhesion to silicone rubber seems to be moderated by acid-base interaction free energy, which involves the presence of short-range forces . Based on these results, it can be assumed that the substratum surface properties are directly related to the kind of force acting on the initial microbial adhesion process, while cell surface properties dictate the changes in the strength of the force between different samples. J Colloid Interface Sci, 2004 Mar 15, 271(2), 342 - 50 Study of bioadhesion on a flat plate with a yeast/glass model system; Mercier-Bonin M et al.; The attachment of microorganisms to a surface is a critical first step of biofilm fouling in membrane processes . The shear-induced detachment of baker's yeast in adhesive contact with a plane glass surface was thus experimentally studied, using a specially designed shear stress flow chamber . The yeast was marketed either as rod-shaped pellets (type I yeast) or as spherical pellets (type II yeast) . A complete series of experiments for measuring the shear stress necessary to detach a given proportion of individual yeast cells of type I or II was performed under different environmental conditions (ionic strength, contact time) . In parallel, the surface physicochemical properties of the cells (surface charge, hydrophobicity, and electron donor and electron acceptor components) were determined . For the first type of yeast cells, which were rather hydrophilic, adhesion to the glass plate was weak . This was due to both electrostatic effects and hydrophilic repulsion . Furthermore, adhesion was not sensitive to any variation of the ionic strength . For yeast of the second type, adhesion was drastically increased . This could be explained by their physicochemical surface properties and especially their hydrophobic and electron acceptor components, which caused strong attractive van der Waals and Lewis acid-base interactions, counterbalancing the electrostatic repulsion . For increasing ionic strengths, adhesion was greater, due to lower electrostatic repulsion . The results were quantified through the definition of a critical wall shear stress ( tau w 50% ) required to detach 50% of the yeast cells initially deposited on the glass surface . The influence of the contact time was also evaluated and it was shown that, whatever the type of yeast, macromolecules such as proteins were released into the extracellular medium due to cell lysis and could contribute to the formation of a conditioning film . As a result, the cells were more strongly stuck to the glass plate. J Environ Sci (China), 2004, 16(1), 79 - 85 Lead adsorption capacities of different components in natural surface coatings; Dong DM et al.; Pb adsorption capacities of Fe oxide, Mn oxide and organic materials in natural surface coatings( biofilms and associated minerals) collected in three lakes, two ponds and a river in Jilin Province, China and Cayuga Lake in US were studied . A novel extraction technique was employed to remove one or more component(s) from the surface coatings . Pb adsorption to surface coatings before and after extraction was performed to determine the adsorptive properties of the extracted component(s) . The statistical analysis of observed Pb adsorption was carried out using nonlinear least squares fitting(NLSF) to estimate the Pb adsorption capacity of each component of surface coatings . For each body of water, the estimated Pb adsorption capacity of Mn oxide(mol Pb/mol Mn) was significantly higher than that of Fe oxide(mol Pb/ mol Fe) . The value of estimated adsorption capacities of organic materials with the unit mol Pb per kg COD was similar to or less than that of Fe oxides with the unit mol Pb per mol Fe . Comparison of components of surface coatings in different waters showed that the estimated Pb adsorption capacities of components in surface coatings developed in different natural waters were different, especially for Mn oxides. Proc Natl Acad Sci U S A, 2004 Mar 9, 101(10), 3587 - 90 Epub 2004 Feb 17. Inactivation of a Pseudomonas aeruginosa quorum-sensing signal by human airway epithelia; Chun CK et al.; Mammalian airways protect themselves from bacterial infection by using multiple defense mechanisms including antimicrobial peptides, mucociliary clearance, and phagocytic cells . We asked whether airways might also target a key bacterial cell-cell communication system, quorum-sensing . The opportunistic pathogen Pseudomonas aeruginosa uses two quorum-sensing molecules, N-(3-oxododecanoyl)-l-homoserine lactone (3OC12-HSL) and N-butanoyl-l-homoserine lactone (C4-HSL), to control production of extracellular virulence factors and biofilm formation . We found that differentiated human airway epithelia inactivated 3OC12-HSL . Inactivation was selective for acyl-HSLs with certain acyl side chains, and C4-HSL was not inactivated . In addition, the capacity for inactivation varied widely in different cell types . 3OC12-HSL was inactivated by a cell-associated activity rather than a secreted factor . These data suggest that the ability of human airway epithelia to inactivate quorum-sensing signal molecules could play a role in the innate defense against bacterial infection. J Med Microbiol, 2004 Mar, 53(Pt 3), 259 - 61 Enterococcus durans endocarditis in a patient with transposition of the great vessels; Stepanovic S et al.; A case of native valve endocarditis caused by Enterococcus durans in a patient with transposition of the great vessels is reported . The patient was treated initially with gentamicin and ceftriaxone; after isolation of enterococci, ceftriaxone was switched to ampicillin . The only virulence factors established in the strain were haemolytic activity and biofilm formation. J Food Prot, 2004 Feb, 67(2), 322 - 7 Behavior of Listeria monocytogenes in a Pseudomonas putida biofilm on a condensate-forming surface; Hassan AN et al.; Listeria monocytogenes has been isolated from condensate-forming surfaces in food processing plants . The objective of this research was to observe the behavior of L . monocytogenes on condensate-covered stainless steel with a Pseudomonas putida biofilm . L . monocytogenes-containing biofilms, either with or without added chicken protein, were incubated in a high humidity chamber at 12 degrees C to allow formation of condensate . Samples were analyzed for attached and unattached L . monocytogenes and total plate count periodically for 35 days . Samples were also taken for microscopic observation of Listeria and bacterial extracellular polymeric substances (EPS) . L . monocytogenes attached in significantly greater numbers (> 3-log difference) to surfaces with preexisting P . putida biofilms than to Pseudomonas-free surfaces . L . monocytogenes survived in the presence or absence of P . putida with no added nutrients for 35 days, with numbers of survivors in the range of 3 to 4 log CFU/cm2 in the presence of P . putida and less than 2.9 log CFU/cm2 in pure culture . Attached and unattached L . monocytogenes were at similar levels throughout the incubation under all conditions studied . The addition of protein to the biofilms allowed growth of L . monocytogenes in pure culture during the first 7 days of incubation . Numbers of L . monocytogenes were not affected by the presence of P . putida when protein was present . Unattached L . monocytogenes were at levels of 3.6 to 6.7 log CFU/cm2 on the protein-containing surfaces . Microscopic observation of the condensate-covered biofilms indicated that L . monocytogenes formed microcolonies embedded within an EPS matrix over a 28-day period . This research demonstrates that L . monocytogenes can survive on condensate-forming stainless steel in low and high nutrient conditions, with or without the presence of Pseudomonas biofilm . The Listeria can detach and, therefore, have the potential to contaminate product. Ultrastruct Pathol, 2004 Jan-Feb, 28(1), 23 - 7 Microbial biofilms in the gut: visualization by electron microscopy and by acridine orange staining; Palestrant D et al.; The expression of colonization factors by gut bacteria, the growth rate of gut bacteria, and the rate of plasmid exchange by gut bacteria indicate that biofilms are a normal component of bacterial growth in the large bowel . Further, in vitro experiments demonstrate that growth of normal enteric bacteria in biofilms can be facilitated by secretory IgA (SIgA) and by mucins, 2 major components of the gut milieu . However, biofilms have not been previously observed in the normal gut . In this study, bacterial colonies characteristic of biofilms were observed by electron microscopy in normal rat, baboon, and human gut by electron microscopy . Confirming these results, acridine orange staining of flash-frozen tissues revealed biofilms in the mucus lining along normal gut epithelium . Immunofluorescenct microscopy supported this finding and demonstrated an association between IgA and the biofilms . These findings provide direct evidence that biofilms are present and may play an important role in the commensal relationship between enteric bacteria and their hosts . Hematoxylin and eosin staining of formalin-fixed tissues resulted in dissociation of the luminal contents from the epithelium, suggesting that the association between biofilms and the gut epithelium is sensitive to some conditions used to preserve tissue for histologic evaluation. J Appl Microbiol, 2004, 96(3), 455 - 63 Immigration and emigration of Burkholderia cepacia and Pseudomonas aeruginosa between and within mixed biofilm communities; Al-Bakri AG et al.; AIMS: To investigate the dynamics of binary culture biofilm formation through use of both the Sorbarod model of biofilm growth and the constant depth film fermenter (CDFF) . METHODS AND RESULTS: Pseudo steady-state biofilm cultures of laboratory and clinical strains of Pseudomonas aeruginosa, selected on the basis of their ability to produce a Burkholderia cepacia growth-inhibitory substance, were established on Sorbarod filters and challenged with corresponding planktonic grown cultures of B . cepacia . Reverse challenges were also conducted . Both B . cepacia and P . aeruginosa were able to form steady-state monoculture biofilms after 48 h growth . When steady-state biofilms of B . cepacia NTCT 10661 were challenged with planktonically grown P . aeruginosa PAO1 known to produce a B . cepacia growth-inhibitory substance, the immigrant population was rapidly and almost completely bound to the biofilm, displacing B . cepacia . By contrast, established biofilms of P . aeruginosa PAO1 resisted immigration of B . cepacia 10661 . Similar experiments conducted with a nongrowth inhibitory substance producing clinical pairing of P . aeruginosa 313113 and B . cepacia 313113 led to the formation of stable, mixed biofilm populations in both instances . Moreover, co-inoculation with these clinical isolates resulted in a stable, mixed steady-state biofilm . Similar observations were made for biofilms generated in CDFFs . In such instances following pan-swapping between two monoculture CDFFs, B . cepacia 313113 was able to integrate into an established P . aeruginosa 313113 biofilm to form a stable binary biofilm . CONCLUSIONS: Establishment of a mixed species community follows a specific sequence of inoculation that may either be due to some degree of match between co-colonizers or that P . aeruginosa predisposes uncolonized sections of the surface to permit B . cepacia colonization . SIGNIFICANCE AND IMPACT OF THE STUDY: Colonization of a surface with one bacterial species confers colonization resistance towards other species . Disinfection of a surface might well increase the probability of pathogen harbourage. Lett Appl Microbiol, 2004, 38(3), 211 - 6 Minimizing prion risk without compromising the microbial composition of biofilms grown in vivo in a human plaque model; Watson PS et al.; AIMS: To determine whether the stringency of sterilization procedures for biological components of in vivo dental plaque-generating devices based on enamel can be increased to minimize prion risk without compromising natural biofilm composition . METHODS AND RESULTS: The composition of in vitro biofilms, grown on hypochlorite-treated and untreated autoclaved enamel surfaces, was determined using culture-based methods and checkerboard DNA: DNA hybridization analysis . No differences were found between biofilms recovered from either substrate . SIGNIFICANCE: Several in situ models allow generation of plaque in the oral cavity, followed by recovery of intact biofilms for experimentation . Approaches allowing plaque formation on natural tooth surfaces are most valuable, but present a possible infection risk to volunteers wearing plaque-collecting devices, particularly with respect to prions . Hypochlorite treatment of biological material, as an adjunct to autoclaving, reduces infection risk without compromising biofilm composition and should be adopted in all future studies using plaque-generating devices incorporating enamel, where there is a potential prion threat, and further investigated in other biological hard tissues. Clin Otolaryngol, 2004 Feb, 29(1), 38 - 46 Is otitis media with effusion a biofilm infection? Fergie N, Bayston R, Pearson JP, Birchall JP. Recent attention has focused on the possibility that otitis media with effusion (OME) may represent a chronic infective state such as those evidenced in conditions secondary to biofilms or small colony variants . This review discusses the evidence suggesting that this may indeed be the case and explains why this may prove to be important in the future management of this condition by discussing recent advances in understanding these bacterial phenotypic variants. Mar Biotechnol (NY), 2002 Sep, 4(4), 356 - 66 Surface attachment induced production of antimicrobial compounds by marine epiphytic bacteria using modified roller bottle cultivation; Yan L et al.; A modified roller bottle culture method elicited the production of antimicrobial compounds from 2 epibiotic marine bacterial strains, EI-34-6 and II-111-5, isolated from the surface of the marine alga Palmaria palmata . These isolates, tentatively identified as Bacillus species, were grown as a biofilm on the surface of nutrient glycerol ferric agar (NGFA) and marine Columbia glycerol agar (MCGA) on the inside of a rolling bottle . The biofilm was shown to be stable, and the cells were difficult to remove from the agar surface . The culture supernatant exhibited a different antibiotic spectrum when the strains were grown using the agar roller bottle method compared with shake flask cultures or nonagar roller bottle cultures . These results suggest that biofilm formation is an important factor in the production of antimicrobial compounds by these 2 strains, and roller bottle cultivation also allowed production of these compounds to be increased . The methodology used here has the potential to allow increased production of useful secondary metabolites such as antibiotics from marine epibiotic bacteria. Nature, 2004 Mar 4, 428(6978), 37 - 43 Epub 2004 Feb 01. Community structure and metabolism through reconstruction of microbial genomes from the environment; Tyson GW et al.; Microbial communities are vital in the functioning of all ecosystems; however, most microorganisms are uncultivated, and their roles in natural systems are unclear . Here, using random shotgun sequencing of DNA from a natural acidophilic biofilm, we report reconstruction of near-complete genomes of Leptospirillum group II and Ferroplasma type II, and partial recovery of three other genomes . This was possible because the biofilm was dominated by a small number of species populations and the frequency of genomic rearrangements and gene insertions or deletions was relatively low . Because each sequence read came from a different individual, we could determine that single-nucleotide polymorphisms are the predominant form of heterogeneity at the strain level . The Leptospirillum group II genome had remarkably few nucleotide polymorphisms, despite the existence of low-abundance variants . The Ferroplasma type II genome seems to be a composite from three ancestral strains that have undergone homologous recombination to form a large population of mosaic genomes . Analysis of the gene complement for each organism revealed the pathways for carbon and nitrogen fixation and energy generation, and provided insights into survival strategies in an extreme environment. Chest, 2004 Feb, 125(2 Suppl), 62S - 69S; quiz 69S Effects of subinhibitory concentrations of macrolide antibiotics on Pseudomonas aeruginosa; Wozniak DJ et al.; Biofilm-forming bacteria such as Staphylococcus, Haemophilus, and Pseudomonas species resist phagocytosis by host immune cells and the actions of antimicrobial agents . In susceptible individuals, such as patients with cystic fibrosis (CF) or diffuse panbronchiolitis (DPB), strains of Pseudomonas aeruginosa produce a number of virulence determinants that permit colonization and infection of the respiratory tract . P aeruginosa strains isolated from CF and DPB patients typically have a mucoid colony morphology . This is due to the overproduction of alginate, an exopolysaccharide capsule that is composed of D-mannuronic and L-guluronic acids . In addition, the P aeruginosa type IV pilus mediates cell surface translocation by a process known as twitching motility . Both alginate production and twitching motility contribute to the virulence of P aeruginosa, as does the formation of biofilms . Biofilms bind cells and organic and inorganic materials to each other, and to a variety of substrata . Their tightly formed structure reduces antimicrobial activity, promotes bacterial adhesion to lung epithelia, and prevents bacterial dehydration . Prior work has suggested that macrolides have therapeutic value in patients with DPB and CF . We hypothesized that the improved clinical status of these patients was due, in part, to macrolides inhibiting the production of P aeruginosa virulence determinants . Traditionally, macrolides have not been considered to exhibit antipseudomonal activity, as their mean inhibitory concentration (MIC) values for clinical and environmental strains of the microbe range from 50 to 550 microg/mL . In this study, we found that sub-MIC levels of clarithromycin substantially inhibited twitching motility . In addition, the incubation of biofilm-grown P aeruginosa with clarithromycin altered the structure and architecture of the biofilm . Investigating the potential nonribosomal effects of macrolides on opportunistic pathogens such as P aeruginosa and elucidating the molecular mechanisms that underlie the inhibition of twitching motility may lead to more effective treatments of pulmonary infections in patients with CF and DPB. Environ Microbiol, 2004 Mar, 6(3), 218 - 26 Microcolonies, quorum sensing and cytotoxicity determine the survival of Pseudomonas aeruginosa biofilms exposed to protozoan grazing; Matz C et al.; This study was based on the hypothesis that biofilms of the opportunistic pathogen Pseudomonas aeruginosa are successfully adapted to situations of protozoan grazing . We tested P . aeruginosa wild type and strains that were genetically altered, in structural and regulatory features of biofilm development, in response to the common surface-feeding flagellate Rhynchomonas nasuta . Early biofilms of the wild type showed the formation of grazing resistant microc