J Microbiol, 2004 Mar, 42(1), 64 - 7 Formation and dispersion of mycelial pellets of Streptomyces coelicolor A3(2); Kim YM et al.; The pellets from a culture of Streptomyces coelicolor A3(2) that were submerged shaken were disintegrated into numerous hyphal fragments by DNase treatment . The pellets were increasingly dispersed by hyaluronidase treatment, and mycelial fragments were easily detached from the pellets . The submerged mycelium grew by forming complexes with calcium phosphate precipitates or kaolin, a soil particle . Therefore, the pellet formation of Streptomyces coelicolor A3(2) can be considered a biofilm formation, including the participation of adhesive extracellular polymers and the insoluble substrates. Lett Appl Microbiol, 2004, 39(4), 359 - 62 Attachment and biofilm formation on stainless steel by Escherichia coli O157:H7 as affected by curli production; Ryu JH et al.; AIMS: The aim of this study was to determine the role of curli in attachment and biofilm formation by Escherichia coli O157:H7 on stainless steel . METHODS AND RESULTS: Three curli-deficient strains (43895-, 43894- and E0018-) and three curli over-producing strains (43895+, 43894+ and E0018+) of E . coli O157:H7 were studied . Stainless steel coupons (SSC) were immersed in cell suspensions of each strain for 24 h at 4 degrees C . The number of cells attached to SSC was determined . To determine the ability of attached cells to form biofilm, SSC were immersed in 10% of tryptic soya broth up to 6 days at 22 degrees C . Curli-deficient and curli-producing strains did not differ in their ability to attach to SSC, but only curli-producing strains formed biofilms . CONCLUSIONS: Curli production by E . coli O157:H7 does not affect attachment of cells on stainless steel but curli-producing strains are better able to form biofilms . SIGNIFICANCE AND IMPACT OF THE STUDY: Curli production by E . coli O157:H7 enhances its ability to form biofilm on stainless steel, thereby potentially resulting in increased difficulty in removing or killing cells by routine cleaning and sanitizing procedures used in food-processing plants. Water Res, 2004 Oct, 38(17), 3769 - 79 Microbiology, chemistry and biofilm development in a pilot drinking water distribution system with copper and plastic pipes; Lehtola MJ et al.; We studied the changes in water quality and formation of biofilms occurring in a pilot-scale water distribution system with two generally used pipe materials: copper and plastic (polyethylene, PE) . The formation of biofilms with time was analysed as the number of total bacteria, heterotrophic plate counts and the concentration of ATP in biofilms . At the end of the experiment (after 308 days), microbial community structure, viable biomass and gram-negative bacterial biomass were analysed via lipid biomarkers (phospholipid fatty acids and lipopolysaccharide 3-hydroxy fatty acids), and the numbers of virus-like particles and total bacteria were enumerated by SYBR Green I staining . The formation of biofilm was slower in copper pipes than in the PE pipes, but after 200 days there was no difference in microbial numbers between the pipe materials . Copper ion led to lower microbial numbers in water during the first 200 days, but thereafter there were no differences between the two pipe materials . The number of virus-like particles was lower in biofilms and in outlet water from the copper pipes than PE pipes . Pipe material influenced also the microbial and gram-negative bacterial community structure in biofilms and water. Water Res, 2004 Oct, 38(17), 3671 - 84 Influence of growth history on sloughing and erosion from biofilms; Telgmann U et al.; The development of biofilms is determined by the balance of growth and detachment . But while the growth of biofilms is well studied, the influence of growth history and detachment on biofilm development is not . Here we report on laboratory scale experiments where heterotrophic biofilms were grown in a tubular reactor . Biofilm detachment was categorized based on particle size as erosion or sloughing . Erosion results in small particles and was approximated by the effluent suspended solids while sloughing was determined from the larger pieces of biomass that settled in a mixing tank . It was found that for all experiments, overall detachment was a combination of erosion and sloughing where erosion had a slightly larger contribution to the overall solids removal . However, sloughing had a significant influence on the biofilm morphology . Once the smooth biofilm surface was disturbed by a sloughing event (e.g., initiated through increasing liquid shear in the reactor), the biofilm became unstable resulting in spontaneous sloughing during subsequent operation . We propose that experimental investigations should consider sloughing events as an integral part of biofilm development rather than a disturbance. Mol Cell, 2004 Sep 10, 15(5), 677 - 87 Salmonella typhimurium recognizes a chemically distinct form of the bacterial quorum-sensing signal AI-2; Miller ST et al.; Bacterial populations use cell-cell communication to coordinate community-wide regulation of processes such as biofilm formation, virulence, and bioluminescence . This phenomenon, termed quorum sensing, is mediated by small molecule signals known as autoinducers . While most autoinducers are species specific, autoinducer-2 (AI-2), first identified in the marine bacterium Vibrio harveyi, is produced and detected by many Gram-negative and Gram-positive bacteria . The crystal structure of the V . harveyi AI-2 signaling molecule bound to its receptor protein revealed an unusual furanosyl borate diester . Here, we present the crystal structure of a second AI-2 signal binding protein, LsrB from Salmonella typhimurium . We find that LsrB binds a chemically distinct form of the AI-2 signal, (2R,4S)-2-methyl-2,3,3,4-tetrahydroxytetrahydrofuran (R-THMF), that lacks boron . Our results demonstrate that two different species of bacteria recognize two different forms of the autoinducer signal, both derived from 4,5-dihydroxy-2,3-pentanedione (DPD), and reveal new sophistication in the chemical lexicon used by bacteria in interspecies signaling . J Mater Sci Mater Med, 1998 Mar 1, 9(3), 147 - 57 In vitro and in vivo microbial adhesion and growth on argon plasma-treated silicone rubber voice prostheses; Everaert EP et al.; Patients who undergo a total laryngectomy usually receive a silicone rubber voice prosthesis for voice rehabilitation . Unfortunately, biofilm formation on the esophageal side of voice prostheses limits their lifetime to 3-4 mon on average . The effects of repeated argon plasma treatment of medical grade, hydrophobic silicone rubber on in vitro adhesion and growth of bacteria and yeasts isolated from voice prostheses, as well as in vivo biofilm formation are presented here . In vitro experiments demonstrated that initial microbial adhesion over a 4 h time span to plasma-treated, hydrophilized, silicone rubber was generally less than on original, hydrophobic silicone rubber, both in the absence and presence of a salivary conditioning film on the biomaterial . Growth studies over a time period of 14 d at 37 degrees C in a modified Robbins device, showed that fewer Candida cells adhered on plasma-treated, hydrophilized silicone rubber as compared to on original, hydrophobic silicone rubber . For the in vivo evaluation of biofilm formation on plasma-treated silicone rubber voice prostheses, seven laryngectomized patients received a partly hydrophilized "Groningen Button" voice prosthesis for a planned evaluation period of 4 wk . After removal of the voice prostheses, the border between the hydrophilized and the original, hydrophobic side of the prostheses was clearly visible . However, biofilm formation was, unexpectedly, less on the original, hydrophobic sides, although the microbial compositions of the biofilms on both sides were not significantly different . Summarizing, this study demonstrates that in vitro microbial adhesion and growth on silicone rubber can be reduced by plasma treatment, but in vivo biofilm formation on silicone rubber voice prostheses is oppositely enhanced by hydrophilizing the silicone rubber surface . Nevertheless, from the results of this study the important conclusion can be drawn that in vivo biofilm formation on voice prostheses is controlled by the hydrophobicity of the biomaterials surface used . J Mater Sci Mater Med, 2002 Aug, 13(8), 717 - 22 Pathogenesis and prevention of biomaterial centered infections; Gottenbos B et al.; One of the major drawbacks in the use of biomedical materials is the occurrence of biomaterials centered infections . After implantation, the host interacts with a biomaterial by forming a conditioning film on its surface and an immune reaction towards the foreign material . When microorganisms can reach the biomaterials surface they can adhere to it . Adhesion of microorganisms to an implant is mediated by their physico-chemical surface properties and the properties of the biomaterials surface itself . Subsequent surface growth of the microorganisms will lead to a mature biofilm and infection, which is difficult to eradicate by antibiotics . The purpose of this review is to give an overview of the mechanisms involved in biomaterials centered infection and the possible methods to prevent these infections. J Mater Sci Mater Med, 2003 Nov, 14(11), 967 - 72 Multi-technique characterization of retrieved bone cement from revised total hip arthroplasties; Eliades T et al.; The purpose of this study was to assess the chemical composition, structure and degree of double bond conversion of retrieved bone cement from 29 total hip replacement revision arthroplasties, employing a multi-technique approach . Scanning electron microscopy revealed a porous cement surface, which replicated the characteristics of bone or femoral stem surface irregularities . Fourier transform infrared spectroscopy indicated that the retrieved bone cement samples were covered by a well-organized proteinaceous film rich in amides and alcohols, probably because of the adsorption of species from body tissues and fluids . X-ray fluorescence spectrometry showed the presence of potassium, sodium, calcium and phosphorus, implying the development of a mineralization process of the adsorbed biofilm . X-ray microtomography demonstrated a dense porous network in the bulk material comprised of macropores with a mean diameter >1 mm . FTIR analysis of the degree of double bond conversion of retrieved samples was in the order of 70%, similar to that of samples prepared in vitro in air, but 30% lower relative to their counterparts mixed in vitro and set in water . The effect of the adsorption of species onto bone cement surface on the reactivity of the material with the surrounding tissues and materials, is currently unknown . The results of this investigation reveal that the in vivo aging pattern of bone cements may involve alterations, which cannot be simulated under current in vitro protocols, emphasizing the necessity for adopting in vivo approaches including retrieval studies in assessing bone cement properties . Environ Technol, 2004 Jul, 25(7), 809 - 17 Development and analysis of anaerobic biofilms onto hydrophobic and hydrophilic surfaces; Araujo JC et al.; Fluorescent in situ hybridization (FISH) with domain and group specific probes that target intracellular 16S rRNA were used to investigate microbial composition of anaerobic biofilms developed on polypropylene (hydrophobic) and glass (hydrophilic) surfaces fitted inside a Modified Robbins Device (MRD) . Crushed anaerobic granular sludge was used as inoculum for biofilm development in the MRD . The inoculum and biofilms formed showed nearly the same microbial composition, both were dominated by hydrogenotrophic methanogenic Archaea related to the Methanobacteriaceae as detected by the specific probe (MB1174) . This group accounted for 44 to 90% of the DAPI-stained cells . Cells which hybridized to the Bacteria specific probe (EUB338) accounted for 3-18% of the DAPI-stained cells . After the first day of the biofilm formation experiment, a larger number of cells, 4.6 x 10(4) cells mm-2, could be seen colonizing the polypropylene coupon compared to the glass, 8.2 x 10(3) cells mm-2 . However, after 9 days these numbers were very similar, i.e . 6.3 x 10(5) cells mm-2 and 7.2 x 10(5) cells mm-2, for the glass and polypropylene coupons, respectively . Our data suggest that the hydrophobicity of the support material did not influence the initial development and the microbial composition of anaerobic biofilms developed in the MRD. J Infect Dis, 2004 Oct 1, 190(7), 1245 - 53 Epub 2004 Aug 26. Loss of microbicidal activity and increased formation of biofilm due to decreased lactoferrin activity in patients with cystic fibrosis; Rogan MP et al.; Intractable formation of biofilm by and infection with the opportunistic pathogen Pseudomonas aeruginosa are hallmarks of cystic fibrosis (CF) . Lactoferrin, an innate immunity protein, has recently been shown to inhibit the formation of P . aeruginosa biofilm . Partial cleavage of lactoferrin by the proteases neutrophil elastase and Pseudomonas elastase has previously been described in CF . Here, we show that cathepsins in CF secretions are responsible for complete and rapid cleavage of lactoferrin . We demonstrate that levels of lactoferrin in P . aeruginosa-positive sputum samples are decreased when corrected for inflammatory burden and that P . aeruginosa-positive sputum samples have significantly higher cathepsin activity and significantly reduced ability to inhibit formation of biofilm, compared with P . aeruginosa-negative sputum samples . We also show that cleavage of lactoferrin by cathepsin results in loss of both its microbicidal and antibiofilm activity . Loss of such a vital innate immunity protein clearly has important implications for the pathogenesis of chronic P . aeruginosa lung infection in patients with CF. Appl Environ Microbiol, 2004 Sep, 70(9), 5682 - 4 Effect of Escherichia coli morphogene bolA on biofilms; Vieira HL et al.; Biofilm physiology is established under a low growth rate . The morphogene bolA is mostly expressed under stress conditions or in stationary phase, suggesting that bolA could be implicated in biofilm development . In order to verify this hypothesis, we tested the effect of bolA on biofilm formation . Overexpression of bolA induces biofilm development, while bolA deletion decreases biofilms. Appl Environ Microbiol, 2004 Sep, 70(9), 5094 - 101 Diversity and seasonal changes of uncultured Planctomycetales in river biofilms; Brummer IH et al.; Cell counts of planctomycetes showed that there were high levels of these organisms in the summer and low levels in the winter in biofilms grown in situ in two polluted rivers, the Elbe River and the Spittelwasser River . In this study 16S rRNA-based methods were used to investigate if these changes were correlated with changes in the species composition . Planctomycete-specific clone libraries of the 16S rRNA genes found in both rivers showed that there were seven clusters, which were distantly related to the genera Pirellula, Planctomyces, and Gemmata . The majority of the sequences from the Spittelwasser River were affiliated with a cluster related to Pirellula, while the majority of the clones from the Elbe River fell into three clusters related to Planctomyces and one deeply branching cluster related to Pirellula . Some clusters also contained sequences derived from freshwater environments worldwide, and the similarities to our biofilm clones were as high as 99.8%, indicating the presence of globally distributed freshwater clusters of planctomycetes that have not been cultivated yet . Community fingerprints of planctomycete 16S rRNA genes were generated by temperature gradient gel electrophoresis from Elbe River biofilm samples collected monthly for 1 year . Sixteen bands were identified, and for the most part these bands represented organisms related to the genus Planctomyces . The fingerprints showed that there was strong seasonality of most bands and that there were clear differences in the summer and the winter . Thus, seasonal changes in the abundance of Planctomycetales in river biofilms were coupled to shifts in the community composition. Microbes Infect, 2004 Sep, 6(11), 965 - 71 Involvement of Mycobacterium smegmatis undecaprenyl phosphokinase in biofilm and smegma formation; Rose L et al.; We describe a Mycobacterium smegmatis mutant with impaired biofilm and smegma formation . A gene homologous to Escherichia coli bacA, which has been proposed to play a role as undecaprenyl phosphokinase (Upk) was unmarked in-frame deleted from M . smegmatis . Though Upk is involved in cell wall synthesis, the surface of the mutant strain appeared virtually comparable to that of the wild type by electron microscopy . The absence of Upk influenced colony morphology and bacitracin resistance . The M . smegmatis Deltaupk mutant developed a biofilm characterized by scattered islands of bacteria distinct from the completely covered biofilm surface observed for wild-type bacteria . We further demonstrate biological consequences of upk deletion for smegma development in an in vivo model . These results suggest the upk gene to be essential in biofilm and smegma development. Environ Microbiol, 2004 Oct, 6(10), 1086 - 95 Low archaeal diversity linked to subseafloor geochemical processes at the Lost City Hydrothermal Field, Mid-Atlantic Ridge; Schrenk MO et al.; The recently discovered Lost City Hydrothermal Field (LCHF) represents a new type of submarine hydrothermal system driven primarily by exothermic serpentinization reactions in ultramafic oceanic crust . Highly reducing, alkaline hydrothermal environments at the LCHF produce considerable quantities of hydrogen, methane and organic molecules through chemo- and biosynthetic reactions . Here, we report the first analyses of microbial communities inhabiting carbonate chimneys awash in warm, high pH fluids at the LCHF and the predominance of a single group of methane-metabolizing Archaea . The predominant phylotype, related to the Methanosarcinales, formed tens of micrometre-thick biofilms in regions adjacent to hydrothermal flow . Exterior portions of active structures harboured a diverse microbial community composed primarily of filamentous Eubacteria that resembled sulphide-oxidizing species . Inactive samples, away from regions of hydrothermal flow, contained phylotypes related to pelagic microorganisms . The abundance of organisms linked to the volatile chemistry at the LCHF hints that similar metabolic processes may operate in the subseafloor . These results expand the range of known geological settings that support biological activity to include submarine hydrothermal systems that are not dependent upon magmatic heat sources. J Bacteriol, 2004 Sep, 186(18), 6327 - 31 Biofilm mode of growth of Streptococcus intermedius favored by a competence-stimulating signaling peptide; Petersen FC et al.; Gram-positive and gram-negative bacteria use quorum sensing to coordinate population behavior . In several streptococci, quorum sensing mediated by competence-stimulating peptides (CSP) is associated with development of competence for transformation . We show here that a synthetic CSP favored the biofilm mode of growth of Streptococcus intermedius without affecting the rate of culture growth. J Bacteriol, 2004 Sep, 186(18), 6208 - 19 Inactivations of rsbU and sarA by IS256 represent novel mechanisms of biofilm phenotypic variation in Staphylococcus epidermidis; Conlon KM et al.; Expression of ica operon-mediated biofilm formation in Staphylococcus epidermidis RP62A is subject to phase variable regulation . Reversible transposition of IS256 into icaADBC or downregulation of icaADBC expression are two important mechanisms of biofilm phenotypic variation . Interestingly, the presence of IS256 was generally associated with a more rapid rate of phenotypic variation, suggesting that IS256 insertions outside the ica locus may affect ica transcription . Consistent with this, we identified variants with diminished ica expression, which were associated with IS256 insertions in the sigmaB activator rsbU or sarA . Biofilm development and ica expression were activated only by ethanol and not NaCl in rsbU::IS256 insertion variants, which were present in approximately 11% of all variants . sigmaB activity was impaired in rsbU::IS256 variants, as evidenced by reduced expression of the sigmaB-regulated genes asp23, csb9, and rsbV . Moreover, expression of sarA, which is sigmaB regulated, and SarA-regulated RNAIII were also suppressed . A biofilm-forming phenotype was restored to rsbU::IS256 variants only after repeated passage and was not associated with IS256 excision from rsbU . Only one sarA::IS256 insertion mutant was identified among 43 biofilm-negative variants . Both NaCl and ethanol-activated ica expression in this sarA::IS256 variant, but only ethanol increased biofilm development . Unlike rsbU::IS256 variants, reversion of the sarA::IS256 variant to a biofilm-positive phenotype was accompanied by precise excision of IS256 from sarA and restoration of normal ica expression . These data identify new roles for IS256 in ica and biofilm phenotypic variation and demonstrate the capacity of this element to influence the global regulation of transcription in S . epidermidis. J Cataract Refract Surg, 2004 Sep, 30(9), 1972 - 6 Evaluation of biofilm formation on nylon sutures removed from clinically noninfected eyes after cataract surgery; Pan JC et al.; PURPOSE: To determine the presence of bacterial biofilm on nylon sutures removed from clinically noninfected eyes after cataract surgery . SETTING: The Eye Institute, Tan Tock Seng Hospital, Singapore, Singapore . METHODS: Sutures were removed from 10 eyes after cataract surgery at different time periods . Immediately after removal, the sutures were fixed and dehydrated . All sutures were viewed by scanning electron microscopy, and 6 were also viewed by transmission electron microscopy (TEM) . RESULTS: There was no evidence of bacterial biofilm formation on the nylon sutures . Significant cellular debris was seen, mainly at the knots . Clusters of coccoid-shaped structures were visible; however, examination by TEM showed they were not bacteria . CONCLUSION: There was no evidence of biofilm formation on sutures removed after cataract surgery from clinically noninfected eyes. Mol Microbiol, 2004 Sep, 53(6), 1563 - 71 Quorum sensing and signal interference: diverse implications; Zhang LH et al.; Quorum sensing (QS) is a community genetic regulation mechanism that controls microbiological functions of medical, agricultural and industrial importance . Discovery of microbial QS signals and the signalling mechanisms led to identification of numerous enzymatic and non-enzymatic signal interference mechanisms that quench microbial QS signalling . Evidence is accumulating that such signal interference mechanisms can be developed as promising approaches to control microbial infection and biofilm formation . In addition, these mechanisms exist not only in microorganisms but also in the host organisms of bacterial pathogens, highlighting their potential implications in microbial ecology and in host-pathogen interactions . Investigation of QS and signal interference mechanisms might significantly broaden the scope of research in microbiology. Sci Total Environ, 2004 Oct 1, 332(1-3), 253 - 60 Determination of biodegradable dissolved organic carbon in waters: comparison of batch methods; Trulleyova S et al.; An effect of different types of bacterial inocula upon the final biodegradable dissolved organic carbon (BDOC) result was investigated in samples of both low and high BDOC concentrations . Stream water and leaf leachate samples were incubated either with free, suspended bacteria or with bacteria attached to the stream sediment particles or attached to artificial substrata . The time course of dissolved organic carbon (DOC) decomposition was observed using absorbance analysis of DOC . BDOC determination by means of commonly used suspended bacteria as the inoculum made for an underestimation of BDOC between 5% and 25%, compared with attached bacterial community (biofilm) . The reason for these findings could be the higher microbial diversity, higher metabolic activity of attached bacteria and abiotic adsorption of organic molecules to inorganic support and biofilm matrix surfaces . Adsorbed DOC is easily hydrolyzed and utilized by biofilm bacteria. FEMS Microbiol Lett, 2004 Sep 1, 238(1), 167 - 74 ComX activity of Streptococcus mutans growing in biofilms; Aspiras MB et al.; In many streptococci, including Streptococcus mutans, genetic competence is regulated by a quorum sensing system mediated by a competence stimulating peptide (CSP) pheromone, encoded by the comC gene . In Streptococcus pneumoniae, a central component of this system is ComX, which acts as an alternative sigma factor to activate competence genes involved in DNA uptake and processing . The quorum sensing system responsible for genetic competence induction in S . mutans has been linked to biofilm formation and the acid tolerance response . To examine the response of comX to CSP in S . mutans, a transcriptional fusion of the comX promoter (pcomX) with lacZ was constructed to generate reporter vector pcomx::pALH122 (replicative vector) and transformed into S . mutans UA159 comC-, which is unable to produce endogenous CSP . CSP was added and pcomX::lacZ relative expression index (REI) examined, revealing a 2-fold increase in maximal beta-gal activity 5 and 10 min after CSP addition . The effect of endogenous CSP on pcomX::lacZ expression was also examined by measuring REI in cells grown as a biofilm; peak pcomX activity was observed at 3 h . To determine the temporal pattern of transformation frequency, pMA2, a Spr shuttle vector, was transformed into biofilm-grown cells, with maximal transformation frequency observed at 3 h . Confocal microscopy was performed to examine pcomX activity using a similarly constructed green fluorescent protein reporter vector, pcomX::gfp, in a 4-h biofilm, revealing active pcomX activity in high cell density areas within the biofilm population . These results demonstrated a positive correlation between pcomX activity, natural transformation and competence development in biofilms. Expert Opin Biol Ther, 2004 Sep, 4(9), 1519 - 31 Treatment and prevention of enterococcal infections--alternative and experimental approaches; Koch S et al.; Enterococci are one of the leading types of organisms isolated from infections of hospitalised patients and the third most common cause of nosocomial bloodstream infections . They contribute significantly to patient mortality and morbidity, as well as healthcare costs . The emergence of resistance against virtually all clinically available antibiotics and the ability to transfer these resistance determinants to other pathogens demonstrates the urgency for an improved understanding of enterococcal virulence mechanisms, and the development of alternative treatment and prevention options . This article reviews new antimicrobials, vaccine targets, bacteriophage therapy, as well as treatments targeting virulence factors and biofilm, for their potential to treat and/or prevent enterococcal infections . Although clinical isolates often cause serious infections, so-called 'non-pathogenic' strains are used as therapeutics in the form of probiotics . Understanding the differences between true pathogens and beneficial commensals may help to evaluate future treatment and prophylactic options. Biotechnol Bioeng, 2004 Sep 30, 87(7), 874 - 83 Modeling hexavalent chromium removal in a Bacillus sp . fixed-film bioreactor; Nkhalambayausi-Chirwa EM et al.; A one-dimensional diffusion-reaction model was developed to simulate Cr(VI) reduction in a Bacillus sp . pure culture biofilm reactor with glucose as a sole supplied carbon and energy source . Substrate utilization and Cr(VI) reduction in the biofilm was best represented by a system of (second-order) partial differential equations (PDEs) . The PDE system was solved by the (fourth-order) Runge-Kutta method adjusted for mass transport resistance using the (second-order) Crank-Nicholson and Backward Euler finite difference methods . A heuristic procedure (genetic search algorithm) was used to find global optimum values of Cr(VI) reduction and substrate utilization rate kinetic parameters . The fixed-film bioreactor system yielded higher values of the maximum specific Cr(VI) reduction rate coefficient and Cr(VI) reduction capacity (kmc = 0.062 1/h, and Rc = 0.13 mg/mg, respectively) than previously determined in batch reactors (kmc = 0.022 1/h and Rc = 0.012 mg/mg) . The model predicted effluent Cr(VI) concentration well with 98.9% confidence (sigmay2 = 2.37 mg2/L2, N = 119) and effluent glucose with 96.4 % confidence (sigmay(w)2 = 5402 mg2/L2, N = 121, w = 100) over a wide range of Cr(VI) loadings (10-498 mg Cr(VI)/L/d) . Biotechnol Bioeng, 2004 Sep 30, 87(7), 855 - 62 An impedance study on admiralty brass dezincification originated by microbiologically influenced corrosion; Ibars JR et al.; In this article we describe a field study of biofouling and microbiologically influenced corrosion (MIC) of admiralty brass heat exchanger tubes in contact with running fresh water on the river Tagus close to Almaraz nuclear power plant in Spain . Dezincification originated by biofouling and MIC was studied using impedance, polarization resistance, gravimetric, scanning electron microscopy (SEM), and X-ray diffraction (XRD) measurements . Close correlation was observed between the biofilms formed and the corrosion process (dezincification) using the different experimental techniques . Impedance data showed a capacitive behavior including two time constants . Kramers-Kronig (KK) transforms were used to validate impedance data . The admiralty tubes' impedance data satisfied the KK relations . J Environ Sci Health A Tox Hazard Subst Environ Eng, 2004, 39(8), 2183 - 93 Mixing characteristics and whey wastewater treatment of a novel moving anaerobic biofilm reactor; Rodgers M et al.; A novel moving anaerobic biofilm reactor was used to treat whey wastewater . In this process, biofilm was grown on a plastic biofilm media module, which was vertically moved up and down in the bulk fluid . The objectives of the study were to investigate the mixing and performance characteristics of the new process in treating whey wastewater . The mixing efficiency was indicated by a dispersion number, D(L)/uL . D(L)/uL was up to 1.34, showing that the anaerobic reactor can be taken as a completely mixed reactor . At mesophilic conditions (35+/-2 degrees C), the admissible volumetric COD loading rate up to 11.6kg COD m(-3) day(-1) was achieved with the COD removal efficiency of 89% and the hydraulic retention time (HRT) of 1 day . When the HRT was 0.6 days, the volumetric COD loading rate was 15.2 kg COD m(-3) day(-1), but COD removal efficiency decreased to 81% . The percentage of methane (CH4) in the biogas was 63% on average and the yield of methane was 333.4 L CH4 kg(-1) COD removal at ambient conditions. J Mater Sci Mater Med, 2004 Apr, 15(4), 403 - 6 Bacterial biosynthesis of a calcium phosphate bone-substitute material; Thackray AC et al.; A species of Serratia bacteria produces nano-crystalline hydroxyapatite (HA) crystals by use of a cell-bound phosphatase enzyme, located both periplasmically and within extracellular polymeric materials . The enzyme functions in resting cells by cleaving glycerol-2-phosphate (G-2-P) to liberate free phosphate ions which combine with calcium in solution to produce a cell-bound calcium phosphate material . Bacteria grown as a biofilm on polyurethane reticulated foam cubes were challenged with calcium and G-2-P in a bioreactor to produce a 3-D porous bone-substitute material . The scaffold has 1 mm macropores and 1 microm micropores . XRD showed the crystallites to be 25-28 nm in size, resembling HA before sintering and beta-tricalcium phosphate (beta-TCP, whitlockite) after . When biofilm was grown on titanium discs and challenged with calcium and G-2-P, a calcium phosphate layer formed on the discs . Biomineralisation is therefore a potential route to production of precursor nanophase HA, which has the potential to improve strength . The scaffold material produced by this method could be used as a bone-filler or as an alternative method for coating implants with a layer of HA. Huan Jing Ke Xue, 2004 Jan, 25(1), 99 - 102 {Study on bio-contact oxidation A/O process of Guanting Reservior water under low temperature}; He XH et al.; The results of the experiments showed that biological contact A/O process could run steadily under low temperature and had better removal effect for ammonia nitrogen and had some removal effect for COD and TN from water of Guanting Reservoir . When the temperature dropped greatly, removal ratio of ammonia nitrogen dropped evidently, but gradually rose and remained at high removal level at last . Under the conditions of the experiment that the temperature was 0-5 degrees C and influent ammonia nitrogen was about 10 mg/L, ammonia nitrogen removal rate remained more than 95% at last . The change of temperature had no evident influence on removal effect of COD . And the conclusion could be got by microscope that under the temperature at 0-5 degrees C the microorganism in the biofilm still had a good activity. J Chemother, 2004 Jun, 16(3), 244 - 7 Effects of antibiotics on Pseudomonas aeruginosa NK125502 and Pseudomonas fluorescens MF0 biofilm formation on immobilized fibronectin; Gagniere H et al.; The effect of subminimal inhibitory concentration (1/2 MIC) of antibiotics on the biofilm formation on immobilized fibronectin by Pseudomonas was investigated by examining the reference strains NK125502 P . aeruginosa and MF0 P . fluorescens in a microtiter plates assay . When the antibiotics were added during bacterial growth and biofilm development, gentamicin was the only antimicrobial agent tested which decreased significantly the biofilm formation by the two strains . Cefsulodin and chloramphenicol also decreased the P . aeruginosa biofilm development (P<0.01), whereas polymyxin B inhibited biofilm formation by P . fluorescens (p<0.05) . When the antibiotics were only present during bacterial growth and not during biofilm development, gentamicin was the only antibiotic tested to decrease significantly the biofilm formation by P . aeruginosa for incubation times of 20 and 72h (P<0.01), whereas P . fluorescens was not affected . This persistent inhibition of P . aeruginosa biofilm formation may be interesting in intermittent antibiotherapy treatments. Antimicrob Agents Chemother, 2004 Sep, 48(9), 3358 - 66 Adherence of Candida albicans to silicone induces immediate enhanced tolerance to fluconazole; Mateus C et al.; Wild-type and efflux pump-deficient cells of Candida albicans adhering to silicone were compared with planktonic cells by flow cytometry for their relative resistance to fluconazole (FCZ) . Flow cytometry data on cells carrying a fusion of green fluorescent protein to efflux pump promoters confirmed that enhanced tolerance of attached cells to FCZ was due in part to increased expression of CaMDR1 and CDR1 promoters . Within 2 h of their attachment to silicone, the adherent cells demonstrated levels of FCZ tolerance shown by cells from 24-h biofilms . Following their mechanical detachment, this subset of cells retained a four- to eightfold increase in tolerance compared with the tolerance of planktonic cells for at least two generations . Enhanced efflux pump tolerance to FCZ appeared to be induced within the initial 15 min of attachment in a subset of cells that were firmly attached to the substrata. Antimicrob Agents Chemother, 2004 Sep, 48(9), 3291 - 7 Penetration of Candida biofilms by antifungal agents; Al-Fattani MA et al.; A filter disk assay was used to investigate the penetration of antifungal agents through biofilms containing single and mixed-species biofilms containing Candida . Fluconazole permeated all single-species Candida biofilms more rapidly than flucytosine . The rates of diffusion of either drug through biofilms of three strains of Candida albicans were similar . However, the rates of drug diffusion through biofilms of C . glabrata or C . krusei were faster than those through biofilms of C . parapsilosis or C . tropicalis . In all cases, after 3 to 6 h the drug concentration at the distal edge of the biofilm was very high (many times the MIC) . Nevertheless, drug penetration failed to produce complete killing of biofilm cells . These results indicate that poor antifungal penetration is not a major drug resistance mechanism for Candida biofilms . The abilities of flucytosine, fluconazole, amphotericin B, and voriconazole to penetrate mixed-species biofilms containing C . albicans and Staphylococcus epidermidis (a slime-producing wild-type strain, RP62A, and a slime-negative mutant, M7) were also investigated . All four antifungal agents diffused very slowly through these mixed-species biofilms . In most cases, diffusion was slower with biofilms containing S . epidermidis RP62A, but amphotericin B penetrated biofilms containing the M7 mutant more slowly . However, the drug concentrations reaching the distal edges of the biofilms always substantially exceeded the MIC . Thus, although the presence of bacteria and bacterial matrix material undoubtedly retarded the diffusion of the antifungal agents, poor penetration does not account for the drug resistance of Candida biofilm cells, even in these mixed-species biofilms. Oral Microbiol Immunol, 2004 Oct, 19(5), 322 - 6 Biofilm growth of Lactobacillus species is promoted by Actinomyces species and Streptococcus mutans; Filoche SK et al.; The ability of oral bacteria to integrate within a biofilm is pivotal to their survival . A dependence on the amount of biofilm growth by noncoaggregating Lactobacillus rhamnosus and Lactobacillus plantarum on coculture with Actinomyces naeslundii, Actinomyces gerencseriae, Streptococcus mutans and Veillonella parvula was investigated using an artificial-mouth culture system . Biofilm formation by the lactobacilli in mono-culture was poor . In coculture with Actinomyces species the amount of L . rhamnosus increased 7-20 times and L . plantarum 4-7 times compared to its mono-culture biofilm . S . mutans also promoted substantial biofilm growth of lactobacilli but V . parvula had no effect . We conclude that these Actinomyces species promoted growth of key Lactobacillus species in a biofilm, as did S . mutans to a smaller extent, and that the ability of individual bacteria to form mono-culture biofilms is not necessarily an indicator of their survival and pathogenic potential in a complex multispecies biofilm community. Oral Microbiol Immunol, 2004 Oct, 19(5), 297 - 302 A simple approach to examine early oral microbial biofilm formation and the effects of treatments; Sreenivasan PK et al.; BACKGROUND/AIMS: A simple in vivo approach to examine early dental plaque formation in the human mouth and to determine the effects of common dietary and oral hygiene procedures on biofilm formation is reported . METHODS: A custom designed device that fits securely behind the teeth of the mandibular arch provides a surface for microbial colonization . This device is prepared with denture acrylic and can be repeatedly used by the subject, exposing a large and constant surface area for microbial accumulation . RESULTS: Large numbers of oral bacteria colonized the device by 2 h; these increased significantly by 4 h (P < 0.05) . Bacterial colonization increased significantly after rinsing with a sucrose solution (P < 0.05) but remained unaffected after rinsing with water, a commercially available fluoride mouthrinse without antimicrobial agents, or brushing with a fluoride dentifrice (P > 0.05) . Rinsing with mouthrinses formulated with chlorhexidine, cetylpyridinium chloride or triclosan/copolymer significantly inhibited colonization (P < 0.05) . A dose-dependent inhibition was noted with chlorhexidine rinses (P < 0.05) . Brushing with a triclosan/copolymer dentifrice significantly inhibited microbial colonization compared with a control (P < 0.05) . CONCLUSION: This simple approach was useful for examining the effects of common dietary and oral hygiene procedures . Significant biofilm inhibitory effects were noted with formulations that demonstrated efficacy in previous clinical studies. Huan Jing Ke Xue, 2004 May, 25(3), 98 - 101 {The degradation characteristics of degrading bacterium of 2,6-di-tert-butylphenol}; Fang ZW et al.; A degrading bacterial strain F-3-4 for 2,6-Di-tert-butylphenol (2,6-DTBP) was isolated from biofilm in acrylic fiber wastewater treatment structures . By acclimation, its capacity for degradation of 2,6-DTBP was enhanced by 26% . It was identified as Alcaligenes sp . according to morphological, physiological and biochemical characters . By tests in shaking flasks, the effects of the conditions of growth was studied, and it was determined that the optimum conditions of growth for the strain was 37 degrees C, pH 7.0 and inoculum amount 0.1% . Under these conditions, the kinetics of degradation for 2,6-DTBP of initial concentration 100 mg/L was studied, and the result indicated that the removal rate of 2,6-DTBP within 11 days was 62.4%, and the degradation process followed Eckenfelder kinetics . The half life of 2,6-DTBP was 9.38 days . The effect of initial concentration on degradation ability of the strain also was investigated . The results showed that the optimum initial concentration was 200 mg/L . When the initial concentrations were below it, the growth of strain and removal of 2,6-DTBP increased with the increase of initial concentration, while when above the value, they were inhibited. Arch Med Res, 2004 Jul-Aug, 35(4), 275 - 8 Neuraminidase produces dose-dependent decrease of slime production and adherence of slime-forming, coagulase-negative staphylococci; Sakarya S et al.; BACKGROUND: Slime is one of the important structures of certain bacterial strains involved in nonspecific adherence . This study was conducted to determine the role of neuraminidase on slime formation and adherence of slime-forming coagulase-negative staphylococci to inert surface . METHODS: Quantitative biofilm and qualitative bacterial adherence assays were performed with increasing concentrations of neuraminidase extracted from Clostridium perfringens-treated bacteria in polystyrene plates and polypropylene tubes . RESULTS: Slime production of slime-forming, coagulase-negative staphylococci was significantly decreased dose dependently at > or =100 mU/mL (p <0.001) . Bacterial adherence to smooth surface was impeded at > or =100 mU/mL of neuraminidase treatment and adherence results were comparable with slime production assay results . CONCLUSIONS: Sialic acid may be a constituent molecule of slime and involved in bacterial adherence to inert surface . These results represent new insight into the mechanism of slime production and adherence of slime-forming, coagulase-negative staphylococci to inert surface. Int J Antimicrob Agents, 2004 Sep, 24(3), 234 - 40 Use of an oxonol dye in combination with confocal laser scanning microscopy to monitor damage to Staphylococcus aureus cells during colonisation of silver-coated vascular grafts; Strathmann M et al.; The antimicrobial silver-coating of medical prostheses is regarded as a means to reduce the risk of bacterial colonisation after implantation . The effect of a silver-coating of vascular grafts on biofilm formation was assessed in batch cultures of Staphylococcus aureus, using confocal laser scanning microscopy . Total cells in biofilms were analysed by staining with the DNA-binding fluorochrome SYTO 62 and the proportion of damaged cells was quantified with the membrane potential-sensitive dye bis-(1,3-dibutylbarbituric acid) trimethine oxonol . Both the extent of biofilm formation and the proportion of viable biofilm cells were significantly diminished on the surface of the silver-coated vascular grafts compared with uncoated controls, probably due to the antimicrobial activity of silver ions released from the silver-coated graft surface. Water Res, 2004 Sep, 38(16), 3614 - 26 Interactions between laponite and microbial biofilms in porous media: implications for colloid transport and biofilm stability; Leon-Morales CF et al.; Quartz sand columns and sand-filled microscope flow cells were used to investigate the transport characteristics of the clay colloid laponite, and a biofilm-forming bacterium, Pseudomonas aeruginosa SG81 . Separate experiments were performed with each particle to determine their individual transport characteristics in clean sand columns . In a second set of experiments, bacterial biofilms were formed prior to introduction of the clay colloids . In the independent transport experiments, bacteria and laponite each conformed to known physicochemical principles . A sodium chloride concentration of 7 x 10(-2) M caused complete retention of the laponite within the sand columns . P . aeruginosa SG81 was generally less influenced by ionic strength effects; it showed relatively low mobility at all ionic strengths tested and some (albeit reduced) mobility when introduced to the columns in 1M NaCl, the highest concentration tested, but nevertheless showed reproducible trends . Under conditions favourable to laponite retention and biofilm stability (7 x 10(-2) MNaCl), laponite suspensions were able to remobilise a portion of the attached bacterial biomass . At low ionic strength, the profile of laponite elution was also altered in the presence of a P . aeruginosa biofilm . These observations suggest that while a reduction in ionic strength has a dominant influence on the mobilisation of biological and inorganic colloids, the presence of laponite and biomass can have a distinct influence on the mobility of both types of colloids . Since these events are likely to occur in subsurface environments, our results suggest that colloid-biofilm interactions will have implications for colloid-bound contaminant transport and the remobilisation of pathogens. Langmuir, 2004 Aug 31, 20(18), 7753 - 9 Evaluating protein attraction and adhesion to biomaterials with the atomic force microscope; Wang MS et al.; Failure of implanted biomaterials is commonly due to nonspecific protein adsorption, which in turn causes adverse reactions such as the formation of fibrous capsules, blood clots, or bacterial biofilm infections . Current research efforts have focused on modifying the biomaterial interface to control protein reactions . Designing biomaterial interfaces at the molecular level, however, requires an experimental technique that provides detailed, dynamic information on the forces involved in protein adhesion . The goal of this study was to develop an atomic force microscope (AFM)-based technique to evaluate protein adhesion on biomaterial surfaces . In this study, the AFM was used to evaluate (i) protein-protein, (ii) protein-substrate, and (iii) protein-dextran interactions . The AFM was first used to measure the pull-off forces between bovine serum albumin (BSA) tips/BSA surfaces and BSA tips/anti-BSA surfaces . Results from these protein-protein studies were consistent with the literature . More importantly, the successful measurement of antibody-antigen binding interactions demonstrates that both the BSA and anti-BSA proteins retain their folded conformation and remain functional following our immobilization protocol . The AFM was also used to quantify the physiochemical interactions of proteins during adhesion to various self-assembled monolayers (SAMs) and dextran-coated substrates representative of potential biomaterial interface modifications . Dextran, which renders surfaces very hydrophilic, was the only surface coating that BSA protein did not adhere to . Hydrophobic interactions were not found to play a significant role in BSA adhesion . Therefore, the dextran molecules may resist protein adhesion by repulsive steric effects or hydration pressure . Moreover, the AFM-based methodology provides dynamic, quantitative information about protein adhesion at the nanoscale level. Braz Dent J, 2004, 15(1), 41 - 5 Epub 2004 Aug 16. Control of gingival inflammation in a teenager population using ultrasonic prophylaxis; Novaes Junior AB et al.; Gingival inflammation is clinically characterized by gingival redness, swelling and increased tendency of bleeding of the soft tissue . Bacterial biofilm is the etiological agent . If, at this stage, the bacterial biofilm is removed and appropriate control methods are applied, remission of gingival inflammation occurs . This study evaluated the effectiveness of a single session of ultrasonic prophylaxis for the reduction of gingivitis in an adolescent population using the Plaque Index (PI) and Gingival Index (GI) . The study sample consisted of 15 male adolescent students selected at a dentist's office of a public high school . Prior to treatment (baseline), plaque index (PI) and bleeding on probing (BOP) were recorded . The patients then received oral hygiene instructions and ultrasonic prophylaxis . Follow-up exams were made 15 and 30 days after the ultrasonic prophylaxis, again recording PI and BOP . The data were analyzed by the Student's t-test for dependent samples . Correlation analysis between presence of biofilm and bleeding on probing was also made using the Pearson correlation test . There was a statistically significant decrease in the plaque index and bleeding on probing between baseline and examinations at both 15 days and 30 days (p<0.05) . However, the difference between the means at 15 and 30 days was statistically similar . The correlation analysis showed correlation between both parameters (p<0.05) . The results indicate that a single session of ultrasonic prophylaxis associated to oral hygiene instructions is efficient to reverse gingivitis in adolescents. FEMS Microbiol Lett, 2004 Aug 15, 237(2), 341 - 53 Gene expression profile of the plant pathogen Xylella fastidiosa during biofilm formation in vitro; de Souza AA et al.; A biofilm is a community of microorganisms attached to a solid surface . Cells within biofilms differ from planktonic cells, showing higher resistance to biocides, detergent, antibiotic treatments and host defense responses . Even though there are a number of gene expression studies in bacterial biofilm formation, limited information is available concerning plant pathogen . It was previously demonstrated that the plant pathogen Xylella fastidiosa could grow as a biofilm, a possibly important factor for its pathogenicity . In this study we utilized analysis of microarrays to specifically identify genes expressed in X . fastidiosa cells growing in a biofilm, when compared to planktonic cells . About half of the differentially expressed genes encode hypothetical proteins, reflecting the large number of ORFs with unknown functions in bacterial genomes . However, under the biofilm condition we observed an increase in the expression of some housekeeping genes responsible for metabolic functions . We also found a large number of genes from the pXF51 plasmid being differentially expressed . Some of the overexpressed genes in the biofilm condition encode proteins involved in attachment to surfaces . Other genes possibly confer advantages to the bacterium in the environment that it colonizes . This study demonstrates that the gene expression in the biofilm growth condition of the plant pathogen X . fastidiosa is quite similar to other characterized systems. J Bacteriol, 2004 Sep, 186(17), 5692 - 8 The Bvg virulence control system regulates biofilm formation in Bordetella bronchiseptica; Irie Y et al.; Bordetella species utilize the BvgAS (Bordetella virulence gene) two-component signal transduction system to sense the environment and regulate gene expression among at least three phases: a virulent Bvg+ phase, a nonvirulent Bvg- phase, and an intermediate Bvgi phase . Genes expressed in the Bvg+ phase encode known virulence factors, including adhesins such as filamentous hemagglutinin (FHA) and fimbriae, as well as toxins such as the bifunctional adenylate cyclase/hemolysin (ACY) . Previous studies showed that in the Bvgi phase, FHA and fimbriae continue to be expressed, but ACY expression is significantly downregulated . In this report, we determine that Bordetella bronchiseptica can form biofilms in vitro and that the generation of biofilm is maximal in the Bvgi phase . We show that FHA is required for maximal biofilm formation and that fimbriae may also contribute to this phenotype . However, expression of ACY inhibits biofilm formation, most likely via interactions with FHA . Therefore, the coordinated regulation of adhesins and ACY expression leads to maximal biofilm formation in the Bvgi phase in B . bronchiseptica. ORL J Otorhinolaryngol Relat Spec, 2004, 66(3), 155 - 8 Evidence of bacterial biofilms in human chronic sinusitis; Cryer J et al.; The purpose of this study was to evaluate whether bacterial biofilms exist on the sinus mucosa surfaces of human subjects with recalcitrant chronic sinusitis . Scanning electron microscopy was used to evaluate patients with continued symptoms of chronic sinusitis despite prior appropriate medical and surgical management . Morphologic structures that confirm the presence of bacterial biofilms were identified on the sinus mucosa of patients infected with Pseudomonas aeruginosa, a known biofilm former . The presence of bacterial biofilms may explain the recalcitrant nature of some forms of chronic sinusitis . Caries Res, 2004 Sep-Oct, 38(5), 448 - 53 A method for mapping the distribution pattern of cariogenic streptococci within dental plaque in vivo; Kato K et al.; This study was carried out to develop a method for mapping the distribution of cariogenic oral streptococci, Streptococcus mutans and Streptococcus sobrinus, from the outermost to the innermost plaque . Ten consenting subjects were asked to form plaque by abstaining from tooth brushing over 3 days within in situ plaque-generating devices, which were placed on the upper molars . The plaque formed in the devices was separated into 8-10 layered fractions (100 microm thick) . Genomic DNA was extracted from each plaque fraction by a commercial DNA purification kit and used for the amplification of the 16S ribosomal RNA gene sequences by polymerase chain reaction (PCR) with universal primers . The products were then amplified by PCR with S . mutans- or S . sobrinus-specific nested primers . The final products were separated on agarose gels, stained and photographed to confirm the existence of S . mutans and S . sobrinus . The results showed that S . mutans was detected in the plaque obtained from all of the 10 subjects and S . sobrinus in the plaque of 7 subjects . However, the distribution patterns of fractions positive for S . mutans and S . sobrinus varied among the subjects, with a tendency for frequent detection of both species in the outer to middle layers of dental plaque . There were no plaque fractions in which only S . sobrinus was found . This method could be useful to map the distribution of cariogenic microorganisms and to estimate the bacterial ecology for oral biofilm. Caries Res, 2004 Sep-Oct, 38(5), 442 - 7 Individual vitality pattern of in situ dental biofilms at different locations in the oral cavity; Arweiler NB et al.; The aim of the study was to examine the three-dimensional vitality structure of dental biofilms grown simultaneously at different locations in the oral cavity over a 48-hour period . Eight healthy volunteers wore special acrylic appliances . On each buccal side of the upper and the lower jaw three glass slabs were inserted, allowing for growth of a biofilm mimicking approximal plaque . After 48 h, the specimens were removed and biofilms were stained using two fluorescent dyes which selectively stain vital bacteria green and dead bacteria red . Under the confocal laser scanning microscope optical sections of 1 microm throughout the biofilm were made . To assess the vitality values (proportion of vital bacteria) of the whole biofilm as well as the vitality distribution in the different plaque sections an image analysis program was used . Plaque from the different locations revealed mean vitality values between 64.4 and 75.7% in the upper jaw and between 64.3 and 76.8% in the lower jaw, which were not statistically different . However, a great variation of the vitality values for the different layers and among the 8 subjects was found . Nevertheless, the analysis of the data of each single volunteer revealed a very similar vitality pattern in all twelve locations. J Med Microbiol, 2004 Sep, 53(Pt 9), 903 - 10 Effect of subinhibitory concentration of piperacillin/tazobactam on Pseudomonas aeruginosa; Fonseca AP et al.; Subinhibitory concentrations (sub-MICs) of antibiotics, although not able to kill bacteria, can modify their physico-chemical characteristics and the architecture of their outermost surface and may interfere with some bacterial functions . This study investigated the ability of sub-MIC piperacillin/tazobactam (P/T) to interfere with the bacterial virulence parameters of adhesiveness, cell-surface hydrophobicity, motility, biofilm formation and sensitivity to oxidative stress . Antimicrobial activity against five Pseudomonas aeruginosa clinical isolates, representative of clonal lineages of 96 strains of nosocomial origin, and six control strains (ATCC 27853, PAO1, AK1, MT1562, PT623, PAO1algC) was evaluated in vitro using the NCCLS microdilution method . The effects of sub-MIC on bacterial adhesion and biofilm formation were studied using a modified microtitre plate assay . The relative cell-surface hydrophobicity of P . aeruginosa strains was determined by measuring their ability to adhere to n-hexadecane . P . aeruginosa that had been exposed overnight to P/T and incubated with P/T in the plate were also screened for their ability to swim using flagella and to twitch and for their sensitivity to oxidative stress . The results obtained showed that the impact of sub-MIC P/T on bacterial characteristics was different for the various strains of P . aeruginosa . There was a change in bacterial morphology and hydrophobicity that could explain a significant decrease in adhesion values in all clinical isolates and controls tested, a decrease in biofilm formation, a significant increase in sensitivity to oxidative stress, a significant decrease in flagellum-mediated swimming and a decrease in type IV fimbriae-mediated twitching . The results obtained indicate that sub-MIC P/T interferes with the pathogenic potential of P . aeruginosa. J Med Microbiol, 2004 Sep, 53(Pt 9), 841 - 53 Analysis of quorum sensing-deficient clinical isolates of Pseudomonas aeruginosa; Schaber JA et al.; Pseudomonas aeruginosa produces multiple virulence factors and causes different types of infections . Previous clinical studies identified P . aeruginosa isolates that lack individual virulence factors . However, the impact of losing several virulence factors simultaneously on the in vivo virulence of P . aeruginosa is not completely understood . The P . aeruginosa cell-to-cell communication system, or quorum sensing (QS), controls the production of several virulence factors . Animal studies using constructed QS mutants indicated that loss of the QS system severely impacts the virulence of P . aeruginosa . In this study, we tried to determine if deficiency within the QS system compromises the ability of P . aeruginosa to establish infections in humans . We have identified five QS-deficient strains through screening 200 isolates from patients with urinary tract, lower respiratory tract and wound infections . These strains lacked LasB and LasA activities and produced either no or very low levels of the autoinducers N-(3-oxododecanoyl) homoserine lactone and N-butyryl homoserine lactone . PCR analysis revealed that three isolates contained all four QS genes (lasI, lasR, rhlI and rhlR) while two isolates lacked both the lasR and rhlR genes . We also examined the five isolates for other virulence factors . The isolates produced variable levels of exotoxin A and, with one exception, were deficient in pyocyanin production . One isolate produced the type III secretion system (TTSS) effector proteins ExoS and ExoT, two isolates produced ExoT only and two isolates produced no TTSS proteins . The isolates produced weak to moderate biofilms on abiotic surfaces . Analysis of the patients' data revealed that two of the isolates represented a single strain that was isolated twice from the same patient within a 1 month interval . One QS-deficient clinical isolate (CI-1) lacked all tested virulence factors and produced a weak biofilm . These results suggest that naturally occurring QS-deficient strains of P . aeruginosa do occur and are capable of causing infections; and, that besides the known virulence factors, additional factors may contribute to the ability of certain strains such as CI-1 to establish an infection. J Mol Biol, 2004 Sep 3, 342(1), 195 - 205 Structural analysis of Escherichia coli OpgG, a protein required for the biosynthesis of osmoregulated periplasmic glucans; Hanoulle X et al.; Osmoregulated periplasmic glucans (OPGs) G protein (OpgG) is required for OPGs biosynthesis . OPGs from Escherichia coli are branched glucans, with a backbone of beta-1,2 glucose units and with branches attached by beta-1,6 linkages . In Proteobacteria, OPGs are involved in osmoprotection, biofilm formation, virulence and resistance to antibiotics . Despite their important biological implications, enzymes synthesizing OPGs are poorly characterized . Here, we report the 2.5 A crystal structure of OpgG from E.coli . The structure was solved using a selenemethionine derivative of OpgG and the multiple anomalous diffraction method (MAD) . The protein is composed of two beta-sandwich domains connected by one turn of 3(10) helix . The N-terminal domain (residues 22-388) displays a 25-stranded beta-sandwich fold found in several carbohydrate-related proteins . It exhibits a large cleft comprising many aromatic and acidic residues . This putative binding site shares some similarities with enzymes such as galactose mutarotase and glucodextranase, suggesting a potential catalytic role for this domain in OPG synthesis . On the other hand, the C-terminal domain (residues 401-512) has a seven-stranded immunoglobulin-like beta-sandwich fold, found in many proteins where it is mainly implicated in interactions with other molecules . The structural data suggest that OpgG is an OPG branching enzyme in which the catalytic activity is located in the large N-terminal domain and controlled via the smaller C-terminal domain. Res Microbiol, 2004 Sep, 155(7), 514 - 21 Anaerobic growth does not support biofilm formation in Escherichia coli K-12; Colon-Gonzalez M et al.; Association with a surface in a structure known as biofilm is the prevailing microbial lifestyle . Here we show the kinetics of biofilm formation of Escherichia coli W3110 in static cultures growing under aerobic or anaerobic conditions . Aerobically growing cells in LB medium started to produce detectable amounts of biofilm after 4 to 8 h, displaying maximal accumulation of formed biofilm at 24 h, corresponding to the onset of stationary phase . Then an abrupt reduction in the biomass of the biofilm was observed . This decrease was not prevented by external addition of fresh nutrients and coincided with the depletion of oxygen as measured by the enzymatic activity of the AdhE protein . No biofilm formation was detected in cultures grown anaerobically in LB or LB supplemented with nitrate, nitrite, DMSO or fumarate, even after 72 h of incubation, well inside the stationary phase, suggesting that under anaerobic growth conditions E . coli cannot form biofilms. J Clin Periodontol, 2004 Sep, 31(9), 749 - 57 The long-term effect of a plaque control program on tooth mortality, caries and periodontal disease in adults . Results after 30 years of maintenance; Axelsson P et al.; BACKGROUND: The biofilm that forms and remains on tooth surfaces is the main etiological factor in caries and periodontal disease . Prevention of caries and periodontal disease must be based on means that counteract this bacterial plaque . OBJECTIVE: To monitor the incidence of tooth loss, caries and attachment loss during a 30-year period in a group of adults who maintained a carefully managed plaque control program . In addition, a comparison was made regarding the oral health status of individuals who, in 1972 and 2002, were 51-65 years old . MATERIAL AND METHODS: In 1971 and 1972, more than 550 subjects were recruited . Three hundred and seventy-five subjects formed a test group and 180 a control group . After 6 years of monitoring, the control group was discontinued but the participants in the test group was maintained in the preventive program and was finally re-examined after 30 years . The following variables were studied at Baseline and after 3, 6, 15 and 30 years: plaque, caries, probing pocket depth, probing attachment level and CPITN . Each patient was given a detailed case presentation and education in self-diagnosis . Once every 2 months during the first 2 years, once every 3-12 months during years 3-30, the participants received, on an individual need basis, additional education in self-diagnosis and self-care focused on proper plaque control measures, including the use of toothbrushes and interdental cleaning devices (brush, dental tape, toothpick) . The prophylactic sessions that were handled by a dental hygienist also included (i) plaque disclosure and (ii) professional mechanical tooth cleaning including the use of a fluoride-containing dentifrice/paste . RESULTS: Few teeth were lost during the 30 years of maintenance; 0.4-1.8 in different age cohorts . The main reason for tooth loss was root fracture; only 21 teeth were lost because of progressive periodontitis or caries . The mean number of new caries lesions was 1.2, 1.7 and 2.1 in the three groups . About 80% of the lesions were classified as recurrent caries . Most sites, buccal sites being the exception, exhibited no sign of attachment loss . Further, on approximal surfaces there was some gain of attachment between 1972 and 2002 in all age groups . CONCLUSION: The present study reported on the 30-year outcome of preventive dental treatment in a group of carefully monitored subjects who on a regular basis were encouraged, but also enjoyed and recognized the benefit of, maintaining a high standard of oral hygiene . The incidence of caries and periodontal disease as well as tooth mortality in this subject sample was very small . Since all preventive and treatment efforts during the 30 years were delivered in one private dental office, caution must be exercised when comparisons are made with longitudinal studies that present oral disease data from randomly selected subject samples. Arch Oral Biol, 2004 Oct, 49(10), 789 - 98 Biofilm formation of Candida albicans is variably affected by saliva and dietary sugars; Jin Y et al.; The pathogenesis of both superficial and systemic candidiasis is closely dictated by properties of the yeast biofilms . Despite extensive investigations on bacterial biofilms, the characteristics of candidal biofilms, and various factors affecting this process remain to be determined . Therefore we examined the effect of human whole saliva and dietary sugars, glucose and galactose on the adhesion and biofilm formation of Candida albicans . Biofilms of C . albicans isolate 192 887 g were developed on polystyrene, flat-bottomed 96-well microtiter plates and monitored using ATP bioluminescence and tetrazolium (XTT) reduction assays as well as the conventional colony forming unit (CFU) evaluation . Our data showed that both the ATP and the XTT assays strongly correlated with the CFU assay (ATP versus CFU: r = 0.994, P = 0.006; XTT versus CFU: r = 0.985, P = 0.015) . Compared with a glucose-supplemented (100 mM) medium, galactose containing (500 mM) medium generated consistently lower levels of both candidal adhesion and biofilm formation (all P < 0.05), but a higher pace of biofilm development over time (96 h) . Whist the presence of an immobilised saliva coating had little effect on either the candidal adhesion or biofilm formation, the addition of saliva to the incubation medium quantitatively affected biofilm formation especially on day 3 and 4, without any significant effect on yeast adhesion . To conclude, biofilm formation of C . albicans within the oral milieu appears to be modulated to varying extents by dietary and salivary factors and, further investigations are required to elucidate these complex interactions. Mol Microbiol, 2004 Aug, 53(4), 1075 - 87 Pseudomonas aeruginosa attachment and biofilm development in dynamic environments; Ramsey MM et al.; Biofilm formation by Pseudomonas aeruginosa is hypothesized to follow a developmental pattern initiated by attachment to a surface followed by microcolony formation and mature biofilm development . Swimming and twitching motility are important for attachment and biofilm development in P . aeruginosa . However, it is clear that many P . aeruginosa strains lacking swimming motility exist as biofilms in the lungs of cystic fibrosis patients . Consequently, we have developed a dynamic attachment assay to identify motility-independent attachment-defective mutants . Using transposon mutagenesis, we identified 14 novel dynamic attachment-deficient (dad) mutants including four mutants specific to dynamic assay conditions (dad specific) . Two of the dad-specific mutants contain insertions in genes involved in sensing and responding to external stimuli, implying a significant impact of external factors on the biofilm developmental pathway . Observations of initial attachment and long-term biofilm formation characterized our dad mutants into two distinct classes: biofilm delayed and biofilm impaired . Biofilm-delayed mutants form wild-type biofilms but are delayed at least 24 h compared with the wild type, whereas biofilm-impaired mutants never form wild-type biofilms in our assays . We propose a dynamic model for attachment and biofilm formation in P . aeruginosa including these two classes. Mol Microbiol, 2004 Aug, 53(4), 1035 - 49 MotPS is the stator-force generator for motility of alkaliphilic Bacillus, and its homologue is a second functional Mot in Bacillus subtilis; Ito M et al.; The stator-force generator that drives Na+-dependent motility in alkaliphilic Bacillus pseudofirmus OF4 is identified here as MotPS, MotAB-like proteins with genes that are downstream of the ccpA gene, which encodes a major regulator of carbon metabolism . B . pseudofirmus OF4 was only motile at pH values above 8 . Disruption of motPS resulted in a non-motile phenotype, and motility was restored by transformation with a multicopy plasmid containing the motPS genes . Purified and reconstituted MotPS from B . pseudofirmus OF4 catalysed amiloride analogue-sensitive Na+ translocation . In contrast to B . pseudofirmus, Bacillus subtilis contains both MotAB and MotPS systems . The role of the motPS genes from B . subtilis in several motility-based behaviours was tested in isogenic strains with intact motAB and motPS loci, only one of the two mot systems or neither mot system . B . subtilis MotPS (BsMotPS) supported Na+-stimulated motility, chemotaxis on soft agar surfaces and biofilm formation, especially after selection of an up-motile variant . BsMotPS also supported motility in agar soft plugs immersed in liquid; motility was completely inhibited by an amiloride analogue . BsMotPS did not support surfactin-dependent swarming on higher concentration agar surfaces . These results indicate that BsMotPS contributes to biofilm formation and motility on soft agar, but not to swarming, in laboratory strains of B . subtilis in which MotAB is the dominant stator-force generator . BsMotPS could potentially be dominant for motility in B . subtilis variants that arise in particular niches. Water Sci Technol, 2004, 49(11-12), 371 - 7 Growth, structure and oxygen penetration in particle supported autotrophic biofilms; Boessmann M et al.; Particle supported autotrophic biofilms were cultivated in external-loop airlift reactors at two different pumice concentrations . Oxygen microelectrodes were used to investigate substrate transport and conversion . A special flow cell was designed for the measurement of oxygen concentration profiles in the particle supported biofilms under defined hydrodynamic conditions . The oxygen concentration profiles inside the biofilms were found to be steeper at high flow velocities in the bulk phase of the flow cell compared to those at low flow velocities . Furthermore, the oxygen flux increased and the thickness of the concentration boundary layer decreased with increasing flow velocity . This dependence was found to be more pronounced in less dense biofilms out of airlift reactors with lower pumice concentrations . In addition confocal laser scanning microscopy (CLSM) was used to visualize the biofilm structure . The volume fractions of bacteria and extracellular polymeric substances (lectin-specific EPS-glycoconjugates) were measured in living fully hydrated biofilms . Both the microelectrode and CLSM measurement showed the influence of shear stress on particle supported biofilms . A higher particle concentration led to dense biofilms with a homogeneous surface, lower thickness of the concentration boundary layer and steeper oxygen concentration profiles . The combination of both techniques allows a detailed and quantitative characterisation of particle associated biofilm structure and function. Water Sci Technol, 2004, 49(11-12), 359 - 64 Reproducibility of biofilm processes and the meaning of steady state in biofilm reactors; Lewandowski Z et al.; The need for reproducing biofilm processes is undisputable - the quality of biofilm research depends on this reproducibility . However, as many biofilm researchers know, long-term biofilm processes are notoriously difficult to reproduce . To avoid problems related to biofilm reproducibility two strategies are used: (1) to study very young biofilms that have accumulated for a few hours to a few days only, and (2) to run biofilm experiments only once . The first approach trades reproducibility for relevance because natural biofilms are usually older, often much older than a few days . This approach can be applied to answer questions relevant to initial events of biofilm formation but not questions relevant to long-term biofilm accumulation . The second approach conceals the problem of biofilm reproducibility . To assure reproducibility of biofilm processes, we methodically followed a procedure for growing biofilms in terms of microbial makeup, media composition, temperature, surface preparation, etc . Despite all this effort the reproducibility of our results for long term growth is unimpressive . Consequently, the question had to be asked: Are biofilm processes reproducible? The experiments described in this paper address this question . Biofilms grown in two identical and identically operated biofilm reactors had comparable structure only until the first sloughing event . After that, biofilms had different patterns of accumulation. Water Sci Technol, 2004, 49(11-12), 353 - 8 Microsensor measurement of oxygen concentration in biofilms: from one dimension to three dimensions; Yu T et al.; In this study, we measured oxygen concentration in biofilms in one dimension in field conditions and in three dimensions in laboratory conditions by using a robust oxygen microsensor in combination with an automation and data acquisition system . The biofilms were on the discs of rotating biological contactors treating domestic wastewater . The results of this study provide experimental evidence on oxygen distribution in wastewater biofilms and on biofilm structure . (1) The three dimensional measurements of oxygen concentration in biofilms revealed "pockets" of oxygen in deep sections of biofilms . In these isolated "pockets," located 600-760 microm from the biofilm surface, dissolved oxygen concentration was as high as 1 mg/L . This depth of oxygen diffusion is deeper than what was determined based on one dimensional measurements . (2) The heterogeneity of oxygen distribution was related to the surface structure of biofilms . The structure of the biofilm surface affected the diffusion boundary layer over the surface and, in turn, the oxygen diffusion and distribution inside biofilms . (3) Oxygen concentration in biofilms changed generally from a high degree of heterogeneity near the biofilm surface to a low degree of heterogeneity in deep sections of biofilms, indicating a cell-clusters-like structure near the surface and a more compact base layer close to the substratum. Water Sci Technol, 2004, 49(11-12), 345 - 51 Behaviour of biofilm systems under varying hydrodynamic conditions; Leon Ohl A et al.; Heterotrophic biofilms were cultivated in long-term experiments in biofilm tube reactors . During the biofilm cultivation the substrate loading of glucose was kept constant while the hydrodynamic conditions were changed stepwise . To describe the behaviour of the biofilm structure under these varying flow conditions the mass transfer and transport at the bulk/biofilm interface and inside the biofilm was investigated with oxygen microelectrodes . Furthermore, the biofilm density was used to describe the biofilm compactness before and after the change of the hydrodynamic condition . The obtained results show that the biofilm density and also the substrate flux decreased with decreasing flow velocity in the bulk phase . Additionally the slope of the oxygen concentration profiles decreased and the thickness of the concentration boundary layer increased . On the other hand, increasing the flow velocity in the bulk phase led both to a higher biofilm density and a higher maximum substrate flux . The biofilm surface became more homogenous and the thickness of the concentration boundary layer decreased . The time for adaptation of the biofilm structure after changing the hydrodynamic conditions ranged between 1 and 3 weeks. Water Sci Technol, 2004, 49(11-12), 337 - 44 Bioaugmentation of a sequencing batch biofilm reactor by horizontal gene transfer; Bathe S et al.; Bioaugmentation by introduction of catabolic genes residing on mobile genetic elements into the microbial community of a soil or wastewater environment might be an alternative to bioaugmentation by addition of bacterial cells with chromosomally encoded catabolic genes . This study investigates the possibility to enhance degradation of the xenobiotic model compound 2,4-dichlorophenoxyacetic acid in a sequencing batch biofilm reactor (SBBR) by using the conjugative plasmid pJP4 carrying genes for 2,4-D degradation . After introduction of a plasmid donor strain to a lab-scale SBBR operated without 2,4-D, the number of plasmid-carrying cells first dropped, and then increased after switching to 2,4-D as the sole carbon source . The donor cells were unable to grow in the applied synthetic wastewater with 2,4-D as the sole carbon source . Transconjugants could be detected both by culture-dependent and culture-independent methods in the 2,4-D degrading biofilm . In contrast to 90% 2,4-D degradation in the bioaugmented reactor within 40 h, a control reactor which had not received the plasmid still contained 60% of the initial 2,4-D concentration after 90 h . This experiment clearly demonstrates the introduction of 2,4-D degradative genes into a microbial biofilm and indicates that horizontal gene transfer is a promising tool for bioaugmentation of reactors treating wastewater. Water Sci Technol, 2004, 49(11-12), 319 - 25 Full scale fluidized bed anaerobic reactor for domestic wastewater treatment: performance, sludge production and biofilm; Mendonca NM et al.; This paper describes the performance, sludge production and biofilm characteristics of a full scale fluidized bed anaerobic reactor (32 m3) for domestic wastewater treatment . The reactor was operated with 10.5 m x h(-1) upflow velocity, 3.2 h hydraulic retention time, and recirculation ratio of 0.85 and it presented removal efficiencies of 71+/-8% of COD and 77+/-14% of TSS . During the apparent steady-state period, specific sludge production and sludge age in the reactor were (0.116+/-0.033) kgVSS . kgCOD(-1) and (12+/-5)d, respectively . Biofilm formed in the reactor presented two different patterns: one of them at the beginning of the colonization and the other of mature biofilm . These different colonization patterns are due to bed stratification in the reactor, caused by the difference in local-energy dissipation rates along the reactor's height, and density, shape, etc . of the bioparticles . The biofilm population is formed mainly of syntrophic consortia among sulfate reducing bacteria, methanogenic archaea such as Methanobacterium and Methanosaeta-like cells. Water Sci Technol, 2004, 49(11-12), 287 - 94 Treatment of leachate from the anaerobic fermentation of solid wastes using two biofilm support media; Comett I et al.; Biofilms growing on different carrier media have a different response to the nutrients contained in wastewater . Biofilms have proven to be an alternative to the treatment of wastewater containing higher concentrations of contaminants . The main objective of this research was to compare two biofilm support media for the treatment of leachate from the anaerobic fermentation of solid wastes . The removal of organic matter and ammonia was achieved in two fixed bed biofilm reactors containing Kaldnes and Linpor support materials with specific surface areas of 490 and 270 m2/m3, respectively, and operating under the sequencing batch procedure during 204 days . The Linpor reactor achieved higher total COD removal than the Kaldnes reactor (47% and 39%, respectively) . Linpor was shown to be less sensitive to influent COD changes than Kaldnes . The effluent total COD values of Kaldnes were higher than Linpor . The dissolved COD removal was 21% for both reactors . The average ammonia removal for Linpor was 72% and 42% for Kaldnes . The matrix of Linpor allows higher concentrations of microorganisms (as dry mass) than Kaldnes . The dry mass concentration was related to the "active" exposed surface area of the biofilm . This is considered to be the cause for the better performance of Linpor when compared with Kaldnes. Water Sci Technol, 2004, 49(11-12), 277 - 86 Contamination potential of drinking water distribution network biofilms; Wingender J et al.; Drinking water distribution system biofilms were investigated for the presence of hygienically relevant microorganisms . Early biofilm formation was evaluated in biofilm reactors on stainless steel, copper, polyvinyl chloride (PVC) and polyethylene coupons exposed to unchlorinated drinking water . After 12 to 18 months, a plateau phase of biofilm development was reached . Surface colonization on the materials ranged between 4 x 10(6) and 3 x 10(7) cells/cm2, with heterotrophic plate count (HPC) bacteria between 9 x 10(3) and 7 x 10(5) colony-forming units (cfu)/cm2 . Established biofilms were investigated in 18 pipe sections (2 to 99 years old) cut out from distribution pipelines . Materials included cast iron, galvanized steel, cement and PVC . Colonization ranged from 4 x 10(5) to 2 x 10(8) cells/cm2, HPC levels varied between 1 and 2 x 10(5) cfu/cm2 . No correlation was found between extent of colonization and age of the pipes . Using cultural detection methods, coliform bacteria were rarely found, while Escherichia coli, Pseudomonas aeruginosa and Legionella spp . were not detected in the biofilms . In regular operation, distribution system biofilms do not seem to be common habitats for pathogens . However, nutrient-leaching materials like rubber-coated valves were observed with massive biofilms which harboured coliform bacteria contaminating drinking water. Water Sci Technol, 2004, 49(11-12), 255 - 62 Engineering aspects of a mixed methanotrophic culture in a membrane-aerated biofilm reactor; Casey E et al.; Methanotrophic biodegradation using the membrane-aerated biofilm reactor (MABR) is a technology offering several advantages over both conventional biofilm reactors and suspended-cell processes . In this study the oxidation efficiency of a methanotrophic biofilm in a 1.5 litre MABR was investigated . Measurements of oxygen and methane uptake rates together with biofilm thickness were taken for developing biofilms . It was found that the specific rate of metabolic activity of the biofilm was unusually high as determined by the methane and oxygen uptake rates . Microbial activity stratification was evident and the location of stratified layers of oxygen consuming components of the consortium could be manipulated via the intra-membrane oxygen pressure. Water Sci Technol, 2004, 49(11-12), 231 - 6 Methanotrophic biodegradation of cis-1,2-dichloroethylene in a continuously fed fixed-film bioreactor; Arcangeli JP et al.; Co-metabolic biodegradation of cis-dichloroethylene (cis-DCE) was investigated in a bench-scale fixed-film bioreactor inoculated with a mixed culture of methane oxidising bacteria . The aim of this work was to identify factors that affect the cis-DCE biodegradation . It was observed that the presence of methane was necessary to enhance the biodegradation of cis-DCE, but an excess of methane inhibited the cis-DCE removal . cis-DCE did not inhibit the methane biodegradation at concentrations up to 300 microg/L . Maximum cis-DCE removal was observed with a methane bulk concentration ranging from 0.2 to 0.7 mg/L . It was found that the activity of the biofilm was located in the upper 100 microm of the biofilm . On the basis of this study it is concluded that careful control of the oxygen and methane concentrations as well as of the biofilm thickness is necessary in order to optimise the biodegradation of cis-DCE in fixed film bioreactors. Water Sci Technol, 2004, 49(11-12), 199 - 205 Increasing the capacity for treatment of chemical plant wastewater by replacing existing suspended carrier media with Kaldnes Moving Bed media at a plant in Singapore; Wessman FG et al.; The Kaldnes biomedia K1, which is used in the patented Kaldnes Moving Bed biofilm process, has been tested along with other types of biofilm carriers for biological pretreatment of a complex chemical industry wastewater . The main objective of the test was to find a biofilm carrier that could replace the existing suspended carrier media and at the same time increase the capacity of the existing roughing filter-activated sludge plant by 20% or more . At volumetric organic loads of 7.1 kg COD/m3/d the Kaldnes Moving Bed process achieved much higher removal rates and much lower effluent concentrations than roughing filters using other carriers . The Kaldnes roughing stage achieved more than 85% removal of organic carbon and more than 90% removal of BOD5 at the tested organic load, which was equivalent to a specific biofilm surface area load of 24 g COD/m2/d . Even for the combined roughing filter-activated sludge process, the Kaldnes carriers outperformed the other carriers, with 98% removal of organic carbon and 99.6% removal of BOD5 . The Kaldnes train final effluent concentrations were only 22 mg FOC/L and 7 mg BOD5/L . Based on the successful pilot testing, the full-scale plant was upgraded with Kaldnes Moving Bed roughing filters . During normal operation the upgraded plant has easily met the discharge limits of 100 mg COD/L and 50 mg SS/L . For the month of September 2002, with organic loads between 100 and 115% of the design load for the second half of the month, average effluent concentrations were as low as 9 mg FOC/L, 51 mg COD/L and 12 mg SS/L. Water Sci Technol, 2004, 49(11-12), 193 - 8 Two-dimensional cellular automaton model for mixed-culture biofilm; Pizarro GE et al.; Structural and microbial heterogeneity occurs in almost any type of biofilm system . General approaches for the design of biofilm systems consider biofilms as homogeneous and of constant thickness . In order to improve the design of biofilms systems, models need to incorporate structural heterogeneity and the effect of inert microbial mass . We have improved a 2D biofilm model based on cellular automata (CA) and used it to simulate multidimensional biofilms with active and inert biomass including a self-organizing development . Results indicate that the presence of inert biomass within biofilm structures does not change considerably the substrate flux into the biofilm because the active biomass is located at the surface of the biofilm . Long-term simulations revealed that although the biofilm system is highly heterogeneous and the microstructure is continuously changing, the biofilm reaches a dynamic steady-state with prediction of biofilm thickness and substrate flux stabilizing on a delimited range. Water Sci Technol, 2004, 49(11-12), 187 - 92 A new mathematical model for chemotactic bacterial colony growth; Alpkvist E et al.; A new continuum model for the growth of a single species biofilm is proposed . The geometry of the biofilm is described by the interface between the biomass and the surrounding liquid . Nutrient transport is given by the solution of a semi-linear Poisson equation . In this model we study the morphology of a chemotactic bacterial colony, which grows in the direction of increasing nutrient concentration . Numerical simulations using the level set method and finite difference schemes are presented . The results show rich heterogeneous morphology. Water Sci Technol, 2004, 49(11-12), 169 - 76 Results from the multi-species benchmark problem 3 (BM3) using two-dimensional models; Noguera DR et al.; In addition to the one-dimensional solutions of a multi-species benchmark problem (BM3) presented earlier (Rittmann et al., 2004), we offer solutions using two-dimensional (2-D) models . Both 2-D models (called here DN and CP) used numerical solutions to BM3 based on a similar mathematical framework of the one-dimensional AQUASIM-built models submitted by Wanner (model W) and Morgenroth (model M1), described in detail elsewhere (Rittmann et al., 2004) . The CP model used differential equations to simulate substrate gradients and biomass growth and a particle-based approach to describe biomass division and biofilm growth . The DN model simulated substrate and biomass using a cellular automaton approach . For several conditions stipulated in BM3, the multidimensional models provided very similar results to the 1-D models in terms of bulk substrate concentrations and fluxes into the biofilm . The similarity can be attributed to the definition of BM3, which restricted the problem to a flat biofilm in contact with a completely mixed liquid phase, and therefore, without any salient characteristics to be captured in a multidimensional domain . On the other hand, the models predicted significantly different accumulations of the different types of biomass, likely reflecting differences in the way biomass spread within the biofilm is simulated. Water Sci Technol, 2004, 49(11-12), 155 - 62 Modelling a spatially heterogeneous biofilm and the bulk fluid: selected results from benchmark problem 2 (BM2); Eberl HJ et al.; The numerical simulation of mass transfer and conversion in spatially heterogeneous biofilms on the meso-scale requires an accurate description of the hydrodynamics in the biofilm systems and of spatial effects . This leads to systems of three-dimensional nonlinear partial differential equations that are numerically very expensive to solve and to data requirements that are not easy to meet . In this paper several modeling approaches to reduce the physical complexity and, hence, accelerate the computation are compared . They range from a mere reduction of dimensionality by lumping the problem along a secondary flow direction to global mass balances or empirical correlations, at the core of which a one-dimensional boundary value problem must be solved . It is found that even strongly simplified models can describe the qualitative behaviour of the model with regard to variations in the geometrical and hydrodynamic model parameters quite well . In order to obtain also quantitatively reliable results the hydrodynamics must be considered in an appropriate manner. Water Sci Technol, 2004, 49(11-12), 145 - 54 Comparing biofilm models for a single species biofilm system; Morgenroth E et al.; A benchmark problem was defined to evaluate the performance of different mathematical biofilm models . The biofilm consisted of heterotrophic bacteria degrading organic substrate and oxygen . Mathematical models tested ranged from simple analytical to multidimensional numerical models . For simple and more or less flat biofilms it was shown that analytical biofilm models provide very similar results compared to more complex numerical solutions . When considering a heterogeneous biofilm morphology it was shown that the effect of an increased external mass transfer resistance was much more significant compared to the effect of an increased surface area inside the biofilm. Water Sci Technol, 2004, 49(11-12), 137 - 44 Biofilm modeling with AQUASIM; Wanner O et al.; AQUASIM is a computer program for the identification and simulation of aquatic systems . The program includes a one-dimensional multisubstrate and multispecies biofilm model and represents a suitable tool for biofilm simulation . The program can be used to calculate substrate removal in biofilm reactors for any user specified microbial system . One-dimensional spatial profiles of substrates and microbial species in the biofilm can be predicted . The program also calculates the development of the biofilm thickness and of the substrates and microbial species in the biofilm and in the bulk fluid over time . Detachment and attachment of microbial cells at the biofilm surface and in the biofilm interior can be considered, and simulations of sloughing events can be performed . Furthermore, AQUASIM allows pseudo two-dimensional modeling of plug flow biofilm reactors by a series of biofilm reactor compartments . The most significant limitation of the model is that it only considers spatial gradients of substrates and microbial species in the biofilm in the direction perpendicular to the substratum. Water Sci Technol, 2004, 49(11-12), 131 - 6 Introduction to the IWA task group on biofilm modeling; Noguera DR et al.; An International Water Association (IWA) Task Group on Biofilm Modeling was created with the purpose of comparatively evaluating different biofilm modeling approaches . The task group developed three benchmark problems for this comparison, and used a diversity of modeling techniques that included analytical, pseudo-analytical, and numerical solutions to the biofilm problems . Models in one, two, and three dimensional domains were also compared . The first benchmark problem (BM1) described a monospecies biofilm growing in a completely mixed reactor environment and had the purpose of comparing the ability of the models to predict substrate fluxes and concentrations for a biofilm system of fixed total biomass and fixed biomass density . The second problem (BM2) represented a situation in which substrate mass transport by convection was influenced by the hydrodynamic conditions of the liquid in contact with the biofilm . The third problem (BM3) was designed to compare the ability of the models to simulate multispecies and multisubstrate biofilms . These three benchmark problems allowed identification of the specific advantages and disadvantages of each modeling approach . A detailed presentation of the comparative analyses for each problem is provided elsewhere in these proceedings. Water Sci Technol, 2004, 49(11-12), 53 - 60 Difficulties in maintaining long-term partial nitritation of ammonium-rich sludge digester liquids in a moving-bed biofilm reactor (MBBR); Fux C et al.; Nitrogen can be eliminated effectively from sludge digester effluents by anaerobic ammonium oxidation (anammox), but 55-60% of the ammonium must first be oxidized to nitrite . Although a continuous flow stirred tank reactor (CSTR) with suspended biomass could be used, its hydraulic dilution rate is limited to 0.8-1 d(-1) (30 degrees C) . Higher specific nitrite production rates can be achieved by sludge retention, as shown here for a moving-bed biofilm reactor (MBBR) with Kaldnes carriers on laboratory and pilot scales . The maximum nitrite production rate amounted to 2.7 gNO2-Nm(-2)d(-1) (3 gO2m(-3)d(-1), 30.5 degrees C), thus doubling the dilution rate compared to CSTR operation with suspended biomass for a supernatant with 700 gNH4-Nm(-3) . Whenever the available alkalinity was fully consumed, an optimal amount of nitrite was produced . However, a significant amount of nitrate was produced after 11 months of operation, making the effluent unsuitable for anaerobic ammonium oxidation . Because the sludge retention time (SRT) is relatively long in biofilm systems, slow growth of nitrite oxidizers occurs . None of the selection criteria applied - a high ammonium loading rate, high free ammonia or low oxygen concentration - led to selective suppression of nitrite oxidation . A CSTR or SBR with suspended biomass is consequently recommended for full-scale operation. Water Sci Technol, 2004, 49(11-12), 19 - 25 The effect of intermittent feeding on aerobic granule structure; McSwain BS et al.; Self-immobilized biofilms, or aerobic granules without the addition of carrier material, have only been reported in one suspended growth system, the Sequencing Batch Reactor (SBR) with a very short fill time (dump fill) . The SBR utilizes intermittent feeding which creates a period of high load followed by starvation (often referred to as feast-famine) . In this experiment, three identical SBRs were operated with different feeding conditions to determine the role of feast-famine on granule formation . All three SBRs were operated with a total volumetric load of 2.4 kg/m3 x d . The 90 minute Fill phase was altered for each reactor, providing an increasing time of Aerated Fill . A dump fill condition was applied for one reactor, while the other two reactors were aerated for different times during Fill, resulting in a smaller COD load at the beginning of each React phase . Aerobic granules formed in all reactors, but the structural properties and content of filamentous organisms were clearly dependent on a high feast condition . Only the reactor with dump fill formed compact, stable granules . It is concluded that intermittent feeding associated with the SBR affects the selection and growth of filamentous organisms and has a critical role in granule structure and composition. Eukaryot Cell, 2004 Aug, 3(4), 1062 - 5 The two-component signal transduction protein Chk1p regulates quorum sensing in Candida albicans; Kruppa M et al.; Regulation of hyphal morphogenesis in Candida albicans can occur through quorum sensing (QS) . A QS signal, farnesol, is produced during high-density growth and inhibits morphogenesis . However, the signal transduction pathway that regulates QS is unknown . Here, we show that a C . albicans mutant lacking Chk1p but not either the Sln1p or the Nik1p histidine kinase is refractory to the inhibitory effect of farnesol both in cell suspension and during the formation of a biofilm . This study is the first to demonstrate a role for a two-component signal transduction protein in QS by a eukaryotic organism. J Clin Microbiol, 2004 Aug, 42(8), 3827 - 30 Real-time TaqMan PCR for quantifying oral bacteria during biofilm formation; Suzuki N et al.; A TaqMan PCR was developed for quantifying early colonizer microorganisms in dental biofilms . To design species-specific primers and TaqMan probes, genomic subtractive hybridization was used . This quantitative assay in combination with subtractive hybridization may be of value in the study of microbial ecosystems consisting of related species that are involved in the formation and etiology of biofilms. Biotechnol Prog, 2004 Jul-Aug, 20(4), 1082 - 90 Characteristics of a methanotrophic culture in a membrane-aerated biofilm reactor; Rishell S et al.; The membrane-aerated biofilm reactor (MABR) shows considerable potential as a bioprocess that can exploit methanotrophic biodegradation and offers several advantages over both conventional biofilm reactors and suspended-cell processes . This work seeks primarily to investigate the oxidation efficiency in a methanotrophic MABR . A mixed methanotrophic biofilm was immobilized on an oxygen-permeable silicone membrane in a single tube hollow fiber configuration . Under the conditions used the maximum oxygen uptake rate reached values of 16 g/m2.d, and the rate of biofilm growth achieved was 300 microm/d . Both indicators reflect a very high metabolic rate . It was shown that the biofilm was predominantly in a dual-substrate limitation regime but below about 250 microm was fully penetrated by both substrates . Oxygen limitation was not observed . Analysis indicated that microbial activity stratification was evident and the location of stratified layers of oxygen-consuming components of the consortium could be manipulated via the intramembrane oxygen pressure . The results confirm that an MABR can be employed to minimize substrate diffusion limitations in thick biofilms. Commun Agric Appl Biol Sci, 2003, 68(2 Pt A), 147 - 50 Engineering the interaction between micro-organisms and construction materials; De Windt W et al.; The influence of micro-organisms on degradation of mineral materials, cement bound systems, wood and steel is a rather new subject of research slowly becoming recognised by the 'classical' technical disciplines . An increasing amount of literature appears on biodeterioration of construction materials and microbial activity can not be neglected as a determining factor in the deterioration process . Microbial communities interact in many different ways with mineral materials and their external environment . They can be present on the surface or in crevices and fissures within the material and often their actions become organized in a biofilm . The interaction with the material and its environment can give rise to biodeterioration . Yet recent findings show that in some cases the microbial interaction can lead to protection of materials . It is our mission for the future to engineer the microbiological processes with positive impact on construction materials with a view to practical applications. J Infect Dis, 2004 Sep 1, 190(5), 957 - 66 Epub 2004 Jul 26. Production of exopolysaccharide by Burkholderia cenocepacia results in altered cell-surface interactions and altered bacterial clearance in mice; Conway BA et al.; Despite the characterization of some Burkholderia cepacia complex exopolysaccharides (EPSs), little is known about the role of EPSs in the pathogenicity of B . cepacia complex organisms . We describe 2 Burkholderia cenocepacia (genomovar III) isolates obtained from a patient with cystic fibrosis (CF): the nonmucoid isolate C8963 and the mucoid isolate C9343 . Both isolates had identical random amplified polymorphic DNA patterns . C9