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Lack of Association between Hypermutation and Antibiotic Resistance Development in Pseudomonas aeruginosa Isolates from Intensive Care Unit Patients. Olivia Gutiérrez, 2004.Hypermutation is a common feature of Pseudomonas aeruginosa isolates from chronically infected cystic fibrosis patients that is linked with antibiotic resistance development . In this work, using a large collection of sequential P . aeruginosa isolates from ICU patients, we found that despite the fact that mutational antibiotic resistance development is a frequent outcome, the prevalence of hypermutable strains is low (found in isolates from only 1 of 103 patients) and there is no evidence of coselection of the hypermutable and antibiotic resistance phenotypes . Inactivation of Caliciviruses. Erwin Duizer, 2004.The viruses most commonly associated with food- and waterborne outbreaks of gastroenteritis are the noroviruses . The lack of a culture method for noroviruses warrants the use of cultivable model viruses to gain more insight on their transmission routes and inactivation methods . We studied the inactivation of the reported enteric canine calicivirus no . 48 (CaCV) and the respiratory feline calicivirus F9 (FeCV) and correlated inactivation to reduction in PCR units of FeCV, CaCV, and a norovirus . Inactivation of suspended viruses was temperature and time dependent in the range from 0 to 100°C . UV-B radiation from 0 to 150 mJ/cm2 caused dose-dependent inactivation, with a 3 D (D = 1 log10) reduction in infectivity at 34 mJ/cm2 for both viruses . Inactivation by 70% ethanol was inefficient, with only 3 D reduction after 30 min . Sodium hypochlorite solutions were only effective at >300 ppm . FeCV showed a higher stability at pH <3 and pH >7 than CaCV . For all treatments, detection of viral RNA underestimated the reduction in viral infectivity . Norovirus was never more sensitive than the animal caliciviruses and profoundly more resistant to low and high pH . Overall, both animal viruses showed similar inactivation profiles when exposed to heat or UV-B radiation or when incubated in ethanol or hypochlorite . The low stability of CaCV at low pH suggests that this is not a typical enteric (calici-) virus . The incomplete inactivation by ethanol and the high hypochlorite concentration needed for sufficient virus inactivation point to a concern for decontamination of fomites and surfaces contaminated with noroviruses and virus-safe water . RsmA and the Quorum-Sensing Signal, N-[3-Oxohexanoyl]- L-Homoserine Lactone, Control the Levels of rsmB RNA in Erwinia carotovora subsp . carotovora by Affecting Its Stability. Asita Chatterjee, 2002.RsmA (for regulator of secondary metabolism), RsmC, and rsmB RNA, the components of a posttranscriptional regulatory system, control extracellular protein production and pathogenicity in Erwinia carotovora subsp . carotovora. RsmA, an RNA binding protein, acts as a negative regulator by promoting message decay . rsmB RNA, on the other hand, acts as a positive regulator by neutralizing the effect of RsmA . RsmC modulates the levels of RsmA and rsmB RNA by positively regulating rsmA and negatively controlling rsmB. The level of rsmB RNA is substantially higher in RsmA+ bacteria than in RsmA- mutants . We show that rsmB RNA is more stable in the presence of RsmA than in its absence . RsmA does not stimulate the expression of an rsmB-lacZ transcriptional fusion; in fact, the ß-galactosidase level is somewhat higher in RsmA- bacteria than in RsmA+ bacteria . We also investigated the basis for increased levels of rsmA and rsmB RNAs in the absence of the quorum-sensing signal, N-[3-oxohexanoyl]-L-homoserine lactone (OHL) . The absence of OHL activates transcription of rsmA but not of rsmB. Instead, increased stability of rsmB RNA in the presence of RsmA accounts for the elevated levels of the rsmB RNA in OHL- bacteria . Mutant studies disclosed that while RsmA, OHL, and RsmC control the levels of rsmB RNA, high levels of rsmB RNA occur in the absence of RsmC or OHL only in RsmA+ bacteria, indicating a critical role for RsmA in modulating the levels of rsmB RNA . The findings reported here firmly establish that the quorum-sensing signal is channeled in E . carotovora subsp . carotovora via the rsmA-rsmB posttranscriptional regulatory system . The VirB4 Family of Proposed Traffic Nucleoside Triphosphatases: Common Motifs in Plasmid RP4 TrbE Are Essential for Conjugation and Phage Adsorption. Christian Rabel, 2003. Radioisotopic, Culture-Based, and Oligonucleotide Microchip Analyses of Thermophilic Microbial Communities in a Continental High-Temperature Petroleum Reservoir. Elizaveta A. Bonch-Osmolovskaya, 2003.Activity measurements by radioisotopic methods and cultural and molecular approaches were used in parallel to investigate the microbial biodiversity and its physiological potential in formation waters of the Samotlor high-temperature oil reservoir (Western Siberia, Russia) . Sulfate reduction with rates not exceeding 20 nmol of H2S liter-1 day-1 occurred at 60 and 80°C . In upper horizons (AB, A, and B), methanogenesis (lithotrophic and/or acetoclastic) was detected only in wells in which sulfate reduction did not occur . In some of the wells from deeper (J) horizons, high-temperature sulfate reduction and methanogenesis occurred simultaneously, the rate of lithotrophic methanogenesis exceeding 80 nmol of CH4 liter-1 day-1 . Enrichment cultures indicated the presence of diverse physiological groups representing aerobic and anaerobic thermophiles and hyperthermophiles; fermentative organotrophs were predominant . Phylogenetic analyses of 15 isolates identified representatives of the genera Thermotoga, Thermoanaerobacter, Geobacillus, Petrotoga, Thermosipho, and Thermococcus, the latter four being represented by new species . Except for Thermosipho, the isolates were members of genera recovered earlier from similar habitats . DNA obtained from three samples was hybridized with a set of oligonucleotide probes targeting selected microbial groups encompassing key genera of thermophilic bacteria and archaea . Oligonucleotide microchip analyses confirmed the cultural data but also revealed the presence of several groups of microorganisms that escaped cultivation, among them representatives of the Aquificales/Desulfurobacterium-Thermovibrio cluster and of the genera Desulfurococcus and Thermus, up to now unknown in this habitat . The unexpected presence of these organisms suggests that their distribution may be much wider than suspected .
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