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Dynamic Patterns of Subcellular Protein Localization during Spore Coat Morphogenesis in Bacillus subtilis. Christiaan van Ooij, 2004.Endospores of Bacillus subtilis are encased in a thick, proteinaceous shell known as the coat, which is composed of a large number of different proteins . Here we report the identification of three previously uncharacterized coat-associated proteins, YabP, YheD, and YutH, and their patterns of subcellular localization during the process of sporulation, obtained by using fusions of the proteins to the green fluorescent protein (GFP) . YabP-GFP was found to form both a shell and a ring around the center of the forespore across the short axis of the sporangium . YheD-GFP, in contrast, formed two rings around the forespore that were offset from its midpoint, before it eventually redistributed to form a shell around the developing spore . Finally, YutH-GFP initially localized to a focus at one end of the forespore, which then underwent transformation into a ring that was located adjacent to the forespore . Next, the ring became a cap at the mother cell pole of the forespore that eventually spread around the entire developing spore . Thus, each protein exhibited its own distinct pattern of subcellular localization during the course of coat morphogenesis . We concluded that spore coat assembly is a dynamic process involving diverse patterns of protein assembly and localization . Population Pharmacokinetics of Daptomycin. Barry Dvorchik, 2004.Data from subjects in nine phase 1 (n = 153) and six phase 2/3 (n = 129) clinical trials were combined to identify factors contributing to interindividual variability in daptomycin pharmacokinetics (PK) . Over 30 covariates were considered . A two-compartment model with first-order elimination provided the best fit for data on daptomycin concentrations in plasma over time . In the final population PK model, daptomycin plasma clearance (CL) was a function of renal function, body temperature, and sex . Of these factors, renal function contributed most significantly to interindividual variability . CL varied linearly with the estimated creatinine clearance . CL among dialysis subjects was approximately one-third that of healthy subjects (0.27 versus 0.81 liter/h) . CL in females was 80% that in males; however, in clinical trials, the outcome was not affected by sex and therefore this effect is not considered clinically meaningful . The relationship with body temperature should be interpreted cautiously since the analysis included only a limited number of subjects who were hyperthermic . The volume of distribution of the peripheral compartment (V2) and intercompartmental clearance (Q) were linearly related to body weight . V2 increased approximately twofold in the presence of an acute infection . No factors were identified that significantly impacted V1 . This analysis supports the dosing of daptomycin on a milligram-per-kilogram-of-body-weight basis and suggests that modified dosing regimens are indicated for patients with severe renal disease and for those undergoing dialysis . Methylation of Inorganic and Organic Selenium by the Bacterial Thiopurine Methyltransferase. Lionel Ranjard, 2002.Escherichia coli cells expressing the tpm gene encoding the bacterial thiopurine methyltransferase (bTPMT) are shown to methylate selenite and (methyl)selenocysteine into dimethylselenide (DMSe) and dimethyldiselenide (DMDSe) . E . coli cells expressing tpm from a gene library cosmid clone (harboring a Pseudomonas syringae insert of about 20 kb) also methylated selenate into DMSe and DMDSe . bTPMT is the first methyltransferase shown to be involved in the methylation of these selenium derivatives . Cadaverine Inhibition of Porin Plays a Role in Cell Survival at Acidic pH. Hrissi Samartzidou, 2003.When grown at acidic pH, Escherichia coli cells secrete cadaverine, a polyamine known to inhibit porin-mediated outer membrane permeability . In order to understand the physiological significance of cadaverine excretion and the inhibition of porins, we isolated an OmpC mutant that showed resistance to spermine during growth and polyamine-resistant porin-mediated fluxes . Here, we show that the addition of exogenous cadaverine allows wild-type cells to survive a 30-min exposure to pH 3.6 better than cells expressing the cadaverine-insensitive OmpC porin . Competition experiments between strains expressing either wild-type or mutant OmpC showed that the lack of sensitivity of the porin to cadaverine confers a survival disadvantage to the mutant cells at reduced pH . On the basis of these results, we propose that the inhibition of porins by excreted cadaverine represents a novel mechanism that provides bacterial cells with the ability to survive acid stress . Effects of Soil pH on the Biodegradation of Chlorpyrifos and Isolation of a Chlorpyrifos-Degrading Bacterium. Brajesh K. Singh, 2003.We examined the role of microorganisms in the degradation of the organophosphate insecticide chlorpyrifos in soils from the United Kingdom and Australia . The kinetics of degradation in five United Kingdom soils varying in pH from 4.7 to 8.4 suggested that dissipation of chlorpyrifos was mediated by the cometabolic activities of the soil microorganisms . Repeated application of chlorpyrifos to these soils did not result in the development of a microbial population with an enhanced ability to degrade the pesticide . A robust bacterial population that utilized chlorpyrifos as a source of carbon was detected in an Australian soil . The enhanced ability to degrade chlorpyrifos in the Australian soil was successfully transferred to the five United Kingdom soils . Only soils with a pH of  6.7 were able to maintain this degrading ability 90 days after inoculation . Transfer and proliferation of degrading microorganisms from the Australian soil to the United Kingdom soils was monitored by molecular fingerprinting of bacterial 16S rRNA genes by PCR-denaturing gradient gel electrophoresis (DGGE) . Two bands were found to be associated with enhanced degradation of chlorpyrifos . Band 1 had sequence similarity to enterics and their relatives, while band 2 had sequence similarity to strains of Pseudomonas . Liquid enrichment culture using the Australian soil as the source of the inoculum led to the isolation of a chlorpyrifos-degrading bacterium . This strain had a 16S rRNA gene with a sequence identical to that of band 1 in the DGGE profile of the Australian soil . DNA probing indicated that genes similar to known organophosphate-degrading (opd) genes were present in the United Kingdom soils . However, no DNA hybridization signal was detected for the Australian soil or the isolated degrader . This indicates that unrelated genes were present in both the Australian soil and the chlorpyrifos-degrading isolate . These results are consistent with our observations that degradation of chlorpyrifos in these systems was unusual, as it was growth linked and involved complete mineralization . As the 16S rRNA gene of the isolate matched a visible DGGE band from the Australian soil, the isolate is likely to be both prominent and involved in the degradation of chlorpyrifos in this soil .
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