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Rv2686c-Rv2687c-Rv2688c, an ABC Fluoroquinolone Efflux Pump in Mycobacterium tuberculosis. Maria Rosalia Pasca, 2004.The Mycobacterium tuberculosis Rv2686c-Rv2687c-Rv2688c operon, encoding an ABC transporter, conferred resistance to ciprofloxacin and, to a lesser extent, norfloxacin, moxifloxacin, and sparfloxacin to Mycobacterium smegmatis . The resistance level decreased in the presence of the efflux pump inhibitors reserpine, carbonyl cyanide m-chlorophenylhydrazone, and verapamil . Energy-dependent efflux of ciprofloxacin from M . smegmatis cells containing the Rv2686c-Rv2687c-Rv2688c operon was observed . Effect of Dilution Rate on Metabolic Pathway Shift between Aceticlastic and Nonaceticlastic Methanogenesis in Chemostat Cultivation. Toru Shigematsu, 2004.Acetate conversion pathways of methanogenic consortia in acetate-fed chemostats at dilution rates of 0.025 and 0.6 day–1 were investigated by using 13C-labeled acetates, followed by gas chromatography-mass spectrometry (GC-MS) analysis of the CH4 and CO2 produced . Nonaceticlastic syntrophic oxidation by acetate-oxidizing syntrophs and hydrogenotrophic methanogens was suggested to occupy a primary pathway (approximately 62 to 90%) in total methanogenesis at the low dilution rate . In contrast, aceticlastic cleavage of acetate by aceticlastic methanogens was suggested to occupy a primary pathway (approximately 95 to 99%) in total methanogenesis at the high dilution rate . Phylogenetic analyses of transcripts of the methyl coenzyme M reductase gene (mcrA) confirmed that a significant number of transcripts of the genera Methanoculleus (hydrogenotrophic methanogens) and Methanosarcina (aceticlastic methanogens) were present in the chemostats at the low and high dilution rates, respectively . The mcrA transcripts of the genus Methanosaeta (aceticlastic methanogens), which dominated the population in a previous study (T . Shigematsu, Y . Tang, H . Kawaguchi, K . Ninomiya, J . Kijima, T . Kobayashi, S . Morimura, and K . Kida, J . Biosci . Bioeng . 96:547-558, 2003), were poorly detected at both dilution rates due to the limited coverage of the primers used . These results demonstrated that the dilution rate could cause a shift in the primary pathway of acetate conversion to methane in acetate-fed chemostats . Characterization of LytH, a Differentiation-Associated Peptidoglycan Hydrolase of Bacillus subtilis Involved in Endospore Cortex Maturation. Gavin J. Horsburgh, 2003.The cortex peptidoglycan from endospores of Bacillus subtilis is responsible for the maintenance of dormancy . LytH (YunA) has been identified as a novel sporulation-specific component with a role in cortex structure determination . The lytH gene was expressed only during sporulation, under the control of the mother cell-specific sigma factor  K . Spores of a lytH mutant have slightly reduced heat resistance and altered staining when viewed by electron microscopy . Analysis of the peptidoglycan structure of lytH mutant spores shows the loss of muramic acid residues substituted with L-alanine and a corresponding increase in muramic acid residues substituted with tetrapeptide compared to those in the parent strain . In a lytH cwlD mutant, the lack of muramic acid residues substituted with L-alanine and
 -lactam leaves 97% of residues substituted with tetrapeptide . These results suggest that lytH encodes an L-Ala-D-Glu peptidase involved in production of single L-alanine side chains from tetrapeptides in the spore cortex . The lack of di- or tripeptides in a lytH mutant reveals the enzyme is an endopeptidase .
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