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Community-Onset Disease Caused by Citrobacter freundii Producing a Novel CTX-M ß-Lactamase, CTX-M-30, in Canada. Baha Abdalhamid, 2004.Strains of Citrobacter freundii intermediate to cefotaxime but sensitive to ceftazidime were isolated from four different patients in Canada . Sequencing of PCR products by use of CTX-M-specific primers revealed a new combination of four amino acid substitutions . This new gene was designated blaCTX-M-30 and was encoded on a 3-kb plasmid . The pI of CTX-M-30 was 8.0 . Characterization of an Autotrophic Nitrogen-Removing Biofilm from a Highly Loaded Lab-Scale Rotating Biological Contactor. Kris Pynaert, 2003.In this study, a lab-scale rotating biological contactor (RBC) treating a synthetic NH4+ wastewater devoid of organic carbon and showing high N losses was examined for several important physiological and microbial characteristics . The RBC biofilm removed 89% ± 5% of the influent N at the highest surface load of approximately 8.3 g of N m-2 day-1, with N2 as the main end product . In batch tests, the RBC biomass showed good aerobic and anoxic ammonium oxidation (147.8 ± 7.6 and 76.5 ± 6.4 mg of NH4+-N g of volatile suspended solids [VSS]-1 day-1, respectively) and almost no nitrite oxidation (< 1 mg of N g of VSS-1 day-1) . The diversity of aerobic ammonia-oxidizing bacteria (AAOB) and planctomycetes in the biofilm was characterized by cloning and sequencing of PCR-amplified partial 16S rRNA genes . Phylogenetic analysis of the clones revealed that the AAOB community was fairly homogeneous and was dominated by Nitrosomonas-like species . Close relatives of the known anaerobic ammonia-oxidizing bacterium (AnAOB) Kuenenia stuttgartiensis dominated the planctomycete community and were most probably responsible for anoxic ammonium oxidation in the RBC . Use of a less specific planctomycete primer set, not amplifying the AnAOB, showed a high diversity among other planctomycetes, with representatives of all known groups present in the biofilm . The spatial organization of the biofilm was characterized using fluorescence in situ hybridization (FISH) with confocal scanning laser microscopy (CSLM) . The latter showed that AAOB occurred side by side with putative AnAOB (cells hybridizing with probe PLA46 and AMX820/KST1275) throughout the biofilm, while other planctomycetes hybridizing with probe PLA886 (not detecting the known AnAOB) were present as very conspicuous spherical structures . This study reveals that long-term operation of a lab-scale RBC on a synthetic NH4+ wastewater devoid of organic carbon yields a stable biofilm in which two bacterial groups, thought to be jointly responsible for the high autotrophic N removal, occur side by side throughout the biofilm . Glycolytic Breakdown of Sulfoquinovose in Bacteria: a Missing Link in the Sulfur Cycle. Alexander B. Roy, 2003.Sulfoquinovose (6-deoxy-6-sulfo-D-glucopyranose), formed by the hydrolysis of the plant sulfolipid, is a major component of the biological sulfur cycle . However, pathways for its catabolism are poorly delineated . We examined the hypothesis that mineralization of sulfoquinovose to inorganic sulfate is initiated by reactions of the glycolytic and/or Entner-Doudoroff pathways in bacteria . Metabolites of [U-13C]sulfoquinovose were identified by 13C-nuclear magnetic resonance (NMR) in strains of Klebsiella and Agrobacterium previously isolated for their ability to utilize sulfoquinovose as a sole source of carbon and energy for growth, and cell extracts were analyzed for enzymes diagnostic for the respective pathways . Klebsiella sp . strain ABR11 grew rapidly on sulfoquinovose, with major accumulations of sulfopropandiol (2,3-dihydroxypropanesulfonate) but no detectable release of sulfate . Later, when sulfoquinovose was exhausted and growth was very slow, sulfopropandiol disappeared and inorganic sulfate and small amounts of sulfolactate (2-hydroxy-3-sulfopropionate) were formed . In Agrobacterium sp . strain ABR2, growth and sulfoquinovose disappearance were again coincident, though slower than that in Klebsiella sp . Release of sulfate was still late but was faster than that in Klebsiella sp., and no metabolites were detected by 13C-NMR . Extracts of both strains grown on sulfoquinovose contained phosphofructokinase activities that remained unchanged when fructose 6-phosphate was replaced in the assay mixture with either glucose 6-phosphate or sulfoquinovose . The results were consistent with the operation of the Embden-Meyerhoff-Parnas (glycolysis) pathway for catabolism of sulfoquinovose . Extracts of Klebsiella but not Agrobacterium also contained an NAD+-dependent sulfoquinovose dehydrogenase activity, indicating that the Entner-Doudoroff pathway might also contribute to catabolism of sulfoquinovose .
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