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Point Mutations in Transmembrane Helices 2 and 3 of ExbB and TolQ Affect Their Activities in Escherichia coli K-12. Volkmar Braun, 2004.Replacement of glutamate 176, the only charged amino acid in the third transmembrane helix of ExbB, with alanine (E176A) abolished ExbB activity in all determined ExbB-dependent functions of Escherichia coli . Combination of the mutations T148A in the second transmembrane helix and T181A in the third transmembrane helix, proposed to form part of a proton pathway through ExbB, also resulted in inactive ExbB . E176 and T148 are strictly conserved in ExbB and TolQ proteins, and T181 is almost strictly conserved in ExbB, TolQ, and MotA . In Vitro Antimicrobial Susceptibilities of Streptococcus pneumoniae Clinical Isolates Obtained in Canada in 2002. Jeff Powis, 2004.Empirical treatment is best guided by current surveillance of local resistance patterns . The goal of this study is to characterize the prevalence of antimicrobial nonsusceptibility within pneumococcal isolates from Canada . The Canadian Bacterial Surveillance Network is comprised of laboratories from across Canada . Laboratories collected a defined number of consecutive clinical and all sterile site isolates of S . pneumoniae in 2002 . In vitro susceptibility testing was performed by broth microdilution with NCCLS guidelines . Rates of nonsusceptibility were compared to previously published reports from the same network . A total of 2,539 isolates were tested . Penicillin nonsusceptibility increased to 15% (8.5% intermediate, 6.5% resistant) compared to 12.4% in 2000 (P  0.025,
 2) . Only 32 (1.3%) isolates had an amoxicillin MIC of
 4 µg/ml and only 2 of 32 cerebrospinal fluid isolates had an intermediate susceptibility to ceftriaxone by meningeal interpretive criteria (MIC = 1 µg/ml) . A total of 354 (13.9%) isolates were macrolide nonsusceptible (46.3% MLSB, 56.7% M phenotype), increasing from 11.4% in 2000 (P
0.0075,
2) . Only 13 (<1%) isolates had a telithromycin MIC of >1 µg/ml . Ciprofloxacin nonsusceptibility (defined as an MIC of
4 µg/ml) increased to 2.7% compared to 1.4% in 2000 (P
0.0025,
2) and was primarily found in persons
18 years old (98.5%) . Nonsusceptibility to penicillin, macrolides, and fluoroquinolones is increasing in Canada . Nonsusceptibility to amoxicillin and ceftriaxone remains uncommon . Newer antimicrobials such as telithromycin and respiratory fluoroquinolones have excellent in vitro activity .
Geomicrobiology of High-Level Nuclear Waste-Contaminated Vadose Sediments at the Hanford Site, Washington State. James K. Fredrickson, 2004.Sediments from a high-level nuclear waste plume were collected as part of investigations to evaluate the potential fate and migration of contaminants in the subsurface . The plume originated from a leak that occurred in 1962 from a waste tank consisting of high concentrations of alkali, nitrate, aluminate, Cr(VI), 137Cs, and 99Tc . Investigations were initiated to determine the distribution of viable microorganisms in the vadose sediment samples, probe the phylogeny of cultivated and uncultivated members, and evaluate the ability of the cultivated organisms to survive acute doses of ionizing radiation . The populations of viable aerobic heterotrophic bacteria were generally low, from below detection to  104 CFU g–1, but viable microorganisms were recovered from 11 of 16 samples, including several of the most radioactive ones (e.g., >10 µCi of 137Cs/g) . The isolates from the contaminated sediments and clone libraries from sediment DNA extracts were dominated by members related to known gram-positive bacteria . Gram-positive bacteria most closely related to Arthrobacter species were the most common isolates among all samples, but other phyla high in G+C content were also represented, including Rhodococcus and Nocardia . Two isolates from the second-most radioactive sample (>20 µCi of 137Cs g–1) were closely related to Deinococcus radiodurans and were able to survive acute doses of ionizing radiation approaching 20 kGy . Many of the gram-positive isolates were resistant to lower levels of gamma radiation . These results demonstrate that gram-positive bacteria, predominantly from phyla high in G+C content, are indigenous to Hanford vadose sediments and that some are effective at surviving the extreme physical and chemical stress associated with radioactive waste .
Substrate Preferences in Biodesulfurization of Diesel Range Fuels by Rhodococcus sp . Strain ECRD-1. Roger C. Prince, 2003.The range of sulfur compounds in fuel oil and the substrate range and preference of the biocatalytic system determine the maximum extent to which sulfur can be removed by biodesulfurization . We show that the biodesulfurization apparatus in Rhodococcus sp . strain ECRD-1 is able to attack all isomers of dibenzothiophene including those with at least four pendant carbons, with a slight preference for those substituted in the  -position . With somewhat less avidity, this apparatus is also able to attack substituted benzothiophenes with between two and seven pendant carbons . Some compounds containing sulfidic sulfur are also susceptible to desulfurization, although we have not yet been able to determine their molecular identities .
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