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Distribution of Human Immunodeficiency Virus Type 1 Protease and Reverse Transcriptase Mutation Patterns in 4,183 Persons Undergoing Genotypic Resistance Testing. Soo-Yon Rhee, 2004.In a sample of 6,156 sequences from 4,183 persons, the top 30 patterns of protease inhibitor, nucleoside reverse transcriptase (RT) inhibitor, and nonnucleoside RT inhibitor mutations accounted for 55, 46, and 66%, respectively, of sequences with drug resistance mutations . Characterization of the phenotypic and clinical significance of these common patterns may lead to improved treatment recommendations for a large proportion of patients for whom antiretroviral therapy is failing . Virulence Conversion of Legionella pneumophila by Conjugal Transfer of Chromosomal DNA. Hiroshi Miyamoto, 2003.In this study, we examined whether virulence conversion occurs in Legionella pneumophila by conjugal transfer of chromosomal DNA . A virulent strain, K6, which has the genes for Kmr and LacZ+ transposed in the chromosome of strain Philadelphia-1, which belongs to serogroup 1, was used as one parent, and an avirulent strain, Chicago-2S, which is a spontaneous streptomycin-resistant derivative of strain Chicago-2 belonging to serogroup 6, was used as the other parent . Experiments in which K6 (approximately 2.6 x 109 CFU) and Chicago-2S (approximately 8.9 x 109 CFU) were mated typically yielded 103 Kmr Smr LacZ+ transconjugants . Thirty-two (about 2.8%) of 1,152 transconjugants belonging to serogroup 6 acquired the ability to grow intracellularly in Acanthamoeba castellanii and guinea pig macrophages . When guinea pigs were infected with sublethal doses of Legionella aerosols generated from one of these transconjugants (HM1011), they developed a severe pneumonia similar to that caused by donor strain K6 . These results show that avirulent strain Chicago-2S changed into virulent strain HM1011 through conjugation with virulent strain K6 . Furthermore, we showed that Legionella chromosomal virulence genes (icm-dot locus) were horizontally transferred by the conjugation system . The chromosomal conjugation system may play a role(s) in the evolution of L . pneumophila . Hydrophilic Domains of Scaffolding Protein CbpA Promote Glycosyl Hydrolase Activity and Localization of Cellulosomes to the Cell Surface of Clostridium cellulovorans. Akihiko Kosugi, 2004.CbpA, the scaffolding protein of Clostridium cellulovorans cellulosomes, possesses one family 3 cellulose binding domain, nine cohesin domains, and four hydrophilic domains (HLDs) . Among the three types of domains, the function of the HLDs is still unknown . We proposed previously that the HLDs of CbpA play a role in attaching the cellulosome to the cell surface, since they showed some homology to the surface layer homology domains of EngE . Several recombinant proteins with HLDs (rHLDs) and recombinant EngE (rEngE) were examined to determine their binding to the C . cellulovorans cell wall fraction . Tandemly linked rHLDs showed higher affinity for the cell wall than individual rHLDs showed . EngE was shown to have a higher affinity for cell walls than rHLDs have . C . cellulovorans native cellulosomes were found to have higher affinity for cell walls than rHLDs have . When immunoblot analysis was carried out with the native cellulosome fraction bound to cell wall fragments, the presence of EngE was also confirmed, suggesting that the mechanism anchoring CbpA to the C . cellulovorans cell surface was mediated through EngE and that the HLDs play a secondary role in the attachment of the cellulosome to the cell surface . During a study of the role of HLDs on cellulose degradation, the mini-cellulosome complexes with HLDs degraded cellulose more efficiently than complexes without HLDs degraded cellulose . The rHLDs also showed binding affinity for crystalline cellulose and carboxymethyl cellulose . These results suggest that the CbpA HLDs play a major role and a minor role in C . cellulovorans cellulosomes . The primary role increases cellulose degradation activity by binding the cellulosome complex to the cellulose substrate; secondarily, HLDs aid the binding of the CbpA/cellulosome to the C . cellulovorans cell surface . Differences in Hyporheic-Zone Microbial Community Structure along a Heavy-Metal Contamination Gradient. Kevin Feris, 2003.The hyporheic zone of a river is nonphotic, has steep chemical and redox gradients, and has a heterotrophic food web based on the consumption of organic carbon entrained from downwelling surface water or from upwelling groundwater . The microbial communities in the hyporheic zone are an important component of these heterotrophic food webs and perform essential functions in lotic ecosystems . Using a suite of methods (denaturing gradient gel electrophoresis, 16S rRNA phylogeny, phospholipid fatty acid analysis, direct microscopic enumeration, and quantitative PCR), we compared the microbial communities inhabiting the hyporheic zone of six different river sites that encompass a wide range of sediment metal loads resulting from large base-metal mining activity in the region . There was no correlation between sediment metal content and the total hyporheic microbial biomass present within each site . However, microbial community structure showed a significant linear relationship with the sediment metal loads . The abundances of four phylogenetic groups (groups I, II, III, and IV) most closely related to  -, ß-, and
 -proteobacteria and the cyanobacteria, respectively, were determined . The sediment metal content gradient was positively correlated with group III abundance and negatively correlated with group II abundance . No correlation was apparent with regard to group I or IV abundance . This is the first documentation of a relationship between fluvially deposited heavy-metal contamination and hyporheic microbial community structure . The information presented here may be useful in predicting long-term effects of heavy-metal contamination in streams and provides a basis for further studies of metal effects on hyporheic microbial communities .
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