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Enzyme Production-Based Approach for Determining the Functions of Microorganisms within a Community. Kohei Nakamura, 2004.The functions of specific microorganisms in a microbial community were investigated during the composting process . Cerasibacillus quisquiliarum strain BLxT and Bacillus thermoamylovorans strain BTa were isolated and characterized in our previous studies based on their dominance in the composting system . Strain BLxT degrades gelatin, while strain BTa degrades starch . We hypothesized that these strains play roles in gelatinase and amylase production, respectively . The relationship between changes in the abundance ratios of each strain and those of each enzyme activity during the composting process was examined to address this hypothesis . The increase in gelatinase activity in the compost followed a dramatic increase in the abundance ratio of strain BLxT . Zymograph analysis demonstrated that the pattern of active gelatinase bands from strain BLxT was similar to that from the compost . Gelatinases from both BLxT and compost were partially purified and compared . Homologous N-terminal amino acid sequences were found in one of the gelatinases from strain BLxT and that of compost . These results indicate strain BLxT produces gelatinases during the composting process . Meanwhile, the increase in the abundance ratio of strain BTa was not concurrent with that of amylase activity in the compost . Moreover, the amylase activity pattern of strain BTa on the zymogram was different from that of the compost sample . These results imply that strain BTa may not produce amylases during the composting process . To our knowledge, this is the first report demonstrating that the function of a specific microorganism is directly linked to a function in the community, as determined by culture-independent and enzyme-level approaches . Gene Transfer between Salmonella enterica Serovar Typhimurium inside Epithelial Cells. Gayle C. Ferguson, 2002.Virulence and antibiotic resistance genes transfer between bacteria by bacterial conjugation . Conjugation also mediates gene transfer from bacteria to eukaryotic organisms, including yeast and human cells . Predicting when and where genes transfer by conjugation could enhance our understanding of the risks involved in the release of genetically modified organisms, including those being developed for use as vaccines . We report here that Salmonella enterica serovar Typhimurium conjugated inside cultured human cells . The DNA transfer from donor to recipient bacteria was proportional to the probability that the two types of bacteria occupied the same cell, which was dependent on viable and invasive bacteria and on plasmid tra genes . Based on the high frequencies of gene transfer between bacteria inside human cells, we suggest that such gene transfers occur in situ . The implications of gene transfer between bacteria inside human cells, particularly in the context of antibiotic resistance, are discussed .
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