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Richness and Diversity of Bacterioplankton Species along an Estuarine Gradient in Moreton Bay, Australia. Ian Hewson, 2004.Bacterioplankton community diversity was investigated in the subtropical Brisbane River-Moreton Bay estuary, Australia (27°25'S, 153°5'E) . Bacterial communities were studied using automated rRNA intergenic spacer analysis (ARISA), which amplifies 16S-23S ribosomal DNA internally transcribed spacer regions from mixed-community DNA and detects the separated products on a fragment analyzer . Samples were collected from eight sites throughout the estuary and east to the East Australian Current (Coral Sea) . Bacterioplankton communities had the highest operational taxonomic unit (OTU) richness, as measured by ARISA at eastern bay stations (S [total richness] = 84 to 85 OTU) and the lowest richness in the Coral Sea (S = 39 to 59 OTU) . Richness correlated positively with bacterial abundance; however, there were no strong correlations between diversity and salinity, NO3– and PO43– concentrations, or chlorophyll a concentration . Bacterioplankton communities at the riverine stations were different from communities in the bay or Coral Sea . The main differences in OTU richness between stations were in taxa that each represented 0.1% (the detection limit) to 0.5% of the total amplified DNA, i.e., the "tail" of the distribution . We found that some bacterioplankton taxa are specific to distinct environments while others have a ubiquitous distribution from river to sea . Bacterioplankton richness and diversity patterns in the estuary are potentially a consequence of greater niche availability, mixing of local and adjacent environment communities, or intermediate disturbance . Furthermore, these results contrast with previous reports of spatially homogeneous bacterioplankton communities in other coastal waters . Adaptive, or Stationary-Phase, Mutagenesis, a Component of Bacterial Differentiation in Bacillus subtilis. Huang-Mo Sung, 2002.Adaptive (stationary-phase) mutagenesis occurs in the gram-positive bacterium Bacillus subtilis . Furthermore, taking advantage of B . subtilis as a paradigm for the study of prokaryotic differentiation and development, we have shown that this type of mutagenesis is subject to regulation involving at least two of the genes that are involved in the regulation of post-exponential phase prokaryotic differentiation, i.e., comA and comK . On the other hand, a functional RecA protein was not required for this type of mutagenesis . The results seem to suggest that a small subpopulation(s) of the culture is involved in adaptive mutagenesis and that this subpopulation(s) is hypermutable . The existence of such a hypermutable subpopulation(s) raises important considerations with respect to evolution, the development of specific mutations, the nature of bacterial populations, and the level of communication among bacteria in an ecological niche . Type 4 Pilus Biogenesis and Type II-Mediated Protein Secretion by Vibrio cholerae Occur Independently of the TonB-Facilitated Proton Motive Force. Niranjan Bose, 2002.In Vibrio cholerae, elaboration of toxin-coregulated pilus and protein secretion by the extracellular protein secretion apparatus occurred in the absence of both TonB systems . In contrast, the cognate putative ATPases were required for each process and could not substitute for each other .
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