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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of mercury resistance mechanisms in marine sediment microbial communities (1999)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 30 (1999), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: While estuarine sediments are often severely polluted with mercury, few studies have focused on the mechanisms of adaptation to mercury contamination in marine sediment microbial communities. In this study, we report a high frequency of Gram-negative bacterial isolates that are resistant to the heavy metal mercury obtained from the aerobic culturable marine microbial community. We detected a low frequency of genes homologous to mer(Tn21) in isolates from three out of four different estuarine environments. Other mercury resistant culturable bacterial isolates lacking homology to the known mer genes were able to reduce Hg(II) to its volatile Hg(0) form, indicating the presence of divergent mer genes. In addition, a number of mercury resistant isolates, obtained from three of the four marine sites investigated, exhibited decreased resistance to mercury in the presence of the protonophore carbonyl cyanide m-chlorophenylhydrazone. Representative mercury resistant bacterial isolates were identified by phylogenetic analysis as belonging to the α and γ subclasses of the class Proteobacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1999.tb00655.x
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  • 2
    Electronic Resource
    Electronic Resource
    Plasmid transfer to indigenous marine bacterial populations by natural transformation (1994)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 15 (1994), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Horizontal gene transfer among microbial populations has been assumed to occur in the environment, yet direct observations of this phenomenon are rare or limited to observations where the mechanism(s) could not be explicitly determined. Here we demonstrate the transfer of exogenous plasmid DNA to members of indigenous marine bacterial populations by natural transformation, the first report of this process for any natural microbial community. Ten percent of marine bacterial isolates examined were transformed by plasmid DNA while 14% were transformed by chromosomal DNA. Transformation of mixed marine microbial assemblages was observed in 5 of 14 experiments. In every case, acquisition of the plasmid by members of the indigenous flora was accompanied by modification (probably from genetic rearrangement or methylation) that altered its restriction enzyme digestion pattern. Estimation of transformation rates in estuarine environments based upon the distribution of competency and transformation frequencies in isolates and mixed populations ranged from 5 × 10−4 to 1.5 transformants/1 day. Extrapolation of these rates to ecosystem scales suggests that natural transformation may be an important mechanism for plasmid transfer among marine bacterial communities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.1994.tb00237.x
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    Paper (German National Licenses)
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