A genomic island provides <Emphasis Type="Italic">Acidithiobacillus ferrooxidans</Emphasis> ATCC 53993 additional copper resistance: a possible competitive advantage |
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Authors: | Luis H Orellana Carlos A Jerez |
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Institution: | (1) Laboratory of Molecular Microbiology and Biotechnology, Department of Biology, and Millennium Institute for Cell Dynamics and Biotechnology, Faculty of Sciences, University of Chile, Santiago, Chile; |
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Abstract: | There is great interest in understanding how extremophilic biomining bacteria adapt to exceptionally high copper concentrations
in their environment. Acidithiobacillus ferrooxidans ATCC 53993 genome possesses the same copper resistance determinants as strain ATCC 23270. However, the former strain contains
in its genome a 160-kb genomic island (GI), which is absent in ATCC 23270. This GI contains, amongst other genes, several
genes coding for an additional putative copper ATPase and a Cus system. A. ferrooxidans ATCC 53993 showed a much higher resistance to CuSO4 (>100 mM) than that of strain ATCC 23270 (<25 mM). When a similar number of bacteria from each strain were mixed and allowed
to grow in the absence of copper, their respective final numbers remained approximately equal. However, in the presence of
copper, there was a clear overgrowth of strain ATCC 53993 compared to ATCC 23270. This behavior is most likely explained by
the presence of the additional copper-resistance genes in the GI of strain ATCC 53993. As determined by qRT-PCR, it was demonstrated
that these genes are upregulated when A. ferrooxidans ATCC 53993 is grown in the presence of copper and were shown to be functional when expressed in copper-sensitive Escherichia coli mutants. Thus, the reason for resistance to copper of two strains of the same acidophilic microorganism could be determined
by slight differences in their genomes, which may not only lead to changes in their capacities to adapt to their environment,
but may also help to select the more fit microorganisms for industrial biomining operations. |
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