Vestigialization of arsenic resistance phenotypes/genotypes in Chromobacterium violaceum strains thriving in pristine Brazilian sites. (October 2013)

• Record Type: Journal Article
• Authors: Silva-Rocha, Rafael; de Azevedo, Juliana Simão Nina; Carepo, Marta S. P.; Lopes de Souza, Ricardo; Silva, Artur; de Lorenzo, Víctor; Schneider, Maria Paula Cruz
• Is Part Of: Biocatalysis and biotransformation. Volume 31:Number 5(2013)
• Page Start: 281
• Page End: 291
• Publication Date: 2013-10
• Subjects: Enzymes -- Biotechnology -- Periodicals; Enzymes -- Industrial applications -- Periodicals; Biotransformation (Metabolism) -- Periodicals; 660.63
• DOI: 10.3109/10242422.2013.843170
• Languages: English
• ISSNs: 1024-2422

Abstract

<abstract> <title>Abstract</title> <p>The performance of the arsenic resistance <italic>arsRCB</italic> operon of the ubiquitous bacterium <italic>Chromobacterium violaceum</italic> has been employed as a descriptor of the genomic persistence of traits for long-ceased environmental conditions. To this end, a reliable reference for arsenic resistance/sensitivity was created in the <italic>C. violaceum</italic> ATCC 12472-type strain by deleting its genomic <italic>ars</italic> operon. This allowed tracing all of the arsenic resistance of this bacterium to the <italic>ars</italic> gene cluster. A sample of 15 environmental <italic>C. violaceum</italic> strains isolated from pristine Amazonian sites (both rain forest and savannah) were then examined for the presence of <italic>arsRCB</italic> amplicons, for arsenic resistance, and for indications of decay of <italic>ars</italic> genes into pseudogenes. While the sites of origin of such strains have no record of industrial or geological exposure to arsenic, all of them bore the standard <italic>arsRCB</italic> cluster in their genome, but they did differ in their resistance to the metalloid. This ranged from complete sensitivity to tolerance levels above the reference <italic>C. violaceum</italic> ATCC12472. Inspection of relevant DNA sequences, phenotypic analyses and monitoring expression profiles of the <italic>ars</italic> genes in each strain exposed a distinct genetic drift of the system toward vestigialization, that is, accumulation of mutations leading to the loss of a non-used character. In particular, quantitative PCR revealed inducibility by arsenic to be the first trait to be lost in the route toward decaying and eventual nonfunctionalization. The data presented fit evolutionary predictions on elimination of non-used characters through a mere genetic drift accumulating neutral mutations.</p> </abstract>