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Gayana (Concepción)

On-line version ISSN 0717-6538

Abstract

MELLADO, Carolina; CAMPOS, Víctor  and  MONDACA, María A. Distribution of arsenic-resistant genes in bacteria from sediments with different concentrations of arsenic. Gayana (Concepc.) [online]. 2011, vol.75, n.2, pp.131-137. ISSN 0717-6538.  http://dx.doi.org/10.4067/S0717-65382011000200001.

Arsenic is a toxic element, widely distributed in terrestrial and aquatic environments. Microbial biotransformation processes play a key role in the biogeochemical cycle of arsenic and can be involved in the mobility, distribution and bioavailability of the arsenic species in the environment. The objective of this study was to relate the presence of the arsCBA genes of arsenate-reducing bacteria isolated from sediments coming from different sectors of the Camarones River (Arica y Parinacota region, Chile) showing different arsenic concentrations. We isolated 34 arsenate-resistant bacteria for which tolerance levels to As (III) and As (V) were determined as the arsenate reducing activity by semi-quantitative technique with AgNO3 and the presence of the ars genes, by PCR. All strains were tolerant to As (III) and As (V) and showed the arsC gene, which is capable of reducing As (V) to As (III). The arsB gene was detected in 86% of the strains present in the sediments with higher concentrations of arsenic (Illapata sector) while and the the arsA gene was detected in 71%. The strains isolated from sediments with lower arsenic concentrations showed the presence of the arsB and arsA genes in the 80% and 40% of isolates from the "Esquiña" sector and in 50% and 25% of isolates from the "Desembocadura" sector. According to this, we can conclude that detection frequency of ars genes of the strains under study increase in those river sections having higher arsenic concentrations, but the resistance to arsenic does not increase concomitantly.

Keywords : arsenate; arsenate-reducing bacteria; arsCBA genes.

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