Arsenic tolerance and presence of specificrsistance genes in heterotrophic consortia obtained from Copahue geothermal system

LIMA, A; URBIETA, M. S.; DONATI, E. R.

San Miguel de Tucumán

Congreso; XII Congreso Argentino de Microbiologia General ? SAMIGE 2017; 2017

Asociación Civil de Microbiología General

The major sources of arsenic (As) pollution are related to anthropogenic intervention. This carcinogenic metalloid can be found mainly in two oxidizing states: As(III) and As(V), being the first the most toxic form. Fortunately some microorganisms are able to metabolize arsenic contaminants through several specific enzymes and proteins contributing to remediate polluted sites. The present work describes the influence of As on microbial growth and the presence of a variety of genes related to As metabolism and As resistance in two heterotrophic consortia obtained from a sample collected from Caviahue-Copahue geothermal system (Salto del Agrio) and enriched in LB medium at 30°C supplemented with increasing concentrations of NaAsO2 or Na2HAsO4.7 H2O. The consortia proved to be able to adapt to concentrations up to 20 mM of As(III) (culture called Het(As+3 20 mM)) and 450 mM of As(V) (culture called Het(As+5 450 mM)). The phylogenetic analysis indicated the prevalence of Paenibacillus profundus in both cultures. Control cultures, without As added, were carried out to compare growth profiles ((As+3 0 mM) and (As+5 0 mM)). Growth was measured by OD 600 every 24 hours. After 4 days of incubation, Het(As+5 450 mM) reached their maximum OD600 meanwhile Het(As+5 0 mM) did that after 3 days; Het(As+3 20 mM) reached their maximum OD600 after 8 days instead of 2 days for Het(As+3 0 mM. Due to the lower toxicity of As(V), its influence on growth of Het(As+5 450 mM) was less than As(III) on Het(As+3 20 mM). The growth profiles also showed that the cultures supplemented with As had longer lag phases than the controls without As, although final concentration of cells was similar in both. The screening of As resistance genes was done using 12 primer sets. Interestingly, Het(As+3 20 mM) showed positive amplifications with 6 primers setcorresponding to two types of arrA genes that coded for a respiratory arsenate reductase, the acr3 gen that coded for an arsenite transporter, two types of aioA genes that coded for an arsenite oxidase and the arsC gen that coded for a cytoplasmic arsenate reductase. Curiously, the culture Het(As+5450mM) did not amplify with any of the primers assayed in spite of a great optimization effort. Our study opens the door for the study of many diverse aspects of As tolerant icroorganisms, from the genetic resistant characteristics to the potential use in the remediation of contaminated sites.