Arsenic tolerance in bacterial cultures isolated from metal contaminated soil

Abstract

Several centuries of uninterrupted mining activities in Zacatecas, Mexico becomes a problem of soil pollution with toxic metals and metalloids as the arsenic. In this study, the arsenic-tolerance of ten bacterial isolates from a metal contaminated site were analyzed and high tolerance was observed in both solid (40 - 300 mM of sodium arseniate and 4 - 25 mM of sodium arsenite) and liquid media (7.2 and 11.3 mM arsenite). The arsenic tolerant isolates were identified by biochemical and 16S rRNA-encoding gene amplification analysis as members of the Bacillus, Micrococcus and Acinetobacter genus. A study of resistance to antibiotics revealed a high prevalence of resistance to beta-lactams and moderate prevalence to nitrofurantoin, vancomycin and ceftriaxone suggesting that antibiotic multiresistance of this isolates is probably related to arsenic tolerance throughout a plasmid or chromosomally encoded resistance mechanism.