Arsenic, boron and salt resistant Bacillus safensis MS11 isolated from Mongolia desert soil

Abstract

Arsenic (As) is a toxic metalloid, having both properties of a metal and a non-metal. Boron (B) is a nonmetal, essential micronutrient for plants growth and development but its excess can be toxic to plants with various levels. In this study arsenic, boron and salt resistant bacteria were isolated from desert soil, Mongolia. The bacterial screening was carried out by serial dilution method. One hundred colonies were screened initially using of (2 mM) arsenic and (2 mM) boron containing LB agar medium. From this population, 10 bacterial isolates were selected based on arsenic and boron resistance, boron accumulation, salt tolerance and arsenic oxidizing capability. One of the potent strain, MS 11 from Mongolia desert soil, was tentatively identified as Bacillus sp. The phylogenetic and comparative analysis of 16S rRNA gene sequence with closely related validly published species available in the database showed that the isolate MS11 was closely related to Bacillus safensis FO-036b(T) with the highest sequence similarity (99.439%). The 16S rRNA gene sequence of the strain MS11 was submitted in the NCBI database with the accession number JF836885. B. safensis MS11 exhibited high level of resistance to arsenite (40 mM), arsenate (400 mM), boron (200 mM) and 15% salt tolerance in LB agar medium. B. safensis MS11 was also associated with resistance to multiple heavy metals such as Cd, Cr, Cu, Ni, Pb and Zn. Hence, this bacterium could be useful in the remediation of salt affected soils and biogeochemical cycles of arsenic pollution.

Key words: Desert soil, toxic metals, Bacillus, salt tolerant, bioremediation.