Isolation and characterization of heavy metal resistant bacteria from soil

Abstract

The exploitation of microbes to remove heavy metals from contaminated sites and industrial effluents is an extensive area of research. In this study, isolation of heavy metal resistant bacteria was done from potentially heavy metal contaminated agricultural soil of Bathinda region. The ICAP-AES analysis of soil revealed toxic concentrations of lead and nickel whereas most other heavy metals were also present in considerable amounts. The organisms showing maximum resistance to eight heavy metals tested (Pb, Cu, Ni, Cr, Co, Cd, Fe and As) were screened. The 29 potent metal resistant organisms were subjected to biochemical characterization and 16S rDNA sequencing, and tentatively identified as strains of Bacillus and Streptomyces spp. All the strains showed multiple heavy metal resistance with varied degrees of resistance. A strain of B. megaterium FE1 exhibited maximum resistance to all the heavy metals- Pb (2.5 mg/ml), Cu (1.5 mg/ml), Ni (1.0 mg/ml), Cr (3.0 mg/ml), Co (0.5 mg/ml), Cd (2.5 mg/ml) and As (2.5 mg/ml). The incidence of such extent of heavy metal resistance in native bacteria suggest that agricultural soil is undergoing stress which needs more intensive studies.