Isolation and identification of some chromium resistant bacteria from some contaminated sites

Abstract

Heavy metals have fundamentally effect on the biological system and they are straightforwardly harmful to living creatures, particularly human. Expulsion of these pollutants requires advanced and exorbitant technologies. Along these lines, bioremediation with hefty metal-resistant microorganisms could fillin as a less expensive solution. The aims of this study were to select some chromium resistant bacteria in contaminated sites and to determine the inhibitory concentration values for each species. Selection of the chromium resistant isolates was done using nutrient agar plates containing 100mg/l of (K2Cr2O7), and the values of the inhibitory concentrations were determined by agar diffusion method. Strains that resisted the highest concentrations were diagnosed based on the morphological and molecular methods. Molecular diagnosis was performed based on the analysis of the sequence of nitrogenous bases of 16sr RNA gene as well as the genetic tree relationship. Cr(VI) resistant isolates were chosen from a sum of 40 separates and analyzed as follows: Brevibacillus agri, staphylococcus sp., Bacillus sp., Pseudomonas sp., Exigobacterium sp., and Atlantibacter sp. The MIC values were 2500mg/l for Brevibacillus agri and staphylococcus sp. and 1500mg/l for the remaining species. In this paper, various bacteria strains, resistant to high chromium concentration, were isolated and identified, and these native microorganisms can be utilized for bioremediation of chromium.