Plasmid mediated Chromium resistance of bacteria

Abstract

Plasmid-mediated Cr(VI) resistant bacteria are naturally found in environments contaminated with chromium releasing industrial effluents. These envirnments may contain microorganisms those have genetically regulated mechanisms to overcome elevated Cr(VI) levels. Such mechanisms could be regulated by genes found either in chromosomal DNA or plasmid DNA. In order to understand the exact mechanism and for the possible use of such mechanisms in monitoring and control of heavy metal pollution, it is important to determine whether the resistance is plasmid borne or controlled by chromosomal DNA. There are certain plasmids which contain genes to resist highly toxic hexavalent chromium (chromates and dichromates). Resistance to chromate is determined by decreased chromate transport by the resistant cells. The genes for a hydrophobic polypeptide, ChrA, have been identified in Cr(VI) resistance plasmids of Pseudomonas aeruginosa and Alcaligenes eutrophus.