The role of exopolysaccharides from a chromate reducing Pseudomonas aeruginosa in resistance to hexavalent chromium and antibiotics

Cr (VI) is one of the strongest oxidizing agents and is classified as carcinogen group A which presents in various industrial wastewaters. Exopolysaccharides (EPS) are natural polymers that are secreted from several environmental bacterial groups especially in response to adverse conditions. Therefore, exopolysaccharides from bacterial species of these astewaters may contribute in increasing their resistance to unfavorable factors. Thus the aim of this study was to investigate the role of exopolysaccharides from chromate resistant bacteria in chromate reduction and antibiotic resistance. This research was a laboratory crossectional study that was performed on chromate resistant bacterial species in different kinds of wastewaters. Maximum tolerable concentration (MTC), amount of exopolysaccharides secretion, chromate reduction by EPS and antibiotics resistance of selected isolation were determined. The data were analyzed by determining the standard error and agreed confidence intervals (P<0.05). An effective isolation showed the highest MTC and EPS production: 128 mM and 0.117 mg.ml-1 respectively was identified as Pseudomonas aeruginosa based on biochemical test results. Comparison between chromate reduction efficiency by EPS solely (61%) and chromate reduction efficiency by bacterial cell (78%) indicated considerable role of EPS in chromate reduction. These bacteria also indicated resistance to a wide range of antibiotics. Environmental increasing of Cr(VI) concentration leads to increasing in bacterial resistance using various types of adaptable mechanisms such as higher EPS production. This resistance is very important in terms of a medicine subject and can be valuable information for us in the relationship to the mechanisms of antibiotic resistance, plasmid genetics and the desired isolated ecology.