Screening and Evaluation of Multi-metal Tolerance of Chromate Resistant Marine Bacteria Isolated from Water and Sediment Samples of Paradip Port, Odisha Coast

Abstract

Contamination with various toxic metal ions has been detected in sediment and water samples of Paradip Port environment caused by various metal handling operations. Presence of chromium in the sediment and water samples has led to isolate Cr(VI) resistant marine bacteria from these environments. In total 44 chromate resistant bacteria were isolated from surface water, bottom water and sediment samples using nutrient agar medium supplemented with 50 mg/l Cr(VI) which were screened for their tolerance to increasing Cr concentrations in nutrient agar medium. The screening test has resulted in selection of 11 bacterial isolates tolerating Cr(VI) concentrations as high as 1500 mg/l. These 11 strains were then subjected to purification by two subsequent quadrant streak in nutrient agar plates and evaluated for determination of their minimum inhibitory concentration (MIC) towards Cr(VI) in nutrient broth by broth dilution method with further increasing concentrations from 1500 to 2500 mg/l of Cr(VI). Based on MIC test, a bacterium, CrRPSD40 isolated from marine sediment was selected because of very high tolerance towards Cr(VI) with MIC value of 2100 mg/l. This strain was found to exhibit multiple metal tolerance capacity when screened for tolerance towards other 6 toxic heavy metals such as Cd(II), Cu(II), As(III), Zn, Pb(II) and Ni in nutrient broth medium. Based on morphological and biochemical characterisation the bacterium was identified as a Brevibacillus sp. Identification of Brevibacillus sp as a high chromium resistant bacteria with multi-metal tolerance ability could be a potential candidate for bioremediation of chromium along with other metals from saline industrial waste effluents.