Screening of zinc resistant bacteria isolated from coal mine overburden soil

Abstract

Heavy metal pollution of coal mine spoils is a significant environmental problem affecting both flora and fauna. These degraded soils can be remediated by using heavy metal resistant microorganisms. Zinc has been usually reported in high concentration from coal mine spoils. The present study, therefore, deals with screening of Zinc, resistant bacteria isolated from coal mine spoils. The bacterial isolates were isolated from coal mine spoils of Tinsukia district of Assam. For the isolation of bacteria, King's B Medium and Pikovskaya's Agar Media were used. Heavy metal resistance of the bacterial isolates against zinc was tested on nutrient agar and sucrose-minimal salt low phosphate (SLP) medium. The results showed that out of the 20 test isolates 11 isolates were resistant. The minimum inhibitory concentration (MIC) ranged from 0.001 M to 0.02 M. Antibiotic resistance was studied for two most resistant isolates. The optimal growth conditions with reference to pH and temperature of the two most resistant bacterial isolates were evaluated. Growth pattern of the most resistant isolates was determined in different concentrations of zinc amended broth media. On the basis of cultural and biochemical characters, the resistant isolates were identified as Pseudomonas sp, Bacillus sp and Rhizobium sp. Some of these isolates also exhibited plant growth promoting (PGP) traits and phosphate solubilizing ability.