Abstract

Kartiki Kale, Piyusha Anupkumar Das, Dr. Sandhya Mulchandani*

ABSTRACT

Heavy metal contamination is a major environmental concern due to its toxic effects on living organisms and long-term persistence in the environment. The present study evaluated the tolerance and antimicrobial activity of four heavy metals-cadmium chloride, potassium dichromate, copper sulphate, and lead nitrate—against different microbial isolates using agar ditch method, agar cup method, microdilution assay, and Diphenyl Carbazide assay. The antimicrobial activity was determined by measuring the zone of inhibition at different concentrations, while MIC and MBC values were assessed using microtitre plate techniques. The results showed that all heavy metals exhibited concentration-dependent antimicrobial activity. Among the tested compounds, cadmium chloride demonstrated the highest and most consistent antimicrobial effect, followed by potassium dichromate and copper sulphate, whereas lead nitrate showed the least activity. Certain isolates, particularly S-2 and S-8, exhibited high tolerance toward multiple heavy metals. In the chromium reduction study, isolate S-2 (Bacillus subtilis) showed nearly 75% reduction of Cr (VI) within 24 hours, indicating strong bioremediation potential. Overall, the findings suggest that heavy metal-tolerant microorganisms can serve as promising candidates for sustainable and eco-friendly bioremediation applications.