Comparative studies on the effect of lead on free and immobilized systems of Bacillus sp.

Abstract

Heavy metals are widespread pollutants of great environmental concern as they are non-biodegradable and thus persistent. Lead is a non-essential element, highly toxic to microorganisms due to its ability to replace functional metals leading to denaturation of proteins, nucleic acids, enzymes and is present in significant quantities in many soils. Awareness of the biological effects of pollutants on microorganisms has lead to their use as indicators in bioassay systems and as biological monitors of environmental contamination. The application of immobilized systems in the environmental applications has been studied with greater extent as immobilized systems have several advantages over free cells, but limited work has been reported on the toxicological studies using immobilized microbial systems. In this investigation we are reporting the comparative study of the effect of lead on free and immobilized cells of Bacillus sp. using different parameters like growth, nucleic acids, protein content, catalase activity, phosphatase activity and glucose utilization. Inhibition on growth of Bacillus sp. was found to be at lower concentrations. The effect of lead on DNA and RNA content indicated slightly higher inhibition in free cells than in immobilized cells. Protein synthesis inhibition was more in free cells compared to immobilized cells in the presence of lower concentrations of lead. Enzyme activities of free cells were more affected by lead than that of immobilized cells. Increasing concentrations of lead affected the glucose utilization.