Microbial Biomass and Bacterial Community Changes by Pb Contamination in Acidic Soil.

Heavy metals contamination of soil above a threshold can adversely affect soil ecology and health. Until recently studies are carried out for modest levels of metals present in the sludges where effect of individual metal could not be segregated. Microbial biomass and bacterial community structure was determined in an acidic soil loaded with 0, 200, 400, 600, 800, and 1000 mg Pb kg-1 soil incubated at 25 oC for 60 days. Decrease in soil microbial biomass carbon (Cmic) and nitrogen (Nmic) and widening C: N ratio was noted with increasing levels of Pb in soil. The diversity of soil bacteria assessed by PCR-DGGE method illustrated the simplification of DGGE patterns in soil with increasing Pb concentration, and less bacterial diversity for Pb > 400 mg kg-1 compared with the control. Such decreases in soil microbial biomass and bacterial diversity by Pb contamination may help to evaluate heavy metals contaminated soil ecologies.