Microbial removal of lead from solid media and soil

We have isolated a Pseudomonas aeruginosa strain designated CHL004 which is able to remove lead from solidified media and soil. The process for testing removal was generally the same for all experiments. A piece of sterile filter paper was placed on the surface of a plate containing solidified media and lead carbonate or lead contaminated soil and incubated at 29 degrees C for 30 days. Lead was removed from yeast malt plates but generally not from R2A plates. Dextrose was shown to be a critical component in the YM; without it almost no lead was removed. Sucrose, maltose and lactose could not be substituted for the dextrose although these carbon sources allowed for survival and growth of the isolate. In order to study the initial kinetics of lead uptake, lead nitrate was used in an aqueous environment. The rate of uptake of lead nitrate by CHL004 was very rapid initially then decreased greatly. Sodium azide treated cells did not remove lead. The removal of lead from an urban soil was affected by the pH of the soil. The pH of the soil in YM was 6.9 and 3.3% of the total lead in the soil was removed. When the pH was adjusted to a pH of 5, 8% of the total lead was removed but at a pH of 6, 6.4% was removed.