Conversion of inorganic lead into a highly-toxic organic derivative by marine microorganisms

It has been reported that certain microorganisms isolated from lake sediments may transform inorganic lead compounds to organic derivatives, which are by at least one order of magnitude more toxic than the parent (inorganic) compounds. The purpose of this study was to investigate whether microorganisms isolated from a marine sediment could also produce such metabolites in an in vitro system simulating the marine ecosystem. The experimental setup included: 1) A sterile control system containing added inorganic lead (referred to as Pb2+); 2) a nonsterile control system without added Pb2+; 3) a nonsterile experimental system containing added Pb2+. The amount of added Pb2+ ranged from 5 to 1,000 ppm. Aliquots were taken at different intervals from the nonsterile systems and the surviving microorganisms were identified and counted. The main results were as follows: 1) The higher lead levels were toxic to all microorganisms. 2) Organic lead was only detected in the nonsterile experimental system, apparently due to microbial action, since none was found in the sterile systems. 3) Several bacteria exhibiting various degrees of tolerance for lead were isolated.