FORMATION OF ORGANIC CADMIUM BY MARINE MICROORGANISMS

This research was designed with a view to finding out whether or not t here is a microbial or spontaneous transformation of inorganic cadmium into a highly toxic organic derivative of this metal by microorganism obtained from the Eastern Mediterranean marine environment. Sterile a nd nonsterile marine bottom sediment samples were incubated at ambient temperature for different time intervals, under aerobic and anaerobic conditions, with different concentrations of CdCl2, and the medium, t he atmosphere in the incubation flasks, and the sediments were assayed for their organic cadmium contents. The results were: (a) There was m icrobial growth in all systems containing up to 250 mu g cadmium per m illiliter of growth medium; however, with higher concentrations a comp lete growth-inhibition was observed. (b) Organic cadmium was found in the bottom sediments, at all cadmium levels permitting considerable mi crobial growth, but not in the systems' atmospheres or in the liquid g rowth media. (c) Under aerobic conditions higher levels of organic cad mium were found than in the anaerobic systems. (d) The microorganisms occurring in the different experimental systems were isolated and iden tified. The predominating species in all systems were bacteria. (C) 19 95 Academic Press, Inc.