MICROBIAL TRANSFORMATION OF MERCURY(II) .1. ISOLATION OF MICROBES ANDCHARACTERIZATION OF THEIR TRANSFORMATION CAPABILITIES

Using immobilized yeast cells as energy and nutrient source, microbial consortia could be isolated in the presence of mercury (HgCl2). Most of the 37 strains isolated from the mixed population exhibited high to lerancy against Hg(II). In fixed bed experiments the bacterial consort ia retained 82-99% of the total mercury influent over a period of 4-7 weeks. Experiments with resting cells clearly reveal that passive (phy sical) processes are not responsible for the high mercury retention ob served in fixed beds. Instead, as shown by experiments with growing mi crobes, Hg(II) is reduced to elemental Hg. Hence, the resistance of th e isolated strains against HgCl2 is based on a detoxification mechanis m which involves the transformation of Hg(II) to the less toxic Hg0.