Heat sensitivity of mercuric ion and organomercurial degrading enzymes of aquatic, mercury-resistant bacteria.

Activities of both Hg(2+)-reductase and organomercurial lyase of Hg-resistant aquatic bacteria were stable at 20°C for several days within whole cells. Organomercurial lyase activity degrading specifically thimersol, an organomercurial, was more stable than the corresponding enzyme activity degrading other organomercurials like phenylmercuric acetate (PMA) and methoxyethyl mercuric chloride (MEMC). Hg(2+)-reductases of Gram-negative bacteria in cell-free extract were more heat resistant than those of Gram-positive bacteria, except for those of two species of Bacillus, which were as heat resistant as those of the Gram-negative bacteria. Differences in the heat resistances of organomercurial lyases of two different broad-spectrum Hg-resistant bacteria indicate the presence of two enzyme systems for degrading thimersol, PMA and MEMC.