Diversity of mercury resistance determinants among Bacillus strains isolated from sediment of Minamata Bay

Thirty mercury-resistant (Hg-R) Bacillus strains were isolated from mercury-polluted sediment of Minamata Bay, Japan. Mercury resistance phenotypes were classified into broad-spectrum (resistant to inorganic Hg2+ and organomercurials) and narrow-spectrum (resistant to inorganic Hg2+ and sensitive to organomercurials) groups. Polymerase chain reaction (PCR) product sizes and the restriction nuclease site maps of mer operon regions from all broad-spectrum Hg-R Bacillus were identical to that of Bacillus megaterium MB1. On the other hand, the PCR products of the targeted merP (extracellular mercury-binding protein gene) and merA (intracellular mercury reductase protein gene) regions from the narrow-spectrum Hg-R Bacillus were generally smaller than those of the R megaterium MB1 mer determinant. Diversity of gene structure configurations was also observed by restriction fragment length polymorphism (RFLP) profiles of the merA PCR products from the narrow-spectrum Hg-R Bacillus. The genetic diversity of narrow-spectrum mer operons was greater than that of broad-spectrum ones. (C) 2003 Published by Elsevier Science B.V. on behalf of the Federation of European Microbiological Societies