Acidithiobacillus ferrooxidans AP19-3, ATCC 23270, and MON-1 are mercury-sensitive, moderately mercury-resistant, and highly mercury-resistant strains respectively. It is known that 2,3,5,6-tetramethyl-
p-phenylendiamine (TMPD) and reduced cytochrome
c are used as electron donors specific for cytochrome
c oxidase. Resting cells of strain MON-1 had TMPD oxidase activity and volatilized metal mercury with TMPD as an electron donor. Cytochrome
c oxidase purified from strain MON-1 reduced mercuric ions to metalic mercury with reduced mammalian cytochrome
c as well as TMPD. These mercury volatilization activities with reduced cytochrome
c and TMPD were completely inhibited by 1 m
M NaCN. These results indicate that cytochrome
c oxidase is involved in mercury reduction in
A. ferrooxidans cells. The cytochrome
c oxidase activities of strains AP19-3 and ATCC 23270 were completely inhibited by 1 μ
M and 5 μ
M of mercuric chloride respectively. In contrast, the activity of strain MON-1 was inhibited 33% by 5 μ
M, and 70% by 10 μ
M of mercuric chloride, suggesting that the levels of mercury resistance in
A. ferrooxidans strains correspond well with the levels of mercury resistance of cytochrome
c oxidase.
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