Affiliation:
1. Science and Technology for Energy Conversion,1
2. Administration Center for Environmental Science and Technology,2 and
3. Department of Biological Function, Faculty of Agriculture,3 Okayama University, Tsushima Naka, Okayama 700-8530, Japan
Abstract
ABSTRACT
Of 100 strains of iron-oxidizing bacteria isolated,
Thiobacillus ferrooxidans
SUG 2-2 was the most resistant to mercury toxicity and could grow in an Fe
2+
medium (pH 2.5) supplemented with 6 μM Hg
2+
. In contrast,
T. ferrooxidans
AP19-3, a mercury-sensitive
T. ferrooxidans
strain, could not grow with 0.7 μM Hg
2+
. When incubated for 3 h in a salt solution (pH 2.5) with 0.7 μM Hg
2+
, resting cells of resistant and sensitive strains volatilized approximately 20 and 1.7%, respectively, of the total mercury added. The amount of mercury volatilized by resistant cells, but not by sensitive cells, increased to 62% when Fe
2+
was added. The optimum pH and temperature for mercury volatilization activity were 2.3 and 30°C, respectively. Sodium cyanide, sodium molybdate, sodium tungstate, and silver nitrate strongly inhibited the Fe
2+
-dependent mercury volatilization activity of
T. ferrooxidans
. When incubated in a salt solution (pH 3.8) with 0.7 μM Hg
2+
and 1 mM Fe
2+
, plasma membranes prepared from resistant cells volatilized 48% of the total mercury added after 5 days of incubation. However, the membrane did not have mercury reductase activity with NADPH as an electron donor. Fe
2+
-dependent mercury volatilization activity was not observed with plasma membranes pretreated with 2 mM sodium cyanide. Rusticyanin from resistant cells activated iron oxidation activity of the plasma membrane and activated the Fe
2+
-dependent mercury volatilization activity of the plasma membrane.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
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