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J. Bacteriol., Jan 1996, 6-11, Vol 178, No. 1
KB Hallberg, M Dopson and EB Lindstrom
The oxidation of reduced inorganic sulfur compounds was studied by using
resting cells of the moderate thermophile Thiobacillus caldus strain KU.
The oxygen consumption rate and total oxygen consumed were determined for
the reduced sulfur compounds thiosulfate, tetrathionate, sulfur, sulfide,
and sulfite in the absence and in the presence of inhibitors and
uncouplers. The uncouplers 2,4-dinitrophenol and carbonyl cyanide
m-chlorophenyl-hydrazone had no affect on the oxidation of thiosulfate,
suggesting that thiosulfate is metabolized periplasmically. In contrast,
the uncouplers completely inhibited the oxidation of tetrathionate,
sulfide, sulfur, and sulfite, indicating that these compounds are
metabolized in the cytoplasm of T. caldus KU. N-Ethylmaleimide inhibited
the oxidation of tetrathionate and thiosulfate at the stage of elemental
sulfur, while 2-heptyl-4- hydroxyquinoline-N-oxide stopped the oxidation of
thiosulfate, tetrathionate, and elemental sulfur at the stage of sulfite.
The following intermediates in the oxidation of the sulfur compounds were
found by using uncouplers and inhibitors: thiosulfate was oxidized to
tetrathionate, elemental sulfur was formed during the oxidation of
tetrathionate and sulfide, and sulfite was found as an intermediate of
tetrathionate and sulfur metabolism. On the basis of these data we propose
a model for the metabolism of the reduced inorganic sulfur compounds by T.
caldus KU.
Copyright © 1996, American Society for Microbiology
Reduced sulfur compound oxidation by Thiobacillus caldus
Department of Applied Cell and Molecular Biology, Umea University, Sweden.
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