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J. Bacteriol., Aug 1995, 4748-4756, Vol 177, No. 16
K Ma, H Loessner, J Heider, MK Johnson and MW Adams
The strictly anaerobic archaeon Thermococcus strain ES-1 was recently
isolated from near a deep-sea hydrothermal vent. It grows at temperatures
up to 91 degrees C by the fermentation of peptides and reduces elemental
sulfur (S(o)) to H2S. It is shown here that the growth rates and cell
yields of strain ES-1 are dependent upon the concentration of S(o) in the
medium, and no growth was observed in the absence of S(o). The activities
of various catabolic enzymes in cells grown under conditions of sufficient
and limiting S(o) concentrations were investigated. These enzymes included
alcohol dehydrogenase (ADH); formate benzyl viologen oxidoreductase;
hydrogenase; glutamate dehydrogenase; alanine dehydrogenase; aldehyde
ferredoxin (Fd) oxidoreductase; formaldehyde Fd oxidoreductase; and
coenzyme A- dependent, Fd-linked oxidoreductases specific for pyruvate,
indolepyruvate, 2-ketoglutarate, and 2-ketoisovalerate. Of these, changes
were observed only with ADH, formate benzyl viologen oxidoreductase, and
hydrogenase, the specific activities of which all dramatically increased in
cells grown under S(o) limitation. This was accompanied by increased
amounts of H2 and alcohol (ethanol and butanol) from cultures grown with
limiting S(o). Such cells were used to purify ADH to electrophoretic
homogeneity. ADH is a homotetramer with a subunit M(r) of 46,000 and
contains 1 g-atom of Fe per subunit, which, as determined by electron
paramagnetic resonance analyses, is present as a mixture of ferrous and
ferric forms. No other metals or acid-labile sulfide was detected by
colorimetric and elemental analyses. ADH utilized NADP(H) as a cofactor and
preferentially catalyzed aldehyde reduction. It is proposed that, under So
limitation, ADH reduces to alcohols the aldehydes that are generated by
fermentation, thereby serving to dispose of excess reductant.
Copyright © 1995, American Society for Microbiology
Effects of elemental sulfur on the metabolism of the deep-sea hyperthermophilic archaeon Thermococcus strain ES-1: characterization of a sulfur-regulated, non-heme iron alcohol dehydrogenase
Department of Biochemistry and Molecular Biology, University of Georgia, Athens 30602, USA.
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