The metabolism of hydrogen by extremely thermophilic, sulfur-dependent bacteria

Extremely thermophilic organisms, defined here as having the ability to grow at 90 degree C with optimum growth at 80 degree C and above, have been isolated mainly from sulfur-rich, marine geothermal environments, both shallow and deep sea. The majority of the extremely thermophilic genera metaboliz...

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Bibliographic Details
Main Author: Adams, MWW
Format: Conference Proceeding
Language:English
Subjects:
bacteria
hydrogen
hydrogenase
metabolism
oxidation
sulphur
temperature tolerance
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Summary:Extremely thermophilic organisms, defined here as having the ability to grow at 90 degree C with optimum growth at 80 degree C and above, have been isolated mainly from sulfur-rich, marine geothermal environments, both shallow and deep sea. The majority of the extremely thermophilic genera metabolize elemental sulfur (S degree ) and a survey of the various organisms reveals that most of them also depend upon the oxidation of hydrogen gas (H sub(2)) as an energy source. In addition, two extremely thermophilic genera are known that actively produce H sub(2) as end-products of novel fermentative metabolisms. The enzyme hydrogenase, which is responsible for catalysing H sub(2) activation and H sub(2) production, appears to play several roles in electron and energy transfer during the growth of these organisms. The hydrogenase responsible for catalysing H sub(2) oxidation in extremely thermophilic organisms may be an extremely thermostable version of the mesophilic enzyme, and a new type of "evolution" hydrogenase, lacking the Ni-S or Fe-S catalytic sites of the mesophilic enzymes, is required for catalysing H sub(2) evolution at temperatures near and above 100 degree C.
ISSN:0168-6445