The 'strict' anaerobe Desulfovibrio gigas contains a membrane-bound oxygen-reducing respiratory chain

Sulfate-reducing bacteria are considered as strict anaerobic microorganisms , in spite of the fact that some strains have been shown to tolerate the tr ansient presence of dioxygen, This report shows that membranes from Desulfo vibrio gigas grown in fumarate/sulfate contain a respiratory chain fully co mpetent to reduce dioxygen to water. In particular, a membrane-bound termin al oxygen reductase, of the cytochrome bd family, was isolated, characteriz ed, and shown to completely reduce oxygen to water. This oxidase has two su bunits with apparent molecular masses of 40 and 29 kDa, Using NADH or succi nate as electron donors, the oxygen respiratory rates of D, gigas membranes are comparable to those of aerobic organisms (3.2 and 29 nmol O-2 min(-1) mg protein(-1), respectively). This 'strict anaerobic' bacterium contains a ll the necessary enzymatic complexes to live aerobically, showing that the relationships between oxygen and anaerobes are much more complex than origi nally thought, (C) 2001 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.