REGULATION OF ANAEROBIC RESPIRATORY PATHWAYS IN WOLINELLA-SUCCINOGENES BY THE PRESENCE OF ELECTRON-ACCEPTORS

In Wolinella succinogenes ATP synthesis and consequently bacterial growth can be driven by the reduction of either nitrate (E0' = +0.42 V), nitrite (E0' = +0.36 V), fumarate (E0' = +0.03 V) or sulphur (E0' = -0.27 V) with formate as the electron donor. Bacteria growing in the presence of nitrate and fumarate were found to reduce both acceptors simultaneously, while the reduction of both nitrate and fumarate is blocked during growth with sulphur. These observations were paralleled by the presence and absence of the corresponding bacterial reductase activities. Using a specific antiserum, fumarate reductase was shown to be present in bacteria grown with fumarate and nitrate, and to be nearly absent from bacteria grown in the presence of sulphur. The contents of polysulphide reductase, too, corresponded to the enzyme activities found in the bacteria. This suggests that the activities of anaerobic respiration are regulated at the biosynthetic level in W. succinogenes. Thus nitrate and fumarate reduction are repressed by the most electronegative acceptor of anaerobic respiration, sulphur. By contrast, in Escherichia coli a similar effect is exerted by the most electropositive acceptor, O2. W. succinogenes also differs from E. coli in that fumarate reductase is not repressed by nitrate.