CYTOCHROME-PRODUCING ANAEROBIC VIBRIO, VIBRIO SUCCINOGENES , SP. N

Abstract

A new species of the genus Vibrio has been isolated from bovine rumen fluid. The vibrio is restricted to a limited number of oxidation-reduction reactions for the production of energy for growth. These oxidation-reduction reactions involve H2 and formate as the only known satisfactory electron donors and fumarate, malate or NO3- as the electron acceptors. O2 can serve as an electron acceptor which supports limited growth only when it is present at concentrations of 2% or less in the atmosphere. Higher O2 concentrations are toxic. Carbohydrates are not fermented. Studies with cell suspensions have demonstrated that fumarate is reduced to succinate in the presence of H2. The stoichiometry of NO3- reduction by H2 indicates almost a complete reduction of NO3- to NH3. NO2-does accumulate, however, in growing cultures when NO3- is used as an electron acceptor. The vibrio lacks a hydrogenylase system which accounts for the lack of H2 production during growth when formate is used as an electron donor. Spectra of extracts show the presence of cytochromes b and c when the vibrio is grown with fumarate as an electron acceptor. When NO3- is substituted for fumarate in the growth medium, only the c type of cytochrome is observed in extracts.