A survey of EPR-detectable components in sulfur-reducing bacteria

Abstract A survey was made of components of sulfur-reducing bacteria that can be detected by EPR spectroscopy. To this purpose, whole cells were examined and a membrane and cytoplasm fraction obtained by centrifugation at 120 000 × g after cell lysis by suitable procedures. Attempts were made to obtain spectra on these materials with their electron acceptors in the oxidized and reduced states, respectively. Desulfuromonas strains 5071, 2873, Go 10, Go 20, NZ 27, Spirillum 5175, and Desulfovibrio baculatus strain 9974 were studied. Fe-S proteins were recognized from their characteristic EPR behavior; and low-spin cytochromes, largely of the c type, were clearly observed. Signals obviously originating from unknown types of components were also found. Partial segregation of some of the observed species into the cytoplasm or membrane fraction was achieved. Tentative assignments of the various resonances seen in the EPR spectra, based on behavior with fractionation, on oxidation-reduction or on change of microwave power are presented.