Formation of cobalt-free corrinoids in Rhodopseudomonas spheroides.

Co-free corrinoids (CFCs) were found in the cells of Rhodopseudomonas spheroides grown without cobalt salt. A predominant fraction of three CFCs on paper-electrophoregram was further purified, and investigated physico-chemically as well as microbiologically in comparison with that isolated by Toohey from Chromatium. The electrophoretic as well as spectrophotometric patterns of CFC from Rh. spheroides were partly different from those of Chromatium CFC. The former CFC was a competitive inhibitor of cyanocobalamin in Ochromonas malhamensis. The findings obtained indicate that the CFC from Rh. spheroides resembles that from Chromatium in chemical structure with some difference, and that the compound has an anti-vitamin B12 activity in O. malhamensis.