Studies on the vitamin B12 auxotrophy of Rhodocyclus purpureus and two other vitamin B12-requiring purple nonsulfur bacteria |
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Authors: | E. Siefert V. B. Koppenhagen |
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Affiliation: | (1) Gesellschaft für Biotechnologische Forschung mbH., Mascheroder Weg 1, D-3300 Braunschweig-Stöckheim, Federal Republic of Germany |
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Abstract: | The vitamin B12 requirement of Rhodocyclus purpureus 6770, Rhodospirillum tenue 1/67, and Rhodopseudomonas palustris G 53/2 was determined. A wide variety of biogenetic precursors of the vitamin including cobinamide, cobyric acid, cobinic acid and several partially amidated cobyrinic acids showed growth-promoting activity in all three strains. In R. purpureus vitamin B12 could even be substituted by cobyrinic acid which is the first cobalt-containing precursor of vitamin B12 so far established. Neither methionine, deoxynucleosides, dimethylbenzimidazole nor increased amounts of cobalt could replace vitamin B12 as growth factor.Cupribalamin, which is a strong antimetabolite of vitamin B12 in Escherichia coli 113-3 and Lactobacillus leichmannii ATCC 7830, exhibited only a weak antagonistic effect on growth of R. purpureus and R. tenue. Growth of R. palustris was not inhibited by cupribalamin. The cells of all three strains were shown to contain metal-free corrinoids in addition to cobalt-containing corrinoids. The principal products were identified as 5-deoxyadenosylcobalamin and hydrogenobalamin, the metal free analogue of vitamin B12. The latter does not originate from the vitamin by removal of cobalt but is de novo biosynthesized as could be demonstrated in the case of R. purpureus by a labelling experiment with [13C] methyl-l-methionine. |
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Keywords: | Vitamin B12 auxotrophy Phototrophic bacteria Metal-free corrinoids Growth-promoting activity of corrinoid compounds Vitamin B12 antimetabolites |
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