Utilization of catechin and its metabolites by Bradyrhizobium japonicum

Catechin, a condensed tannin was utilized as sole carbon source by Bradyrhizobium japonicum. Protocatechuic acid, phloroglucinolcarboxylic acid, phloroglucinol, resorcinol and hydroxyquinol were identified as intermediates of catechin degradation. The aromatic substrates favoured good growth up to 5 or 10 mM: . B. japonicum tolerated up to 50 mM: catechin and phloroglucinolcarboxylic acid, 40 mM: phloroglucinol and resorcinol, 30mM: protocatechuic acid and 10 mM: hydroxyquinol. Catechin-induced cells oxidized catechin more rapidly than uninduced cells. The two final ring compounds of the catechin catabolic pathway, protocatechuic acid and hydroxyquinol, were oxidized differentially. The enzymes of the catechin degradative pathway were inducible in B. japonicum.