Proposed convergent pathway for abietane diterpenoid degradation by LB400. I, abietic acid; II, palustric acid; III, dehydroabietic acid; IV, 7-oxo-palustric acid; V, 7-hydroxy-dehydroabietic acid; VI, 7-oxo-dehydroabietic acid; VII, 7-oxo-11,12-dihydroxy-8,13-abietadiene acid.