Temporal Metabolomics Reveals Additional Diterpene Resin Acid Metabolites in <i>Pseudomonas abietaniphila</i>

Diterpene resin acids are abundant oleoresin compounds in conifer trees and persistent pollutants in pulp mill effluents. The bacterium Pseudomonas abietaniphila BKME-9 has previously been reported to metabolize abietane-type diterpene resin acids, but the complete catabolic pathway and the identities of downstream metabolites are not yet fully elucidated. In this study, time-resolved metabolomics was used to characterize the metabolism of dehydroabietic acid (1) by P. abietaniphila. In addition to the known intermediates 7β-hydroxy-dehydroabietic acid (2), 7-oxo-dehydroabietic acid (3), and 11,12-dihydroxy-7-oxoabieta-8,13-dien-18-oic acid (4), four previously undescribed diterpenoid acids were detected at later incubation times. These new metabolites were identified as 5-hydroxy-dehydroabietic acid (5), 5,7β-dihydroxyabietan-18-oic acid (6), 5-hydroxy-pimara-8-en-18-oic acid (7), and 5-hydroxy-7-oxo-pimara-8-en-18-oic acid (8) by spectroscopic analysis. Time-course data revealed sequential formation and accumulation of these compounds through new oxidations and rearrangements of dehydroabietic acid. These findings expand the known diversity of microbial diterpene metabolites and provide insights into the metabolic network of P. abietaniphila involved in transforming plant-derived diterpenoids.