Deletion of the genes, encoding protocatechuate 3,4-dioxygenase in RHA1, gives a gene deletion strain still able to grow on protocatechuic acid as the sole carbon source, indicating a second degradation pathway for protocatechuic acid. Metabolite analysis of wild-type RHA1 grown on medium containing vanillin or protocatechuic acid indicated the formation of hydroxyquinol (benzene-1,2,4-triol) as a downstream product. Gene cluster ro01857-ro01860 in RHA1 contains genes encoding hydroxyquinol 1,2-dioxygenase and maleylacetate reductase for degradation of hydroxyquinol but also putative mono-oxygenase (ro01860) and putative decarboxylase (ro01859) genes, and a similar gene cluster is found in the genome of lignin-degrading species.
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