New metabolic pathway for o-cresol degradation by Pseudomonas sp CP4 as evidenced by H-1 NMR spectroscopic studies

Degradation intermediates of o-, m- and p-cresols extracted from resting ce lls of Pseudomonas sp. CP4, a potent cresol- and phenol-degrading laborator y isolate, were analysed by using H-1 NMR spectroscopy at 270 MHz. Ortho-, meta- and para-cresols were found to be degraded to 2-methyl-4-oxalocrotona te. 3-Methylcatechol from o-cresol was degraded further to 2-ketohex-cis-4- enoate, 4-methylcatechol from m- and p-cresol was degraded to 2-ketohex-cis -4-enoate. Also 2-ketopent-4-enoate was found to be formed from p-cresol. F ormation of 2-methyl-4-oxalocrotonate was envisaged as taking place from 5- hydroxy-2-methylmuconic semialdehyde, the ring-cleavage product of 4-methyl resorcinol, a possible product by hydroxylation of o-cresol along with 3-me thylcatechol. This is a deviation from the hitherto known pathways of o-cre sol degradation. Based on these observations, pathways for the degradation of all three isomers of cresol are proposed.