METABOLISM OF STYRENE BY RHODOCOCCUS-RHODOCHROUS NCIMB-13259

Rhodococcus rhodochrous NCIMB 13259 grows on styrene, toluene, ethylbe nzene, and benzene as sole carbon sources. Simultaneous induction test s with cells grown on styrene or toluene showed high rates of oxygen c onsumption with toluene cis-glycol and 3-methylcatechol, suggesting th e involvement of a cis-glycol pathway. 3-Vinylcatechol accumulated whe n intact cells were incubated with styrene in the presence of 3-fluoro catechol to inhibit catechol dioxygenase activity. Experiments with O- 18(2) showed that 3-vinylcatechol was produced following a dioxygenase ring attack. Extracts contained a NAD-dependent cis-glycol dehydrogen ase, which converted styrene cis-glycol to 3-vinylcatechol. Both catec hol 1,2- and 2,3-dioxygenase activities were present, and these were s eparated from each other and from the activities of cis-glycol dehydro genase and 2-hydroxymuconic acid semialdehyde hydrolase by ion-exchang e chromatography of extracts. 2-Vinylmuconate accumulated in the growt h medium when cells were grown on styrene, apparently as a dead-end pr oduct, and extracts contained no detectable muconate cycloisomerase ac tivity. 3-Vinylcatechol was cleaved by catechol 2,3-dioxygenase to giv e a yellow compound, tentatively identified as 2-hydroxy-6-oxoocta-2,4 ,7-trienoic acid, and the action of 2-hydroxymuconic acid semialdehyde hydrolase on this produced acrylic acid. A compound with the spectral characteristics of 2-hydroxypenta-2,4-dienoate was produced by the ac tion of 2-hydroxymuconic acid semialdehyde hydrolase on the 2,3-cleava ge product of 3-methylcatechol. Extracts were able to transform 2-hydr oxypenta-2,4-dienoate and 4-hydroxy-2-oxopentanoate into acetaldehyde and pyruvate. These results show that R. rhodochrous NCIMB 13259 metab olizes styrene by dioxygenation to give styrene cis-glycol, followed b y dehydrogenation to form 3-vinylcatechol, which undergoes nonproducti ve ortho cleavage and complete metabolism by a meta-cleavage pathway.