MULTIPLE PATHWAYS FOR TOLUENE DEGRADATION IN BURKHOLDERIA SP. STRAIN JS150

Burkholderia (Pseudomonas) sp, strain JS150 uses multiple pathways for the metabolism of catechols that result from degradation of aromatic compounds, This suggests that the strain also uses multiple upstream p athways for the initial hydroxylation of aromatic substrates, Two dist inct DNA fragments that allowed Pseudomonas aeruginosa PAO1c to grow w ith benzene as a sole carbon source were cloned from strain JS150, One of the recombinant plasmids containing the initial steps for the degr adative pathway contained a 14-kb DNA insert and was designated pRO201 6, We have previously shown that the DNA insert originated from a plas mid carried by strain JS150 and contained genes encoding a multicompon ent toluene-2-monooxygenase (tbmABCDEF) as well as the cognate regulat ory protein (tbmR) that controls expression of the 2-monooxygenase (G, R. Johnson and R. H. Olsen, Appl, Environ. Microbiol. 61:3336-3346, 1 995), Subsequently, we have identified an additional region on this DN A fragment that encodes toluene-4-monooxygenase activity. The toluene- 4-monooxgenase activity was also regulated by the tbmR gene product, A second DNA fragment that allowed P. aeruginosa to grow with benzene w as obtained as a 20-kb insert on a recombinant plasmid designated pRO2 015. The DNA insert contained genes encoding toluene-4-monooxygenase a ctivity but no toluene-2-monooxygenase activity. The pRO2015 insert or iginated from the chromosome of strain JS150, unlike the region cloned in pRO2016, Southern blots and restriction map comparisons showed tha t the genes for the individual 4-monooxygenases were distinct from one another, Thus, strain JS150 has been shown to have at least three tol uene/benzene monooxygenases to initiate toluene metabolism in addition to the toluene dioxygenase reported previously by others.