Phenol degradation by an enterobacterium: a Klebsiella strain carries a TOL-like plasmid and a gene encoding a novel phenol hydroxylase

Although phenol catabolism is described for many different microorganisms, there is no example for such a pathway in an enterobacterial strain. Here w e characterize a Klebsiella oxytoca strain that grows on phenol as the only source of carbon and energy. As the key enzyme of phenol degradation, phen ol hydroxylase was purified to apparent homogeneity. Compared with other ph enol hydroxylases, the Klebsiella enzyme differs with respect to several pr operties: (i) SDS-PAGE and gel-filtration analysis of the purified protein revealed that the enzyme is a monomer with a molecular mass of 156 kDal (ii ) steady-state kinetic measurements resulted in a K-m value of 0.22 mM for phenol; and (iii) the enzyme is both dependent on NADPH/FAD and sensitive t o EDTA. Further degradation of catechol, the reaction product of phenol hyd roxylase, may occur via the effective meta-fission pathway often located on TOL or TOL-like plasmids. Such a plasmid was prepared from the Klebsiella strain and further characterized. The given data demonstrate that the isola ted strain exhibits all characteristics of an efficient phenol-degrading mi croorganism.