Oxidation of phenanthrene by a strain ofMicrococcus: Evidence of protocatechuate pathway

A phenanthrene-degrading bacterium, belonging to the genusMicrococcus, was isolated from petroliferous soil. The strain degraded phenanthrene mainly through protocatechuate, as was evidenced by oxygen uptake and enzymatic studies. Moreover, the strain can utilize naphthalene and anthracene without any lag, and as such catechol-2,3-oxygenase may play an important role, most probably as a constitutive enzyme. The mechanism of degradation of these hydrocarbons and other aromatic compounds seems to be controlled by an extrachromosomal mechanism (i.e., through plasmids), as was evidenced by the loss of the phenanthrene-and naphthalene-assimilating property after subculture in nutrient agar and NAH⁺ phenotype, in benzoate agar medium; this suggests its similarity with other hydrocarbon-assimilating microorganisms in which the degradation is mediated entirely by plasmids.