Metabolism of phenol and cresols by Bacillus stearothermophilus

Abstract

An obligate thermophilic strain of B. stearothermophilus, strain PH24, isolated from industrial sediment by elective culture, grew readily at 55 C on phenol or on one of the isomers of cresol as the major carbon source. Intact cells grown in the presence of phenol, o cresol, m cresol, or p cresol were induced to oxidize, without lag, these substrates together with catechol, 3 methylcatechol, and 4 methylcatechol. Cell extracts prepared from B. stearothermophilus PH24 after growth in the presence of phenol converted phenol to catechol with a concomitant uptake of 1 mol of oxygen per mol of substrate in reaction mixtures supplemented with reduced nicotinamide adenine dinucleotide. These preparations also catalyzed the oxidation of o cresol to 3 methylcatechol and of m cresol and p cresol to 4 methylcatechol. Enzyme activity was inhibited by 1 mM p chloromercuribenzoate and by 0.1 mM o phenanthroline. Catechol and the corresponding methylcatechol intermediates were further dissimilated by cell extracts of phenol grown cells via the meta cleavage route to yield 2 hydroxymuconic semialdehyde and the respective methylated derivatives.