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The oxidation of several mono-hydric phenols by wild type and mutant strains of Pseudomonas aeruginosa T1 has been studied. The data suggest, that a non-specific enzyme sequence of the meta cleavage pathway is induced by all of these phenols, which can catalyze the oxidation of phenol and its analogues to pyruvate, a fatty acid and a carbonyl compound, according to the general scheme of Dagley et al. (1964). Mutants unable to grow on phenol (hydroxylase-negative), have been isolated, and they are also unable to grown on or oxidize the cresols and the xylenols. Revertants of these mutants regain the capacity to grow on all these phenols and are indistinguishable from the wild type. Induced-substrate relationships for the earlier enzymes of the pathway have been determined, e.g., phenol in addition to catechol and the methylcatechols is an inducer for catechol 2,3-oxygenase. Analysis of the enzymic content of cells grown in a variety of steadystate conditions shows (a) that the ratio of the specific activities of the “phenol” hydroxylase and catechol 2,3-oxygenase is constant for each of their analogous substrates; and (b) that induction and catabolite repression of catechol 2,3-oxygenase and the “muconic semialdehyde” hydrolyase are coordinate, but that control of the “phenol” hydroxylase is independent.

Thin sections of the obligate methane oxidizing bacterium, Methanomonas methanooxidans, reveal extensive intracytoplasmic membranes. These always occur in a peripheral arrangement. They appear similar to those in other bacteria which utilize specific energy sources. Their structure and function is discussed.