METHYL KETONE METABOLISM IN HYDROCARBON-UTILIZING MYCOBACTERIA.

Lukins, H. B. (University of Texas, Austin) and J. W. Foster. Methyl ketone metabolism in hydrocarbon-utilizing mycobacteria. J. Bacteriol. 85: 1074-1087. 1963.-Species of Mycobacterium especially M. smegmatis 422, produced the homologous methyl ketones during the oxidation of propane, n-butane, n-pentane, or n-hexane. A carrier-trapping experiment demonstrated the formation of 2-undecanone, as well as 1,11-undecanedioic acid, during the oxidation of undecane-1-C(14). Aliphatic alkane-utilizing mycobacteria were able to grow at the expense of several aliphatic methyl ketones as sole sources of carbon. Other ketones which did not support growth were oxidized by resting bacterial suspensions. M. smegmatis 422 cells grown on propane or acetone were simultaneously adapted to oxidize both substrates, as well as n-propanol. n-Propanol cells were unadapted to propane or acetone. Acetone produced from propane in a medium enriched in D(2)O contained a negligible quantity of D, presumably eliminating propylene as an intermediate in the oxidation. Cells grown at the expense of alkanes or methyl ketones in the presence of O(2) (18) had a higher content of O(18) than did cells grown on terminally oxidized compounds, e.g., primary alcohols or fatty acids. An oxygenase reaction is postulated for the attack on methyl ketones. Acetol was isolated and characterized as an oxidation product of acetone by M. smegmatis 422. Acetol-grown cells had a higher O(18) content than did n-propanol cells, and its utilization appears to involve at least one oxygenase reaction. Acetol produced from acetone in the presence of O(2) (18) was not enriched in the isotope, indicating the occurrence of exchange reactions or of oxygenation reactions at a later stage in the assimilation of acetone and acetol.