METHYL KETONE METABOLISM IN HYDROCARBON-UTILIZING MYCOBACTERIA

Abstract

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-un-decanedioic-acid during the oxidation of undecane-1-C14. 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 D2O 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 O2 18 had a higher content of O18 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 O18 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 O2 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.