Long-chain haloalkanes are incorporated into fatty acids by Rhodococcus rhodochrous NCIMB 13064

Food Science Division, Department of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX, UK The QUESTOR Centre, David Keir Building, The Queen's University of Belfast, Belfast BT9 5AG, UK School of Biology and Biochemistry, David Keir Building, The Queen's University of Belfast, Belfast BT9 5AG, UK Microbial Biochemistry Section, Department of Food Science, The Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX, UK ABSTRACT Summary: The fatty acid composition of the cellular lipids of Rhodococcus rhodochrous NCIMB 13064 grown on various long-chain haloalkanes has been investigated and the influence of halogen substituents, carbon chain length and the position of halogen substitution in the growth substrate explored. Of the total fatty acids present in cells grown on 1-chloro-, 1-bromo- and 1-iodohexadecane, 75, 90 and 81%, respectively, were substituted in the w position by the corresponding halogen but only 1% of the fatty acids present after growth on 1-fluorotetradecane were fluorinated in this position. The extent of the halofatty acid incorporation with different halogen substituents in the growth substrate appears to reflect the degree to which oxygenase attack is restricted to the non-halogenated end of the haloalkane. Studies of the fatty acid composition of cells after growth on a series of 1-chloroalkanes containing an even number of carbon atoms between C 10 and C 18 indicated chlorofatty acid incorporation from C 12 to C 18 substrates at levels ranging from 21% with C 12 to 75% with C 16 . The chlorofatty acids formed by initial oxidation of the chloroalkane were chain-lengthened or chain-shortened by from two to eight carbon atoms, with accompanying desaturation in some instances. Substantial quantities of a methyl-branched C 19:0 chlorofatty acid were also present with several chloroalkane substrates. When the fatty acid composition of cells after growth on 1-bromoalkanes containing an odd number of carbon atoms between C 11 and C 17 was examined, the incorporation of bromofatty acids was observed with C 13 , C 15 and C 17 substrates; a maximum of 76% was recorded for the C 15 bromoalkane. As with even chain-length chloroalkanes, both chain-lengthening and -shortening occurred predominantly via two-carbon units so that most bromoacids present possessed an odd number of carbon atoms. When 1-bromododecane or 2-bromododecane were substrates, overall incorporations of bromofatty acids into the lipid fraction were very sim