Full text loading...
Long-chain haloalkanes are incorporated into fatty acids by Rhodococcus rhodochrous NCIMB 13064
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 C10 and C18 indicated chlorofatty acid incorporation from C12 to C18 substrates at levels ranging from 21% with C12 to 75% with C16. 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 C19:0 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 C11 and C17 was examined, the incorporation of bromofatty acids was observed with C13, C15 and C17 substrates; a maximum of 76% was recorded for the C15 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 similar, demonstrating that the position of halogen substitution in the haloalkane was not critical in determining the extent of incorporation of the haloacids into cellular lipids. The results of the study indicate a mechanism by which degradation products of chlorinated paraffins could enter the biological food chain.
- Received:
- Accepted:
- Revised:
- Published Online:
Keyword(s):
cellular lipids
,
long-chain haloalkanes
,
Rhodococcus rhodocbrous
and
w-halofatty acids
© Society for General Microbiology 1995