PubMed2004
The lipids of the gram-negative marine bacterium Marinobacter hydrocarbonoclasticus, cultivated in synthetic seawater supplemented with 1-chlorooctadecane as sole source of carbon, were isolated, purified, and their structures determined. Three pools of lipids were isolated according to the sequential procedure used: unbound lipids extracted by organic solvents, ester-bound lipids released under alkaline conditions, and amide-bound lipids released by acid hydrolysis. FA isolated from the unbound lipids included omega-chlorinated (21%, w/w, of this fraction; C16 predominant) and nonchlorinated compounds (22%, w/w; C18 predominant). These acids were accompanied by a high proportion of omega-chloro-C18 alcohols (43%, w/w) and a lower amount of omega-chloro-beta-hydroxy-C18, -C16, and -C14 acids (5%, w/w). These data, together with the isolation from the culture medium of gamma-butyrolactone, suggested a metabolism of 1-chlorooctadecane through oxidation into omega-chloro acid and then the classic beta-oxidation pathway. The analysis of the ester-bound and amide-bound lipids revealed that significant amounts of omega-chloro-beta-hydroxy C10-C12 acids were incorporated into the lipopolysaccharides of the bacterium. Incorporation of these omega-chloro-beta-hydroxy acids into the lipopolysaccharides represents a novel route for chloroalkane assimilation in hydrocarbonoclastic gram-negative bacteria. The formation of chlorinated hydroxy acids, like the omega-chloro FA in the cellular lipids, could account for an incomplete mineralization of chloroparaffins in the environment.