Monohydroxy and Dihydroxy Fatty Acid Composition of Legionella Species

Abstract

A total of 28 strains, representing 10 species of Legionella and including strains belonging to most of the known serogroups of each species, were examined for location, content, and composition of cellular nonhydroxy, monohydroxy, and dihydroxy fatty acids. The nonhydroxy fatty acid profiles were in agreement with previously published values. All species contained 5 to 15 mol% (depending on species) monohydroxy fatty acid, the profile of each species being readily distinguishable from the profiles of the other species. Only two species, Legionella pneumophila and Legionella micdadei, contained detectable levels of dihydroxy fatty acids, which comprised 1 to 5 mol% of the total fatty acids. The dihydroxy fatty acid profiles of these two species were significantly different. In all species, the nonhydroxy fatty acids were readily extractable by lipid solvents and were labile when subjected to mild alkaline methanolysis (lipid associated, ester linked), whereas the hydroxylated components were not extractable, were stable when subjected to alkaline methanolysis, and were labile when subjected to acid hydrolysis (bound, amide linked). The monohydroxy fatty acids were shown to be acids of the 3-hydroxy family. The dihydroxy fatty acids were shown to be members of the 2,3-dihydroxy family. The profiles of the hydroxylated fatty acids provide a powerful method for differentiating the Legionella species, particularly those species whose nonhydroxy fatty acid profiles are quite similar.