Newly identified variability inBrucella canisfatty-acid content is associated with geographical origin

SUMMARYThis study compared the fatty-acid profiles ofBrucella canisblood culture isolates obtained from infected dogs in the UK, Germany, Japan, South Africa, Peru, Mexico, Colombia, and Argentina, and from a human clinical case in Argentina, to a bank of isolates obtained from canine outbreaks in the USA. Analysis of a total of 42B. canisisolates and one reference strain found a marked variation within the species. Fatty-acid analysis showed that only the isolates from Argentina, Colombia, and Mexico, which included the humanB. canisisolate, contained a specific fatty acid, 19:0 cyclopropane (lactobacillic acid), w8c (cis-11,12-methylene octadecanoic acid), and that this fatty acid, when present, made up a large percentage of overall fatty-acid content. Prior to this study, the cellular fatty-acid 19:0 cyclopropane had been identified in all of the species ofBrucellaconsidered to be pathogenic to humans (B.abortus,B.melitensis,B.suis) except forB.canis. Discovering that this fatty acid not only occurs inB. canis, but also that it is only present in some strains of the species provides a new focus for investigations aimed at identifying the cause of reported geographical variability in humanB. canisinfection, and at finding predictors of biological behaviour and human pathogenicity within thisBrucellaspecies.

The biosynthesis of cyclopropane fatty acids. III. pH Dependence of methyl hydrogen exchange: gas chromatographic – mass spectral studies

L-Methionine-methyl-d3 was administered to Lactobacillusplantarum and the deuterium content of the biosynthetic lactobacillic acid examined by gc–ms. By conducting the biosynthetic experiments in media of varying pH, it was shown that the production of d1-cyclopropane fatty acid increases with decreasing pH. Factors such as culture age and total activity of cyclopropane synthetase do not directly influence the extent of exchange.