Analysis of fatty acids of the genus Rochalimaea by electron capture gas chromatography: detection of nonanoic acid

Abstract

The fatty acid compositions of Rochalimaea quintana, strains Fuller and Guadalupe, and R. vinsonii, the Canadian vole agent, were determined in an effort to further characterize these bacteria. The cells were saponified with 5% NaOH in 50% methanol and acidified to pH 2. The methanolysates were extracted with chloroform, derivatized with 2,2,2-trichloroethanol, and analyzed using a Hewlett-Packard gas chromatograph equipped with a frequency pulse-modulated electron capture detector and a 3% OV-101 packed-glass column. The fatty acid profiles of the three Rochalimaea strains were similar, with octadecenoic acid (C18:1) the most abundant, followed by octadecanoic (C18:0) and hexadecanoic (C16:0) acids. Moderate to trace amounts of other acids were also present. Unexpectedly, well-defined peaks of nonanoic acid (C9) were found consistently. A portion of this acid, but not all, was extractable with chloroform. Since C9 is not reported as a usual component of bacteria and most analyses do not include a search for this fatty acid, this study was extended to three strains of Legionella and one of Campylobacter. Comparable results were obtained. Since these bacteria were grown in complex media which contain some C9, it is possible that the medium is the source of bacterial C9. Whether this compound can be synthesized by the bacteria remains to be investigated.