The chemical nature of the fatty acids of Lactobacillus arabinosus.

The fundamental observation (2-7), that a number of biotin-requiring lactobacilli grow normally in the absence of this growth factor when they are supplied with certain fatty acids, prompted an inquiry into the chemical nature of the fatty acids of a number of these organisms. These investigations will contribute to a better understanding of fatty acid metabolism of microorganisms and, in addition, might offer important clues on the metabolic r81e of biotin. Investigations on the nutritional requirements of microorganisms have led to the discovery of a number of vitamins. A similar development, with regard to fatty acids may be envisioned, since the isolation from microorganisms of as yet unrecognized fatty acids may lead to their ultimate recognition in animal tissues. This communication presents the results of a study on the chemical nature of the fatty acids of Lactobacillus arabinosus. A large quantity of this organism was grown on a semisynthetic medium, and the lipides of the harvested and washed cells were separated into two major groups, designated as “free” and “bound” lipides. The “free” lipides consisted of the acetone-ether-soluble constituents of the bacteria, while the “bound” lipides contained those substances which became ethersoluble following acid hydrolysis of the defatted cells. No attempts were made to establish the nature of the combination in which the fatty acids existed in these fractions. The crude “bound” lipides were saponified and the resulting products divided into a saponifiable and a non-saponifiable fraction. The fatty acids in the form of their methyl esters were then separated by fractional distillation in a highly efficient fractionating column of the spinning band type. Essentially three fractions were thus obtained, corresponding in their boiling points to methyl esters of acids containing 16, 18, and 19