The metabolism of acetate and mevalonic acid by lactobacilli II. The incorporation of [ 14C]acetate and [ 14C]mevalonic acid into the bacterial lipids

Abstract

Using [ 14C]acetate and [ 14C]mevalonic acid, it was shown that Lactobacillus casei, Lactibacillus arabinosus and Lactobacillus acidophilus incorporate from 20–35 times as much sodium acetate as mevalonic acid, the cellular concentration of mevalonic acid being from 0.5–0.9 μg/mg dry weight. Most of the radioactive material was found in the lipid fraction, probably bound to protein. Acetate was shown to be a precursor of both fatty acids and unsaponifiable lipids, mevalonic acid gave only unsaponifiable material. Part of the fatty acids could only be liberated from the whole lipids by acid hydrolysis and was not hydrolysed under alkaline conditions. Analysis of the unsaponifiable material by reversed-phase paper chromatography showed the presence of at least six components. The chemical nature of these substances was studied. Since mevalonic acid did not yield fatty acids, [ 4C]glucose in absence of acetate was shown to be a precursor of the bacterial fatty acids. Biotin was found to be necessary for fatty acid synthesis from acetate but not for the synthesis of the unsaponifiable lipids from mevalonic acid.