The production of fatty acids by a gram-negative coccus.

We have isolated from the rumen of the sheep an anaerobic Gram-negative coccus which ferments glucose, fructose, maltose, mannitol, sorbitol and DL-lactate with the production of hydrogen and carbon dioxide, acetate, propionate, n-butyrate, npentanoate and n-hexanoate (Elsden, Gilchrist, Lewis & Volcani, 1951). Since it is our intention to discuss the taxonomic position of this organism in a separate publication we propose, for the purpose of this communication, to refer to the organism as LC. When LC is grown on glucose the fatty acids containing an even number of carbon atoms, acetate, n-butyrate and n-hexanoate predominate; whereas during growth on lactate there is a higher proportion of propionate and n-pentanoate. The metabolism of this organism was of interest to us in view of the formation of significant amounts of n-pentanoate and n-hexanoate. As far as is known the only bacteria which produce fatty acids of the n-series higher than n-butyrate are Clostridium kluyveri (Barker & Taha, 1942), Rhodospirillum rubrum (Kohmiller & Gest, 1951) and LC (Elsden et al. 1951). Bornstein & Barker (1948) showed that when Cl. kluyveri was grown upon ethanol plus either acetate, propionate or n-butyrate, the predominant fatty acids formed were n-butyrate and n-hexanoate, npentanoate or n-hexanoate respectively; in addition, traces of n-heptanoate were produced during growth upon ethanol and propionate. Using cellfree preparations of Cl. kluyveri, Stadtman & Barker (1949) showed that ethanol was oxidized in the presence oforthophosphate to acetyl phosphate; and this compound was considered to combine with either acetate, propionate or n-butyrate to form an intermediary which was reduced to the corresponding fatty acid of the n-series containing two more carbon atoms. Subsequent work by Stadtman (1952) on the phosphotransacetylase of Cl. kluyveri has made it probable that acetylcoenzyme A (Lynen, Reichert & Rueff, 1951) and not acetyl phosphate is the active form of acetate in this synthesis, though there is as yet no direct proof. The mechanism of the synthesis of fatty acids by R. rubrum was not investigated by Kohmiller & Gest (1951). * Present address: A.R.C. Institute of Animal Physiology, Babraham, Cambridgeshire. In this paper we report the results of our investigations of the synthesis of fatty acids from pyruvate by washed suspensions of LC.