Isolation of a bacterium producing propionic acid from the rumen of sheep

SUMMARY: A strictly anaerobic micrococcus which produces acetic acid, propionic acid, carbon dioxide and hydrogen by fermentation of lactate was isolated from the lumen of sheep. It failed to ferment sugars and was identified as VeiElonella guzogenes. Its significance in ruminant digestion is uncertain, but a characteristic reaction of this organism, the decarboxylation of succinic acid to yield propionic acid and carbon dioxide, appears to be important in the rumen. This reaction was studied by the Warburg technique with washed suspensions of lumen bacteria. It had been known for a considerable time that volatile acids were amongst the products of rumen fermentation of plant material, but i t was not until Elsden (1946) developed a partition chromatographic method which separated quantitatively mixtures of fatty acids that their identity was definitely esta-blished. Acetic, propionic and butyric acids were always found and traces of higher acids were sometimes detected. Very little is known about the micro-organisms responsible for the digestion of carbohydrate in the ruminant or of the metabolism of the organisms active in rumen fermentation. It is no