The Nutritional Properties of Killed Bacterium coli

A previous investigation had shown that the protein and polysaccharide components of enteric bacteria can be separated by heating the cells in a watery suspension at 80" for I h (Roberts, 1949).In continuation of this work the protein of Bacterium coli was fed to rats and guinea-pigs and it was found that if the diet satisfied the peculiar vitamin requirements of the experimental animals, as, for example, the need of vitamin C in the diet of guinea-pigs, the animals thrived.It was then found that rats receiving both components, i.e. whole cells, grew at the same rate as rats receiving only the bacterial-protein component.Thus, whereas it might have been accepted as highly probable on theoretical grounds that the protein component of an enteric bacterium was edible, this last observation suggested the wider possibility that the whole organism might be edible.As Bact. coli can grow profusely in protein-and vitaminfree media it seemed to be an ideal food organism.A systematic study of the nutritional properties of killed Bact. coli suspensions was therefore undertaken.The plan was first to demonstrate that Bact. coli suspensions could be substituted for animal protein, secondly to ascertain broadly the dietary factors that were complementary to Bact. coli and thirdly to demonstrate its use in a diet for chicks.The work on chicks was undertaken to test the merits of the material in an exacting species, rather than to formulate a practical chick ration.It proved that a suspension of Bact. coli organisms killed by heat could replace substantially the protein supplements customarily added to cereal diets for chicks. EXPERIMENTAL AND RESULTS MaterialsStrain of Bact.coli.The strain was that mainly used in a previous investigation (Roberts, 1949) and possessed the classical characters of Bact.coli.It had been isolated from a lymph node from a calf that died of white scour.Culture medium.This consisted of 0-5 yo ammonium sulphate, 2.0% glucose, 0.2% potassium dihydrogen phosphate, 0.05 yo magnesium sulphate and 0.02 % sodium citrate, in tap water.Bact. coli cultures.During most of the work the cultures used had a viable count of 2 x I O ~O and contained 4 g protein/l.Bact. coli suspension.The organisms were collected alive by centrifuging, resuspended in physiological salt solution and killed by heating at 80" for I h.T h i s suspension was then tested to ensure its sterility and assayed for protein (N x 6.25).For use in feeding experiments it was diluted later to a protein content per IOO ml.equal to 23-2