The Effects of Acids, Alkalies, and Sugars on the Growth and Indole Formation of Bacillus coli

Abstract

IN an earlier paper [Wyeth, 1918] it was shown that the final reaction produced by B. coli grown in 2 0% glucose peptone was dependent upon the initial reaction of the medium, and was not a "physiological constant" as had been suggested by Michaelis and Marcora [1912]. The results obtained by the use of different miedia and acids were recorded for various initial reactions lying between PH-423 and absolute neutrality (PH-= 7.00). Since the introduction of the hydrogen electrode as a means of measuring the reaction (PH) of liquids few results of the investigations of the growth of B. coli in media initially more alkaline than PH = 7 00 have been recorded. It was thought desirable, therefore, to supplement the former research by making an examination of the behaviour of B. coli when grown in 2 % glucose peptone made alkaliie bv the additioni of N sodium hydrate: an endeavour also being made to deternmine a "limiting value" of alkalinity, above which the growth of the organisnm is inhibited. Material and Experimental Methods. Pure cultures of B. coli obtained from human faeces were used. Experiments described in a former paper indicate that no differences in behaviour exist between strains of human and bovine origin. In this connection it may be noted that Murray [1916] made a comparative study of B. coli isolated from the faeces of man, horse, and cow. He agrees that all the strains prepared exhibited remarkable similarity of behaviour, and especially as regards their acid production. A sterile 4 00 glucose peptone medium was prepared by the method described in the former paper. It was then rendered alkaline by the additioni