Anaerobic Growth of Escherichia coli in the Presence of Certain Acids

Abstract

CERTAIN coliform bacteria grow readily under anaerobic conditions in synthetic media containing glucose, ammonium sulphate, phosphate and other necessary inorganic ions. The extent of growth, however, is limited to a definite size of cell population even in the presence of excess concentrations of the substrates, the excess remaining unchanged in the media. This phenomenon has been ascribed to the saturation of the hydrogen acceptor mechanisms, and the evidence supporting this contention is strong¹. The extent of growth depends also on the initial pH and the buffer capacity of the media, being less if the initial pH or the buffer capacity is lower. The dependence on buffer capacity has led to criticism of the above suggestion². The growth of such cultures is accompanied by production of acid, but their final pH depends on the initial, and growth may stop at a higher pH than will permit growth in a fresh medium. Thus, though hydrogen ion concentration is undoubtedly a factor, cessation of growth cannot be due solely to its increase.