The utilization of carbon sources by Bact. lactis aerogenes I. General survey

A survey is made of the ability of various carbon compounds to support growth of Bact. lactis aerogenes. They are classified into those to which the cells (a) cannot become adapted, (b) become adapted by training, (c) are fully adapted on transfer from a glucose medium in which they are normally grown. With class (b) there is usually a long initial lag on the first transfer and an initial growth rate well below the optimum. Phenomena of ‘cross-adaptation’ appear, training to an earlier member of the series acetic acid, succinic acid, fumaric acid entailing adaptation to a later member but not vice versa. With citric acid, aconitic acid and glycerol there is evidence of multiple-growth mechanisms. Additions of certain carboxylic acids shorten the lag of ageing cultures in the glucose medium. The classes (a), (b) and (c) bear no relation to the number of carbon atoms or the functional groups in the molecules of the various substances. They bear, however, certain relations to the ‘tricarboxylic acid cycle’, which are examined in part II.