The formation of papillae on bacterial colonies. II

Abstract

Observations are recorded on the formation of secondary colonies of Bact. lactis aerogenes or of Bact. coli mutabile grown on agar plates containing various sugars to which the particular strain requires adaptation. The papillae arise during a process of ageing and may not appear until long after utilization of the specific sugar begins. Cultures derived from papillae show some at least of the adapted or mutant character, but so also may cultures derived from the primary colony. Consideration of colony morphology and of the inhomogeneities which may arise in dense bacterial cultures, suggests that the occurrence of spontaneous mutants is neither a necessary nor a sufficient condition for secondary colony formation.