LIGHT AS A FACTOR IN THE PRODUCTION OF PIGMENT BY CERTAIN BACTERIA

Abstract

1. Two cultures of acid-fast bacteria have been found which form pigment when cultivated in the presence of light and are wholly devoid of it when cultivated in darkness. 2. Brief exposure to ultra-violet and sunlight, and longer exposures to electric light, confers on fully developed unpigmented cultures the ability to form pigment during a subsequent period in darkness. 3. The mechanism of pigment formation under the influence of light is not known; however, it is evident that it is a vital phenomenon and is not merely the result of a chemical reaction induced by light in substances preformed by the organism. The evidence for this statement is as follows (a) Unpigmented organisms killed by heat or by ultra-violet light do not develop pigment, (b) Pigment is not formed in living cultures incubated at 4[degree] C after exposure, (c) Whereas, alcohol will extract the pigment from cultures grown in the presence of light, alcoholic extracts of non-pigmented cultures do not become colored when so exposed.