Factors influencing pigment production in a mutant strain of Serratia marcescens.

A high frequency of mutations affecting color production is characteristic of the HY strain of Serratia marcescens. After ultraviolet irradiation, mutants ranging from white, through pink and orange, to deep red shades darker than the wild type can be obtained (Labrum and Bunting, 1953). Many of the white and pink mutants emit diffusible substances which can be utilized by other color mutants growing in the same medium to produce red pigment (Rizki, 1954a, b). Some of these substances may be precursors of prodigiosin, the red pigment of the parent strain, as shown by the isolation and chemical analysis of one of these diffusible products from a mutant strain (Santer and Vogel, 1956). It is hoped that this approach to the biosynthesis of red pigment in S. marcescens will help to elucidate the pathways of its production. With this ultimate aim, numerous mutants of S. marcescens have been isolated and tested for their interaction with other mutants, i.e., whether they produce any substance which can be utilized by other mutants to form red pigment, or whether a particular mutant will respond to the presence of another mutant by developing red pigment. During this survey of mutant types, an unusual mutant was isolated and this report presents the conditions under which this mutant of S. marcescens will produce red pigment.