Conditions of the Colour Change of Prodigiosin

Abstract

THERE have been several reports that prodigiosin, the pigment produced by Serratia marcescens, is red in acid solution with an absorption maximum at 535–540 mμ but is yellow–orange in alkaline solution with an absorption maximum at 470 mμ. (refs. 1 and 2). This colour change in strong acid or alkaline solution is recognized by anyone working with the pigment. The observation that the colour of a colony on an agar plate changes from orange to red when the pH, changing with growth, becomes more alkaline rather than more acid, and the report³ that eluates of single pink chromatographic bands show, on redevelopment, separation into both pink and orange bands, suggest that pH is not the only factor involved in the colour change of prodigiosin from red to orarge.