Isolation of a Serratia marcescens that Produces a Water-soluble Reddish-violet Peptide Complex

While screening for aminoacylase-producing bacteria from soil, we found a strain (Z-54) that produces a water-soluble reddish-violet pigment. It was isolated using a synthetic medium containing N-benzyloxycarbonyl-DL-methionine as the sole source of carbon. Taxonomic studies by biochemical and serological tests identified the Z-54 strain as Serratia marcescens 05:H1. The pigment was purified on Sephadex G-25, Asahipak GS-320, and Capcellpak C sub(18) SG-120 columns to a single peak having the highest molecular absorption coefficient (15,500) at 554 nm. The pigment had a single band with a M sub(r) of about 2600 in tricine-SDS-polyacrylamide gel electrophoresis. Gel filtration gave an estimated M sub(r) of 2800. Hydrolysis with 6 N HCl gave several amino acids including two unknown compounds. These properties are different from those of known pigments from microorganisms. Previously, we isolated one hundred of strains which use N-benzyloxycarbonyl-DL-methionine as the sole source of carbon. Microscopic observation of the Z-54 strain showed rods with round ends with peritrichous flagella. To confirm the identification of the Z-54 strain, serological testing was done by Dr. W. H. Ewing, Communicable Disease Center, Atlanta, U.S.A. from these results, the Z-54 strain was identified as Serratia marcescens 05:H1.