Pigment Production and Antibiotic Activity in Cultures of Pseudomonas aeruginosa

Abstract

The production of pigments by P. aeruginosa was found to vary greatly in different culture media. Pyocyanin was produced in potato-glycerol broth; in glycerol broth, both pyocyanin and a fluorescent pigment were formed; veal infusion or blood inhibited both pigments even in the presence of glycerol; and cultures containing enough glucose (over 1%) to maintain an acid reaction showed no pigment formation. Antibiotic activity was detd. for heated whole cultures, extracted pyocyanin, a-oxyphenazine, other ether-soluble substances, and culture residues after chloroform and ether extraction. Test organisms were Staphylococcus aureus, Escherichia coli, and Myco-bacterium smegmatis. Pyocyanin inhibited all 3 organisms. a-Oxyphenazine, ether extracts of acidified, pigmented cultures, and chloroform- and ether-extracted residues of fluorescent cultures inhibited 5. aureus and M. smegmatis, but not E. coli. Cultures producing no pigments showed no antibiotic activity, and residues of non-fluorescent cultures were inactive. [alpha]-Oxyphenazine was found in very small amts. if separated from pyocyanin directly after extraction. In glycerol broth, pyocyanin and the H2O-sol., heat-stable antibiotic associated with fluorescence were most abundant in cultures two to 3 weeks old; the fatty acid fraction from older cultures was more active.