Growth inhibition among strains of Neisseria gonorrhoeae due to production of inhibitory free fatty acids and lysophosphatidylethanolamine: absence of bacteriocins

Abstract

Each of 50 tested strains of Neisseria gonorrhoeae produced growth-inhibitory substances that were active against most strains of gonococci or meningococci, but not against species other than the Neisseria. There were quantitative differences among different strains in production of the inhibitor and sensitivity to it, but not of sufficient magnitude to permit routine strain typing. The inhibitor was associated with the cell pellet (crude cell envelope) and was not inducible with mitomycin C. Inhibitory activity was thermostable and resisted alkali and proteolytic enzymes. The inhibitor was quantitatively recovered from whole cells by chloroform-methanol extraction. Separation of total gonococcal lipids by silica gel chromatography revealed inhibitory activity in both the free fatty acid and the phospholipid fractions. The major phospholipid, phosphatidylethanolamine, had no inhibitory activity, but monoacyl phosphatidylethanolamine, a minor phospholipid, was quite inhibitory. It is likely that the "bacteriocin" of N. gonorrhoeae strains results from the degradation of phosphatidylethanolamine to inhibitory long-chain free fatty acids and monoacyl phosphatidylethanolamine.