A Bacterial Respiratory Burst: Stimulation of the Metabolism of Neisseria Gonorrhoeae by Human Serum

Exposure of Neisseria gonorrhoeae to human serum causes an immediate increase in metabolism, including a fourfold increase in O2 consumption and [14C]adenine uptake and a threefold increase in glucose consumption. These effects were detected at a serum concentration of 1.0% and were maximal at 20%. Serum-stimulated gonococcal metabolism was inhibited by KCN but was not affected by heating or boiling of serum. Dialysis of serum with membrane tubing having a molecular weight exclusion of 3,500 eliminated stimulation of O2 consumption and reduced incorporation of [14C]adenine. Addition of lactate, pyruvate, or cysteine to dialyzed serum had no effect on bacterial metabolism. One in vitro ramification of this observation was demonstrated when gonococci, serum, and polymorphonuclear neutrophils (PMNs) were incubated in an O2 monitor. Under these conditions O2 consumption by bacteria stimulated by serum confounded interpretation of results and would be expected to reduce the O2 concentration in the suspension available for microbicidal metabolism by PMNs.