Effect of glutamate on exogenous citrate catabolism of Neisseria meningitidis and of other species of Neisseria.

Resting cell suspensions of Neisseria meningitidis group B (strain 2091) do not catabolize citrate as the sole substrate to an appreciable degree. When another substrate, such as glutamate, is also present to furnish energy for transport, citrate metabolism is greatly stimulated. Within limits, the amount of CO(2) produced from citrate is proportional to the amount of glutamate added. When the cells are disrupted, citrate is degraded at a rapid rate and the stimulatory effect of glutamate is completely eliminated. Pronounced stimulation of citrate metabolism by glutamate was demonstrated in 12 of 13 strains of N. meningitidis tested and only 1 of 6 strains of N. lactamicus. The remaining strains of N. lactamicus and one each of N. gonorrhoeae, N. flavescens, and N. flava did not utilize significant amounts of citrate in the absence or presence of glutamate. N. catarrhalis shared with Mima polymorpha and Moraxella glucidolytica a capability to catabolize citrate at a rapid rate without added glutamate. It is concluded that tests of glutamate-stimulated citrate metabolism may contribute to species characterization in the genus Neisseria.