Utilization of D-amino acids by Fusobacterium nucleatum and Fusobacterium varium

The utilization of D- and L-amino acids with acidic, basic or polar side ch ains was demonstrated by HPLC. Two species of the anaerobe Fusobacterium ut ilized D-lysine and the L isomers of glutamate, glutamine, histidine, lysin e and serine. Only F. varium used L-arginine, D-glutamate and D-serine as s ubstrates, whereas F. nucleatum specifically utilized D-histidine and D-glu tamine. D-Glutamate accumulated in F. nucleatum cultures supplemented with D-glutamine, and ornithine was detected when either DL- or L-arginine was i ncluded in F. varium cultures. Based on literature precedents, D-glutamate and D-histidine are isomerized to their L isomers prior to degradation, but separate catabolic pathways are possible for each enantiomer of lysine and serine.