Immunological relationships among lactic dehydrogenases in the genera Lactobacillus and Leuconostoc.

Antisera were prepared against pure nicotinamide adenine dinucleotide-dependent d-lactic dehydrogenases of Lactobacillus leichmannii, L. jensenii, and L. fermenti. When tested against these three antisera, crude extracts of almost all species of Lactobacillus containing a d-lactic dehydrogenase give cross-reactions. Extensive pairwise comparisons between cross-reacting crude extracts by double diffusion experiments permit the recognition of groups of identical antigenic specificity among the lactic dehydrogenases of the various nomenspecies of Lactobacillus. The same groups are revealed by each of the three antisera. By analyses of spur formation, the groups of identical antigenic specificity can be arranged in order of decreasing similarity to the homologous d-lactic dehydrogenase used as the reference point. From the combined results obtained with the three antisera, a map of the antigenic relationships among the d-lactic dehydrogenases of lactobacilli can be constructed. Microcomplement fixation experiments with two of the three anti-d-lactic dehydrogenases antisera support the conclusions drawn from double diffusion experiments and provide a quantitative estimation of the antigenic relationships among the various d-lactic dehydrogenases. An antiserum was also prepared against the pure l-lactic dehydrogenase of L. acidophilus group III. It cross-reacts with extracts of almost all lactobacilli containing an l-lactic dehydrogenase. With respect to species that contain both d- and l-lactic dehydrogenases, this antiserum reveals the same groups of identical antigenic specificity as do the antisera directed against d-lactic dehydrogenases. Other than the genus Lactobacillus, only extracts of Leuconostoc cross-react with anti-d-lactic dehydrogenase. No extrageneric cross-reactions were obtained with the anti-l-lactic dehydrogenase.