Phylogenetic Structure of the “Leuconostocs”: An Interesting Case of a Rapidly Evolving Organism

Abstract

Summary Comparative analysis of 16S rRNA sequences shows that the following species of lactic acid bacteria: Lactobacillus confusus, L. halotolerans, L. kandleri, L. minor, L. viridescens, Leuconostoc cremoris, Lc. lactis, Lc. mesenteroides, Lc. oenos, and Lc. paramesenteroides form a natural grouping, which could be called the “leuconostoc branch” of the lactobacilli. This grouping is clearly distinct from other branches of the lactobacilli (e.g., L. casei and its relatives), and it includes all the Leuconostoc strains so far examined. The leuconostoc branch divides into two subgroups — one comprising Leuconostoc species only, the other containing Lc. paramesenteroides and the above named lactobacilli. Within the Lc. paramesenteroides subgroup L. confusus and Lc. paramesenteroides appear to be specific relatives of one another. One member of the leuconostoc branch, Lc. oenos, is noteworthy in that the sequence of its rRNA is more distant than those of the other members of the leuconostoc branch from the rRNAs of outgroup species. Lc. oenos and its rRNA show features typical of rapidly evolving lineages, i.e., a tendency to alter the composition of otherwise highly conserved positions in 16S rRNA, and atypical or unusual phenotypic properties, that set in apart from other members of its natural group.