Abstract
The partial nucleotide sequences encoding elongation factor Tu (tuf gene), 60-kDa heat shock protein (hsp60 gene) and phenylalanyl-tRNA synthase (pheS gene) were determined to assess the suitability as phylogenetic markers for discriminating the closely related species in Lactobacillus acidophilus group, L. casei group and L. plantarum group. A total of 234 lactobacilli were chosen from traditional fermented dairy products that were not exactly assigned to species based on biochemical tests and 16S rRNA gene sequences. The sequencing of partial tuf, hsp60 and pheS gene of all strains was performed, and then, the phylogenetic trees were constructed by neighbor-joining method. Phylogenetic tree revealed three genes provided better resolution of each Lactobacillus species than 16S rDNA, and all of strains were clearly identified as L. casei (63 strains), L. plantarum (58 strains) and L. helveticus (113 strains) by comparison of sequences with the type strains. From our results, the partial sequences of three genes had a higher discriminatory power than 16S rRNA gene sequences and were an alternative molecular tool for the taxonomical analysis of L. casei group, L. plantarum group and L. acidophilus group.
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