<Emphasis Type="Italic">In silico</Emphasis> phylogenetic analysis of lactic acid bacteria and new primer set for identification of <Emphasis Type="Italic">Lactobacillus plantarum</Emphasis> in food samples

Lactic acid bacteria (LAB) include species very closely related both physiologically and genotypically. Therefore, the identification of this bacteria group using conventional phenotypic methods is ambiguous and cumbersome. In this study, we have analyzed a recA gene fragment from 30 bacteria, including LAB and species common in the human gastrointestinal tract, aiming to evaluate the gene conservation among them and the development of primers and PCR conditions able to discriminate Lactobacillus plantarum strains from LAB closely related. The fragment with 995 bp of recA gene has grouped LAB, enterobacteria and bifidobacteria, in different clusters. A novel primer pair, LPrecAF and LPrecAR with 23 and 18 bp, respectively, has allowed the single amplification of a 108 bp fragment of L. plantarum strains contained in culture broth and fermented dairy samples. The observed detection limit for food samples and for cultures broth were 1 × 10³ and 7 × 10² CFU mL⁻¹, respectively. This approach proved to be a simple and efficient method for the identification and monitoring of L. plantarum in food, feeds, and culture broth. Moreover, the assay could be used in the studies from human or environmental microbiota.