Lactobacillus casei,Lactobacillus rhamnosus, andLactobacillus zeaeisolates identified by sequence signature and immunoblot phenotype

Abstract

Species taxonomy within the Lactobacillus casei group of bacteria has been unsettled. With the goal of helping clarify the taxonomy of these bacteria, we investigated the first 3 variable regions of the 16S rRNA gene, the 16S-23S rRNA interspacer region, and one third of the chaperonin 60 gene for Lactobacillus isolates originally designated as L. casei, L. paracasei, L. rhamnosus, and L. zeae. For each genetic region, a phylogenetic tree was created and signature sequence analysis was done. As well, phenotypic analysis of the various strains was performed by immunoblotting. Both sequence signature analysis and immunoblotting gave immediate identification of L. casei, L. rhamnosus, and L. zeae isolates. These results corroborate and extend previous findings concerning these lactobacilli; therefore, we strongly endorse recent proposals for revised nomenclature. Specifically, isolate ATCC 393 is appropriately rejected as the L. casei type strain because of grouping with isolates identified as L. zeae. As well, because all other L. casei isolates, including the proposed neotype isolate ATCC 334, grouped together with isolates designated L. paracasei, we support the use of the single species L. casei and rejection of the name L. paracasei.

Multilocus Sequence Typing ofLactobacillus caseiReveals a Clonal Population Structure with Low Levels of Homologous Recombination

“…The species Lactobacillus zeae, Lactobacillus rhamnosus, Lactobacillus casei, and Lactobacillus paracasei are phylogenetically and phenotypically closely related and are regarded together as the L. casei group. The taxonomic status of these species and identification of strains as these species are still matters of debate (13,14), mostly because the type strain of L. casei, strain ATCC 393, is divergent compared to most L. casei/L. paracasei strains and appears related to L. zeae.…”

DNA Arrays and Membrane Hybridization Methods for Screening of Six Lactobacillus Species Common in Food Products

“…Membrane hybridization with species-specific probes has been shown to be useful in LAB identification following DGGE (Burton et al 2003). Challenges persist in analyzing some Lactobacillus species, such as the L. casei group, including the species L. paracasei, L. zeae, and L. rhamnosus (Dobson et al 2004), and the L. plantarum-a group, made up of the L. plantarum, L. paraplantarum, and L. pentosus species (Felis and Dellaglio 2005).…”

“…These genes have a significant advantage over 16S rDNA because of their higher species-specific discrimination (Dobson et al 2004).…”

Application of molecular identification tools for Lactobacillus, with a focus on discrimination between closely related species: A review

“…Dobson et al (2004) L. casei/L. paracasei from wine 16S ARDRA (Bfa I, Mse I), RAPD, Eco RI ribotyping 13 wine strains typed as L. paracasei/casei, based on similar band pattern as L. paracasei type strain and L. casei ATCC 334 Rodas et al (2005).…”