title: Characterization of the Lactobacillus casei group based on the profiling of ribosomal proteins coded in S10-spc-alpha operons as observed by MALDI-TOF MS.
abstract: The taxonomy of the members of the Lactobacillus casei group is complicated because of their phylogenetic similarity and controversial nomenclatural status. In this study, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) of ribosomal proteins coded in the S10-spc-alpha operon, termed S10-GERMS, was applied in order to classify 33 sample strains belonging to the L. casei group. A total of 14 types of ribosomal protein genes coded in the operon were first sequenced from four type strains of the L. casei group (L. casei JCM 1134(T), L. paracasei subsp. paracasei JCM 8130(T), L. paracasei subsp. tolerans JCM 1171(T), and L. rhamnosus JCM 1136(T)) together with L. casei JCM 11302, which is the former type strain of 'L. zeae'. The theoretical masses of the 14 types of ribosomal proteins used as biomarkers were classified into five types and compiled into a ribosomal protein database. The observed ribosomal proteins of each strain, identified by MALDI-TOF MS, were categorized into types based on their masses, summarized as ribosomal protein profiles, and they were used to construct a phylogenetic tree. The 33 sample strains, together with seven genome-sequenced strains, could be classified into four major clusters, which coincided precisely with the taxa of the (sub)species within the L. casei group. Three "ancient" strains, identified as L. acidophilus and L. casei, were correctly re-identified as L. paracasei subsp. paracasei by S10-GERMS. S10-GERMS would thus appear to be a powerful tool for phylogenetic characterization, with considerable potential for management of culture collections.
authors.affiliation: Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba, Ibaraki 305-8569, Japan. sato-hiroaki@aist.go.jp
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Sato
authors.forename: Masaki
authors.initials: M
authors.lastname: Torimura
authors.forename: Maki
authors.initials: M
authors.lastname: Kitahara
authors.forename: Moriya
authors.initials: M
authors.lastname: Ohkuma
authors.forename: Yudai
authors.initials: Y
authors.lastname: Hotta
authors.forename: Hiroto
authors.initials: H
authors.lastname: Tamura
mesh_terms: D016000:Cluster Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D007780:Lacticaseibacillus casei / Q000737:chemistry* / Q000145:classification* / Q000235:genetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009876:Operon; D010802:Phylogeny; D012269:Ribosomal Proteins / Q000737:chemistry* / Q000235:genetics; D017422:Sequence Analysis, DNA; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D004269:DNA, Bacterial; D012269:Ribosomal Proteins