title: Phylogenetic analysis reveals the coexistence of interfamily and interspecies horizontal gene transfer in Streptococcus thermophilus strains isolated from the same yoghurt.
abstract: Horizontal gene transfer (HGT) is an important evolutionary mechanism that has shaped prokaryotic genomes. For Streptococcus thermophilus, there is no direct evidence that the bacteria might acquire a second paralog from a different origin in the same niche. In this study, we found that four isolates of S. thermophilus (B, C, E and F) from the same yoghurt contained two putative homologs of the eno genes (eno-1 and eno-2) and two putative homologs of the guaB genes (guaB-1 and guaB-2). Both eno-1 and guaB-1 shared 100% nucleotide identity among the four isolates, and with isolate A and S. thermophilus ND03. Phylogenetic and nucleotide divergence analyses indicated that guaB-2 of these isolates may have been acquired from species in the genus Streptococcus, while eno-2 of isolates B and C may have been acquired from a donor in the genus Streptococcus. The eno-2 genes of isolates E and F may have been acquired from a donor in the Enterococcus genera. Relative synonymous codon usage analysis confirmed the eno-2 genes of isolates E and F as being acquired from a donor in genus Enterococcus. This study provides evidence that interfamily and interspecies HGT occur in S. thermophilus strains isolated from the same niche.
authors.affiliation: State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Grazing Animal Diseases of Ministry of Agriculture, CAAS, Lanzhou 730046, China.
authors.forename: Xuerui
authors.initials: X
authors.lastname: Li
authors.forename: Juan
authors.initials: J
authors.lastname: Xing
authors.forename: Baoyu
authors.initials: B
authors.lastname: Li
authors.forename: Fenggang
authors.initials: F
authors.lastname: Yu
authors.forename: Xi
authors.initials: X
authors.lastname: Lan
authors.forename: Jixing
authors.initials: J
authors.lastname: Liu
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D005075:Biological Evolution; D004269:DNA, Bacterial / Q000145:classification* / Q000235:genetics; D016983:Enterococcus / Q000201:enzymology / Q000235:genetics; D022761:Gene Transfer, Horizontal; D007168:IMP Dehydrogenase / Q000235:genetics; D007527:Isoenzymes / Q000235:genetics; D010751:Phosphopyruvate Hydratase / Q000235:genetics; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D048249:Streptococcus thermophilus / Q000145:classification* / Q000201:enzymology / Q000235:genetics; D015014:Yogurt / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D007527:Isoenzymes; D007168:IMP Dehydrogenase; D010751:Phosphopyruvate Hydratase
keywords: Horizontal gene transfer; Streptococcus; Thermophilus; eno; guaB