State Key Laboratory of Veterinary Etiological Biology, Key Laboratory of Grazing Animal Diseases of Ministry of Agriculture, CAAS, Lanzhou 730046, China.
Mol Phylogenet Evol. 2013 Oct;69(1):286-92. doi: 10.1016/j.ympev.2013.06.002. Epub 2013 Jun 12.
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.
水平基因转移 (HGT) 是一种重要的进化机制，它塑造了原核生物的基因组。对于嗜热链球菌，没有直接证据表明细菌可能从同一小生境中的不同来源获得第二个直系同源物。在这项研究中，我们发现了来自同一种酸奶的四个嗜热链球菌（B、C、E 和 F）菌株含有两个假定的 eno 基因（eno-1 和 eno-2）和两个假定的 guaB 基因（guaB-1 和 guaB-2）的同源物。四个菌株的 eno-1 和 guaB-1 之间的核苷酸序列完全相同，与菌株 A 和嗜热链球菌 ND03 也完全相同。系统发育和核苷酸差异分析表明，这些菌株的 guaB-2 可能是从链球菌属的物种中获得的，而菌株 B 和 C 的 eno-2 可能是从链球菌属的供体中获得的。菌株 E 和 F 的 eno-2 基因可能是从肠球菌属的供体中获得的。相对同义密码子使用分析证实了菌株 E 和 F 的 eno-2 基因是从肠球菌属的供体中获得的。本研究提供了证据表明，水平基因转移在从同一小生境中分离的嗜热链球菌菌株中发生了家族间和种间转移。
