噬菌体及其宿主终端酶序列的系统进化研究

Phylogenetic analysis of terminase sequences-evidence for horizontal gene transfer between phages and their bacterial hosts during evolution

在原核生物的进化过程中,基因的横向转移(HGT)是一个重要的进化机制。为了研究HGT在噬菌体及其宿主体内的发生情况,分析多个物种的终端酶蛋白质序列。结果显示,大部分噬菌体与其宿主间的蛋白质序列中,终端酶的大、小亚基的同源性都非常之高,小亚基的序列几乎与其宿主完全一致。相比之下,噬菌体间的蛋白质序列同源性非常低。系统发生分析显示,序列相似性高的噬菌体较容易与其宿主聚集,产生寄生关系。结果表明,在噬菌体及其选择的宿主之间存在HGT,而且这种作用可能对终端酶的进化产生重要的影响。

Horizontal gene transfer （HGT） is an important evolutionary mechanism in prokaryotic genome evolution and has been widely studied. To investigate the occurrence of HGT in phages and their bacterial hosts, we have analyzed protein sequences of terminase across different species. Our results demonstrated that, in most phages, protein sequences of both small and large terminase subunits （small subunits in particular） are almost identical to those of their hosts, while sequences from various phages have much lower identity in between. Phylogenetic analysis also suggests that some phages seem to converge with their hosts rather than other phages. These strongly suggest that HGT probably exists between the selected phages and their bacterial hosts, which may have played an important role in terminase evolution.