McQuiston John R, Fields Patricia I, Tauxe Robert V, Logsdon John M
Graduate Program in Population Biology, Ecology and Evolution, Emory University, Atlanta, GA 30322, USA.
Trends Microbiol. 2008 Apr;16(4):142-8. doi: 10.1016/j.tim.2008.01.009. Epub 2008 Mar 28.
Salmonellae are enterobacteria that have the unique ability to change their flagellar composition by switching expression among two loci that encode the major flagellin protein. This property is not available to all Salmonella, but is species, subspecies and serotype specific. Curiously, the subsequent loss of the second locus in some lineages of Salmonella has apparently been tolerated and, indeed, has led to considerable success for some lineages. We discuss here an evolutionary model for maintenance of this unique function and the possible evolutionary advantages of loss or preservation of this mechanism. We hypothesize that the second flagellin locus is a genetic 'spare tyre' used in particular environmental circumstances.
沙门氏菌是肠杆菌，具有独特的能力，可通过在两个编码主要鞭毛蛋白的基因座之间切换表达来改变其鞭毛组成。并非所有沙门氏菌都具备这种特性，而是具有物种、亚种和血清型特异性。奇怪的是，在沙门氏菌的某些谱系中，第二个基因座随后的缺失显然已被容忍，实际上，这已为某些谱系带来了相当大的成功。我们在此讨论维持这种独特功能的进化模型以及该机制丧失或保留的可能进化优势。我们假设第二个鞭毛蛋白基因座是在特定环境条件下使用的遗传“备用轮胎”。
