Asikyan Miranda L, Kus Julianne V, Burrows Lori L
Department of Biochemistry and Biomedical Sciences, The Michael G. DeGroote Institute for Infectious Diseases Research, Rm. 4H18, Health Sciences Centre, McMaster University, 1200 Main St. W., Hamilton, ON, Canada L8N 3Z5.
J Bacteriol. 2008 Nov;190(21):7022-34. doi: 10.1128/JB.00938-08. Epub 2008 Sep 5.
Pseudomonas aeruginosa uses type IV pili to colonize various materials and for surface-associated twitching motility. We previously identified five phylogenetically distinct alleles of pilA in P. aeruginosa, four of which occur in genetic cassettes with specific accessory genes (J. V. Kus, E. Tullis, D. G. Cvitkovitch, and L. L. Burrows, Microbiology 150:1315-1326, 2004). Each of the five pilin alleles, with and without its associated pilin accessory gene, was used to complement a group II PAO1 pilA mutant. Expression of group I or IV pilA genes restored twitching motility to the same extent as the PAO1 group II pilin. In contrast, poor twitching resulted from complementation with group III or group V pilA genes but increased significantly when the cognate tfpY or tfpZ accessory genes were cointroduced. The enhanced motility was linked to an increase in recoverable surface pili and not to alterations in total pilin pools. Expression of the group III or V pilins in a PAO1 pilA-pilT double mutant yielded large amounts of surface pili, regardless of the presence of the accessory genes. Therefore, poor piliation in the absence of the TfpY and TfpZ accessory proteins results from a net increase in PilT-mediated retraction. Similar phenotypes were observed for tfpY single and tfpY-pilT double knockout mutants of group III strain PA14. A PilAV-TfpY chimera produced few surface pili, showing that the accessory proteins are specific for their cognate pilin. The genetic linkage between specific pilin and accessory genes may be evolutionarily conserved because the accessory proteins increase pilus expression on the cell surface, thereby enhancing function.
铜绿假单胞菌利用IV型菌毛定殖于各种材料表面，并进行与表面相关的颤动运动。我们之前在铜绿假单胞菌中鉴定出了五个系统发育上不同的pilA等位基因，其中四个存在于带有特定辅助基因的遗传盒中（J. V. Kus、E. Tullis、D. G. Cvitkovitch和L. L. Burrows，《微生物学》150:1315 - 1326，2004年）。五个菌毛蛋白等位基因中的每一个，无论有无其相关的菌毛蛋白辅助基因，都被用于互补II组PAO1 pilA突变体。I组或IV组pilA基因的表达恢复颤动运动的程度与PAO1 II组菌毛蛋白相同。相比之下，用III组或V组pilA基因互补导致颤动较差，但当共导入同源的tfpY或tfpZ辅助基因时，颤动显著增加。增强的运动性与可回收的表面菌毛增加有关，而不是与总菌毛蛋白库的改变有关。在PAO1 pilA - pilT双突变体中表达III组或V组菌毛蛋白会产生大量表面菌毛，无论辅助基因是否存在。因此，在没有TfpY和TfpZ辅助蛋白的情况下菌毛形成不佳是由于PilT介导的回缩净增加所致。对于III组菌株PA14的tfpY单敲除和tfpY - pilT双敲除突变体也观察到了类似的表型。一个PilAV - TfpY嵌合体产生的表面菌毛很少，表明辅助蛋白对其同源菌毛蛋白具有特异性。特定菌毛蛋白和辅助基因之间的遗传联系可能在进化上是保守的，因为辅助蛋白增加了细胞表面菌毛蛋白的表达，从而增强了功能。
