Zheng Huiming, Mao Yiling, Teng Jiao, Zhu Qingcheng, Ling Jun, Zhong Zengtao
Department of Microbiology, Nanjing Agricultural University, Nanjing, China,
Curr Microbiol. 2015 Feb;70(2):219-27. doi: 10.1007/s00284-014-0701-x. Epub 2014 Oct 7.
Bacterial motility is most likely a critical factor for rhizobium to chemotactically colonize on the root surface prior to infecting leguminous plant hosts. Several studies of the rhizobium flagellar filament have been reported, but little is known about the rhizobium flagellum hook. To investigate the roles of the hook protein in flagellum synthesis in Mesorhizobium tianshanense, the hook protein-encoding gene flgE of M. tianshanense was amplified by PCR and sequenced. Comparison of the deduced amino acid sequences revealed pronounced similarities in Domain 1 and lower similarities in Domain 2, which are supposed to be related to hook structure assembly and antigenic diversity, respectively. The level of transcription of flgE increased along with the cell growth and reached its maximum at the middle log phase. Disruption of the flgE gene caused a flagellar-less phenotype, thereby causing complete loss of swimming ability, modified nutrient-related swarming ability and biofilm formation. Moreover, the absence of flagellar caused decreased bacterial attachment on the root hair, suggesting that flagellar is involved in the early stage of symbiosis process.
细菌运动性很可能是根瘤菌在感染豆科植物宿主之前在根表面进行趋化性定殖的关键因素。已有多项关于根瘤菌鞭毛丝的研究报道，但对根瘤菌鞭毛钩却知之甚少。为了研究钩蛋白在天山中生根瘤菌鞭毛合成中的作用，通过PCR扩增了天山中生根瘤菌的钩蛋白编码基因flgE并进行测序。推导的氨基酸序列比较显示，结构域1有明显的相似性，结构域2的相似性较低，推测它们分别与钩结构组装和抗原多样性有关。flgE的转录水平随着细胞生长而增加，并在对数中期达到最大值。flgE基因的破坏导致无鞭毛表型，从而导致游泳能力完全丧失、与营养相关的群游能力改变和生物膜形成。此外，鞭毛的缺失导致细菌在根毛上的附着减少，这表明鞭毛参与了共生过程的早期阶段。
