Moens S, Michiels K, Keijers V, Van Leuven F, Vanderleyden J
F. A. Janssens Laboratory of Genetics, Katholieke Universiteit Leuven, Heverlee, Belgium.
J Bacteriol. 1995 Oct;177(19):5419-26. doi: 10.1128/jb.177.19.5419-5426.1995.
Azospirillum brasilense can display a single polar flagellum and several lateral flagella. The A. brasilense Sp7 gene laf1, encoding the flagellin of the lateral flagella, was isolated and sequenced. The derived protein sequence is extensively similar to those of the flagellins of Rhizobium meliloti, Agrobacterium tumefaciens, Bartonella bacilliformis, and Caulobacter crescentus. An amino acid alignment shows that the flagellins of these bacteria are clustered and are clearly different from other known flagellins. A laf1 mutant, FAJ0201, was constructed by replacing an internal part of the laf1 gene by a kanamycin resistance-encoding gene cassette. The mutant is devoid of lateral flagella but still forms the polar flagellum. This phenotype is further characterized by the abolishment of the capacities to swarm on a semisolid surface and to spread from a stab inoculation in a semisolid medium. FAJ0201 shows a normal wheat root colonization pattern in the initial stage of plant root interaction.
巴西固氮螺菌可呈现一根极鞭毛和数根侧鞭毛。分离并测序了巴西固氮螺菌Sp7编码侧鞭毛鞭毛蛋白的基因laf1。推导的蛋白质序列与苜蓿根瘤菌、根癌土壤杆菌、巴氏杆菌和新月柄杆菌的鞭毛蛋白序列高度相似。氨基酸比对表明，这些细菌的鞭毛蛋白聚在一起，明显不同于其他已知的鞭毛蛋白。通过用编码卡那霉素抗性的基因盒替换laf1基因的内部部分构建了laf1突变体FAJ0201。该突变体没有侧鞭毛，但仍能形成极鞭毛。这种表型的进一步特征是丧失了在半固体表面群游以及从半固体培养基中的穿刺接种处扩散的能力。FAJ0201在植物根相互作用的初始阶段显示出正常的小麦根定殖模式。
