Li Yinuo, Sun Hong, Ma Xiaoyuan, Lu Ann, Lux Renate, Zusman David, Shi Wenyuan
Molecular Biology Institute and School of Dentistry, University of California, Los Angeles, CA 90095, USA.
Proc Natl Acad Sci U S A. 2003 Apr 29;100(9):5443-8. doi: 10.1073/pnas.0836639100. Epub 2003 Apr 18.
Myxococcus xanthus is a Gram-negative bacterium with a complex life cycle that includes vegetative swarming and fruiting-body formation. Social (S)-motility (coordinated movement of large cell groups) requires both type IV pili and fibrils (extracellular matrix material consisting of polysaccharides and protein). Little is known about the role of this extracellular matrix, or fibril material, in pilus-dependent motility. In this study, mutants lacking fibril material and, therefore, S-motility were found to be hyperpiliated. We demonstrated that addition of fibril material resulted in pilus retraction and rescued this phenotype. The fibril material was further examined to determine the component(s) that were responsible for triggering pilus retraction. Protein-free fibril material was found to be highly active in correcting hyperpiliation. However, the amine sugars present in hydrolyzed fibril material, e.g., glucosamine and N-acetylglucosamine (GlcNAc) had no effect on fibril(-) mutants, but, interestingly, cause hyperpiliation in wild-type cells. In contrast, chitin, a natural GlcNAc polymer, was found to restore pilus retraction in hyperpiliated mutants, indicating that a polysaccharide containing amine sugars is likely required for pilus retraction. These data suggest that the interaction of type IV pili with amine-containing polysaccharides on cell and slime-trail surfaces may trigger pilus retraction, resulting in S-motility and slime-trailing behaviors.
黄色粘球菌是一种革兰氏阴性细菌，具有复杂的生命周期，包括营养性群体游动和子实体形成。社会性（S）运动性（大细胞群体的协调运动）既需要IV型菌毛，也需要纤丝（由多糖和蛋白质组成的细胞外基质材料）。关于这种细胞外基质或纤丝材料在菌毛依赖性运动中的作用知之甚少。在本研究中，发现缺乏纤丝材料因而缺乏S运动性的突变体菌毛过多。我们证明添加纤丝材料会导致菌毛回缩并挽救这种表型。对纤丝材料进行了进一步研究，以确定负责触发菌毛回缩的成分。发现无蛋白的纤丝材料在纠正菌毛过多方面具有很高的活性。然而，水解纤丝材料中存在的氨基糖，例如葡萄糖胺和N-乙酰葡萄糖胺（GlcNAc）对纤丝缺失突变体没有影响，但有趣的是，会导致野生型细胞菌毛过多。相反，几丁质，一种天然的GlcNAc聚合物，被发现可以恢复菌毛过多突变体中的菌毛回缩，这表明菌毛回缩可能需要一种含有氨基糖的多糖。这些数据表明，IV型菌毛与细胞和黏液痕迹表面含胺多糖的相互作用可能会触发菌毛回缩，从而导致S运动性和黏液拖尾行为。
