The Azospirillum brasilense Chel Chemotaxis Pathway Controls Swimming Velocity, Which Affects Transient Cell-to-Cell Clumping
The Azospirillum brasilense Chel Chemotaxis Pathway Controls Swimming Velocity, Which Affects Transient Cell-to-Cell Clumping
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DOI：
10.1128/jb.00310-12
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发表时间：
2012-07-01
影响因子：
3.2
通讯作者：
Alexandre, Gladys
中科院分区：
文献类型：
--
作者：
Bible, Amber;Russell, Matthew H.;Alexandre, Gladys
Azospirillum brasilense的Chel趋化样途径有助于趋化性和趋氧性，并且还被发现有助于调节影响细胞聚集和絮凝倾向的细胞表面粘附特性的变化。Chel对巴西芽孢杆菌趋化性和絮凝的控制的确切作用尚不清楚。在这里，我们展示了Chel影响可逆的细胞间结块，这是一种细胞行为，在这种细胞行为中，运动细胞在游动分开之前，通过在非鞭毛的极点上相互粘附而短暂地相互作用。结块先于絮凝，是絮凝所必需的，这两个过程似乎是独立调节的。Delta aerC受体突变株和缺乏cheA1、cheY1、cheB1或cheR1（单独或联合）或chel缺失的突变株的表型表明，chel直接介导鞭毛游动速度的变化，这种行为直接调节了短暂的结块性质。我们的研究结果还表明，另一种受体和信号通路参与介导本研究中发现的其他与切尔无关的凝集变化。在过渡到稳定的团块形成之前，短暂的团块形成涉及特定细胞外多糖（EPS）的产生；然而，这些聚集特异性EPS的产生并不直接受Chel活性的控制。螯合依赖的结块可能会拮抗运动性和阻止趋化性，从而维持细胞在代谢有利的生态位。
The Chel chemotaxis-like pathway of Azospirillum brasilense contributes to chemotaxis and aerotaxis, and it has also been found to contribute to regulating changes in cell surface adhesive properties that affect the propensity of cells to clump and to flocculate. The exact contribution of Chel to the control of chemotaxis and flocculation in A. brasilense remains poorly understood. Here, we show that Chel affects reversible cell-to-cell clumping, a cellular behavior in which motile cells transiently interact by adhering to one another at their nonflagellated poles before swimming apart. Clumping precedes and is required for flocculation, and both processes appear to be independently regulated. The phenotypes of a Delta aerC receptor mutant and of mutant strains lacking cheA1, cheY1, cheB1, or cheR1 (alone or in combination) or with chel deleted show that Chel directly mediates changes in the flagellar swimming velocity and that this behavior directly modulates the transient nature of clumping. Our results also suggest that an additional receptor(s) and signaling pathway(s) are implicated in mediating other Chel-independent changes in clumping identified in the present study. Transient clumping precedes the transition to stable clump formation, which involves the production of specific extracellular polysaccharides (EPS); however, production of these clumping-specific EPS is not directly controlled by Chel activity. Chel-dependent clumping may antagonize motility and prevent chemotaxis, thereby maintaining cells in a metabolically favorable niche.