茎瘤固氮根瘤菌ORS571鞭毛马达基因fliN与fliM的功能分析

Function analysis of flagellar genes fliN and fliM in Azorhizobium caulinodans ORS571

【目的】考察茎瘤固氮根瘤菌ORS571中鞭毛马达蛋白FliN、FliM的编码基因分别缺失的突变体表型,初步探究其功能机理。【方法】本研究采用同源重组和三亲本接合转移的方法构建突变体,测定野生型及突变株的生长曲线、趋化性、胞外多糖的分泌、生物膜的形成及细胞絮凝等表型。【结果】三种菌株的生长速率基本无差,与野生型菌株相比突变株鞭毛结构丧失,趋化能力、分泌的胞外多糖和生物膜形成能力均下降,但相同时间内细胞絮凝程度比野生型明显。【结论】实验表明,鞭毛基因fliN、fliM对茎瘤固氮根瘤菌ORS571鞭毛的形成、趋化运动、胞外多糖的分泌、生物膜的形成及细胞絮凝能力等均有调控作用。

[Objective] To investigate the phenotypes of Azorhizobium caulinodans ORS57 mutant strains that lacked the flagellar motor proteins Fli N and Fli M respectively, and the functional mechanism of these proteins. [Methods] The gene knock-out mutant strains（ΔfliN, ΔfliM） were constructed by homologous recombination and triparental conjugation. The phenotypes including cell growth, chemotaxis, exopolysaccharide production, biofilm formation and cell flocculation were investigated. [Results] Mutants ΔfliN and ΔfliM did not shown any difference in cell growth compared with the wild-type strain. However, both mutants lost their flagella when observed under electron microscope. In addition, ΔfliN and ΔfliM were impaired in chemotaxis, exopolysaccharide production, and biofilm formation. To the contrary, the flocculation ratio of both mutants was higher than that of the wild-type strain within the same amount of time. [Conclusion] The flagellar genes fliN and fliM could regulate the flagellum formation, cell motility, exopolysaccharide production, biofilm formation and cell flocculation of Azorhizobium caulinodans ORS571.