关键词: 施氏假单胞菌A1501, RpoN, 鞭毛合成, 根际定殖, 生物膜

Abstract: Many bacteria use the alternative sigma factor σ54 (also known as RpoN) to transcribe specific genes, such as nitrogen assimilation genes, C4-dicarboxylate transport genes and flagellar genes. In this study, the global regulator was investigated to explore its regulatory effect on flagellar biosynthesis in Pseudomonas stutzeri A1501. Deletion mutant and complementary strain were constructed in rpoN to analyze phenotypes in flagellar structure, swimming motility, biofilm formation, rhizosphere colonization and relative expression levels of flagellar genes. The results showed that loss of rpoN could cause impaired flagellar structure and swimming motility, 25-and 10-fold decrease in competitive root colonization and biofilm-forming ability, respectively. Moreover, relative expression levels of flagellar genes in rpoN mutant could significantly decrease when compared to the wild-type. In Pseudomonas, Class Ⅱ and Class Ⅲ flagellar genes were RpoN-dependent. And in this work, putative RpoN binding site was observed in fliC, fliA promoter regions, indicating that RpoN in A1501 could also participate in Class I and Class IV genes regulatory networks. These results suggested that RpoN affected flagellar biosynthesis process by participating different flagellar gene transcriptional hierarchy, thus affecting swimming motility, biofilm formation and root colonization in Pseudomonas stutzeri A1501.

Key words: Pseudomonas stutzeri A1501, RpoN, flagellar biosysthesis, root colonization, biofilm