The Sigma Factor AlgU Regulates Exopolysaccharide Production and Nitrogen-Fixing Biofilm Formation by Directly Activating the Transcription of pslA in Pseudomonas stutzeri A1501

文献类型： 外文期刊

第一作者： Shao, Yahui

作者： Shao, Yahui;Yin, Changyan;Lv, Fanyang;Jiang, Shanshan;Wu, Shaoyu;Han, Yueyue;Xue, Wei;Ma, Yiyuan;Zheng, Juan;Zhan, Yuhua;Ke, Xiubin;Lu, Wei;Lin, Min;Yan, Yongliang;Shang, Liguo

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关键词： nitrogen fixation; biofilm formation; the algU gene; the pslA gene; Pseudomonas stutzeri

期刊名称：GENES （ 影响因子：4.141； 五年影响因子：4.474 ）

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年卷期： 2022 年 13 卷 5 期

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收录情况： SCI

摘要： Pseudomonas stutzeri A1501, a plant-associated diazotrophic bacterium, prefers to conform to a nitrogen-fixing biofilm state under nitrogen-deficient conditions. The extracytoplasmic function (ECF) sigma factor AlgU is reported to play key roles in exopolysaccharide (EPS) production and biofilm formation in the Pseudomonas genus; however, the function of AlgU in P. stutzeri A1501 is still unclear. In this work, we mainly investigated the role of algU in EPS production, biofilm formation and nitrogenase activity in A1501. The algU mutant Delta algU showed a dramatic decrease both in the EPS production and the biofilm formation capabilities. In addition, the biofilm-based nitrogenase activity was reduced by 81.4% in the Delta algU mutant. The transcriptional level of pslA, a key Psl-like (a major EPS in A1501) synthesis-related gene, was almost completely inhibited in the algU mutant and was upregulated by 2.8-fold in the algU-overexpressing strain. A predicted AlgU-binding site was identified in the promoter region of pslA. The DNase I footprinting assays indicated that AlgU could directly bind to the pslA promoter, and beta-galactosidase activity analysis further revealed mutations of the AlgU-binding boxes drastically reduced the transcriptional activity of the pslA promoter; moreover, we also demonstrated that AlgU was positively regulated by RpoN at the transcriptional level and negatively regulated by the RNA-binding protein RsmA at the posttranscriptional level. Taken together, these data suggest that AlgU promotes EPS production and nitrogen-fixing biofilm formation by directly activating the transcription of pslA, and the expression of AlgU is controlled by RpoN and RsmA at different regulatory levels.

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