title: RpoS differentially affects the general stress response and biofilm formation in the endophytic Serratia plymuthica G3.
abstract: The σ(S) subunit RpoS of RNA polymerase functions as a master regulator of the general stress response in Escherichia coli and related bacteria. RpoS has been reported to modulate biocontrol properties in the rhizobacterium Serratia plymuthica IC1270. However, the role of RpoS in the stress response and biofilm formation in S. plymuthica remains largely unknown. Here we studied the role of RpoS from an endophytic S. plymuthica G3 in regulating these phenotypes. Mutational analysis demonstrated that RpoS positively regulates the global stress response to acid or alkaline stresses, oxidative stress, hyperosmolarity, heat shock and carbon starvation, in addition to proteolytic and chitinolytic activities. Interestingly, rpoS mutations resulted in significantly enhanced swimming motility, biofilm formation and production of the plant auxin indole-3-acetic acid (IAA), which may contribute to competitive colonization and environmental fitness for survival. These findings provide further insight into the strain-specific role of RpoS in the endophytic strain G3 of S. plymuthica, where it confers resistance to general stresses encountered within the plant environment. The heterogeneous functionality of RpoS in rhizosphere and endophytic S. plymuthica populations may provide a selective advantage for better adaptation to various physiological and environmental stresses.
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, Zhenjiang 212013, China; Institute of Life Sciences, Jiangsu University, Zhenjiang 212013, China. Electronic address: xgliu66@yahoo.com.
authors.forename: Xiaoguang
authors.initials: X
authors.lastname: Liu
authors.affiliation: School of Food and Biological Engineering, Jiangsu University, Zhenjiang 212013, China; Institute of Life Sciences, Jiangsu University, Zhenjiang 212013, China. Electronic address: wuyan@ujs.edu.cn.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wu
authors.affiliation: Institute of Life Sciences, Jiangsu University, Zhenjiang 212013, China. Electronic address: 996336827@qq.com.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Institute of Life Sciences, Jiangsu University, Zhenjiang 212013, China. Electronic address: 347151488@qq.com.
authors.forename: Fang
authors.initials: F
authors.lastname: Xu
authors.affiliation: School of Life Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK. Electronic address: Nigel.Halliday@nottingham.ac.uk.
authors.forename: Nigel
authors.initials: N
authors.lastname: Halliday
authors.affiliation: Department of Plant Pathology, Shandong Agricultural University, Tai'an 271018, China. Electronic address: kexianggao@yahoo.com.
authors.forename: Kexiang
authors.initials: K
authors.lastname: Gao
authors.affiliation: Division of Genetics and Molecular Biology, Institute of Biological Sciences, Faculty of Science, University of Malaya, Kuala Lumpur 50603, Malaysia. Electronic address: kokgan@um.edu.my.
authors.forename: Kok Gan
authors.initials: KG
authors.lastname: Chan
authors.affiliation: School of Life Sciences, Centre for Biomolecular Sciences, University of Nottingham, Nottingham NG7 2RD, UK. Electronic address: miguel.camara@nottingham.ac.uk.
authors.forename: Miguel
authors.initials: M
authors.lastname: Cámara
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D004252:DNA Mutational Analysis; D060026:Endophytes / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D008124:Locomotion; D010937:Plant Growth Regulators / Q000378:metabolism; D012705:Serratia / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: D001426:Bacterial Proteins; D010937:Plant Growth Regulators; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria
keywords: Environmental fitness; Exoenzymes; Indole-3-acetic acid; Swimming motility