title: An extracytoplasmic function sigma factor-dependent periplasmic glutathione peroxidase is involved in oxidative stress response of Shewanella oneidensis.
abstract: BACKGROUND
  Bacteria use alternative sigma factors (σs) to regulate condition-specific gene expression for survival and Shewanella harbors multiple ECF (extracytoplasmic function) σ genes and cognate anti-sigma factor genes. Here we comparatively analyzed two of the rpoE-like operons in the strain MR-1: rpoE-rseA-rseB-rseC and rpoE2-chrR.
  
  
  RESULTS
  RpoE was important for bacterial growth at low and high temperatures, in the minimal medium, and high salinity. The degP/htrA orthologue, required for growth of Escherichia coli and Pseudomonas aeruginosa at high temperature, is absent in Shewanella, while the degQ gene is RpoE-regulated and is required for bacterial growth at high temperature. RpoE2 was essential for the optimal growth in oxidative stress conditions because the rpoE2 mutant was sensitive to hydrogen peroxide and paraquat. The operon encoding a ferrochelatase paralogue (HemH2) and a periplasmic glutathione peroxidase (PgpD) was identified as RpoE2-dependent. PgpD exhibited higher activities and played a more important role in the oxidative stress responses than the cytoplasmic glutathione peroxidase CgpD under tested conditions. The rpoE2-chrR operon and the identified regulon genes, including pgpD and hemH2, are coincidently absent in several psychrophilic and/or deep-sea Shewanella strains.
  
  
  CONCLUSIONS
  In S. oneidensis MR-1, the RpoE-dependent degQ gene is required for optimal growth under high temperature. The rpoE2 and RpoE2-dependent pgpD gene encoding a periplasmic glutathione peroxidase are involved in oxidative stress responses. But rpoE2 is not required for bacterial growth at low temperature and it even affected bacterial growth under salt stress, indicating that there is a tradeoff between the salt resistance and RpoE2-mediated oxidative stress responses.
authors.affiliation: Institute of Hydrobiology, Chinese Academy of Sciences, 7 South Donghu Road, Wuchang District, Wuhan, 430072, China. daijingcheng@ihb.ac.cn.|University of Chinese Academy of Sciences, Beijing, 100049, China. daijingcheng@ihb.ac.cn.
authors.forename: Jingcheng
authors.initials: J
authors.lastname: Dai
authors.affiliation: Institute of Hydrobiology, Chinese Academy of Sciences, 7 South Donghu Road, Wuchang District, Wuhan, 430072, China. weihehong2011@ihb.ac.cn.|University of Chinese Academy of Sciences, Beijing, 100049, China. weihehong2011@ihb.ac.cn.
authors.forename: Hehong
authors.initials: H
authors.lastname: Wei
authors.affiliation: School of Life Sciences and Technology, Hubei University of Engineering, 272 Jiaotong Avenue, Xiaogan, 432000, China. 2382728765@qq.com.
authors.forename: Chunyuan
authors.initials: C
authors.lastname: Tian
authors.affiliation: Division of Infectious Diseases and International Health, Department of Medicine, University of Virginia, Charlottesville, VA, 22908, USA. fdamron@hsc.wvu.edu.
authors.forename: Fredrick Heath
authors.initials: FH
authors.lastname: Damron
authors.affiliation: Institute for Environmental Genomics and Department of Botany and Microbiology, The University of Oklahoma, Stephenson Research and Technology Center, 101 David L. Boren Blvd, Norman, OK 73019, USA. jzhou@ou.edu.
authors.forename: Jizhong
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Institute of Hydrobiology, Chinese Academy of Sciences, 7 South Donghu Road, Wuchang District, Wuhan, 430072, China. qiu@ihb.ac.cn.|University of Chinese Academy of Sciences, Beijing, 100049, China. qiu@ihb.ac.cn.
authors.forename: Dongru
authors.initials: D
authors.lastname: Qiu
mesh_terms: D003470:Culture Media / Q000737:chemistry; D017353:Gene Deletion; D005979:Glutathione Peroxidase / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000633:toxicity; D016877:Oxidants / Q000633:toxicity; D018384:Oxidative Stress; D010269:Paraquat / Q000633:toxicity; D033903:Periplasmic Proteins / Q000378:metabolism*; D054712:Salinity; D020592:Shewanella / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D012808:Sigma Factor / Q000378:metabolism*; D013312:Stress, Physiological; D013696:Temperature
chemical_list: D003470:Culture Media; D016877:Oxidants; D033903:Periplasmic Proteins; D012808:Sigma Factor; D006861:Hydrogen Peroxide; D005979:Glutathione Peroxidase; D010269:Paraquat