title: Transcriptional profiles of Burkholderia pseudomallei reveal the direct and indirect roles of Sigma E under oxidative stress conditions.
abstract: BACKGROUND
  Burkholderia pseudomallei, the causative agent of melioidosis, is a Gram-negative bacterium widely distributed in soil and water in endemic areas. This soil saprophyte can survive harsh environmental conditions, even in soils where herbicides (containing superoxide generators) are abundant. Sigma factor E (σE) is a key regulator of extra-cytoplasmic stress response in Gram-negative bacteria. In this study, we identified the B. pseudomallei σE regulon and characterized the indirect role that σE plays in the regulation of spermidine, contributing to the successful survival of B. pseudomallei in stressful environments.
  
  
  RESULTS
  Changes in the global transcriptional profiles of B. pseudomallei wild type and σE mutant under physiological and oxidative stress (hydrogen peroxide) conditions were determined. We identified 307 up-regulated genes under oxidative stress condition. Comparison of the transcriptional profiles of B. pseudomallei wild type and σE mutant under control or oxidative stress conditions identified 85 oxidative-responsive genes regulated by σE, including genes involved in cell membrane repair, maintenance of protein folding and oxidative stress response and potential virulence factors such as a type VI secretion system (T6SS). Importantly, we identified that the speG gene, encoding spermidine-acetyltransferase, is a novel member of the B. pseudomallei σE regulon. The expression of speG was regulated by σE, implying that σE plays an indirect role in the regulation of physiological level of spermidine to protect the bacteria during oxidative stress.
  
  
  CONCLUSIONS
  This study identified B. pseudomallei genes directly regulated by σE in response to oxidative stress and revealed the indirect role of σE in the regulation of the polyamine spermidine (via regulation of speG) for bacterial cell protection during oxidative stress. This study provides new insights into the regulatory mechanisms by which σE contributes to the survival of B. pseudomallei under stressful conditions.
authors.forename: Siroj
authors.initials: S
authors.lastname: Jitprasutwit
authors.forename: Catherine
authors.initials: C
authors.lastname: Ong
authors.forename: Niramol
authors.initials: N
authors.lastname: Juntawieng
authors.forename: Wen Fong
authors.initials: WF
authors.lastname: Ooi
authors.forename: Claudia M
authors.initials: CM
authors.lastname: Hemsley
authors.forename: Paiboon
authors.initials: P
authors.lastname: Vattanaviboon
authors.forename: Richard W
authors.initials: RW
authors.lastname: Titball
authors.forename: Patrick
authors.initials: P
authors.lastname: Tan
authors.affiliation: Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand. Sunee.kor@mahidol.ac.th.
authors.forename: Sunee
authors.initials: S
authors.lastname: Korbsrisate
mesh_terms: D000123:Acetyltransferases / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics*; D016957:Burkholderia pseudomallei / Q000235:genetics / Q000254:growth & development*; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects; D017510:Protein Folding / Q000187:drug effects; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D012988:Soil Microbiology; D013095:Spermidine / Q000378:metabolism; D000099228:Diamine N-Acetyltransferase
chemical_list: D000123:Acetyltransferases; D001426:Bacterial Proteins; D006861:Hydrogen Peroxide; D012808:Sigma Factor; D013095:Spermidine; D000099228:Diamine N-Acetyltransferase; C063202:sporulation-specific sigma factors