title: Expression of ompR gene in the acid adaptation and thermal resistance of Salmonella Enteritidis SE86.
abstract: BACKGROUND
  The objective of this study was to evaluate the involvement of the ompR gene in the acid adaptation and thermal resistance of S. Enteritidis SE86, responsible agent of more than 95 % of investigated food-borne diseases, throughout the last decade in Southern Brazil. In this study, we constructed a mutant strain of S. Enteritidis SE86 (ΔompR) that was attenuated by a knockout technique. The OmpR protein expression was determined in a tagged (3XFLAG) strain of S. Enteritidis SE86.
  
  
  METHODS
  The mutant strains were cultivated separately in nutrient broth and nutrient broth supplemented with 1% glucose (NBG) to induce acid adapted cells. The organisms were exposed to different temperature such as 37 ºC, 52 ºC, and 60ºC. The survival of the SE86 wild type (WT) and attenuated strain was determined by bacterial count, and the tagged protein (ompR::3XFLAG cat::FLAG) was detected by SDS-PAGE and immunoblotting with anti-FLAG antibodies.
  
  
  RESULTS
  Results showed that when exposed at 52ºC, the acid-adapted SE86 WT cells were completely inactivated after 300 minutes; however, non-adapted cells (WT and ΔompR) and acid-adapted ΔompR demonstrated higher thermal sensitivity, since they were completely inactivated in 240 minutes. At 60ºC, the acid-adapted SE86 ΔompR also demonstrated higher sensitivity that SE86 WT, being totally inactivated after 15 minutes, while the WT cells were inactivated in 20 minutes.
  
  
  CONCLUSIONS
  The acid adapted cells showed increased expression of OmpR when exposed to 52 ºC and 60ºC, this confirmed the requirement of acid adaptation  for S. Enteritidis SE86 to resist elevated temperatures.
authors.affiliation: Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brasil. anacarolina.ritter@gmail.com.
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: Ritter
authors.forename: Donatella
authors.initials: D
authors.lastname: Bacciu
authors.forename: Lucelia
authors.initials: L
authors.lastname: Santi
authors.forename: Salvatore
authors.initials: S
authors.lastname: Rubino
authors.forename: Sergio
authors.initials: S
authors.lastname: Uzzau
authors.forename: Eduardo Cesar
authors.initials: EC
authors.lastname: Tondo
mesh_terms: D000143:Acids / Q000378:metabolism*; D000222:Adaptation, Physiological / Q000235:genetics*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D001938:Brazil; D015169:Colony Count, Microbial; D003470:Culture Media / Q000737:chemistry; D055786:Gene Knockout Techniques; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D012478:Salmonella Food Poisoning; D012477:Salmonella enteritidis / Q000235:genetics* / Q000378:metabolism; D065288:Serogroup; D013312:Stress, Physiological / Q000235:genetics*
chemical_list: D000143:Acids; D001425:Bacterial Outer Membrane Proteins; D003470:Culture Media