The ompB operon partially determines differential expression of OmpC in Salmonella typhi and Escherichia coli.
Expression of the Escherichia coli OmpC and OmpF outer membrane proteins is regulated by the osmolarity of the culture media. In contrast, expression of OmpC in Salmonella typhi is not influenced by osmolarity, while OmpF is regulated as in E. coli. To better understand the lack of osmoregulation of OmpC expression in S. typhi, we compared the expression of the ompC gene in S. typhi and E. coli, using ompC-lacZ fusions and outer membrane protein (OMP) electrophoretic profiles. S. typhi ompC expression levels in S. typhi were similar at low and high osmolarity along the growth curve, whereas osmoregulation of E. coli ompC in E. coli was observed during the exponential phase. Both genes were highly expressed at high and low osmolarity when present in S. typhi, while expression of both was regulated by osmolarity in E. coli. Complementation experiments with either the S. typhi or E. coli ompB operon in an S. typhi DeltaompB strain carrying the ompC-lacZ fusions showed that both S. typhi and E. coli ompC were not regulated by osmolarity when they were under the control of S. typhi ompB. Interestingly, in the same strain, both genes were osmoregulated under E. coli ompB. Surprisingly, in E. coli DeltaompB, they were both osmoregulated under S. typhi or E. coli ompB. Thus, the lack of osmoregulation of OmpC expression in S. typhi is determined in part by the ompB operon, as well as by other unknown trans-acting elements present in S. typhi.
Martínez-Flores
I
I
Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Cuernavaca, Morelos 62250, México.
Cano
R
R
Bustamante
V H
VH
Calva
E
E
Puente
J L
JL
D000595:Amino Acid Sequence; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics; D017124:Conserved Sequence; D003470:Culture Media; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D000071677:Histidine Kinase; D007700:Kinetics; D009097:Multienzyme Complexes; D009876:Operon; D009994:Osmolar Concentration; D018272:Porins / Q000096:biosynthesis / Q000235:genetics*; D011494:Protein Kinases / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D012485:Salmonella typhi / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D003470:Culture Media; D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; C113724:OmpC protein; C109237:OmpF protein; D018272:Porins; D011993:Recombinant Fusion Proteins; C078167:OMPA outer membrane proteins; D011494:Protein Kinases; D000071677:Histidine Kinase; C057843:envZ protein, E coli