title: The rfaH gene, which affects lipopolysaccharide synthesis in Salmonella enterica serovar Typhi, is differentially expressed during the bacterial growth phase.
abstract: We have cloned and sequenced the rfaH gene from Salmonella enterica serovar Typhi strain Ty2. The gene showed a high degree of similarity to the rfaH genes from Escherichia coli K-12 and S. enterica serovar Typhimurium. A rfaH mutant was constructed by site-directed mutagenesis. This mutant produced a rough lipopolysaccharide (LPS), with an incomplete core region. The defect in LPS expression that results from the rfaH mutation was corrected by a plasmid carrying the intact gene. The plasmid-borne rfaH gene also restored normal LPS synthesis in a rfaH mutant of E. coli. Reverse transcription-polymerase chain reaction analyses were performed to determine the effects of various environmental conditions on the expression of rfaH. The transcription of rfaH showed a growth-phase-dependent regulation, with maximal expression at the late exponential phase. Other environmental conditions, such as temperature or medium osmolarity, did not affect transcription of rfaH.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, P.O. Box 174, Correo 22, Santiago, Chile.
authors.forename: G
authors.initials: G
authors.lastname: Rojas
authors.forename: S
authors.initials: S
authors.lastname: Saldías
authors.forename: M
authors.initials: M
authors.lastname: Bittner
authors.forename: M
authors.initials: M
authors.lastname: Zaldívar
authors.forename: I
authors.initials: I
authors.lastname: Contreras
mesh_terms: D003001:Cloning, Molecular; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D008070:Lipopolysaccharides / Q000096:biosynthesis*; D016297:Mutagenesis, Site-Directed; D010445:Peptide Elongation Factors / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012485:Salmonella typhi / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic
chemical_list: D029968:Escherichia coli Proteins; D008070:Lipopolysaccharides; D010445:Peptide Elongation Factors; C106401:RfaH protein, E coli; D015534:Trans-Activators