title: Characterization of broadly pleiotropic phenotypes caused by an hfq insertion mutation in Escherichia coli K-12.
abstract: The region immediately downstream from the miaA tRNA modification gene at 94.8 min contains the hfq gene and the hflA region, which are important in the bacteriophage Q beta and lambda life cycles. The roles of these genes in bacteria remain largely unknown. We report here the characterization of two chromosomal hfq insertion mutations. An omega (omega) cassette insertion near the end of hfq resulted in phenotypes only slightly different from the parent, although transcript mapping demonstrated that the insertion was completely polar on hflX expression. In contrast, an equally polar omega cassette insertion near the beginning of hfq caused pronounced pleiotropic phenotypes, including decreased growth rates and yields, decreased negative supercoiling of plasmids in stationary phase, increased cell size, osmosensitivity, increased oxidation of carbon sources, increased sensitivity to ultraviolet light, and suppression of bgl activation by hns mutations. hfq::omega mutant phenotypes were distinct from those caused by omega insertions early in the miaA tRNA modification gene. On the other hand, both hfq insertions interfered with lambda phage plaque formation, probably by means of polarity at the hflA region. Together, these results show that hfq function plays a fundamental role in Escherichia coli physiology and that hfq and the hflA-region are in the amiB-mutL-miaA-hfq-hflX superoperon.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas-Houston Medical School 77030.
authors.forename: H C
authors.initials: HC
authors.lastname: Tsui
authors.forename: H C
authors.initials: HC
authors.lastname: Leung
authors.forename: M E
authors.initials: ME
authors.lastname: Winkler
mesh_terms: D019883:Alkyl and Aryl Transferases; D001426:Bacterial Proteins / Q000235:genetics*; D010582:Bacteriophage lambda / Q000502:physiology; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology; D002874:Chromosome Mapping; D003090:Coliphages / Q000502:physiology*; D004274:DNA, Recombinant / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000821:virology; D029968:Escherichia coli Proteins; D019204:GTP-Binding Proteins / Q000235:genetics* / Q000502:physiology; D015964:Gene Expression Regulation, Bacterial; D035001:Host Factor 1 Protein; D034982:Integration Host Factors; D008565:Membrane Proteins / Q000235:genetics* / Q000502:physiology; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009876:Operon; D010641:Phenotype; D012697:Serine Endopeptidases / Q000235:genetics* / Q000502:physiology; D014158:Transcription, Genetic; D014166:Transferases / Q000235:genetics; D014779:Virus Replication
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D004274:DNA, Recombinant; D029968:Escherichia coli Proteins; D035001:Host Factor 1 Protein; D034982:Integration Host Factors; D008565:Membrane Proteins; C440502:integration host factor, E coli; D014166:Transferases; D019883:Alkyl and Aryl Transferases; C024274:adenylate isopentenyltransferase; C057626:Hfla protease; D012697:Serine Endopeptidases; D019204:GTP-Binding Proteins