title: Escherichia coli hha mutants, DNA supercoiling and expression of the haemolysin genes from the recombinant plasmid pANN202-312.
abstract: The hha gene of Escherichia coli was identified as modulating the expression of the haemolysin (hly) genes encoded by the recombinant plasmid pANN202-312. hha mutants harbouring plasmid pANN202-312 showed increased haemolysin production. The product of the hha gene, the Hha protein, shows strong homology to the YmoA protein of Yersinia enterocolitica, which plays a role in the thermoregulation of various Y. enterocolitica virulence genes. We show in this study that the Hha protein modulates the expression of haemolysin at the transcriptional level in cells harbouring plasmid pANN202-312. In addition, hha mutants show alterations in the level of plasmid DNA supercoiling. This suggests that the hha mutation increases haemolysin expression through changes in the DNA topology. This hypothesis is supported by our finding that gyr mutations, inhibitors of DNA gyrase such as novobiocin, or growth in conditions reported to reduce levels of negative supercoiling, such as low osmolarity medium, increase haemolysin production.
authors.affiliation: Departamento de Microbiología, Facultad de Biología, Universidad de Barcelona, Spain.
authors.forename: M
authors.initials: M
authors.lastname: Carmona
authors.forename: C
authors.initials: C
authors.lastname: Balsalobre
authors.forename: F
authors.initials: F
authors.lastname: Muñoa
authors.forename: M
authors.initials: M
authors.lastname: Mouriño
authors.forename: Y
authors.initials: Y
authors.lastname: Jubete
authors.forename: F
authors.initials: F
authors.lastname: De la Cruz
authors.forename: A
authors.initials: A
authors.lastname: Juárez
mesh_terms: D001483:Base Sequence; D015153:Blotting, Western; D003470:Culture Media; D017931:DNA Primers; D004269:DNA, Bacterial / Q000378:metabolism; D004278:DNA, Superhelical / Q000378:metabolism*; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D005798:Genes, Bacterial; D006460:Hemolysin Proteins / Q000096:biosynthesis* / Q000235:genetics; D007700:Kinetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009675:Novobiocin / Q000494:pharmacology; D009994:Osmolar Concentration; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D011995:Recombination, Genetic; D014158:Transcription, Genetic
chemical_list: D003470:Culture Media; D017931:DNA Primers; D004269:DNA, Bacterial; D004278:DNA, Superhelical; D006460:Hemolysin Proteins; D011993:Recombinant Fusion Proteins; D009675:Novobiocin