title: Characterization of hns genes from Erwinia amylovora.
abstract: The small basic histone-like protein H-NS is known for bacteria to attenuate virulence of several animal pathogens. An hns homologue from E. amylovora was identified by complementing an E. coli hns-mutant strain with a cosmid library from E. amylovora. A 1.6 kb EcoRI-fragment complemented the mucoid phenotype and repressed the ss-glucosidase activity of E. coli PD32. The open reading frame encoding an H-NS-like protein of 134 amino acid was later shown to be located on plasmid pEA29 (McGhee and Jones 2000). A chromosomal hns gene was amplified with PCR consensus primers and localized near galU of E. amylovora. E. amylovora mutants were created by insertion of a resistance cassette, and the intact gene was inserted into a high copy number plasmid for constitutive expression. Purified chromosomal H-NS protein preferentially bound to a DNA fragment from the lsc region and bending was predicted for an adjacent fragment with the rlsB-promoter. Levan production was significantly increased by hns mutations. Synthesis of the capsular exopolysaccharide amylovoran and of levan were reduced, when hns from the E. amylovora plasmid was overexpressed. A mutation in chromosomal hns of E. amylovora increased amylovoran synthesis, and both mutations retarded symptom formation on immature pears.
authors.affiliation: Max-Planck-Institut für Zellbiologie, Ladenburg, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Hildebrand
authors.forename: P
authors.initials: P
authors.lastname: Aldridge
authors.forename: K
authors.initials: K
authors.lastname: Geider
mesh_terms: D001483:Base Sequence; D017931:DNA Primers; D004269:DNA, Bacterial; D024202:Electrophoretic Mobility Shift Assay; D044084:Erwinia amylovora / Q000235:genetics* / Q000472:pathogenicity; D005798:Genes, Bacterial; D016297:Mutagenesis, Site-Directed; D016133:Polymerase Chain Reaction; D014774:Virulence / Q000235:genetics
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial