Molecular Genetics and Genomics

, Volume 275, Issue 3, pp 310–319 | Cite as

Characterization of hns genes from Erwinia amylovora

Original Paper


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.


Nucleoid-structuring protein Exopolysaccharide synthesis Amylovoran Levan Gene regulation Fire blight 



We thank S. Jock for a series of experiments to cure cells from pEA29 and B. Schneider for comments on the manuscript.


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Copyright information

© Springer-Verlag 2006

Authors and Affiliations

  1. 1.Max-Planck-Institut für ZellbiologieLadenburgGermany
  2. 2.BBA DossenheimDossenheimGermany

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