Non-viability of Haemophilus parasuis fur-defective mutants

Anna Bigas, Ma Elena Garrido, Ignacio Badiola, Jordi Barbé, Montserrat Llagostera

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By complementation of an Escherichia coli fur mutant, the Haemophilus parasuis fur gene has been isolated from a genomic library of this organism. The H. parasuis fur gene is the distal one of a three-gene operon. Two genes placed upstream of the H. parasuis fur open-reading frame encode for a hypothetical protein and a flavodoxin, respectively. Attempts performed to isolate an H. parasuis fur-defective mutant either through manganese-resistance selection or exchange markers were unsuccessful. Likewise, anaerobic growth conditions do not enable the attainment of H. parasuis fur-defective mutants either. Nevertheless, H. parasuis clones carrying a knockout mutation in the chromosomal fur gene by insertion of a KmR cassette were obtained when a stable plasmid, containing an additional copy of the transcriptional unit to which the fur gene belongs, was present. Likewise, the presence of a plasmid in which the H. parasuis fur gene is under the control of the Escherichia coli tac promoter allows for the isolation of fur::Km mutants of this organism. Nonetheless, no fur-defective mutants may be isolated from H. parasuis cells harbouring a stable plasmid in which only the single fur gene is contained. These data clearly indicate that H. parasuis cell viability requires the presence of a wild-type fur gene. © 2006 Elsevier B.V. All rights reserved.
Original languageEnglish
Pages (from-to)107-116
JournalVeterinary Microbiology
Issue number1-2
Publication statusPublished - 26 Nov 2006


  • fur-defective mutants
  • Haemophilus parasuis
  • Merodiploid
  • Non-viability


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