Demonstration of allelic exchange in the slow-growing bacterium Mycobacterium avium subsp. paratuberculosis, and generation of mutants with deletions at the pknG, relA, and lsr2 loci

Taek Park Kun, John L. Dahl, John P. Bannantine, Raul G Barletta, Jongsam Ahn, Andrew J. Allen, Mary Jo Hamilton, William C. Davis

Research output: Contribution to journalArticle

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Mycobacterium avium subsp. paratuberculosis is the causative pathogen of Johne's disease, a chronic inflammatory wasting disease in ruminants. This disease has been difficult to control because of the lack of an effective vaccine. To address this need, we adapted a specialized transduction system originally developed for M. tuberculosis and modified it to improve the efficiency of allelic exchange in order to generate site-directed mutations in preselected M. avium subsp. paratuberculosis genes. With our novel optimized method, the allelic exchange frequency was 78 to 100% and the transduction frequency was 1.1 × 10-7 to 2.9 × 10-7. Three genes were selected for mutagenesis: pknG and relA, which are genes that are known to be important virulence factors in M. tuberculosis and M. bovis, and lsr2, a gene regulating lipid biosynthesis and antibiotic resistance. Mutants were successfully generated with a virulent strain of M. avium subsp. paratuberculosis (M. avium subsp. paratuberculosis K10) and with a recombinant K10 strain expressing the green fluorescent protein gene, gfp. The improved efficiency of disruption of selected genes in M. avium subsp. paratuberculosis should accelerate development of additional mutants for vaccine testing and functional studies.

Original languageEnglish (US)
Pages (from-to)1687-1695
Number of pages9
JournalApplied and environmental microbiology
Issue number6
Publication statusPublished - Mar 1 2008


ASJC Scopus subject areas

  • Biotechnology
  • Food Science
  • Applied Microbiology and Biotechnology
  • Ecology

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