A DNase encoded by integrated element CJIE1 inhibits natural transformation of Campylobacter jejuni

E.J. Gaasbeek, J.A. Wagenaar, M.R. Guilhabert, M.M.S.M. Wösten, J.P.M. van Putten, L. van der Graaf-van Bloois, C.T. Parker, F.J. van der Wal

    Research output: Contribution to journalArticleAcademicpeer-review


    The species Campylobacter jejuni is considered naturally competent for DNA uptake and displays strong genetic diversity. Nevertheless, nonnaturally transformable strains and several relatively stable clonal lineages exist. In the present study, the molecular mechanism responsible for the nonnatural transformability of a subset of C. jejuni strains was investigated. Comparative genome hybridization indicated that C. jejuni Mu-like prophage integrated element 1 (CJIE1) was more abundant in nonnaturally transformable C. jejuni strains than in naturally transformable strains. Analysis of CJIE1 indicated the presence of dns (CJE0256), which is annotated as a gene encoding an extracellular DNase. DNase assays using a defined dns mutant and a dns-negative strain expressing Dns from a plasmid indicated that Dns is an endogenous DNase. The DNA-hydrolyzing activity directly correlated with the natural transformability of the knockout mutant and the dns-negative strain expressing Dns from a plasmid. Analysis of a broader set of strains indicated that the majority of nonnaturally transformable strains expressed DNase activity, while all naturally competent strains lacked this activity. The inhibition of natural transformation in C. jejuni via endogenous DNase activity may contribute to the formation of stable lineages in the C. jejuni population.
    Original languageEnglish
    Pages (from-to)2296-2306
    Number of pages11
    JournalJournal of Bacteriology
    Issue number7
    Publication statusPublished - 2009


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