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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR BIOLOGY AND GENOMICS OF FOODBORNE PATHOGENS Title: A DNase encoded by integrated element CJIE1 inhibits natural transformation of Campylobacter jejuni

Authors
item Gaasbeck, Ester - CNTL.VET.INST. WAGENINGEN
item Wagenaar, Jaap - UTRECHT UNIVERSITY
item Guilhabert, Magalie - AGRAQUEST, DAVIS, CA
item Wosten, Marc - UTRECHT UNIVERSITY
item Van Putten, Jos - UTRECHT UNIVERSITY
item Parker, Craig
item Van Der Wal, Fimme - CNTL.VET.INST. WAGENINGEN

Submitted to: Journal of Bacteriology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 16, 2009
Publication Date: April 1, 2009
Repository URL: http://jb.asm.org/cgi/content/full/191/7/2296
Citation: Gaasbeck, E.J., Wagenaar, J., Guilhabert, M., Wosten, M.M., Van Putten, J.P., Parker, C., Van Der Wal, F.J. 2009 A DNase encoded by integrated element CJIE1 inhibits natural transformation of Campylobacter jejuni. Journal of Bacteriology. 191:2296-2306.

Interpretive Summary: The species Campylobacter jejuni (C. jejuni) is considered naturally transformable through uptake of extracellular DNA. Yet, non-transformable strains of C. jejuni exist. In the present study, the molecular mechanism responsible for the non-transformability of a subset of C. jejuni strains was investigated. Microarray-based comparative genome hybridization that examines strain differences indicated that the C. jejuni integrated element 1 (CJIE1) was more abundant in non-transformable C. jejuni strains than in transformable strains. Analysis of the Mu-like prophage CJIE1 indicated the presence of the dns gene (CJE0256), which is annotated as an extracellular deoxyribonuclease. DNase assays using a defined dns mutant and complemented strain indicated Dns as an endogenous DNase. The DNA hydrolyzing activity directly correlated with the transformability of the mutant and complemented strain. Analysis of a broader set of strains indicated that the majority of non-transformable strains expressed DNase activity, while all naturally transformable strains lacked this activity. The inhibition of natural transformation in C. jejuni via endogenous DNase activity likely explains the existence of relatively stable clonal lineages in this species.

Technical Abstract: The species Campylobacter jejuni (C. jejuni) is considered naturally competent for DNA uptake and displays strong genetic diversity. Yet, non-transformable strains and several relatively stable clonal lineages exist. In the present study, the molecular mechanism responsible for the non-transformability of a subset of C. jejuni strains was investigated. Comparative genome hybridization indicated that the C. jejuni integrated element 1 (CJIE1) was more abundant in non-transformable C. jejuni strains than in transformable strains. Analysis of the Mu-like prophage CJIE1 indicated the presence of dns (CJE0256), which is annotated as an extracellular deoxyribonuclease. DNase assays using a defined dns mutant and complemented strain indicated Dns as an endogenous DNase. The DNA hydrolyzing activity directly correlated with the transformability of the mutant and complemented strain. Analysis of a broader set of strains indicated that the majority of non-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 likely explains the existence of relatively stable clonal lineages in this species.

Last Modified: 10/21/2014
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