HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Novak, K. F. Articles by Peláez, M. Search for Related Content PubMed PubMed Citation Articles by Novak, K. F. Articles by Peláez, M. Agricola Articles by Novak, K. F. Articles by Peláez, M.

Actinobacillus actinomycetemcomitans harbours type IV secretion system genes on a plasmid and in the chromosome

University of Kentucky, College of Dentistry, Center for Oral Health Research, Lexington, KY 40536-0297, USA¹
Department of Periodontics, University of Pittsburgh School of Dental Medicine, Pittsburgh, PA 15261, USA²

Author for correspondence: Karen F. Novak. Tel: +1 859 323 8705. Fax: +1 859 257 6566. e-mail: knova2{at}pop.uky.ed

Nine contiguous genes encoding a potential type IV secretion system have been identified in the chromosome of Actinobacillus actinomycetemcomitans strain VT747 and on a plasmid (pVT745) in strain VT745. Seven of these genes encode predicted proteins that share significant homology with type IV secretion proteins in Bordetella pertussis (ptl operon), Brucella melitensis biovar suis and Agrobacterium tumefaciens (virB operons), where they are involved in protein secretion, pathogen intracellular survival and multiplication, and DNA transport, respectively. Results of previous studies have demonstrated that pVT745 is a conjugative plasmid and that a secondary plasmid, pMMB67, can be mobilized from strain VT745. Given these results, it was hypothesized that (1) the type IV secretion genes on pVT745 are responsible for these two functions and (2) the type IV VT747 chromosomal genes also play a role in the transport of DNA. Wild-type and mutant strains of VT745 were evaluated for their conjugative abilities. Wild-type mating efficiency was 10^-6 transconjugants per donor, while the mutant strain yielded no transconjugants. Wild-type VT745 harbouring a co-resident plasmid, pMMB67, mobilized pMMB67 at a frequency of 10^-6, while VT747 was unable to mobilize this plasmid. These results support the hypothesis that the plasmid-encoded type IV secretion system on pVT745 is involved in DNA transport. However, the chromosomally encoded secretion system may not play a role in DNA transport in strain VT747. While the precise function of these chromosomal genes in strain VT747 has not been determined, Northern blot analyses demonstrated that these genes are expressed in both Act. actinomycetemcomitans strains VT745 and VT747.

Keywords: type IV secretion, bacterial secretion systems, extrachromosomal, chromosomal

The GenBank accession number for the type IV secretion genes of Act. actinomycetemcomitans reported in this paper is AF332996.

This article has been cited by other articles:

				K. E. Kram, G. A. Hovel-Miner, M. Tomich, and D. H. Figurski Transcriptional Regulation of the tad Locus in Aggregatibacter actinomycetemcomitans: a Termination Cascade J. Bacteriol., June 1, 2008; 190(11): 3859 - 3868. [Abstract] [Full Text] [PDF]

				A. C. Frank, C. M. Alsmark, M. Thollesson, and S. G. E. Andersson Functional Divergence and Horizontal Transfer of Type IV Secretion Systems Mol. Biol. Evol., May 1, 2005; 22(5): 1325 - 1336. [Abstract] [Full Text] [PDF]

				A. Gross, M. Bouaboula, P. Casellas, J.-P. Liautard, and J. Dornand Subversion and Utilization of the Host Cell Cyclic Adenosine 5'-Monophosphate/Protein Kinase A Pathway by Brucella During Macrophage Infection J. Immunol., June 1, 2003; 170(11): 5607 - 5614. [Abstract] [Full Text] [PDF]