Oral Presentation The 3rd Prato Conference on the Pathogenesis of Bacterial Diseases of Animals 2014

Functional biology of conjugative toxin plasmids from Clostridium perfringens (#51)

Julian I Rood 1 2 3 , Vicki Adams 1 2 , Jessica A Wisniewski 1 2 , Lakmini Weeramantri 1 2 , Jackie K Cheung 2 , Robert J Moore 1 2 3 4 , Francisco Uzal 5 , Jihong Li 6 , Bruce A McClane 1 6
  1. ARC Centre of Excellence in Structural and Functional Microbial Genomics, Monash University, Clayton, Vic, Australia
  2. Infection Program, Biomedicine Discovery Institute and Department of Microbiology, Monash University, Clayton, Vic, Australia
  3. Poultry Coooperative Research Centre, Armidale, NSW, Australia
  4. Australian Animal Health Laboratory, CSIRO Biosecurity Flagship, Geelong, Vic, Australia
  5. California Animal Health and Food Safety Laboratory, University of California-Davis, San Bernadino, CA, USA
  6. Department of Molecular Genetics and Biochemistry, University of Pittsburgh, Pittsburgh, PA, USA

The key feature of histotoxic and enterotoxic diseases caused by Clostridium perfringens is the fact that they are mediated by potent toxins, most of which are extracellular. The division of C. perfringens isolates into five toxinotypes (A to E) is based on their ability to produce combinations of four typing toxins and relies upon the presence of large toxin-encoding plasmids. These plasmids generally have 35 to 40 kb of sequence similarity, including the gene regions encoding plasmid replication, maintenance and conjugative transfer. This plasmid family also includes several very closely related tetracycline resistance plasmids, which are typified by the 47 kb plasmid pCW3. Functional genetic analysis of the common conjugation locus has led to the identification of nine conserved genes that are required for efficient conjugative transfer of pCW3 and the development of a model that describes the conjugative transfer process. The unique gene regions carried by members of this plasmid family are generally located downstream of a common dcm gene and encode one or more toxins. We have mutated several of these toxin genes and determined the role of the toxin in disease, using both small and large animal models. A unique feature of this conjugative plasmid family is that many C. perfringens strains can carry from two to four of these closely related plasmids in the same cell. This occurrence can be explained on the basis of variation in the plasmid partitioning system carried by these plasmids. Finally, based on comparative sequence analysis we have developed a model that describes the evolution of these toxin and resistance plasmids from a hypothetical progenitor plasmid.