Conserved virulence factor regulation and secretion systems in bacterial pathogens of plants and animals

Recent research has revealed the emergence of common themes in the molecular mechanisms of virulence in bacterial pathogens of plants and animals. In particular, the systems used for the global control of virulence factor synthesis and for the secretion of virulence determinants in diverse bacterial pathogens show strong conservation, implying evolutionary relatedness. Global control of virulence factor synthesis can be affected by a variety of environmental factors, bacterial 'hormones' and programmed genetic rearrangements. Protein secretion in Gram-negative bacteria occurs via a number of targeting pathways. Type I and type III secretion systems mediate translocation across both the inner and outer membrane in a single step, while type II secretion proceeds via a periplasmic intermediate. Type II and type III secretion systems have been shown to target virulence determinants in both plant and animal bacterial pathogens.