The virulence plasmid of Salmonella typhimurium contains an autoregulated gene, rlgA, that codes for a resolvase-like DNA binding protein

The pYV virulence plasmids of Yersinia pseudotuberculosis and Y. pestis contain a conserved DNA region responsible for the mobilization by the self-transmissible plasmid pYE854

Pathogenic Yersinia strains possess a 70 kb virulence plasmid which can be transmitted to other strains by conjugation systems expressed by co-resident plasmids. We isolated a 720 bp fragment of the Yersinia pseudotuberculosis virulence plasmid p1340 that mediated mobilization of the vector pIV2 by the self-transmissible plasmid pYE854. The p1340 mobilization region contains the resolvase gene tnpR and its proposed resolution site res. Both elements are required for mobilization. Plasmid transfer was associated with the formation of co-integrates in which res was fused to pYE854 fragments by short nucleotide stretches similarly present within res. blast searches and PCR experiments revealed the presence of the mobilization region in the virulence plasmids of other Y. pseudotuberculosis and Y. pestis strains but not in pYV of Yersinia enterocolitica.

E622, a miniature, virulence-associated mobile element

Miniature inverted terminal repeat elements (MITEs) are nonautonomous mobile elements that have a significant impact on bacterial evolution. Here we characterize E622, a 611-bp virulence-associated MITE from Pseudomonas syringae, which contains no coding region but has almost perfect 168-bp inverted repeats. Using an antibiotic coupling assay, we show that E622 is transposable and can mobilize an antibiotic resistance gene contained between its borders. Its predicted parent element, designated TnE622, has a typical transposon structure with a three-gene operon, consisting of resolvase, integrase, and exeA-like genes, which is bounded by the same terminal inverted repeats as E622. A broader genome level survey of the E622/TnE622 inverted repeats identified homologs in Pseudomonas, Salmonella, Shewanella, Erwinia, Pantoea, and the cyanobacteria Nostoc and Cyanothece, many of which appear to encompass known virulence genes, including genes encoding toxins, enzymes, and type III secreted effectors. Its association with niche-specific genetic determinants, along with its persistence and evolutionary diversification, indicates that this mobile element family has played a prominent role in the evolution of many agriculturally and clinically relevant pathogenic bacteria.

Peripheral sequences of the Serratia entomophila pADAP virulence-associated region

Some strains of the Enterobacteriaceae Serratia entomophila and Serratia proteamaculans cause amber disease in the grass grub, Costelytra zealandica (Coleoptera: Scarabaeidae), an important pasture pest in New Zealand. The genes responsible for this disease reside on a large, 155-kb plasmid designated amber disease-associated plasmid (pADAP). Herein, we report the DNA sequencing of approximately 50 kb upstream and 10 kb downstream of the virulence-encoding region. Based on similarity with proteins in the current databases, and potential ribosome-binding sites, 63 potential ORFs were determined. Eleven of these ORFs belong to a type IV pilus cluster (pilL-V) and a further eight have similarities to the translated products of the plasmid transfer traH-N genes of the plasmid R64. In addition, a degenerate 785-nt direct repeat flanks a 44.7-kb region with the potential to encode three Bacillus subtilis Yee-type proteins, a fimbrial gene cluster, the sep virulence-associated genes and several remnant IS elements.

Complete DNA sequence and comparative analysis of the 50-kilobase virulence plasmid of Salmonella enterica serovar Choleraesuis

The complete nucleotide sequence of pKDSC50, a large virulence plasmid from Salmonella enterica serovar Choleraesuis strain RF-1, has been determined. We identified 48 of the open reading frames (ORFs) encoded by the 49,503-bp molecule. pKDSC50 encodes a known virulence-associated operon, the spv operon, which is composed of genes essential for systemic infection by nontyphoidal Salmonella. Analysis of the genetic organization of pKDSC50 suggests that the plasmid is composed of several virulence-associated genes, which include the spvRABCD genes, plasmid replication and maintenance genes, and one insertion sequence element. A second virulence-associated region including the pef (plasmid-encoded fimbria) operon and rck (resistance to complement killing) gene, which has been identified on the virulence plasmid of S. enterica serovar Typhimurium, was absent. Two different replicon regions, similar to the RepFIIA and RepFIB replicons, were found. Both showed high similarity to those of the pO157 plasmid of enterohemorrhagic Escherichia coli O157:H7 and the enteropathogenic E. coli (EPEC) adherence factor plasmid harbored by EPEC strain B171 (O111:NM), as well as the virulence plasmids of Salmonella serovars Typhimurium and Enteritidis. Comparative analysis of the nucleotide sequences of the 50-kb virulence plasmid of serovar Choleraesuis and the 94-kb virulence plasmid of serovar Typhimurium revealed that 47 out of 48 ORFs of the virulence plasmid of serovar Choleraesuis are highly homologous to the corresponding ORFs of the virulence plasmid of serovar Typhimurium, suggesting a common ancestry.