Mobilization of the incQ plasmid R300B with a chromosomal conjugation system in Salmonella enterica serovar typhi

Abstract

Salmonella pathogenicity island 7 (SPI-7) in Salmonella enterica serovar Typhi appears to be related to other genomic islands. Evidence suggests that SPI-7 is susceptible to spontaneous circularization, loss, and transposition. Here, we demonstrate that a region within SPI-7 has the ability to mobilize the small incQ plasmid R300B.

FIG. 1.

Alignment of SPI-7 from S. enterica serovar Typhi with HAI2 from Erwinia carotovora subsp. atroseptica SCRI1043. Schematic representation of a pairwise alignment of SPI-7 from S. enterica serovar Typhi CT18 with HAI2 from Erwinia carotovora subsp. atroseptica SCRI1043. Regions of significant amino acid homology are represented by gray bars. The arrows represent the coding sequences, and the colors of the arrows correspond to the predicted functions: blue, mob; yellow, pil; and purple, tra (Table 1). The gene names correspond to the gene names in the respective genome sequences. The numbers at the top and bottom of the figure correspond to the coordinates within the respective genomes (left and right) and the approximate sizes of the compared fragments that have been calculated (center). Also highlighted are the locations of the constructed mutations in SPI-7, ΔpilS, ΔpilV, Δ1, Δ2, and Δ3.

FIG. 2.

Graph showing the number of transconjugants obtained after mating S. enterica serovar Typhi BRD948, ΔpilS, ΔpilV, Δ1, Δ2, and Δ3 (all containing R300B) with S. enterica serovar Typhimurium. Transconjugants for each experiment were selected on medium containing tetracycline and streptomycin, where S. enterica serovar Typhimurium alone acted as a negative control for each experiment. The data presented are background-corrected mean averages of the results from three experiments, each containing three replicates (i.e., nine replicates in total). Significant P values (P < 0.05) determined by Student's t test calculated by comparing data from S. enterica serovar Typhi BRD948 with the corresponding experimental strain are demonstrated.