Examination of the restricted DNA (Figure 3B) showed that only one clone (lane 12) had the pYA4590 dimer-specific BX-795 molecular weight 1643-bp band. The most prominent band in the other lanes was a 4245-bp band Selleck LY2835219 expected for pACYC184-like recombination products. Nine clones contained a mixture of pACYC184 and pYA4590 (lane 1, 3-5, 8, 9, 14-16). Interplasmid recombination products Plasmids extracted from TcR clones of χ3761(pYA4464, pYA4465) were digested with NcoI and BglII. Both pYA4464 and pYA4465 are linearized into

a DNA fragment about 4 kb. Therefore, in cells containing each or both monomeric plasmids, the digested product will be a single band. The pYA4464-pYA4465 selleck kinase inhibitor hybrid will be cut into two fragments (5510 bp and 2481 bp). All four of the TcR clones we isolated and examined showed recombination product specific bands and the 4-kb band expected when each plasmid exists separately in the cell. Four tetracycline sensitive (TcS) isolates were examined and only a single band was observed, as expected (Figure 3C). These results suggest that interplasmid recombination occurred in the TcR cells and that both dimer and individual monomers corresponding to at least one of the two starting plasmids can coexist in

the same bacterial cell. We performed a similar experiment in S. Typhi strain Ty2(pYA4464, pYA4465) and obtained

identical results (data not shown). Construction of rec deletion strains We constructed a series of strains for these studies carrying deletions in either recA, recF or recJ in S. Typhimurium UK-1, S. Typhi Ty2 and S. Paratyphi A (Table 2). We also constructed ΔrecAΔ recF and ΔrecJ Δ recF double mutants in S. Typhimurium. Deletion of recA, recF and recJ results in an increase in sensitivity to UV irradiation [36, 37]. To verify the presence of these deletions phenotypically in our strains, the UV sensitivity of the S. Typhimurium mutant strains was measured. The ΔrecF and ΔrecJ mutants showed significantly lower surviving fractions than the wild type strain after the same exposure dose (Figure 4). By contrast, after five seconds of UV exposure (16 J/m2) to 2.2 × 109 CFU of the ΔrecA62 mutant Dichloromethane dehalogenase (χ9833), we were unable to recover any surviving cells (not shown). UV resistance similar to the wild-type strain χ3761 was restored to S. Typhimurium ΔrecA and ΔrecF mutants strains after introduction of recA plasmid (pYA5002) or either recF plasmid (pYA5005/pYA5006), respectively. Transformation of either mutant strain with vector plasmid pYA5001 did not restore UV resistance (Figure 4 and data not shown for recA mutant). Table 2 The bacterial strains used in this study Strain Genotype* [parental strain] Reference or source S.