Fig 3. HU is essential for CTXϕ replication.

(A and B) Relative colony-forming ability after conjugation with a replicative form of RS2 in the indicated strains. After 3 h of conjugation, serial dilutions were plated on chloramphenicol and incubated overnight at 42°C (A) and 37°C (B). Relative colony forming units (cfu) correspond to the ratio of the number of colonies obtained in the indicated strain over the mean number of colonies obtained in ∆xerC cells. Results are shown in a logarithmic scale and represent the mean and standard deviation of 3 independent experiments. The detection limit of the experiment is indicated by a dotted line. (C and D) Colonies obtained at 37°C were re-streaked on plate and incubated overnight at 42°C (C) and 37°C (D). (E) Complementation assay of ΔhupAB cells with a pUC18 vector carrying the V. cholerae hupA gene (pUC-hupA) or hupB gene (pUC-hupB). RS2 was conjugated into ΔxerC ΔhupAB + pUC18, ΔxerC ΔhupAB + pUC-hupA and ΔxerC ΔhupAB + pUC-hupB. The conjugants were then streaked on a plate supplemented with ampicillin and chloramphenicol. The plate was incubated overnight at 37°C.