FIG. 2.

Genetic organization of pSK41. Genes are represented by open boxes with names shown within or below and with arrowheads indicating the direction of transcription; smaller open boxes represent interrupted genes. Copies of IS257 are denoted by black boxes containing the element’s designation (A through G), whereas inverted copies of truncated IS256 elements are indicated by open triangles. Hatched segments indicate integrated small plasmids. RC plasmid replication-initiation genes are suffixed (RC) to differentiate them from the probable theta-mode rep gene of pSK41. Kilobase coordinates are shown below, as are the positions of EcoRI restriction sites (E) and oriT (vertical arrow). The position in pSK41 corresponding to the insertion site of the Tn552-like transposon in pUW3626 is indicated by an asterisk (∗). The position and genetic organization of the additional DNA segment present in pJE1 is also indicated; the tnp genes of the IS257 elements have been omitted for clarity. The pSK639-like rep gene remnant is suffixed (639) to differentiate it from pSK41 rep. Genetic nomenclature is as described for Fig. 1 and as follows: numbers, size in codons of deduced ORF of unknown function; res, resolvase; oriT, origin of conjugative transfer; nes, oriT nickase; rep/repU, replication initiation; tnp, transposase; pre, recombinase; artA/traA-M, transfer-associated genes; thyE, thymidilate synthetase.