Construction of gene delivery vectors for L. lactis. Details of the constructions are outlined in Materials and Methods. Of the resulting vectors (names indicated in boxes), only the sections relevant to integration are shown. (A) Vectors for delivery of genes to the chromosome. DNA fragments subcloned from the chromosomal leu operon of strains MG1363 and CHCC377 (i) were interrupted by the insertion of the nisRK genes isolated from pNZ9573 (ii). (B) Vectors for delivery of genes to the sex factor. A DNA fragment subcloned from the tel operon of the sex factor (i) was interrupted by the insertion of the multiple-cloning site (mcs) from pBluescriptIISK (ii). The multiple-cloning site was used to insert six different PnisA::pep fusions isolated from pUK200 derivatives (iii), the nisRK genes isolated from pNZ9573 (iv), or nisRK together with PnisA::pepI (v). pUK300pep stands for six different derivatives of pUK300 (pUK300I, pUK300Q, pUK300L, pUK300G, pUK300W, and pUK300C) containing fusions of PnisA with pepI, pepQ, pepL, pepG, pepW, and pepC, respectively.