Cloning of xcp genes located at the 55 min region of the chromosome and involved in protein secretion in Pseudomonas aeruginosa

Pleiotropic mutations (xcp) affecting secretion of proteins in Pseudomonas aeruginosa have been previously characterized and mapped at 0 min, 55 min and 65 min. Genomic libraries of this organism have been constructed and the genes xcp‐5 and xcp‐54, located at the 55 min region, were cloned using the adjacent met allele as a marker, and complementation of xcp strains. From our linkage and cloning analysis, the most probable gene order in this region appears to be pyrD., xcp‐5/xcp‐54/met‐9011/oru‐314/trpF/leu‐10. Restriction mapping and transposon (Tn 1725) insertion mutagenesis demonstrated that: (i) the overall size of DNA necessary for xcp expression was 9 kb, (ii) the two loci are not adjacent on the chromosome, and (iii) the two loci are expressed independently. The xcp‐5 gene has been subcloned on a 4 kb Eco RI fragment.