As more microbial genome sequence information becomes available, the field of bacterial pathogenesis would benefit from the development of new genetic tools designed to facilitate gene function studies on a genomic scale. The complete DNA sequence of the bacterium Pseudomonas aeruginosa provides an opportunity to apply functional genomics to a major opportunistic human pathogen. Here, I describe the development of a new gene replacement scheme termed "SCE jumping" in P. aeruginosa. The system uses the yeast I-SceI homing endonuclease in conjunction with in vitro mariner-transposon mutagenesis to generate mutations within targeted regions of the chromosome for genetic footprinting. Use of SCE jumping for generating transposon insertion mutants is anticipated to be widely applicable to other bacterial organisms. This allelic exchange strategy is discussed in context with other methods of gene replacement strategies available in P. aeruginosa. Development of SCE jumping provides an excellent example of the power of importing systems from unrelated organisms to circumvent practical challenges in molecular genetics.