Selection of Fimbriate Transductants of Salmonella typhimurium Dependent on Motility

The ability to form type 1 fimbriae (Fim(+)) was readily transduced to 159 out of 161 wild-type motile Fim(-) FIRN strains of Salmonella typhimurium with phage P22 propagated on a Fim(+) donor strain. Fim(+) clones were isolated from about 35% of tests after the fimbriate bacteria in the transduction mixture had been enriched by culture in aerobic static broth for 48 to 96 hr. A Fim(+) transductant was isolated from only 1 out of 280 tests made with 10 nonmotile recipient FIRN strains that were nonflagellate (Fla(-))- or possessed "paralyzed" flagella (Fla(+) Mot(-)), though motile variants from these strains were fully competent in yielding Fim(+) transductants. The property of motility was thought to facilitate the selective outgrowth of Fim(+) transductant bacteria by enabling them to migrate aerotactically to the surface of the broth where their fimbriae permitted them to float and grow in a pellicle stimulated by the free supply of atmospheric oxygen.