SUMMARY

A phage able to transduce a streptomycin resistance marker in Proteus mirabilis can also separately transduce the swarming characteristic between variants of two strains of P. mirabilis. Motile non-swarming variants were made to swarm on agar by incorporation of a swarming gene via a phage lysate of a swarming strain. The production of swarms by motile non-swarming variants when treated with phage lysates of other pheno-typically similar strains indicated that a t least three non-homologous factors control swarming.,4n 0 variant could also act as a donor of the swarming gene. This is because the 0 strain possesses an intact swarming centre which is masked by the absence of active flagella. This 0 variant was transduced to swarming by phage lysates of motile non-swarming strains or of a swarming strain. The gene transduced here was concerned with the presence of flagella. Factors controlling two morphological varieties of swarming were separately transduced to suitable recipients and a locus able to modify wild-type swarms was identified