The relationship of two invertible segments in bacteriophage Mu and Salmonella typhimurium DNA.

A Mu gin- mutant which lacks the function required for inversion of the G segment can be complemented by hybrid plasmids and phages carrying the invertible segment that controls flagellar phase variation in Salmonella typhimurium. This suggests that the same kind of site-specific recombination mechanism is responsible for these inversions. Based on the different features of the two invertible segments we propose a model for their evolutionary relationship.