Identification of Site-Specific Recombination Genes int and xis of the Rhizobium Temperate Phage 16-3

Abstract

ABSTRACT Phage 16-3 is a temperate phage of Rhizobium meliloti 41 which integrates its genome with high efficiency into the host chromosome by site-specific recombination through DNA sequences of attB and attP . Here we report the identification of two phage-encoded genes required for recombinations at these sites: int (phage integration) and xis (prophage excision). We concluded that Int protein of phage 16-3 belongs to the integrase family of tyrosine recombinases. Despite similarities to the cognate systems of the lambdoid phages, the 16-3 int xis att system is not active in Escherichia coli , probably due to requirements for host factors that differ in Rhizobium meliloti and E. coli . The application of the 16-3 site-specific recombination system in biotechnology is discussed.