This review summarises current information on the site-specific recomb
inases encoded by the plasmids of the Gram-positive bacteria that have
low guanine and cytosine content in their DNA. It focuses on the pecu
liar biological features of the recombination systems encoded by the t
heta-replicating plasmids and compares them with the site-specific rec
ombinases encoded by transposons or plasmids originally isolated from
Gram-negative bacteria.