The recent complete sequencing of several genomes allows to systematically search for the presence of DNA transfers in species, especially in prokaryotes where the probability of occurrence is higher (10) (11) (12) (13) (14) . It has been reported in particular that (i) HTs in bacteria account for up to 25% of the genome (8, (14) (15) (16) ; (ii) archaebacteria and non-pathogenic bacteria are more prone to transfers than pathogenic bacteria (15, 16) ; and (iii) operational genes are more likely transferred than genes dealing with information management (15) (16) (17) .