Phylogenetic analysis of the streptococcal tyrosine recombinases Tyrosine recombinase protein sequences were obtained from BLASTp searches

Supporting Materials and Methods pGh9-derivative plasmids and E. coli strains constructions pGh9-derivative plasmids were constructed as follows: relevant pairs of oligonucleotides containing XmaI linkers were annealed together, generating DNA duplexes with two XmaI-compatible ends. Only the left end of the duplexes recreated a full XmaI site, allowing further determination of its orientation by restriction analysis (only the synthetic sequences cloned in counterclockwise orientation were selected for experiments). These duplexes were 5’-phosphorylated and ligated with dephosphorylated XmaI-digested pCL52 or pGh9 vectors. The sequence of each cloned oligonucleotide was confirmed by DNA sequencing. The dif-Km-dif cassette was introduced in E. coli strain LN2772 by integration-excision experiment [1], using pCL294 plasmid (Table S1). E. coli E359-derivative mutants carrying xerC2::Ap, xerD::Ap, or ftsKC::Ap were obtained by P1-mediated transduction using phage lysates kindly provided by F. Cornet. The ftsKC::Ap disruption corresponds to the replacement of FspI internal fragments of ftsK by the bla gene, and allows the synthesis of only the 316 first amino acids of FtsK (F. Cornet, personal communication). Allelic replacements were verified by PCR, and the xer phenotype was tested by in vivo plasmid resolution assay using plasmid pFX142 [2]. The recA56 allele was introduced by conjugation by co-transfer with srl::Tn10 from strain JC10240 [3], and the recA phenotype was verified by UV-radiation sensitivity.