Recombination proteins differently control the acquisition of homeologous DNA duringBacillus subtilisnatural chromosomal transformation

AbstractIn naturally competentBacillus subtiliscells the acquisition of closely related genes occursviahomology-directed chromosomal transformation (CT), and its frequency decreases log-linearly with increased sequence divergence (SD) up to 15%. Beyond this and up to 23% SD the interspecies boundary prevails, the CT frequency marginally decreases, and short (<10-nucleotides) segments are integratedviahomology-facilitated micro-homologous integration. Both poorly known CT mechanisms are RecA-dependent. Here we identify the recombination proteins required for the acquisition of interspecies DNA. The absence of AddAB, RecF, RecO, RuvAB or RecU, crucial for repair-by-recombination, does not affect CT. However, inactivation ofdprA, radA, recJ, recXorrecD2strongly interfered with CT. Interspecies CT was abolished beyond ~8% SD in ΔdprA, ~10% in ΔrecJ, ΔradA, ΔrecXand 14% in ΔrecD2cells. We propose that DprA, RecX, RadA/Sms, RecJ and RecD2 help RecA to unconstrain speciation and gene flow. These functions are ultimately responsible for generating genetic diversity and facilitate CT and gene acquisition from bacteria of the same genus.