Evolution of Chi motifs in Proteobacteria

Abstract

AbstractHomologous recombination is a key pathway found in nearly all bacterial taxa. The recombination complex allows bacteria to repair DNA double strand breaks but also promotes adaption through the exchange of DNA between cells. In Proteobacteria, this process is mediated by the RecBCD complex, which relies on the recognition of a DNA motif named Chi to initiate recombination. The Chi motif has been characterized inEscherichia coliand analogous sequences have been found in several other species from diverse families, suggesting that this mode of action is widespread across bacteria. However, the sequences of Chi-like motifs are known for only five bacterial species:E. coli, Haemophilus influenzae,Bacillus subtilis,Lactococcus lactisandStaphylococcus aureus. In this study we detected putative Chi motifs in a large dataset of Proteobacteria and we identified four additional motifs sharing high sequence similarity and similar properties to the Chi motif ofE. coliin 85 species of Proteobacteria. Most Chi motifs were detected inEnterobacteriaceaeand this motif appears well conserved in this family. However, we did not detect Chi motifs for the majority of Proteobacteria, suggesting that different motifs are used in these species. Altogether these results substantially expand our knowledge on the evolution of Chi motifs and on the recombination process in bacteria.