Antiviral defence arsenal across members of the Bacillus cereus group

Bacteria co-evolve with bacteriophages to overcome each other's defence arsenal. Bacillus cereus group gathers bacteria of medical and agricultural importance, including foodborne pathogens. So far, few studies have portrayed a complete defence arsenal of microorganisms, and the role of antiviral systems in the Bacillus cereus group has been overlooked. Here, we investigate the repertoire of defence systems in 6354 B. cereus group's genomic assemblies, using bioinformatics tools DefenseFinder and PADLOC. Our analyses provide an overview of the diversity and abundance of defence systems in this group, with 83,738 systems distributed by 2 to 33 within each assembly. Comparing PADLOC and DefenseFinder predictions showed that the most prevalent strategy is Restriction-Modification, but many abortive infection systems also intervene in the group's defence, such as Septu, Gabija and Lamassu. Most defences were encoded on both plasmids and the chromosome, though some tend to have a preferential genomic location. We also studied the defence systems associations within the genomic assemblies. Overall, our results establish a baseline picturing the rich and complex antiviral arsenal encoded by B. cereus group's species and provide clues for studying co-existing strategies displayed by these bacteria to subvert phages and other MGEs invasions.