Characterization of the molecular interaction between the intranuclear bacterial parasite Ca. Endonucleobacter and its deep-sea mussel host "Bathymodiolus" childressi.. Molecular biology of Ca. Endonucleobacter

Inhibitors of apoptosis (IAPs), animal proteins that stop programmed cell death by sequestering caspases, have been found in viruses but not in bacteria. By characterizing Ca. Endonucleobacter infectious cycle, we described the first intranuclear bacterial pathogen that impairs its host cell apoptosis using IAPs. Despite it inflates the nucleus of its host cell up to 50 fold, Ca. Endonucleobacter does not collapse its host cell prematurely. Transcriptomic analysis of specific infection stages revealed that Ca. Endonucleobacter and its host cell engage respectively in an antiapoptosis – proapoptosis arms race. Ca. Endonucleobacter has acquired IAPs from its bathymodiolin mussels hosts through horizontal gene transfer, and herpes viruses might have mediated the process. Collectively, our findings highlight innovative solutions for bacteria to cope with the antiapoptosis perquisites of intracellular pathogenesis. These findings invite to speculate about the potential role of viruses as shuttles of genes between life domains, driving innovation and evolution in symbiosis.