Intracellular symbiont with vertical transmission that is widespread across insect orders

However, only a small number of bacterial taxa managed to successfully colonize a wide diversity of insects, by evolving mechanisms for host-cell entry, immune evasion, germline tropism, reproductive manipulation, and/or by providing benefits to the host that stabilize the symbiotic association. Here we report on the discovery of an Enterobacterales endosymbiont (‘Candidatus Dolus’) that is widespread across at least six insect orders and occurs at high prevalence within host populations.

Fluorescence in situ hybridization in several Coleopteran and one Dipteran species revealed Dolus’ intracellular presence in all host life stages and across tissues, with a high abundance in the adult germline, indicating transovarial vertical transmission. Symbiont genome sequencing across 16 different host taxa revealed a high degree of functional conservation in the eroding and transposon-rich genomes. All sequenced Dolus genomes encode for multiple secretion systems, alongside effectors and toxin-antitoxin systems, which likely facilitate host-cell entry and interactions with the host.