One highly diverse phylogenetic group of Bacteria,
Ca
. Patescibacteria, remains poorly understood, but, from the few cultured representatives and metagenomic investigations, they are thought to live symbiotically or parasitically with other bacteria or even with eukarya.
The bacterium “
Candidatus
Hydrogenosomobacter endosymbioticus” is an intracellular symbiont of anaerobic scuticociliate GW7, which is associated with hydrogenosome together with methanogenic archaea. Here, we report a complete genome sequence of the symbiont consisting of 827 kbp. Knowing this sequence would contribute to the understanding of the metabolic interactions and evolution of the tripartite symbiosis.