Polynucleobacter necessarius

Polynucleobacter necessarius is a bacterium of the genus Polynucleobacter. Since the last revision of the species, it contains exclusively obligate endosymbionts dwelling in cells of the ciliate Euplotes aediculatus and related species. This is in contrast to other species of the genus Polynucleobacter, which exclusively harbour free-living bacteria dwelling in the water column of freshwater systems (lake, ponds, puddles and running waters). The genome of P. necessarius has been completely sequenced.