Recently, several new Polynucleobacter species were described,[2][3][4][5][6][7][8][9][10] which all represent free-living (i.e. not host-associated) planktonic freshwater bacteria.
The type strains of the planktonic species were isolated from freshwater systems located in Antarctica, Armenia, Austria, China, Czech Republic, Finland, France, Germany, Norway, Spain, Uganda, and the United States.
Free-living Poynucleobacter bacteria represent important members of bacterioplankton in freshwater systems such as lakes, ponds, and streams.
[11] Two genome projects are finished on P. necessarius strains: one project on an obligately freeliving strain isolated from an acidic freshwater pond,[12] and one project on an obligate endosymbiont of the ciliate Euplotes aediculatus.
Analyses of the genome sequences resulted in the discovery of a conserved RNA motif.