Polynucleobacter asymbioticus

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Polynucleobacter asymbioticus is a small, free-living bacterium found in freshwater. It is aerobic, and it tests positive for catalase and oxidase. It uses organic compounds for energy (chemo-organotrophic) and does not move on its own (nonmotile).

Taxonomy and discovery
- Domain: Bacteria; Genus: Polynucleobacter; Species: P. asymbioticus.
- The type strain QLW-P1DMWA-1 (also known as DSM 18221 and CIP 109841) was isolated from a small pond in the Austrian Alps near Salzburg.
- In 2009, it was described as a new subspecies of Polynucleobacter necessarius because its closest relative was an obligate endosymbiont and could not be cultured for standard tests.
- Later genome sequencing showed it is a distinct species, so it was reclassified as Polynucleobacter asymbioticus.

Habitat and lifestyle
- P. asymbioticus lives as planktonic cells in acidic, humic-rich freshwater systems.
- Its genome is relatively small for the Burkholderiaceae family, and it has a notably passive lifestyle compared with many related bacteria.

Research highlights
- A study of 37 P. asymbioticus strains from ponds in the Austrian Alps has provided insights into how Polynucleobacter bacteria evolve.