Rhabdochromatium roseum

(Cohn, 1875) Winogradsky 1888

Most likely ID: n.a.


Synonym: Chromatium okenii


Sampling location: Radolfzell pond


Phylogenetic tree: n.a.



  • cells fusiformed with blunt ends
  • outline sometimes irregularly
  • length 20 – 48 µm, width 3.5 – 5.7 µm
  • cells filled with yellowish sulphur granules.
  • unipolar flagellum present, shorter than cell
  • pink or flesh-like colored
Rhabdochromatium roseum

I found Rhabdochromatium roseum in a drainage ditch adjacent to the industrial area of Radolfzell. The ditch was mostly filled with rotting willow leaves. The specimens in the sample vessel collected at the bottom.


The species Rhabdochromatium roseum was transferred to Chromatium okenii according to the “Encyclopedia of Life” in April 2022 and is no longer valid. The reason for this is that Rhabdochromatium roseum is considered as a form variant, which arises due to the habitat and the content of sulfur deposits. I cannot follow this synonymization, because I know Chromatium okenii very well and could observe never any form variants. The differences to Chromatium okenii seem to me so significant not least with regard to cell size, so that I would like to stay here with the name Rhabdochromatium roseum.


Fig. 1 a-c: Rhabdochromatium roseum. Three freely swimming specimen. a) before cell division, L = 28 µm, b) starting cell dicvision, L = 42 µm, c) almost completed cell division, L = 46 µm. Obj. 100 X.


Fig. 1 a-c: Rhabdochromatium roseum. L = 46 µm. The slightly squashed specimen in the status of cell division. F = flagellum, S = sulfure globules. Obj. 100 X.