CLASSIFICATION

The classification of these organisms is based on the shape and flagellation. C. okenii are motile rods 4.5-6µm x 8-15 µm. They do not produce slime or gas vacuoles. They have a requirement for vitamin B12. A cell suspension is purple-red. The predominant carotenoid pigment is okenone. The GC content of the DNA is 48-50 mol%.

BIOCHEMISTRY

Chromatium okenii is a typical purple sulphur bacterium. In light ATP is produced by cyclic photophosphorylation. There is a relationship between CO2 fixation and sulphide oxidation. C. okenii is obligately photolithoautotrophic and requires CO2 and sulphide even when utilising acetate and pyruvate. Generally anaerobic growth in the dark is poor. During dark fermentation they store "suphur" globules, which act as an electron sink. In the dark in the presence of oxygen they have the usual respiratory pathways. C. okenii is not able to grow in the dark at low oxygen tension. It requires vitamin B12 for growth.

There is no information.

There is no information.

There are none known to be produced.

They live predominantly in stratified meromictic lakes, where they sometimes form purple-red layer blooms.

They are not pathogenic.

Strains of C. okenii can be isolated from natural environments using special inorganic media, containing a variety of rare ions and vitamin B12 and 10% sodium sulphide in light.

Normally found in water.

They could be used for the removal of excess sulphide, but this has not been done.

None.

Chromatiaceae

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