Type 0581
Type 0581 is a filamentous bacterium possessing the following characteristics:
- not branched;
- immobile;
- bowed/twisted filaments, free in the water or along the flocs;
- filament length < 200 µm;
- cell diameters 0.3 - 0.4 µm;
- no attached growth;
- no sheath;
- septa not visible;
- no sulphur storage;
- Gram negative;
- Neisser negative.

Type 0581 morphologically resembles M. parvicella. Clear distinctions between both species can only be identified by Gram and Neisser staining. Type 0581 filaments are also a little thinner. In spite of these differences, it is not out of the question that the two growth forms concern the same species.

Occurrence in activated sludge
Type 0581 is chiefly observed at sludge loading levels of 0.05 - 0.1 kg BOD/kg MLSS.day.

Control strategies
Nothing is known.