Type 0041 and Type 0675...

Although Type 0041 (and / or Type 0675) is frequently reported in bulking and foaming activated sludges, the literature on it is not so ample as in the case of the above described four filaments.

Type 0041 trichomes morphologically resemble the trichomes of colorless Cyanophyceae, especially when the trichome is not covered by any attached growth. In such a case, Type 0041 can be confused with Type 021N when observed in wet mounts only. According to an author, both types can be distinguished by the presence (Type 0041) and the absence (Type 021N) of the sheath. Unfortunately, this is not a very reliable distinguishing feature as far as light microscopy is concerned. Some authors were warned that "it may be hard to detect the sheath of Type 0041 and differentiate it from the pseudosheath sometimes formed by Type 021N". Also, the individual cells of Type 0041 may resemble the cells of Type 021N. Most commonly, Type 0041 cells are rectangular and clearly divided by septa. But barrel-shaped and discoid cells as in Type 021N can also be found. However, the appearance of Type 0041 trichomes is more "smooth" in comparison with Type 021N as there are no indentations at septa.

The problem of the observation of a sheath in phase contrast light microscopy for Type 0041 results from an extreme transparency of the sheath. An author was studied the morphology and anatomy of Type 0041 trichomes by means of scanning (SEM) and transmission (TEM) electron microscopy. Their paper brings excellent TEM and SEM microphotographs of Type 0041 rectangular cells arranged in a hose-like transparent cover. The TEM and SEM microphotographs of Type 0041 also show how the sheath of trichomes is colonized by unicellular epiphytic bacteria.

The presence of attached growth is very typical of Type 0041 filaments. Usually, the attached growth is very massive, so that the structure of the trichomes is hard to see. The presence of attached growth can interfere with staining, because the stain components have to penetrate through the biofilm to the trichome. Type 0041 itself reacts positively to the Gram stain, but the epiphytic attached growth is mostly Gram negative. The reactions to the Neisser stain are generally negative but according to some authors, a Neisser positive slime coating may be observed around Type 0041 trichomes.

The trichomes of Type 0041 are robust and long. They grow both in the flocs and protruding from the floc, so they can cause both kinds of filamentous bulking. On the other hand, by attracting colonizing epiphytic bacteria, Type 0041 filaments may give rise to flocs formed on the skeleton of the filaments.

Morphological properties and reactions to the Gram and Neisser stains of Type 0675 are very similar to those of Type 0041. Some authors term this filament "small 0041" because the dimension of the cells as well as the trichome length is less for Type 0675 than for Type 0041. However, a direct proof of the relatedness of both types is still missing. According to an author, Types 0041 and 0675 probably represent two species of the same genus, but their taxonomic position has not yet been recognized.

As results from the surveys described above section, Types 0041 and / or 0675 are quite frequently found in biological foams. Some researchers were explained the ability of Type 0041 to be concentrated in biological foams by a biosynthesis of surface active agents. From their results, they concluded that the biosurfactant produced by Type 0041 was a saturated-lipid / protein complex.