One way Eickelboom filament type 0092 is unique is that for morphotype identification purposes, Neisser positive staining characteristics must apply. Filament type 0092 diameter is typically between 0.8-1.0 µm and these filament types are generally less than 200 µm in length. Type 0092 filaments are usually located within the floc, and if they are causing/contributing to filamentous bulking, it is usually due to these filaments creating open/diffuse flocs.

In certain issues, type 0092 filaments appear capable of also growing dispersed. The recognized growth cause of type 0092 filaments is elevated concentrations of low molecular weight organic acids. Organic acids are a portion of soluble BOD (very readily available substrate) that may be naturally occurring in many industrial wastes and septage, or formed in areas of septicity/fermentation (lift stations, equalization basins).

Generally, type 0092 filaments occur in wastewater at slightly higher sludge retention time values and in the presence of anaerobic/aerobic cycling (for example, selector cells for enhanced biological nutrient removal) or upstream anaerobic pretreatment prior to secondary activated sludge processes.

Type 0092 identification

Identifying type 0092 can often be challenging because it does not solely fit into any identification tables prior to staining, and therefore, cannot be readily identified at 1000x oil immersion only. In some occurrences, faint rectangular cell shapes may be viewed. If cell walls (septa) are not visible, type 0092 filaments may often resemble Haliscomenobacter filament types. Note: The diameter is larger for type 0092 filament types than it is for Haliscomenobacter types.

It is suspected that minor differences observed in type 0092 morphotypes are attributed to factors such as genetic diversity within the morphotype, growth rates of the filament, and the particular substrate the filament may be utilizing. From a genetic standpoint, Ca Promineofilum is the genus most frequently listed as possessing type 0092 morphological traits. The MIDAS field guide references 10 likely species within the Ca Promineofilum genus, of which only one species has a proposed name at the time of this writing. Some Ca Promineofilum members are recognized to be able to store sugars under anaerobic conditions, and in general, type 0092 filament types are believed to likely play an important role in enhanced biological phosphorous removal processes.

Another genus that is linked to type 0092 morphotypes is Ca Amarolinea. The Ca Amarolinea genus has three recognized species and is recognized to be capable of aerobic respiration, fermentation and dissimilartory nitrate reduction to ammonia. Other genus that are candidates for type 0092 morphological traits include Belilinea, Flexilinea, Leuilnea, Anaerolinea and Leuilnea. In our experience comparing microscpy findings to 16S rRNA sequencing, it also appears very common for type 0092 morphoytpes to correlate to unclassified readings from the Chloroflexi phylum such as Aster Bio taxonomy identification numbers 474964, 292625 and 292628.

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About the author: Ryan Hennessy is the principal scientist at Ryan Hennessy Wastewater Microbiology. He was trained and mentored by Dr. Michael Richard for over 10 years in wastewater microbiology, and serves as a microbiology services consultant. Hennessy is a licensed wastewater treatment and municipal waterworks operator in the state of Wisconsin and fills in as needed for operations at several facilities. He can be reached at ryan@rhwastewatermicrobiology.com.