You Have Found The Satan...!
Characteristics : Bent and irregularly - coiled filaments, 1.2 - 1.4 micron in diameter and 100 - 200 micron in
length, found mostly within the floc. Cell septa are clear, with oval cells (1.2 - 1.4 micron in diameter) and indentations
at septa. No sheath and no sulfur granules. PHB granules commonly are observed. Gram and Neisser staining reactions are
viable. Most observed is Gram negative, but a Gram - positive reaction occurs. Most often the entire trichome stains
Neisser positive (purple), but can be Neisser negative at times. Incidental branching is observed.
Identification : Medium length , non-motile filaments (100-200 µm). Bent and irregularly coiled filaments with
incidental true branching. Knots sometimes seen. Cell septa are clear with indentations. Cells are oval or disc shaped
(1.2-1.4 µm). Filaments are found within the floc structure but may occur in the bulk solution. The filament staining is
variable, it is usually Gram negative but sometimes positive and Neisser positive. Usually easy to identify due to its
Neisser staining properties. Stains entirely purple and looks like stacked discs (or hockey pucks). In industrial wastes,
an organism that is Gram negative and Neisser negative occurs. There is no sheath and there are no sulfur granules.
Poly-ß-hydroxybutric acid (PHB) granules are frequently observed as dark intracellular granules. Attached growth is
usually uncommon.
Similar Organisms : Three subtypes are known. Resembles M. parvicella except in its Neisser staining
properties. The Neisser staining always makes it easy to identify N. limicola. The twists, kinks and knots usually make
it easier to identify than the similar type 021N. Both have no sheath and irregular cells, but Type 021N has a more flat,
ribbon like twist, while N. limicola has more twists and turns and knots. The real dead give away though, if all else
fails, is the Neisser stain. Type 021N is negative and N. limicola is positive.
Environment : This filament is usually found in environments where there is low DO or low F/M and the presence of
organic wastes. Wastes containing starch seem more selective to this filament. Bulking is more common in industrial wastes.
The filament appears to be facultative fermentative, which is unique for most filaments.
Control : Manipulation of F/M (usually an increase) and DO concentration can be used to control the filaments. A
selector may be used and chlorination. System changes include changing from a complete mix to plug flow aeration basin
configuration.
Rank : N. limicola ranks 12th in number of predominance in industry. Typically not found in kraft mills.
Common in municipalities.
