''Katabia'' is a genus of soil-dwelling

heterotrophic A heterotroph (; ) is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are primary, secondary and tertiary consumers, but ...

flagellate cercozoans containing the single species ''Katabia gromovi'', and the only member of family Katabiidae.

Morphology

''Katabia'' are drop-shaped unicellular flagellates with a broad anterior end and a tapering posterior end. They have two heterodynamic (with different movements) flagella. Inside their cells are a microbody, refractile granules shaped like mushrooms, kinetocysts and a well-developed

cytoskeleton The cytoskeleton is a complex, dynamic network of interlinking protein filaments present in the cytoplasm of all cells, including those of bacteria and archaea. In eukaryotes, it extends from the cell nucleus to the cell membrane and is com ...

similar to the one found in '' Heteromita''. Their life cycle has two forms: a free-living

trophozoite A trophozoite (G. ''trope'', nourishment + ''zoon'', animal) is the activated, feeding stage in the life cycle of certain protozoa such as malaria-causing ''Plasmodium falciparum'' and those of the ''Giardia'' group. (The complement of the trophozoi ...

that feeds on

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

through pseudopodia while swimming, and a

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubble) ...

that is surrounded by a thick

mucilage Mucilage is a thick, gluey substance produced by nearly all plants and some microorganisms. These microorganisms include protists which use it for their locomotion. The direction of their movement is always opposite to that of the secretion of m ...

-like wall. Instead of gliding upon the substrate, like other cercozoans, they have secondarily lost the ability to glide with cilia, and only swim freely using their flagella.
In particular, the species ''Katabia gromovi'' is a soil-dwelling flagellate with a prominent dorsal side and a flattened ventral side, whose length is between 8 and 12 μm while its width is between 5 and 7 μm. Its flagella appear approximately one fourth of the cell's length starting from the anterior broad end. The posterior

flagellum A flagellum (; ) is a hairlike appendage that protrudes from certain plant and animal sperm cells, and from a wide range of microorganisms to provide motility. Many protists with flagella are termed as flagellates. A microorganism may have f ...

is approximately 2.5 times the cell's length, while the anterior

is 1.5 times the cell's length and has a shorter acronema (a thin hair-like projection found at the end of each flagella). Katabia gromovi full 2003

Etymology

While the genus' name has no meaning, the species' epithet was chosen to commemorate the late Professor Boris Vasilievich Gromov, an important

Russian Russian(s) refers to anything related to Russia, including: *Russians (, ''russkiye''), an ethnic group of the East Slavic peoples, primarily living in Russia and neighboring countries *Rossiyane (), Russian language term for all citizens and peo ...

microbiologist and protistologist.

Taxonomic affinities

Following its discovery in 2003 multiple similarities were found between ''Katabia'' and the

cercomonad Cercomonads are small flagellates, widespread in aqueous habitats and common in soils. Characteristics The cells are generally around 10 μm in length, without any shell or covering. They produce filose pseudopods to capture bacteria, but do n ...

'' Heteromita'' in

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines * Morphology (archaeology), study of the shapes or forms of artifacts * Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies ...

, behavior, life cycle and

structure, and was placed inside the order Cercomonadida of class

Sarcomonadea The sarcomonads () or class Sarcomonadea are a group of amoeboid biciliate protists in the phylum Cercozoa. They are characterized by a propensity to move through gliding on their posterior cilium or through filopodia, a lack of scales or ext ...

. However, in 2012 the species was placed as

incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...

'', under its own family Katabiidae, because of the uncertainty of its phylogenetic relationships and because it shares similarities with both cercomonads in the structure of the flagella and with glissomonads in the structure of the cillia.

References

{{Taxonbar, from=Q19833376 Cercomonadida Monotypic SAR supergroup genera Cercozoa genera