Protistology 3 (1) 30–41 (2003) Katabia gromovi nov. gen., nov. sp. – a new soil flagellate with affinities to Heteromita (Cercomonadida)
Serguei A. Karpov 1, 2, Flemming Ekelund 2 and
Øjvind Moestrup 3
1 Biological Faculty, St. Petersburg State University, St. Petersburg, Russia
Summary
An unusual flagellate from soil has been investigated in culture using LM and TEM,
with special reference to the structure of the flagellar apparatus. Trophic forms have
two smooth heterodynamic flagella; cysts are surrounded by a thick translucent wall.
Flagellates swim permanently and attach to the substratum only just before encystment.
They ingest bacteria by pseudopodia whilst swimming. A preliminary study of the partial
sequence of SSU rDNA strongly suggests that its closest relatives are Heteromita,
Cercomonas, and Cryothecomonas. In general morphology, cytoskeleton structure,
behaviour, and life cycle the new strain revealed close affinity to the cercomonad
Heteromita. The cell is covered by only a plasmalemma underlain by kinetocysts; the
basal body of the posterior flagellum lies at approximately right angles and in a different
plane to the anterior one; there is a cylinder connected with the A-tubules of the
axoneme in the flagellar transition zone; flagellar rootlet homology is clear; the nucleus
has a prominent nucleolus; a microbody with amorphous contents is located near the
nucleus; mitochondria have vermiform tubular or vesicular cristae. The flagellate differs
from Heteromita in behaviour as well as in general morphology (presence of unusual
mushroom-like bodies) and in details of the cytoskeleton structure. On the basis of
behavioural, morphological and molecular data we establish a new genus and species
for our strain: Katabia gromovi gen et sp. nov., of the order Cercomonadida. Key words: Katabia gromovi, cercomonads, ultrastructure, cytoskeleton, soil flagellates,
partial SSU gene sequence
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