''Pseudoblepharisma'' is a genus of
heterotrich
The heterotrichs are a class of ciliates. They typically have a prominent adoral zone of membranelles circling the mouth, used in locomotion and feeding, and shorter cilia on the rest of the body. Many species are highly contractile, and are ...
ciliates
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different ...
inhabiting oxygen depleted freshwater habitats. Most sources report that it contains one species, ''Pseudoblepharisma tenue'',
but at least four have been seen in literature.
''Pseudoblepharisma tenue'' was originally described in Germany as ''Blepharisma tenuis''. It was discovered by biologist
Alfred Kahl
Alfred Detlef Fritz Kahl (18 February 1877 – November, 1946) was a German schoolteacher who took up microscopy in mid-life and became a leading authority on ciliated protozoa. In a burst of scientific productivity that lasted just nine years, h ...
in 1926 in the Simmelried
moorland
Moorland or moor is a type of Habitat (ecology), habitat found in upland (geology), upland areas in temperate grasslands, savannas, and shrublands and the biomes of montane grasslands and shrublands, characterised by low-growing vegetation on So ...
near
Konstanz
Konstanz ( , , , ), traditionally known as Constance in English, is a college town, university city with approximately 83,000 inhabitants located at the western end of Lake Constance in the Baden-Württemberg state of south Germany. The city ho ...
, and was then ignored for decades. Starting in 2006, it was recognized that the German strain may have two bacterial symbionts, one pink, one green. In 2021, both symbionts were confirmed to be photosynthetic: a ''
Chlorella
''Chlorella'' is a genus of about thirteen species of single- celled or colonial green algae of the division Chlorophyta. The cells are spherical in shape, about 2 to 10 μm in diameter, and are without flagella. Their chloroplasts contain t ...
'' sp. K10 (
green algae
The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...
), discovered earlier as a symbiont of ''
Hydra viridissima
''Hydra viridissima'' is a species of cnidarian which is commonly found in still or slow-moving freshwater in the Northern temperate zone. ''Hydra viridissima'' is commonly called green hydra due to its coloration, which is due to the symbiotic g ...
''; and Ca. ''
Thiodictyon
''Thiodictyon'' is a genus of gram-negative bacterium classified within purple sulfur bacteria (PSB).
* ''T. elegans'' forms "netlike aggregates under certain culture conditions." It is obligately phototrophic and strictly anaerobic.
* ''T. bac ...
intracellulare'' (
Chromatiaceae
The Chromatiaceae are one of the two families of purple sulfur bacteria, together with the Ectothiorhodospiraceae. They belong to the order Chromatiales of the class Gammaproteobacteria, which is composed by unicellular Gram-negative bacteria, Gr ...
), a
purple sulfur bacterium with a genome just half the size of their closest known relatives, and has lost genes essential for nitrogen and sulfur metabolism, and the ability to use
hydrogen sulfide
Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...
as an electron donor for photosynthesis. The complexity of such a
tripartite symbiosis
Tripartite symbiosis is a type of symbiosis involving three species. This can include any combination of plants, animals, fungi, bacteria, or archaea, often in interkingdom symbiosis.
Ants
Fungus-growing ants
Ants of Attini cultivate fung ...
is novel to science.
The ciliate likely prefer an aerobic environment when in the dark, and because it is
mixotroph
A mixotroph is an organism that uses a mix of different sources of energy and carbon, instead of having a single trophic mode, on the continuum from complete autotrophy to complete heterotrophy. It is estimated that mixotrophs comprise more than ...
ic, it is hypothesized its anoxygenic photosynthesising bacterial endosymbionts allows it to enter anoxic environments where it will have access to the microbial prey living there.
TODAY49:2 October 2022 - Microbiology Society
/ref>
European reports also mentioned a variant ''P. tenue'' var. ''viride'', which only has green symbionts. In 2022, one strain matching these descriptions was found in tropical freshwaters of Florida
Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
, North America. Unlike its the bicolor European counterpart, it builds a lorica (shell) around itself.SSU rRNA
Small subunit ribosomal ribonucleic acid (SSU rRNA) is the smaller of the two major RNA components of the ribosome.
Associated with a number of ribosomal proteins, the SSU rRNA forms the small subunit of the ribosome. It is encoded by SSU- rDNA.
...
; the latter places the genus sister to ''Spirostomum
''Spirostomum'' is a genus of ciliated protists in the class Heterotrichea. It is known for being very contractile.Fernandes, N.M.; da Silva Neto, I.D. (2013). “Morphology and 18S rDNA gene sequence of ''Spirostomum minus'' and ''Spirostomum te ...
''.
References
{{Taxonbar, from=Q25363698
Heterotrichea
Ciliate genera