Pseudoblepharisma

{{Short description|Genus of protozoans}}

{{Automatic taxobox

|image = Abg4102.F1.large.jpg

|image_caption = Pseudoblepharisma tenue with its two photosynthetic symbionts{{cite journal |last1=Muñoz-Gómez |first1=SA |last2=Kreutz |first2=M |last3=Hess |first3=S |title=A microbial eukaryote with a unique combination of purple bacteria and green algae as endosymbionts. |journal=Science Advances |date=June 2021 |volume=7 |issue=24 |doi=10.1126/sciadv.abg4102 |pmid=34117067 |pmc=8195481 |bibcode=2021SciA....7.4102M |doi-access=free}}

|taxon = Pseudoblepharisma

|authority = Kahl 1926

|subdivision = See text

}}

Pseudoblepharisma is a genus of heterotrich ciliates inhabiting oxygen depleted freshwater habitats. Most sources report that it contains one species, Pseudoblepharisma tenue,{{cite journal |last1=Hines |first1=Hunter N. |last2=McCarthy |first2=Peter J. |last3=Esteban |first3=Genoveva F. |title=A Case Building Ciliate in the Genus Pseudoblepharisma Found in Subtropical Fresh Water |journal=Diversity |date=27 February 2022 |volume=14 |issue=3 |pages=174 |doi=10.3390/d14030174 |doi-access=free}} but at least four have been seen in literature.{{cite web |title=Pseudoblepharisma Kahl, 1927 |url=https://www.gbif.org/species/8031283 |website=www.gbif.org |language=en}}

Pseudoblepharisma tenue was originally described in Germany as Blepharisma tenuis. It was discovered by biologist Alfred Kahl in 1926 in the Simmelried moorland near Konstanz, and was then ignored for decades.[https://www.the-scientist.com/news-opinion/a-protist-hosts-both-green-algae-and-purple-bacteria-symbionts-68875 A Protist Hosts Both Green Algae and Purple Bacteria Symbionts | The Scientist Magazine®] 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 sp. K10 (green algae), discovered earlier as a symbiont of Hydra viridissima; and Ca. Thiodictyon intracellulare (Chromatiaceae), 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 as an electron donor for photosynthesis.{{cite journal | pmc=10063809 | date=2023 | last1=Christian | first1=R. | last2=Labbancz | first2=J. | last3=Usadel | first3=B. | last4=Dhingra | first4=A. | title=Understanding protein import in diverse non-green plastids | journal=Frontiers in Genetics | volume=14 | doi=10.3389/fgene.2023.969931 | doi-access=free | pmid=37007964 }} The complexity of such a tripartite symbiosis is novel to science.

The ciliate likely prefer an aerobic environment when in the dark, and because it is mixotrophic, 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.[https://microbiologysociety.org/static/ac545e09-c898-4265-bc65cb17702cc07f/Oct-22-MT-Web.pdf TODAY49:2 October 2022 - Microbiology Society]

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, North America. Unlike its the bicolor European counterpart, it builds a lorica (shell) around itself.

The current taxonomy is inconsistent with molecular phylogeny using SSU rRNA; the latter places the genus sister to Spirostomum.