The systematics of Zoochlorella revisited employing an integrative approach

Thomas Pröschold, Tatyana Darienko, Paul C Silva, Werner Reisser, Lothar Krienitz

Research output: Contribution to journalArticlepeer-review


Symbiosis of green algae with protozoa and invertebrates has been studied for more than 100 years. Endosymbiotic green algae are widely distributed in ciliates (e.g. Paramecium, Stentor, Climacostomum, Coleps, Euplotes), heliozoa (e.g. Acanthocystis) and invertebrates (e.g. Hydra, Spongilla), and have traditionally been identified as named or unnamed species of Chlorella Beij. or Zoochlorella K. Brandt or referred to as Chlorella-like algae or zoochlorellae. We studied 17 strains of endosymbionts isolated from various hosts and geographical localities using an integrative approach (nuclear encoded small subunit and internal transcribed spacer regions of rRNA gene sequences including their secondary structures, morphology, physiology and virus sensitivity). Phylogenetic analyses have revealed them to be polyphyletic. The strains examined belong to five independent clades within the Trebouxiophyceae (Choricystis-, Elliptochloris-, Auxenochlorella- and Chlorella-clades) and Chlorophyceae (Scenedesmus-clade). The most studied host organism, Paramecium bursaria, harbours endosymbionts representing at least five different species. On the basis of our results, we propose a taxonomic revision of endosymbiotic 'Chlorella'-like green algae. Zoochlorella conductrix K. Brandt is transferred to Micractinium Fresen. and Zoochlorella parasitica K. Brandt to Choricystis (Skuja) Fott. It was shown that Choricystis minor (Skuja) Fott, the generitype, is a later heterotypic synonym of Choricystis parasitica (K. Brandt) comb. nov. A new species, Chlorella heliozoae, is proposed to accommodate the endosymbiont of Acanthocystis turfacea.
Original languageEnglish
Pages (from-to)350-64
Number of pages15
JournalEnvironmental Microbiology
Issue number2
Publication statusPublished - Feb 2011


  • Base Sequence
  • Chlorella
  • DNA, Plant
  • DNA, Ribosomal Spacer
  • Genes, rRNA
  • Nucleic Acid Conformation
  • Paramecium
  • Phylogeny
  • Symbiosis


Dive into the research topics of 'The systematics of Zoochlorella revisited employing an integrative approach'. Together they form a unique fingerprint.

Cite this