The systematics of Zoochlorella revisited employing an integrative approach
Article first published online: 27 SEP 2010
© 2010 Society for Applied Microbiology and Blackwell Publishing Ltd
Volume 13, Issue 2, pages 350–364, February 2011
How to Cite
Pröschold, T., Darienko, T., Silva, P. C., Reisser, W. and Krienitz, L. (2011), The systematics of Zoochlorella revisited employing an integrative approach. Environmental Microbiology, 13: 350–364. doi: 10.1111/j.1462-2920.2010.02333.x
- Issue published online: 1 FEB 2011
- Article first published online: 27 SEP 2010
- Received 16 September, 2009; accepted 29 July, 2010.
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.