Prochloron

NCBI: Taxonomy Genome

Prochloron. Image from College of Biological Sciences, University of Tsukuba.

Classification

Higher order taxa:

Bacteria; Cyanobacteria; Prochlorales; Prochloraceae

Species:

Prochloron didemni, P. sp.

Description and Significance

Species of the Prochloron genus are oxyphotobacteria, or oxygenic photosynthetic prokaryotes. They are most prominent in tropical waters as symbionts with ascidians, commonly known as sea squirts. These organisms' unique photosynthetic morphology make them interesting to scientists who study the evolution of the features in photosynthesizers.

Genome Structure

Learning more about the genetics of Prochloron will help researchers to determine relationships between these bacteria and other photosynthesizers, especially because of their distinct functional and structural photosynthetic features.

Cell Structure and Metabolism

Image from Kuhl, et al. Cellular origin and life in extreme habitats Vol 3.

Currently there are studies being performed on Prochloron's photosynthetic machinery, as its morphology is unique among prokaryotes. Physically they are structurally similar to the photosynthetic apparatus of green plastids, with the thylakoids (the saclike membranes which house the chlorophyll within the cells) located in the peripheral cytoplasm of the bacteria's cells. This feature is one of the bases for the hypothesis that this bacteria is similar to the bacteria which evolved to become the first chloroplast within photosynthesizing eukaryotes. The photosynthetic pigment composition of Prochloron has similar characteristics of both cyanobacteria and chlorophytes.

Ecology

Ascidian, symbiont of Prochloron. Image from Glenelg Scuba Diving.

Prochlorons are distributed within the tissues of didemnid ascidians, mainly in the cloacal cavities under the upper tunic of the organism (see above image). Ascidians, or "sea squirts", are primarily known as a nusciance to humans. These sessile tunicates are found on most solid marine surfaces, including rocks, reefs, and algae.

References

Kuhl, Michael et al. The Microenvironment and Photosynthetic Performance of Prochloron sp. in Symbiosis with Didemnid Ascidians. Seckbach, J. (ed) Cellular origin and life in extreme habitats Vol 3: Symbiosis, mechanisms, and model systems. Klewer Acad. Publ., Dordrecht (2002). 273-290.

Shimada, A. et al. Molecular phylogenetic relationship between two symbiotic photo-oxygenic prokaryotes, Prochloron sp. and Synechocystis trididemni. Phycologia March 2003.