Glaucophyta

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Glaucophyta
Glaucocystis sp.

Glaucocystis sp.

Systematics
Classification : Creature
Domain : Eukaryotes (eukaryota)
without rank: Diaphoreticks
without rank: Archaeplastida
Department : Glaucophyta
Scientific name
Glaucophyta
Skuja 1954

The Glaucophyta (from ancient Greek γλαυκός, glaucos: blue-green and φυτόν, phyton: plant) are a small group of algae that occur exclusively in freshwater . They consist of only about eight genera with a good 20 species. The Glaucophyta, together with the green plants ( Chloroplastida or Viridiplantae) and the red algae (Rhodophyceae), are one of the three basic lines of development of the Archaeplastida , so they have probably existed as an independent group since the Archean .

features

Glaucophyta occur in the phytoplankton of freshwater, they either form single cells ( monadal ) or small cell colonies from a few, undifferentiated cells in a common extracellular matrix.

The name-giving feature of the Glaucophyta is the characteristic blue-green color of the photosynthetic organelles , the plastids , also called muroplasts or cyanelles in the case of glaucophytes. This color is based on the pigments chlorophyll a and the characteristic accessory pigments , the phycobilins C- phycocyanin and allophycocyanin . The accessory pigments are arranged in so-called phycobilisomes and increase the effectiveness of photosynthesis by making a wider range of wavelengths of light usable (so-called photosynthetic antennas). The plastids of the glaucophyta, like those of the green plants and the red algae, are surrounded by two membranes , not by four as in numerous other photosynthetically active groups of algae, which are now grouped together to form the ochrophyta within the chromista (or stramenopil ). This is interpreted in such a way that in the Glaucophyta, as in the other archaeplastids, an originally free-living cyanobacterium was taken up as an endosymbiont in an originally colorless, heterotrophic cell, whereas in the Chromista another unicellular alga, i.e. a eukaryotic organism, including its plastids. The cell membrane of this unicellular alga and the vesicle absorbing it during phagocytosis form the two additional membranes. Historically, however, the nature of the plastids in the Glaucophyta has long been controversial. Some researchers even assumed that it was due to an uptake of a cyanobacterium that had only recently taken place independently of the other plants, so one researcher even described this as a separate species. Today it is assumed that the plastids of all archaeplastida are homologous to one another, i.e. that they go back to the uptake of the same cyanobacterium in the early Precambrian.

The plastids of the Glaucophyta have indentations of the cell membrane called thylakoids , which are not arranged in a stack (as in green plants); they have this feature in common with red algae. However, unlike this one, they have a thin coating made of peptidoglycan (or murein), the characteristic building material of the cell wall of bacteria. They also contain so-called carboxysome-like bodies, analogues of the organelles of cyanobacteria called carboxysomes . Both are considered to be an ancient feature that was common to the archaeplastid tribe and has been lost in the other lines of development (a plesiomorphism ).

The genome of the cyanelles is a tenth the size of free-living cyanobacteria, so it is in the order of magnitude of chloroplasts .

There are cells or stages with active movement as well as without active movement. The cells with active movement receive this ability through two flagella of different lengths, which are covered with a thin border of hairs ( fibrils ). The cells without active movement are surrounded by a cell wall, the main component of which is usually cellulose .

Like the green plants, the Glaucophyta store starch as a storage polysaccharide, but in the cytoplasm, not like the green plants within the plastids.

Glaucophyta reproduce asexually (via mitosis ), whereby, depending on the species, either flagellated and thus actively moving zoospores or autospores without active movement are formed as stages of spread. Sexual reproduction has not yet been proven.

Phylogeny and Systematics

Formally, a single class Glaucophyceae Bohlin with an order Glaucocystales Bessey and the only family Glaucocystaceae GS West is formed within the division Glaucophyta . Within this, six to eight genera with around 20 species are usually recognized, whereby within the genus Glaucocystis some cryptic species ( strains bred in pure culture , which can only be distinguished genetically, not morphologically) are detected.

Neither cultures nor molecular data are available for the last four genera mentioned.

According to genetic data, the following cladogram results for the genera for which corresponding data are available  :





 Cyanoptyche


   

 Gloeochaete



   

 Glaucocystis



   

 Cyanophora



According to the current system of Adl u. a. In 2012 the glaucophytes together with the red algae and chloroplastida form the archaeplastida .

proof

  1. ↑ a b c Christopher Jackson, Susan Clayden, Adrian Reyes-Prieto (2014): The Glaucophytes - the blue-green plants in a nutshell. Acta Societatis Botanicorum Poloniae 84 (2): 149-165. doi: 10.5586 / asbp.2015.020 .
  2. ↑ Sina M. Adl, Alastair GB Simpson, Mark A. Farmer, Robert A. Andersen, O. Roger Anderson, John A. Barta, Samual S. Bowser, Guy Bragerolle, Robert A. Fensome, Suzanne Fredericq, Timothy Y. James , Sergei Karpov, Paul Kugrens, John Krug, Christopher E. Lane, Louise A. Lewis, Jean Lodge, Denis H. Lynn, David G. Mann, Richard M. McCourt, Leonel Mendoza, Øjvind Moestrup, Sharon E. Mozley-Standridge , Thomas A. Nerad, Carol A. Shearer, Alexey V. Smirnov, Frederick W. Spiegel, Max FJR Taylor: The New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of Protists. The Journal of Eukaryotic Microbiology 52 (5), 2005; Pages 399-451. doi : 10.1111 / j.1550-7408.2005.00053.x
  3. ^ Peter Sitte , Elmar Weiler , Joachim W. Kadereit , Andreas Bresinsky , Christian Körner : Textbook of botany for universities . Founded by Eduard Strasburger . 35th edition. Spektrum Akademischer Verlag, Heidelberg 2002, ISBN 3-8274-1010-X , p. 651 .
  4. ↑ Algaebase (accessed on September 16, 2017)
  5. ↑ Adl, SM, Simpson, AGB, Lane, CE, Lukeš, J., Bass, D., Bowser, SS, Brown, MW, Burki, F., Dunthorn, M., Hampl, V., Heiss, A. , Hoppenrath, M., Lara, E., le Gall, L., Lynn, DH, McManus, H., Mitchell, EAD, Mozley-Stanridge, SE, Parfrey, LW, Pawlowski, J., Rueckert, S., Shadwick, L., Schoch, CL, Smirnov, A. and Spiegel, FW: The Revised Classification of Eukaryotes. Journal of Eukaryotic Microbiology , 59: 429-514, 2012. doi : 10.1111 / j.1550-7408.2012.00644.x .

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