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Cell filaments from Nostoc sp.

Cell filaments from Nostoc sp.

Classification : Creature
Domain : Bacteria (bacteria)
Department : Cyanobacteria
Class : Cyanobacteria
Scientific name of the  department
(ex Stanier 1974) Cavalier-Smith 2002
Scientific name of the  class

The cyanobacteria (from Greek κυανός kyanós , "blue", hence also blue-green bacteria ) form a division of the Bacteria domain . They are distinguished from all other bacteria by their mostly, but not in every kind, existing ability of oxygenic photosynthesis . In the past they were counted among the Phycophyta ( algae ) and listed as the class Cyanophyceae (blue-green algae). Some cyanobacteria contain blue phycocyanin in addition to other photosynthetic dyesand their color is therefore blue-green. That is why they were called "blue-green algae" and this name was used for all cyanobacteria - even for those that do not contain phycocyanin and are not colored blue-green. In contrast to algae, cyanobacteria do not have a real cell nucleus and, as prokaryotes, are not related to the eukaryotic organisms known as "algae" , but belong to bacteria. Cyanobacteria are among the oldest forms of life. You can perceive the direction of the incidence of light.

About 2000 types of cyanobacteria are named, which are divided into five to seven orders . Cyanobacteria with oxygenic photosynthesis are also called Oxyphotobacteria. Sericytochromatia and Melainabacteria count as non-photosynthetic cyanobacteria .

Features and occurrences

Cyanobacteria are gram-negative and one to multicellular. In multicellular cyanobacteria, the cells are arranged one behind the other in long threads ( e.g. Anabaena and Oscillatoria ), flat ( e.g. Merismopedia ) or three-dimensional ( e.g. Pleurocapsa and Microcystis ).

Cyanobacteria occur ubiquitously mainly in fresh water and wet soils, but also in sea water, on tree bark and on rock surfaces.

Photosynthesis in Oxyphotobacteria

Blue and black "ink streaks" on the northern flank of the Alpspitze
Blue algae in the
Blue Grotto (Malta)

The photosynthesis of the cyanobacteria takes place on or in their thylakoid membranes and takes place there in a similar way to the thylakoids of the chloroplasts of eukaryotic algae, mosses , ferns and seed plants . The cyanobacteria not only use the part of the light spectrum that the green plants use for their photosynthesis , but besides chlorophyll a they have an additional antenna complex in the form of phycobilisomes , in which phycobilins , namely phycocyanin (blue) or phycoerythrin (red), contain are. Phycocyanin gives many cyanobacteria their bluish color, some (e.g. Spirulina , Planktothrix rubescens ) gives phycoerythrin a red color. Since the ratio of the individual pigments to one another can fluctuate greatly, cyanobacteria sometimes appear green or even black ('ink streaks'). Phycobilins enable the use of a larger area of ​​the light spectrum (in the green space of the plants, the wavelength range from approx. 500 to 600 nm). The efficiency of light utilization is even greater with phycoerythrin than with chlorophyll. In this way, cyanobacteria can successfully colonize pronounced weak light areas, such as B. the underside of river debris or deep layers in lakes .

Some cyanobacteria can also carry out anoxygenic photosynthesis with hydrogen sulfide as a reducing agent, so they do not form any oxygen (O 2 ). Recently a cyanobacterium was discovered (UCYN-A, English unicellular N2-fixing cyanobacteria in "group A" ), in which the photosystem II is missing. Photosystem II contains the water-splitting complex so that this cyanobacterium cannot carry out oxygenic photosynthesis. In contrast to oxygenic photoautotrophic living being fixed , this strain is not carbon dioxide (CO 2 ) in the Calvin-Benson cycle Basham and photoheterotroph. UCYN-A assimilates elemental nitrogen (N 2 ) by reducing it .

Nonphotosynthetic cyanobacteria

Genome analyzes of 16S ribosomal RNA identified cyanobacteria that do not photosynthesize. They are listed as Melainabacteria and Sericytochromatia in the literature. Further genome analyzes have shown that the genes for photosynthesis are missing in both strains. As a result, they split off from the precursors of the current Oxyphotobacteria, before they were able to photosynthesize via horizontal gene transfer . This also suggests that the common precursor of all cyanobacteria itself was not photosynthetically active.


"Blue algae bloom" in a dredging pond, heavily concentrated in a corner of the water due to wind drift
Globular colonies of gelatinous freshwater cyanobacteria, so-called pond plums

Many cyanobacteria can fix nitrogen : in heterocysts they convert molecular nitrogen (N 2 ) into ammonium (NH 4 + ).

Cyanobacteria produce very different toxins . The microcystins are best known among representatives of the genus Microcystis . In addition, a neurotoxin , the toxic amino acid β-methylamino-alanine (BMAA), could be detected even in species that are not closely related . Based on the often increased occurrence of cyanobacteria in so-called " algae blooms ", such toxins and also BMAA can get into the human organism via the food chain when fish or mussels are consumed and sometimes lead to fatal poisoning.

Cyanobacteria have been studied very intensively in natural product chemistry. The identified secondary metabolites show very different pharmacological effects.

Researchers at the Carnegie Institution found in early 2006 that the cyanobacteria living in Yellowstone National Park operate a metabolism that changes day and night: photosynthesis during the day and nitrogen fixation at night. As far as we know today, this is unique.


There are several systems for the taxonomy of cyanobacteria.

Taxonomy according to NCBI

The taxonomy database of the US National Center for Biotechnology Information (NCBI) only classifies two of a total of 7 orders into families . Bergey's Manual of Systematic Bacteriology uses the self-invented ranks Subsection and Subgroup instead of order and family , which are denoted by Roman numerals instead of names, since not all common orders and families have been validly described according to the Bacteriological Code .

Taxonomy according to NCBI

  • Order Gloeobacterales (class Gloeobacteria): 1 genus, Gloeobacter

The genus Acaryochloris is not classified by the NCBI in any order.

Cavalier-Smith taxonomy

Thomas Cavalier-Smith names 6 orders, of which he puts the Gloeobacterales (with the only genus Gloeobacter ) in its own subdivision Gloeobacteria and the other subdivision, Phycobacteria , in the classes Chroobacteria (orders Chroococcales, Pleurocapsales, Oscillatoriales) and Hormogoneae , Stigonematales).

Significance for the development of animals and plants

About 2.5 billion years ago, the precursors of today's cyanobacteria, which spread massively in water, decisively changed the living conditions on earth. They used sunlight for photosynthesis and released oxygen (O 2 ) as a waste product . This massive production of oxygen ultimately led to a decisive change from the oxygen-free atmosphere to an oxygen-containing atmosphere ( Great Oxygen Catastrophe ).

According to the endosymbiont theory , the ancestors of today's cyanobacteria were the forerunners of the chloroplasts in green plants. This is supported by the matching cell anatomy as well as a set of matching biochemical characteristics, which distinguish the cyanobacteria, like the chloroplasts, from the properties of the eukaryotic cells.

Water pollution

" Blue algae bloom " in a fish pond (details in the picture description)
Streak-like "blue-algae bloom" with cream on the surface of the water in a fish pond

A mass development of cyanobacteria can greatly reduce the water quality and significantly restrict the use of water. They produce a wide variety of secondary metabolites that act as allelochemicals , antibiotics , hormones and toxins , such as: B. Can damage fish and zooplankton . Some of the toxins are among the most powerful natural poisons and can also be harmful to human health. For example, allergic skin reactions and inflammation can develop in bathers. If you swallow water containing cyanobacteria, stomach and intestinal infections can also occur.

In 2017, the concentration of the cyanobacterial toxin anatoxin A was so high in Tegeler See in Berlin and in 2019 in Mandichosee near Augsburg that animals died from it. They were cyanobacteria of the genus Tychonema , which were also detected microscopically in the lakes. In the summer of 2020 6 dogs died after bathing in Lake Neuchâtel as a result of suspected increased 'blue-green algae concentration', so that a bathing ban was issued.

After the cyanobacterial masses die off, oxygen is consumed during their microbial breakdown. This often greatly reduces the oxygen concentration in the water, which can lead to fish deaths .

The conditions for strong reproduction of cyanobacteria are diverse and cannot always be clearly clarified. High phosphate - and possibly nitrogen content in the water - caused, for example, by untreated wastewater with detergent residues or by animal excrement - can, in connection with higher water temperatures, promote the development of bacteria.

See also


  • Thomas Börner : The toxins of the cyanobacteria: New bioactive compounds. In: Biology in our time , Volume 31, Number 2, 2001, pp. 108-115, ISSN  0045-205X
  • Toxin-forming cyanobacteria (blue-green algae) in Bavarian waters - mass developments, hazard potential, reference to water management. Material volume 125, Bavarian State Office for the Environment, Augsburg December 2006, ISBN 3-940009-08-3 .

Web links

Commons : Cyanobacteria  - Collection of images, videos and audio files
Wikibooks: Cyanobacteria  - learning and teaching materials

Individual evidence

  1. The name Cyanophyceae for the only class in the Cyanobacteria division is still used today, for example by Algaebase .
  2. Nils Schuergers et al .: Cyanobacteria use micro-optics to sense light direction . In: eLife . tape 5 , 2016, ISSN  2050-084X , p. e12620 , doi : 10.7554 / eLife.12620 , PMID 26858197 , PMC 4758948 (free full text) - ( [accessed April 26, 2016]). Cyanobacteria use micro-optics to sense light direction ( Memento of the original from April 26, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot /
  3. Cyanobacteria in the Compact Lexicon of Biology , accessed on January 31, 2017.
  4. ^ Y. Cohen et al .: Sulphide-dependent anoxygenic photosynthesis in the cyanobacterium Oscillatoria limnetica. In: Nature , Vol. 257, 1975, pp. 489-492.
  5. Etana Padan: Facultative anoxygenic photosynthesis in cyanobacteria. In: Annual Review of Plant Physiology , Volume 30, 1979, pp. 27-40.
  6. JP Zehr et al: Globally distributed uncultivated oceanic N2-fixing cyanobacteria lack oxygenic photosystem II. In: Science , Volume 322 (5904), 2008, pp. 1110–1112, PMID 19008448 , doi : 10.1126 / science.1165340
  7. ^ EF DeLong: Interesting things come in small packages. In: Genome Biology , Volume 11, Number 5, 2010, p. 118, doi : 10.1186 / gb-2010-11-5-118
  8. Rochelle M. Soo, et al .: On the origins of oxygenic photosynthesis and aerobic respiration in Cyanobacteria . In: Science . tape 355 , no. 6332 , March 31, 2017, p. 1436-1440 , doi : 10.1126 / science.aal3794 , PMID 28360330 .
  9. ^ Robert E. Blankenship: How Cyanobacteria went green . In: Science . tape 355 , no. 6332 , March 31, 2017, p. 1372-1373 , doi : 10.1126 / science.aam9365 , PMID 28360281 .
  10. Falch B .: What is in cyanobacteria? In: Pharmacy in our time . Volume 25, No. 6, 1996, pp. 311-321,
  11. George M. Garrity (Ed.): Bergey's Manual of Systematic Bacteriology . 2nd edition, Volume 1: The Archaea and the deeply branching and phototrophic Bacteria. Springer, New York 2001. Quoted from JP Euzéby: List of Prokaryotic names with standing in Nomenclature (LPSN) ( Memento of the original from November 28, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. . @1@ 2Template: Webachiv / IABot /
  12. NCBI (National Center for Biotechnology Information) Taxonomy Browser: Cyanobacteria , accessed October 27, 2007
  13. ^ T. Cavalier-Smith: The neomuran origin of archaebacteria, the negibacterial root of the universal tree and bacterial megaclassification. In: Int J Syst Evol Microbiol , Volume 52, Part 1, 2002, pp. 7–76, PMID 11837318 ( PDF  ( page no longer available , search in web archivesInfo: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. ).@1@ 2Template: Dead Link /  
  14. ^ Heinrich D. Holland: The oxygenation of the atmosphere and oceans . In: Philosophical Transactions of the Royal Society B , Volume 361, pp. 903-915. doi : 10.1098 / rstb.2006.1838 .
  15. ^ JM Olson: Photosynthesis in the archean era. In: Photosynthesis Research , Volume 88, Number 2, 2006, pp. 109-117. PMID 16453059 .
  16. Danger from blue-green algae in swimming lakes Retrieved November 17, 2019
  17. Gönül Frey: Dead dog: It was actually the poisonous algae. Lechtstaustufe 23: The cause of death is clearly proven in one out of three dead animals . In: Augsburger Allgemeine, August 23, 2919, p. 29. Online .
  18. New blue algae in Tegeler See killed three dogs Retrieved July 27, 2018
  19. How to protect yourself against blue-green algae Retrieved July 27, 2018
  20. Jutta Fastner, Camilla Beulker, Britta Geiser, Anja Hoffmann, Roswitha Kröger, Kinga Teske, Judith Hoppe, Lars Mundhenk, Hartmud Neurath, Daniel Sagebiel, Ingrid Chorus: Fatal Neurotoxicosis in Dogs Associated with Tychoplanktic, Anatoxin-a Producing Tychonema sp. in Mesotrophic Lake Tegel, Berlin . In: Toxins 2018, 10, 60, DOI: 10.3390 / toxins10020060.
  21. Cyanobacteria suspected in the lake - Neuchâtel closes several beaches Accessed July 31, 2020
  22. Toxin-forming cyanobacteria (blue-green algae) in Bavarian waters - mass developments, risk potential, reference to water management. Material volume 125, Bavarian State Office for the Environment, Augsburg December 2006, ISBN 3-940009-08-3 .