Introduction

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Cyanobacteria, also known as "blue-green algae" plays significant roles in biology from making  contributions to the formation of oxygen, as well as acting as a food-provider during its endosymbiotic relationship with eukaryotic cells. This blog will provide information on Cyanobacteria in areas such as reproduction,  habitat, cell structure and so on. Here's a video giving a brief background on Cyanobacteria:

 [Brief background on
                                                                                      Cyanobacteria on earth]

Scholar, Stem Cyanobacteria:Photosynthetic Prokaryotes (Nov 17, 2011). Retrieved from:http://www.youtube.com/watch?v=uU00tg98Jjw (04/15/2013)

References (APA format):
1. (n.d.). Introduction to the Cyanobacteria Retrieved from: http://www.ucmp.berkeley.edu/bacteria/cyanointro.html (04/12/2013).
2. Gow, Brendan. (n.d). Cyanobacteria Retrieved from: http://academics.smcvt.edu/dfacey/AquaticBiology/Freshwater%20Pages/Cyanobacteria.html (04/11/2013).
3. (n.d.). Endolithic Cyanobacteria and Microbial Bioerosion Retrieved from:
http://people.bu.edu/golubic/marine-cyano.html (04/12/2013).
4. (n.d.). The Changing Earth and Cyanobacteria Retrieved from: http://hoopermuseum.earthsci.carleton.ca/stromatolites/OXYGEN.htm (04/13/2013).
5.(n.d). Algae Control Program Retrieved from: http://www.ecy.wa.gov/programs/wq/plants/algae/publichealth/GeneralCyanobacteria.html (04/13/2013)
6. Essabee (n.d.). Cyanobacteria-The Blue Green Algae Retrieved from: http://www.petfish.net/kb/entry/802/ (04/13/2013).
7. Fedor, Karali (n.d.) Classification Retrieved from: http://bioweb.uwlax.edu/bio203/2011/fedor_kara/classification.htm (04/14/2013).
8. (n.d.). Introduction to Oxygen on Earth Retrieved from: http://draget.net/hoe/index.php?p=p6 (04/14/2013).
9.The Pathological Society of Great Britain and Ireland. (1992) Cyanobacteria and Human Health Retrieved from: http://jmm.sgmjournals.org/content/36/5/301.full.pdf (04/15/2013).
10. (n.d.) Cyanobacteria Retrieved from: http://www.tutorvista.com/content/biology/biology-iii/kingdoms-living-world/cyanobacteria.php#nutrition (04/16/2013).
11. (n.d). The Cyanobacteria and Their Taxonomy Retrieved from: http://www-cyanosite.bio.purdue.edu/taxon79.html (04/17/2013).

Structure & Function(s)

Structure:

Cyanobacteria are typically very small in size, although the way that they grow in colonies makes them appear large enough to be visible. They have a definite cell wall surrounded by a thin or a thick gelatinous coat, along with an inner layer of cell wall made up of peptidoglycans, which are polymers made up of sugar and amino acids.

Cyanobacteria’s inner contents can be separated into two parts: the chromoplasm (outer pigmented area) and the centroplasm (central clear, hyaline area) which contains photosynthetic chlorophyll.   They lack both a nuclues and chloroplast. Below is a diagram of the cell structure for Cyanobacteria:

[Cell Structure]
(n.d) Cell Structure. Retrieved from: http://www.tutorvista.com/content/biology/
biology-iii/kingdoms-living-world/cyanobacteria.php#nutrition (17/04/2013)

Function

·         Cyanobacteria plays a part in the origin of plants, as the chloroplasts that plants use to make themselves food, are actually a cyanobacterium living within the plant’s cells.

·         Play a role in producing food for certain eukaryotic cells, in exchange for a home (endosymbiosis)         

·         Converts atmospheric nitrogen into organic form such as nitrate  or ammonia                                                                           

Relationship With Humans

Cyanobacteria have the potential to cause disease in humans. They can also produce lethal toxins, for example, peptide toxins which can poison, cause diarrhoea and vomiting, cold extremities, and death.
If a human comes in contact with Cyanobateria's algal blooms, they risk the possibility of developing allergic rhinitis, conjunctivitis or dermatitis.

Some positive aspects of Cyanobacteria's existence come from the Proterozoic era where Cyanobacteria were responsible for many oil deposits, thus benefiting humans.
During the same era, many Cyanobacteria generated oxygen that allowed humans to breathe, by their synthesizing of organic compounds from water into carbon dioxide, and releasing of oxygen through the process of photosynthesis.Before this, earth's atmosphere was unsuitable for living things, due to its lack of oxygen. Lastly, through acting as providers of nitrogen fertilizer, Cyanobacteria enabled the cultivation of rice and beans, a food source for humans.

Taxonomy/Phylogeny & Life Cycle

Cyanobacteria have been divided into 5 groups, based on their most recent taxonomic grouping completed by Rippka et al (1979). The classification can be found at this source:
http://www-cyanosite.bio.purdue.edu/taxon79.html

Cyanobacteria are part of the domain "bacteria". Cyanobacteria are their own kingdom, phylum and class called, as well, "Cyanobacteria".
[Phylogenetic tree including Cyanobacteria]
Fedor, Karali. (n.d) Tree of Life. Retrieved from:
             http://bioweb.uwlax.edu/bio203/2011/fedor_kara/classification.htm (04/17/2013)


The classification of Cyanobacteria is commonly debated because of their appearance of algae, their ability to photosynthesise, and their lack of a well-defined nucleus with a nuclear membrane. The above tree shows the relationship between bacteria, (where Cyanobacteria falls under Eubacteria) Archaea and Eukarya, which all stem from a common ancestor. The branches indicate that there is a closer relationship with bacteria (where Cyanobacteria has been classified under), and Archaea, than with Cyanobacteria and those under the domain "Eukarya". 

[Life Cycle of Cyanobacteria]

Beckmann, Aike. (n.d) Cyanobacteria Life Cycle. Retrieved  from:
        http://bioweb.uwlax.edu/bio203/2011/fedor_kara/classification.htm (04/17/2013)

Water is a central part of Cyanobacteria's life cycle, as well as sunlight so that they are able to survive, and photosynthesize. Above is a picture of the general life cycle of Cyanobacterium, which includes the splitting of chain-cells, and as mentioned, the process of photosynthesis. Light provides the cell with the ability to begin the process of photosynthesis, Cyanobacteria germinates, gas vesicles form, filaments grow, nitrogen fixation occurs, oxygen is released and the process repeats itself.

Reproduction

Cyanobacteria reproduce asexually by fission. They have a bacterial chromosome called a genophore, which attaches to the plasma membrane and replicates.

After replication, the bacterium separates into two identical cells, however, Cyanobacteria cannot undergo meiosis and fertilization because they lack a nuceli, putting limitations on Cyanobacteria's genetic recombination.

Cyanobacteria has three ways of completing genetic exchange:
1. through conjugation pilus (connects two adjacent cells)
2. transformation (absorption of free DNA which is then expressed in host)
3. transduction (where virus enters Cyanobacteria and uses its DNA to replace already-present DNA in cell)

Also, mutations are also commonly seen in Cyanobacteria cells. All three of these scenarios help Cyanobacteria overcome its limitations for genetic recombination in reproduction.

[Microscope images of Cyanobacteria.]

(n.d) Introduction of Life on Earth Retrieved from: http://draget.net/hoe/index.php?p=p6 (04/17/2013)

Nutrition & Adaptations

     

    [Cyanobacteria Spriulina]

(n.d) Cyanobacteria Spirulina
 Retrieved from: http://www.ucmp.berkeley.
edu/bacteria/cyanolh.html (04/17/2013)

Nutrition
Most Cyanobacteria are photoautotrophic organisms, meaning they have the ability to produce their own food using the energy from sunlight. Their process for photosynthesis is carried out, in part, by a photosynthetic pigment called Phycobilin.  Phycobilin are light-capturing molecules that bond to water-soluble proteins called phycobiliproteins. Phycobiliproteins pass light energy to  chlorophylls during photosynthesis. As well, in Cyanobacteria, rubisco enzymes help to convert carbon dioxide into sugars. 

In nutrient-rich waters, along with phosphorus-rich waters, Cyanobacteria  bloom.

Although Cyanobacteria can pose a risk to humans' health, it is sometimes consumed as food (the cyanobacterium Spirulina).It is high in protein, and easily accessible at ponds, especially historically in tropical countries where it was regularly eaten by the Aztecs and served in numerous Oriental dishes. Cyanobacteria Spirulinais are also eaten in America due to its health status, and is sold in stores in the form of a dried powder or tablet. 

Adaptations
Through evolution, Cyanobacteria have made adaptations to their environment, such as these listed below:

• use longer wavelengths of light
• use air-filled vacuoles to colonize deeper water
• absorb UV
• survive long spells of darkness

Habitat

Cyanobacteria can be found in terrestrial, marine, and freshwater habitats. They are primarily aquatic, meaning they are most commonly found living in water. However, along with frozen lakes, some other habitats of cyanobacteria include acidic bogs, the interior of solid limestone and dolomite rocks, loose sand grains, shell hash, and volcanoes. 

[frozen lake]

Andrew Brook. (10 Dec 2010). Coastguard Teams Battle the Cold Weather 
                                               Retrieved from:http://www.yachtingmonthly.com/news/509786/coastguard-teams-battle-the-cold-weather (04/17/2013)

Movement/Dispersal

Cyanobacteria have a wide range of organization from unicellular, to filamentous, to colonial. They are often the primary colonizers of new areas because of the fact that they have the ability to inhabit pretty extreme environments.

Cyanobacteria do not have the necessary organs for movement, such as flagella. However, some cyanobacteria exhibit a gliding movement, which may be due to slime secretion or contractile waves on cells.

Here's a video of what Cyanobacteria look like in motion, under a microscope:

[Cyanobacteria at

                                                                                                          1000x magnification]

Source: Wlainer, (Feb 25, 2007). Retrieved from: http://www.youtube.com/watch?feature=player_embedded&v=N6fwKgsLBYQ#! (04/17/2013)