Microcystis aeruginosa

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Microcystis aeruginosa
Scientific classification Edit this classification
Domain: Bacteria
Phylum: Cyanobacteria
Class: Cyanophyceae
Order: Chroococcales
Family: Microcystaceae
Genus: Microcystis
Species:
M. aeruginosa
Binomial name
Microcystis aeruginosa
Kützing, 1846

Microcystis aeruginosa is a species of freshwater

eutrophic fresh water. Cyanobacteria produce neurotoxins and peptide hepatotoxins, such as microcystin and cyanopeptolin.[1] Microcystis aeruginosa produces numerous congeners of microcystin, with microcystin-LR being the most common.[2] Microcystis blooms have been reported in at least 108 countries, with the production of microcystin noted in at least 79.[3]

Characteristics

NOAA MERIS image of large cyanobacterial bloom confirmed as M. aeruginosa[4]
Microcystis aeruginosa outbreak on Lake Albert in Wagga Wagga, Australia

As the etymological derivation implies, Microcystis is characterized by small cells (of only a few micrometers diameter), which lack individual sheaths.[5]

Cells usually are organized into colonies (large colonies of which may be viewed with the naked eye) that begin in a spherical shape, but lose their coherence to become perforated or irregularly shaped over time in culture. Recent evidence suggests one of the drivers of colony formation is disturbance / water column mixing.[6]

The

vesicles; this can be useful as a distinguishing characteristic when using light microscopy. These vesicles provide the buoyancy necessary for M. aeruginosa to stay at a level within the water column
at which they can obtain optimum light and carbon dioxide levels for rapid growth.

Ecology

M. aeruginosa is favored by warm temperatures,[7] but toxicity and maximal growth rates are not totally coupled,[8] as the cyanobacterium has highest laboratory growth rates at 32 °C, while toxicity is highest at 20 °C, lowering in toxicity as a function of increasing temperatures in excess of 28 °C. Growth has been found to be limited below 15 °C.

The aquatic plant

pyrogallic acids and (+)-catechin, allelopathic polyphenols inhibiting the growth of M. aeruginosa.[9]

Toxins

See also: Cyanotoxin

M. aeruginosa can produce both

hepatotoxins (microcystins
).

Economic importance

Because of M. aeruginosa´s microcystin toxin production under the right environmental conditions, it can be a source of

drinking water pollution.[11] Water quality mitigation measures in the form of water filtration facilities can lead to increased economic costs, as well as damage to local tourism caused by lake or other waterway closures.[12] In recent years major incidents have occurred in both China[13] and the United States / Canada[14][15][16]

M. aeruginosa is the subject of research into the natural production of butylated hydroxytoluene (BHT),[17] an antioxidant, food additive, and industrial chemical.

Bio-active peptides called aerucyclamides can be isolated from M. aeruginosa.[18][19]

Ecological importance

In 2009, unprecedented mammal mortality in the southern part of the Kruger National Park led to an investigation which implicated M. aeruginosa. The dead animals included grazers and browsers, which preferred drinking from the leeward side of two dams, a natural point of accumulation for drifting Microcystis blooms. Mammals such as elephants and buffalo that usually wade into water before drinking, were unaffected, as were the resident crocodiles. The source of nutrients that supported the Microcystis growth was narrowed down to the dung and urine voided in the water by a large resident hippo population, unaffected by the bloom. The immediate problem was solved by breaching of the dam walls and draining of the water. M. aeruginosa is the most abundant cyanobacterial genus in South Africa, with both toxic and harmless strains.[20] Some South African water bodies are now highly contaminated, mostly from return flows out of dysfunctional wastewater treatment works that discharge over 4 billion litres (1.1 billion US gallons) of untreated, or at best partially treated sewage into receiving rivers every day, with Hartebeestpoort Dam being among the worst.[21]

Microcystin has been linked to the death of sea otters in 2010, a threatened species in the US.[22] The poisoning probably resulted from eating contaminated bivalves often consumed by sea otters and humans. Such bivalves in the area exhibited significant biomagnification (to 107 times ambient water levels) of microcystin.[23]

Glyphosate metabolism

Algal blooms of cyanobacteria thrive in the large phosphorus content of agricultural runoff. Besides consuming phosphorus, M. aeruginosa thrives on glyphosate, although high concentrations may inhibit it.[24] M. aeruginosa has shown glyphosate resistance as result of preselective mutations, and glyphosate presence serves as an advantage to this and other microbes that are able to tolerate its effects, while killing those less tolerant.[25] In contrast research in Lake Erie has suggested that glyphosate may lead to blooms of another cyanobacterium - Planktothrix - in place of Microcystis.[26]

References

  1. ^ Tooming-Klunderud, Ave (2007). "On the Evolution of Nonribosomal Peptide Synthetase Gene Clusters in Cyanobacteria". University of Oslo. {{cite journal}}: Cite journal requires |journal= (help)
  2. PMID 28073480
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  3. PMID 28073480
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  4. ^ "Ecosystem Research and Harmful Algal Blooms". Center of Excellence for Great Lakes and Human Health. NOAA. Archived from the original on 27 September 2011. Retrieved 27 June 2011.
  5. ^ "Cyanobacteria: Microcystis". The Silica Secchi Disk. Connecticut College: The SilicaSecchi Disk. Archived from the original on 26 March 2008. Retrieved 24 June 2011.
  6. ISSN 0003-4088
    .
  7. S2CID 142881074
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  8. PMID 29522323
    .
  9. doi:10.1016/S0043-1354(00)00039-7
  10. PMID 21362633. Archived from the original
    on 2013-04-15. Retrieved 25 June 2011.
  11. ^ "Cyanobacterial Toxins: Microcystin-LR in drinking water". Background document for development of WHO Guidelines for Drinking Water Quality. World Health Organization (WHO). Retrieved 24 June 2011.
  12. ^ Somek, Hasim. "A Case Report: Algal Bloom of Microcystis aeruginosa in a Drinking-Water Body, Eğirdir Lake, Turkey" (PDF). Turkish Journal of Fisheries and Aquatic Sciences. Archived from the original (PDF) on 4 October 2011. Retrieved 27 June 2011.
  13. S2CID 21108027
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  14. PMID 28535339
    .
  15. PMID 29791446
    .
  16. doi:10.1016/j.hal.2013.12.008
    .
  17. S2CID 26084768
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  18. PMID 18558743
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  19. PMID 18973386
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  20. doi:10.1016/j.ecoenv.2008.12.014
  21. ^ Turton, A.R. 2015. Sitting on the Horns of a Dilemma: Water as a Strategic Resource in South Africa. In @Liberty, No 6, Issue 22. Johannesburg: South African Institute of Race Relations. Available online http://irr.org.za/reports-and-publications/atLiberty/files/liberty-2013-sitting-on-the-horns-of-a-dilemma-2013-water-as-a-strategic-resource-in-south-africa Archived 2017-10-04 at the Wayback Machine
  22. ^ Stephens, Tim (September 10, 2010). "Sea otter deaths linked to toxin from freshwater bacteria". UC Santa Cruz Newscenter.
  23. PMID 20844747
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  24. PMID 23357506
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  25. S2CID 21762370
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  26. doi:10.1016/j.jglr.2011.07.004
    .
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