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Microcystis

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Microcystis
Microcystis aeruginosa
Scientific classification Edit this classification
Domain: Bacteria
Kingdom: Bacillati
Phylum: Cyanobacteriota
Class: Cyanophyceae
Order: Chroococcales
Family: Microcystaceae
Genus: Microcystis
Kützing, 1833
Species

Many (see below)

Microcystis is a genus of freshwater cyanobacteria that includes the harmful algal bloom-forming Microcystis aeruginosa.[1]

Over the last few decades, cyanobacterial blooms caused by eutrophication have become a major environmental problem in aquatic ecosystems worldwide, and the most representative and harmful cyanobacteria is Microcystis.[1] Microcystis blooms have increased due to global climate change, spanning six continents and causing increased health risks to wildlife and humans.[2]

This article will address the conditions for the growth of Microcystis, physical characteristics, ecology, geographic distribution, and health risks of Microcystis.

Conditions for Microcystis

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During the summer in temperate systems, Microcystis can rise to form blooms on the water surface.[3] These blooms, linked to anthropogenic nutrient loading, occur generally when water temperatures exceed 15 °C.[2] But, as the global climate changes, the intensity and occurrence of the blooms is expected to increase.[2]

Physical characteristics

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Microcystis floating colonies in an Erlenmeyer flask

The genus Microcystis derives from the Greek[4] mikros (small) + kystis (bladder).

As the etymological derivation implies, Microcystis is characterized by small cells (a few micrometers in diameter), possessing gas-filled vesicles (also lacking individual sheaths).[4] The cells are usually organized into colonies (aggregations of which are visible with the naked eye) that begin in a spherical shape, losing coherence to become perforated or irregularly shaped over time.[5] These colonies are bound by a thick mucilage composed of complex polysaccharide compounds, including xylose, mannose, glucose, fucose, galactose, and rhamnose, among other compounds.[5]

The coloration of the protoplast is a light blue-green, appearing dark or brown due to optical effects of gas-filled vesicles.[3]

Ecology

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Microcystis wesenbergii colony under epifluorescence microscopy with SYTOX Green DNA staining
Microcystis floas-aquae Kirch.

Microcystis is capable of producing large surface blooms through a combination of rapid division and buoyancy regulation by production of gas-filled vesicles.[6] In nature, Microcystis can exist as single cells or in large colonies containing many cells.[6] Their ability to regulate buoyancy is one of the keys to their dominance of eutrophic waters, by optimally positioning themselves within the photic zone in a stable water column.[6]

Because they can form large surface blooms, they are thought to be able to outcompete other phytoplankton by monopolizing light in the photic zone.[6]

Microcystis spp. are also capable of efficient uptake of phosphate and nitrogen; they are believed to be strongly influenced by nitrogen to phosphorus ratios (N:P ratio).[7] Microcystis cells are also efficient at assimilating carbon from their environment; during large blooms, rampant photosynthesis can drive the pH of communities to > 9.0.[7] Recent efforts have suggested a combination of effective carbon-concentrating mechanisms and a potential ability to use urea as both a carbon and nitrogen source allows Microcystis to persist under these high-pH conditions.[8]

Yuhao Song et al evaluated the relationship between phosphorus sources and Microcystis.[1] This study was essential in building an understanding of the ecological risks of cyanobacterial blooms.[1] These scientists were able to find the following relationships between Microcystis and phosphorus sources: interactions between phosphorus and Microcystis determine the outbreak of Microcystis blooms, different phosphorus conditions affect Microcystis growth and resistance to harmful factors, and Microcystis can drive the distribution of phosphorus sources in aquatic environments.[1] They also concluded that the understanding of endogenous phosphorus should be broadened and more attention should be focused on metabolic processes related to Microcystis cells to provide more support and understanding in control and management of Microcystis blooms.[1]

Geographic Distribution

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The toxic cyanobacterial blooms are expected to become more widespread with climate change because water stratification and increasing temperature favor bloom-forming cyanobacteria.[6]Microcystis is widespread in temperate and subtropical lakes, reservoirs, and rivers in at least 108 countries on six continents.[2]

In South Africa, Hartbeespoort Dam is highly impacted by Microcystis because of elevated phosphate and nitrate levels flowing from the sewers of Johannesburg, one of the few cities in the world that straddles a continental watershed divide,[9] so lies upstream of major dams and rivers.[10]

Lake Erie contains Microcystis algae blooms

In North America, Microcystis blooms have caused issues in numerous freshwater systems over the last two decades.[11] These include large lakes (Erie, Okeechobee) and small regional water masses like Ohio's Grand Lake St Marys.[11] In 2014, detection of the microcystin toxin in treated water of Toledo (OH) resulted in a shutdown of the water supply to more than 400,000 residents.[11] The breakthrough of the toxin in the system was linked to the presence of a virus that lysed cells and released the toxin out of particles into the dissolved phase.[11]

Health risks

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Cyanobacteria can produce neurotoxins and hepatotoxins, such as microcystin and cyanopeptolin.[12][13] The potent hepatotoxin poses a risk to those who use impaired water resources for drinking water supplies, recreational activities, and fisheries.[3] Microcystins are the only cyanotoxins that the World Health Organization has set drinking and recreational water standards.[3]

Countless fatalities and severe poisonings of livestock, wildlife, and pets have been caused by Microcystis blooms.[3] Microcystin-containing Microcystis has also caused human illness via direct consumption of drinking water and accidental ingestion of water or skin contact during recreational use of water.[3] The most severe case of human poisoning took place in Brazil in 1996, when a bloom of Microcystis in a drinking reservoir caused 56 fatalities.[3]

Microcystis has also been reported to produce a compound (or compounds) that can have endocrine-disrupting effects.[14] In 2018, the Great Lakes Center for Fresh Waters and Human Health was founded at Bowling Green State University (OH) with a focus on problems associated with Microcystis blooms in the Laurentian Great Lakes.[14] Under the leadership of inaugural director George S. Bullerjahn, the center engages scientists from nine institutions across six states, and is supported by combined funding from the National Science Foundation and National Institute of Environmental Health Sciences.[14]

Species

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Microcystis species include:[15]

See also

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References

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  1. ^ a b c d e f Song, Yuhao; Li, Ruikai; Song, Wenjia; Tang, Yulu; Sun, Shuangyan; Mao, Guannan (2023-06-20). "Microcystis spp. and phosphorus in aquatic environments: A comprehensive review on their physiological and ecological interactions". Science of The Total Environment. 878: 163136. doi:10.1016/j.scitotenv.2023.163136. ISSN 0048-9697.
  2. ^ a b c d Paerl, Hans W.; Huisman, Jef (2008-04-04). "Blooms Like It Hot". Science. 320 (5872): 57–58. doi:10.1126/science.1155398. ISSN 0036-8075.
  3. ^ a b c d e f g Harke, Matthew J.; Steffen, Morgan M.; Gobler, Christopher J.; Otten, Timothy G.; Wilhelm, Steven W.; Wood, Susanna A.; Paerl, Hans W. (2016-04-01). "A review of the global ecology, genomics, and biogeography of the toxic cyanobacterium, Microcystis spp". Harmful Algae. Global Expansion of Harmful Cyanobacterial Blooms: Diversity, ecology, causes, and controls. 54: 4–20. doi:10.1016/j.hal.2015.12.007. ISSN 1568-9883.
  4. ^ a b "Cyanobacteria: Microcystis". The Silica Secchi Disk. Connecticut College: The SilicaSecchi Disk. Archived from the original on March 26, 2008. Retrieved 24 June 2011.
  5. ^ a b Gademann K, Portmann C, Blom JF, Zeder M, Jüttner F (May 2010). "Multiple toxin production in the cyanobacterium microcystis: isolation of the toxic protease inhibitor cyanopeptolin 1020" (PDF). Journal of Natural Products. 73 (5): 980–984. doi:10.1021/np900818c. PMID 20405925.
  6. ^ a b c d e Dick, Gregory J.; Duhaime, Melissa B.; Evans, Jacob T.; Errera, Reagan M.; Godwin, Casey M.; Kharbush, Jenan J.; Nitschky, Helena S.; Powers, McKenzie A.; Vanderploeg, Henry A.; Schmidt, Kathryn C.; Smith, Derek J.; Yancey, Colleen E.; Zwiers, Claire C.; Denef, Vincent J. (December 2021). "The genetic and ecophysiological diversity of Microcystis". Environmental Microbiology. 23 (12): 7278–7313. doi:10.1111/1462-2920.15615. ISSN 1462-2912.
  7. ^ a b Xie L, Xie P, Li S, Tang H, Liu H (May 2003). "The low TN:TP ratio, a cause or a result of Microcystis blooms?". Water Research. 37 (9): 2073–2080. Bibcode:2003WatRe..37.2073X. doi:10.1016/S0043-1354(02)00532-8. PMID 12691892.
  8. ^ Krausfeldt LE, Farmer AT, Castro Gonzalez HF, Zepernick BN, Campagna SR, Wilhelm SW (2019-05-17). "Urea Is Both a Carbon and Nitrogen Source for Microcystis aeruginosa: Tracking 13C Incorporation at Bloom pH Conditions". Frontiers in Microbiology. 10: 1064. doi:10.3389/fmicb.2019.01064. PMC 6536089. PMID 31164875.
  9. ^ Turton A, Schultz C, Buckle H, Kgomongoe M, Malungani T, Drackner M (June 2006). "Gold, scorched earth and water: the hydropolitics of Johannesburg". Water Resources Development. 22 (2): 313–335. doi:10.1080/07900620600649827. S2CID 54697979.
  10. ^ Turton AR (2015). "Sitting on the Horns of a Dilemma: Water as a Strategic Resource in South Africa". @Liberty. 6 (22). Johannesburg: South African Institute of Race Relations. Archived from the original on 2017-10-04.
  11. ^ a b c d Steffen MM, Davis TW, McKay RM, Bullerjahn GS, Krausfeldt LE, Stough JM, et al. (June 2017). "Ecophysiological Examination of the Lake Erie Microcystis Bloom in 2014: Linkages between Biology and the Water Supply Shutdown of Toledo, OH". Environmental Science & Technology. 51 (12): 6745–6755. Bibcode:2017EnST...51.6745S. doi:10.1021/acs.est.7b00856. PMID 28535339.
  12. ^ Tooming-Klunderud A (2007). On the Evolution of Nonribosomal Peptide Synthetase Gene Clusters in Cyanobacteria (Ph.D. thesis). University of Oslo.
  13. ^ Gademann K, Portmann C, Blom JF, Zeder M, Jüttner F (May 2010). "Multiple toxin production in the cyanobacterium microcystis: isolation of the toxic protease inhibitor cyanopeptolin 1020" (PDF). Journal of Natural Products. 73 (5): 980–984. doi:10.1021/np900818c. PMID 20405925.
  14. ^ a b c Rogers ED, Henry TB, Twiner MJ, Gouffon JS, McPherson JT, Boyer GL, et al. (March 2011). "Global gene expression profiling in larval zebrafish exposed to microcystin-LR and microcystis reveals endocrine disrupting effects of Cyanobacteria". Environmental Science & Technology. 45 (5): 1962–1969. Bibcode:2011EnST...45.1962R. doi:10.1021/es103538b. PMID 21280650.
  15. ^ "Taxonomy Browser Genus: Microcystis". AlgaeBase. Retrieved 24 June 2011.
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