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Microalgae

What are Microalgae?

Microalgae are eukaryotic microscopic algae. They are photosynthetic and produce large oxygen content. They are harvested for their lipid, carbohydrate, protein, and other chemical products such as toxins. Microalgae toxins can also be harvested for their antimicrobial properties and many applications.

Microalgae are found in a diverse array of habitats like aquatic habitats, including lakes, pounds, rivers, oceans, and even wastewater. They can tolerate a wide range of temperatures, salinities, and pH values; different light intensities; and conditions in reservoirs or deserts and can grow alone or in symbiosis with other organisms.

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Some genus of microalgae. Credits to Jorge L. Mejia BSc.

Type of Growth: Microalgae are unicellular microbes that can be found growing as solitary or multiple cells linked together as a colonial (Non-Solitary).

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Type of Growth. Solitary (non-colonial) and Colonial growth

Morphology: The morphology of microalgae refers to the overall shape of the microbe. Microalgae are very diverse and can have Spherical (circular and round), Elliposoidal (oval or elongated oval), Triangular (pyramid like), Helical, Sigmoidal (oval and Curved), and Rectangular.

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Morphological representation of Microalgae shapes

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A variety of microscopic unicellular and colonial freshwater algae

Metabolism: There are multiple factors that can play a role in Microalgae metabolism. Microalgae can be:

Autotrophs: Organisms that use light as a the source of energy to create molecules as a source of food. For Example, Botryococcus braunii is an autotrophic microalgae.

Facilitative Heterotrophs: Rely on available nutrients in their environment to thrive and follow a heterotrophic pathway due to the conditions they are under. Heterotrophic metabolism is used many times in maximizing the harvesting of Microalgal byproducts. For example , Auxenochlorella protothecoides is a facilitative heterotroph.

Mixotrophs: Have the ability to utilize autotrophic and heterotrophic pathways together. This is where a microalgae uses both pathways simultaneously to maximize growth. For example, Chlamydomonas reinhardtii is known to grow utilizing autotrophic and heterotrophic pathways depending on the environmental conditions it is under.

Pigments: Microalgae come in many different colors, which are a result of the pigments they produce. Some of the pigments produced by microalgae are photosynthetic and might have a Biochemical/Biotech applications.

Some example of algal pigments are:

Chlorophyll a

Chlorophyll c

Beta-carotene

Fucoxanthin

Diatoxanthin

Diadinoxanthin

Violaxanthin

Antheraxanthin

Zeaxanthin

Xanthophylls

More info:

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Microalgal Pigments: A Source of Natural Food Colors⁠

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Mobility: Many of microalgae are non-motile, meaning they do not have the ability to move on their own. However, some do possess the ability to move, making them motile, by using hair like structures such as Flagellum and Pilus. Pilus can also be referred to as Fimbria.

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Example of motile microalgae and their motility mechanism.

More info:

Decreased motility of flagellated microalgae long-term acclimated to CO2-induced acidified waters⁠

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Biofilm: Just like Bacteria, biofilm is used by microalgae to stick to each other and surfaces, especially in aquatic environments. Microalgae biofilm has three advantages: (1) resistance to growth stresses, (2) high cell density, and (3) low harvesting and concentration costs in the biotech industry.

More info:

Mixotrophic Microalgae Biofilm: A Novel Algae Cultivation Strategy for Improved Productivity and Cost-efficiency of Biofuel Feedstock Production⁠

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Reproduction and Spores: Microalagae have the ability to do through both sexual and asexual reproduction. Microalgae can go through a process of sex determination to conduct sexual reproduction by producing haploid spores. In asexual reproduction, the microalgae can form asexual spores that allow reproduction. In both cases there may be formation of spores.

More info:

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Algae - Reproduction and life histories⁠

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Factors affecting spore germination in algae — review⁠

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Symbiosis: A symbiotic relationship can be beneficial to both organisms that are interacting with each other. Microalgae have a history maintaining such relationships with bacteria, fungi, animals and plants. Microalgae provides important nutrients to organisms to sustain life in exchange for protection against environment stress, for example the relationship between micro-algae and coral.

More information:

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When corals met algae: Symbiotic relationship crucial to reef survival dates to the Triassic⁠

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Symbiotic Algae and Coral Reefs: Symbionts and Hosts Live in Harmony⁠

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Unlocking genetic secrets of coral symbiosis to preserve iconic Great Barrier Reef Scientists have decoded genomes from algae found in coral, as part of a greater plan to preserve the health of corals and protect the Great Barrier Reef from coral bleaching. UQ Institute for Molecular Bioscience researchers sequenced the genomes of two species of Symbiodinium, co-existing micro-algae that critically provide food and nutrients to corals. This research was published in Communications Biology https://www.nature.com/articles/s42003-018-0098-3 A Behind-the-Paper post is available on the Nature Ecology & Evolution Community https://natureecoevocommunity.nature.com/users/169685-cheong-xin-chan/posts/36054-decoding-the-genomes-of-coral-reef-symbionts Institute for Molecular Bioscience | http://www.imb.uq.edu.au Facebook | https://fb.me/instituteformolecularbioscience Twitter | https://twitter.com/IMBatUQ LinkedIn | https://www.linkedin.com/company/imb-uq www.youtube.com⁠

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Pathogen: Some microalgae have been found to caused infections and diseases to humans, animals and plants. An example of a pathogenic microalgae is the species Prothoteca cutis found in human skin in an infected patient. Since microalgae infections have not been widely report, effective treatment protocols have not been well-established and so the importance of these annotations.

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Prototheca Cutis Sp. Nov., a Newly Discovered Pathogen of Protothecosis Isolated From Inflamed Human Skin - PubMed⁠

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Biological Technology Applications

Content Production: Microalgae have a large variety of products that form as a byproduct of sustaining life. The byproducts have be harvested for use in Bio-tech, medical, or biochemical application. These byproducts can be Lipids, Protein, Carbohydrate, Isopernoids, or Toxins.

Lipids, Protein, and Carbohydrate contents are important because they can be used to create dietary supplements. Isopernoids are precursors to a wide variety of synthetic and natural compounds. Toxins produced by microalgae can contain antimicrobial properties, which are helpful in Biochemical and medical applications.

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Microalgae metabolites production

More info:

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The promising future of microalgae: current status, challenges, and optimization of a sustainable and renewable industry for biofuels, feed, and other products⁠

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The Usefulness of Microalgae Compounds for Preventing Biofilm Infections⁠

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UV Resistance: Microalgae may also be resistant to UV light. This can be a beneficial trait when growing in areas with elevated UV radiation and can be harnessed to Biotechnological or Biochemical applications.

More info:

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UV-B resistance as a criterion for the selection of desert microalgae to be utilized for inoculating desert soils⁠

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Extremophile: Microbes with optimal growth in environmental conditions considered extreme in comparison to the environmental conditions that are comfortable to humans such as low/high temperature, acidity, alkalinity, or chemical concentration. There are different types and degrees of extremophiles. They are not exclusive, meaning that a microbe can be for example an acidophile and thermophile.

There can be microbes that can be more extreme than others within the same extremophile type. For example: There could be slight halophiles that grow on 0.3 to 0.8 M, 1.7 to 4.8 % NaCl, moderate halophiles that grow on 0.8 to 3.4 M, 4.7 to 20 % NaCl and extreme halophiles that grow on 3.4 to 5.1 M, 20 to 30 % NaCl.

Some microbes might tolerate extreme conditions. However they do not do well under these conditions and their optimal conditions are within normal parameters (temperature, salinity, etc). Tolerant microbes are not considered extremophiles.

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Table of different types of extremophiles Microalgae and Diatoms

Microbiome: Although microalgae locations can vary, they are usually closely associated to a water sources. They can be found in or near bodies of water bodies or in sediment inside or near water.

Water biomes can be classified on:

Fresh: Defined as having a low salt concentration usually less than 1%. It includes ponds, lakes, streams, rivers and wetlands.

Marine: Comprises systems of open-ocean and unprotected coastal habitats, characterized by exposure to wave action, tidal fluctuation, and ocean currents as well as systems that largely resemble these. Water in the ocean biome is generally within the salinity range of seawater 30 to 38 ppt.

Mangrove: Composed by Mangrove plants mangroves are able to withstand high levels of salinity as well as regions of anoxia and frequent tidal inundation. This biome often occurs near tropical and sub-tropical estuaries in areas protected from high energy wave action.

Sediment: Is a naturally occurring material that is broken down by processes of weathering and erosion from land to the water by the action of wind, water, or ice.

Brackish: Brackish water is water having more salinity than freshwater, but not as much as seawater. It may result from mixing seawater with fresh water together, as in estuaries, or it may occur in brackish fossil aquifers.

Estuaries: Estuaries and their surrounding wetlands are bodies of water usually found where rivers meet the sea.

Waste waters: Domestic wastewater or sewage produced by a community of people.

Soil Biomes can be classified on:

Tundra: Includes only low-growing vegetation such as dwarf shrubs, sedges and grasses, mosses, and lichens. Tundra biomes rarely have monthly average temperatures above 10 degrees Celsius and have low precipitation ratios. Tundra is also found at the tops of very high mountains elsewhere in the world.

Forest: Includes densely packed vegetation which strongly limits light penetration to the forest floor. Can be classified on Temperate, Boreal and Tropical forest.

Cropland: Is an anthropogenic terrestrial biome which is primarily used for agricultural activity and which contains no village or larger human settlements.

Grassland: Includes large, rolling terrains of grasses, flowers and herbs. The annual precipitation is great enough to support grasses, and in some areas a few trees.

Beach sand: Loose granular material blanketing the beaches, riverbeds, and other bodies of water. Includes sand close to coastal settings.

Sediment: Is a naturally occurring material that is broken down by processes of weathering and erosion from land to the water by the action of wind, water, or ice.

Host Biomes can be classified on:

Animal: Any vertebrate or invertebrate macro-organism.

Coral: Marine invertebrate typically living in compact colonies of many identical individual “polyps”.

Sponges: Multicellular organisms that have bodies full of pores and channels allowing water to circulate through them. Sponges are worldwide in their distribution, living in a wide range of ocean habitats, from the polar regions to the tropics

Plant: Multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae.

Fungi: macro-organisms that includes mushrooms.

Human: Human being of any race. If human host, you need specify the specific part of the body where the microbe is found. Some microbes might be specific to certain parts of the body while some others are generalists, meaning they might be found in multiple parts of the human body. Body sites include: Blood, gastrointestinal tract, skin, oral cavity, urogenital tract, nasal passage.

Extreme biomes can be classified on:

Space: Organisms found out of the Earth’s atmosphere in man-built facilities such as the International Space Station.

Depths: deep sea is the lowest layer in the ocean. Little or no light penetrates this part of the ocean, and most of the organisms that live there rely for subsistence on falling organic matter produced in the photic zone.

Desert: Are the driest of all the biomes. It loses more liquid water by evapotranspiration than is supplied by precipitation.

Polar: It is the coldest, windiest, and driest biomes on Earth, located on the South and North pole.

Volcanic: Surroundings of a volcano. It can be a volcano on the surface or deep on the sea.

Geothermal/Hot Springs: A hot spring, hydrothermal spring, or geothermal spring is a spring produced by the emergence of geothermally heated groundwater that rises from the Earth's crust.

All figures were created in

BioRender⁠

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