«Did you know?» n°6

➡️ First, what is exactly an #extremophile organism?

Kristjansson and Hreggvidsson (1995) defined an extremophile as one whose optimal growth conditions are found beyond their “normal” environments (temperature 4 - 40°C, pH 5 - 8.5, salinity 0.01 - 50 g/L).

💡 In some environments, no one would not expect to find any living organisms… And yet, we can still find life: mainly bacteria and archaea, but also microalgae!

➡️ What are these extreme microalgae environments?

  • Waterfalls 
  • Thermal springs 
  • Snow and ice 
  • Hypersaline waters 
  • Non-aquatic biotops 
  • Anoxic biotops 
  • Acid and alkaline lakes 
  • Non-light biotops
  • Soils and waters with heavy metal concentrations

➡️ So, why are extreme algae species so interesting to cultivate !?

✅ For contamination control: 

Avoid biological contamination in microalgae culture (virus, bacteria, protozoa, fungi, other microalgae, insects…), because an extreme environment is very selective! 

These cultivated microalgae can be either extremophile species, or extreme environment-adapted species (Arthrospira and Haematococcus adapted to saline environments for example).

✅ For valuable #metabolite production and hyperproduction (some examples ⤵️):

👴🏽  Against chronological #aging:

  • Cyanidium caldarium (thermophile + acidic such as the skin ~pH=5) produces the gamma aminobutyric acid which reduces the aging process.
  • Chlamydomonas nivalis (snow algae,psychrophile) stimulate the Klotho longevity gene which activate a "master switch" protein for cellular energy metabolism .

🎨 Valuable #pigment production (antioxidant, anti-inflammatory, etc):

  • Galdiera sulphuraria (thermophile) produces the phycocyanin.
  • Dunaliella salina (halophile = grows at high salinity) produces astaxanthine.

❄️ Antifreezing proteins:

  • Fragilariopsis cylindrus, Pyramimonas gelidicola, Chaetoceros neogracile (arctic and antarctic species) produce antifreeze proteins that can be used for cryopreservation for example.

Ω  Polyunsaturated fatty acids (PUFA):

  • Phaeocystis maritima (psychrophile), accumulates up to 40% of its weight in lipids including PUFA: arachidonic acid (ARA), eicosapentaenoic acid (EPA) and the docosahexapentanoic acid (DHA, most abundant lipid in our brain).

💧 Regulation of #hydration and #digestion:

  • Aphanothece halophytica (halotolerant, alkaliphilic) accumulates betaine, a molecule which helps with liver function and nutrient absorption.

⚡️ UV-resistance:

  • Nostoc commune (radiation-resistant) produces glycosylated Mycosporine-like amino acids (MAA), molecules with strong UV-absorption capacity and highly photostable.


For more details:

✏️ Kristjansson and Hreggvidsson, « Ecology and habitats of extremophiles » (1995), DOI:10.1007/BF00339134

✏️ Seckbach J., « Survey of Algae in Extreme Environments » (2015), DOI:10.1007/978-94-017-7321-8_10

✏️ Gudin, C.,  « Histoire naturelle des micro algues » (2013) 

✏️ Seckbach J. et al., « Algae and Cyanobacteria Under Environmental Extremes » (2007), DOI:10.1007/978-1-4020-6112-7_42