🦠 Between mutualism and parasitism (forms of symbiosis), the coexistence of algae and bacteria has developed throughout the stages of evolution:
🔁 Mutualism:
🔎 Bacteria supply Vitamin B12 (micronutrient) to algae in exchange for fixed carbon.
🔎 Bacteria are able to fix nitrogen (N) contrary to algae, and accumulate N as ammonium that is then used by algae as N supply.
➡️ Parasitism:
🔎 Bacteria can lyse algal cells and utilize the intracellular compounds as nutrients.
🔎 Bacteria and algae can compete for nutrients, at the expense of one of them.
🦠 The « phycosphere » is defined as a zone around the algal cell composed of bacteria benefitting of this close proximity. The main phycospheres are found in lichens, corals, some extreme environments (sea-ice, desert coastal range…)
Using algae-bacteria interactions, several emerging applications are considered:
🚰 Wastewater treatment (nutrient removal)
♻️ Bioremediation
🌊 Bloom control
🧪 Biotechnology (bio refineries, sustainable aquaculture systems)
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For more details, some bibliographic references:
✏️ Ramanan, R. et al.: Algae–bacteria interactions: Evolution, ecology and emerging applications. Biotechnology Advances, 2016, doi:10.1016/j.biotechadv.2015.12.003
✏️ Hernandez, J.P. et al.: Growth promotion of the freshwater microalga Chlorella vulgaris by the nitrogen-fixing, plant growth-promoting bacterium Bacillus pumilus from arid zone soils. European Journal of Soil Biology, 2009, doi:10.1016/j.ejsobi.2008.08.004
✏️ Kim, B.H. et al.: Nutrient removal and biofuel production in high rate algal pond (HRAP) using real municipal wastewater. J. Microbiol. Biotechnol., 2014, doi:10.4014/jmb.1312.12057