Protists attract less attention than other organisms. Here’s some possible reasons:
- They are not big and easily visible to the naked eye (though there are some exceptions), unlike the “macrobes” – animals, plants, and fungi.
- When people talk about “microbes”, they usually refer only to the bacteria and archaea (collectively known as prokaryotes). The eukaryotic microbes are usually ignored.
But they are still important, and here’s why:
- They’re part of the microbial food chain and make up a significant fraction of its biomass. Many graze on bacteria, and are eaten up in turn by other protists and small animals.
- Photosynthetic protists, the algae, are responsible for 40% of primary production on the Earth.
- Certain algal species, especially diatoms and dinoflagellates, are responsible for toxic algal blooms in rivers and oceans, such as the deadly red tide. These cause both environmental and economic problems.
- Several deadly diseases are caused by protist pathogens, such as malaria (Plasmodium), toxoplasmosis (Toxoplasma), and amoebic dysentery (Entamoeba histolytica).
- They can teach us about the origins of complex multicellular organisms like the plants and animals. Many protists, such as the cellular slime moulds and the green algae, display coloniality or simpler forms of multicellularity that illustrate how complex multicellularity may have evolved.
- Some species are important symbiotic partners with other organisms. Certain corals are able to photosynthesize because they have zooxanthellae, which are actually dinoflagellates which have entered into a mutualistic relationship with the coral animals.
Also see: JO Corliss (2004) “Why the world needs protists!” Journal of Eukaryotic Microbiology 51 (1): 8-22.