Aquatic Protists: Thriving on a Viral Diet

Shruti S. Satpute, Institute of Bioinformatics and Biotechnology, Savitribai Phule Pune University.

Wreaking havoc on Earth

Viruses are present in every ecosystem and have paved their way to the top of the food chain by being one of the most notorious microscopic organisms. Their ability to hijack and replicate inside living cells to proliferate using the host’s machinery although ingenious is also devastating for the host. However, some of the other troubles they bring along are also alarming since they can impact various ecological processes. Viruses can lyse microorganisms leading to nutrient leakage, a phenomenon known as “viral shunt” which is observed often in marine ecosystems. Otherwise, they may indirectly induce various irregularities leading ultimately to host death.

Predator becomes prey

Although they seem like an undefeatable and indestructible creation of nature, surprisingly studies have reported that they too sometimes end up becoming food for another class of organisms. Since viruses contain amino acids, nucleic acids, and lipids, the organisms which consume them may depict an impact on their population dynamics. Certain ciliates and flagellates may consume several species of viruses, although it is unknown how virus ingestion, also termed “virovory”, affects the population and evolution.

This article briefs on how virovory might cause an increase in the population of the predators (virovores), and potentially change how energy moves across the food web.

A group of scientists (DeLong et al. 2022) from the Nebraska Center for Virology, University of Nebraska-Lincoln, monitored a population of aquatic protists Paramecium bursaria and Halteria sp. in experiments with and without adding chlorovirus as their only food source. Their observations reported a substantial increase in the population of Halteria sp. while no increase or decrease was observed in the population of P. bursaria, indicating noteworthy distinctions in the proliferation behaviour of the two kinds of ciliates. The statistical data produced from studying the Halteria sp. population was also suggested to be in line with what is considered a typical trophic interaction.

The future of such ecological phenomenon

Aquatic protists make up a significant portion of the living biomass and their grazing has a significant impact on the aquatic food webs but the trophic relationship between viruses and their consumers is not currently included in models of aquatic food webs and ecosystems. Grazers such as protists may therefore impose selection pressure and affect the evolution of viral characteristics in a way that interacts with pressure on viruses to successfully infect and multiply within hosts. However, it is currently uncertain what impact grazing has had on virus evolution.

Reference

DeLong, J. P., Van Etten, J. L., Al-Ameeli, Z., Agarkova, I. V., & Dunigan, D. D. (2023). The consumption of viruses returns energy to food chains. Proceedings of the National Academy of Sciences, 120(1), e2215000120. The consumption of viruses returns energy to food chains | PNAS

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