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Halteria

Context: A study reported that a particular genus of plankton can consume viruses as well as “grow and divide given only viruses to eat.

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• Viruses have a peculiar biology. They are inert outside a living bodyinside but hijack the cellular machinery to feed, replicate and spread.
• The macrophage cells of the human immune system an ‘consume’ viruses in an effort to destroy them
• Plankton of the genus Halteria can consume 10,000 to a million virus particles a day, increase their population using the metabolised energy,and provide more food for the zooplanktons that consume the Halteria. This could be significant for the marine food chain.

What are plankton?

• Plankton are microscopic organismsthat can only move with a current.
• Halteria plankton are ciliates, meaning they have hair-like structures called cilia on their surface.

What do plankton do in the food chain?

• A type of plankton — the phytoplankton — is found nearer the surface of many water bodies.
• It is an autotroph, which means it can make its own food through photosynthesis.
• Small fish and larger plankton called zooplanktoneat phytoplankton for their nutrition; they are in turn eaten by larger fish, and so forth.
• When phytoplankton die, they drift around where they are, becoming part of a coastal nutrient cycle, or they drift down towards the seafloor, where they decompose.
• Their constituents then become available for microbes or are sequestered into the seafloor.
• Phytoplankton bring carbon and other nutrients from the atmosphere and sea surface down to the seafloor and help replenish the food chain (and also ‘trap’ carbon into their own bodies and as sediments).
• They are joined by bacteria that make their own food by oxidising sulphur, iron or hydrogen, in a process called chemosynthesis.

The role of Halteria

• Halteria plankton are found in large numbers in freshwater bodies. They are heterotrophs meaning they can’t produce their own food. They are well-known bacterivores — they consume bacteria to power themselves.
• Viruses “short-circuit” is the process of nutrients moving up the food chain. They infect and kill both bacteria and plankton, releasing organic matter that dissolves in the water.
• The viral shunt is a mechanism that prevents marine microbial particulate organic matter (POM) from migrating up trophic levels by recycling them into dissolved organic matter (DOM), which can be readily taken up by microorganisms.
• The DOM recycled by the viral shunt pathway is comparable to the amount generated by the other main sources of marine DOM.
• In the new study’s paper, the authors wrote that by also consuming viruses for nutrition, Halteria plankton can recover the nutrients lost in the viral shunt and bring them back into the food chain.