Starving Microscopic Algae Will Digest Themselves

Emiliania huxleyi. Clara Hoppe

When there aren’t enough nutrients in the oceans, microscopic algae adjust their metabolism to accommodate. They’ll even partially digest their own cellular parts if necessary, according to findings published in Frontiers in Marine Science last week.

Anthropogenic changes – from climate warming and ocean acidification to fertilizer runoff – affect various chemical and physical properties of the oceans. These include temperature, pH levels, and abundances of nutrients that phytoplankton need for growth. Planktonic primary producers (such as the coccolithophore Emiliania huxleyi, pictured above) are the basis of marine food webs, and they drive a lot of large-scale processes in the oceans.


"Like all living things, algae depend on the nutrients phosphorus and nitrogen, which are introduced into coastal areas by rivers, or – in the open ocean – are carried up from depth by eddies. If the surface water is fertilized by such nutrients, a race for the precious elements begins in which the various algae compete for the nutrients," Sebastian Rokitta of the Alfred Wegener Institute explained in a statement. "This race only ends when the nutrients which are necessary for cell division are exhausted and the algae are suddenly facing a famine situation."

Rokitta’s team studied the activity of more than 10,000 E. huxleyi genes under various degrees of hunger – from one missing nutrient to life-threatening nutrient starvation. Turns out, their genetic programs are able to modify and halt cell division (and hence, growth) when faced with nutrient deficiency. During cases of ongoing nutrient depletion, the starving microalgae will digest their own cellular components. While this helps them stave off cell death a bit longer, the tiny phytoplankton can’t maintain this process for very long. Eventually they’ll rupture, and their nutrients will be made available to their competitors.

Surprisingly, the molecular mechanisms that these single-celled organisms use to switch from rapid cell division to growth-arrest are very similar to that of most other living things. When that switch malfunctions in humans, for example, cells lose their ability to control division activity and proliferation – potentially turning them into cancer cells.


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