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Marine ecology

Bloom or Bust ? Diatoms Decide

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© C. Bowler & K. Osada

Electron microscopy of diatom silica shells.


Diatoms are photosynthetic plankton (microscopic algae) ubiquitous in oceans and freshwater systems. They are a major source of nutrients for marine organisms as well as a major producer of oxygen. They have been dubbed the “lungs of the ocean,” producing about 20 % of the oxygen we breathe–as much as all the rainforests combined. Their ornately-patterned silica cell walls are a source of inspiration for nanotechnologists, who dream of replicating similar structures for the semi-conductor industry. But despite their beauty, usefulness, and environmental importance, their basic biology is still poorly understood. In a recent paper,1 Chris Bowler and his colleagues from the Paris-based Diatom Morphogenesis Laboratory,2 show how diatoms may communicate with each other via aldehyde compounds released by wounded cells.

Diatoms undergo seasonal population explosions, known as phytoplankton blooms. These blooms attract billions of predators, from which diatoms protect themselves by releasing aldehyde compounds. However, these chemicals not only compromise the hatching success of grazers, they also kill the diatoms themselves. Interestingly, diatoms have a sophisticated calcium and nitric oxide-based surveillance system for monitoring environmental stresses that can detect the release of aldehydes by its wounded neighbours. Bowler and his colleagues show that the response to aldehyde is dose-dependent–high doses of aldehyde trigger cell death, which may lead to the termination of a bloom. However, low doses induce resistance to the compound's toxic effect. Diatoms thus adapt cell fate by actively monitoring their environment. Bowler's work suggests that they communicate among themselves and sometimes commit mass suicide.

Bowler is keen to explore other aspects of diatom communication. For example, diatom afficionados have long known that the organisms have sex. However, exactly how they do it and how they find each other in the water is still unknown. Perhaps diatoms are doing a lot more communicating than we think.

 

Min Alverson

Notes :

1. Vardi A et al., “A stress surveillance system based on calcium and nitric oxide in marine diatoms.” PLoS Biol. 4 (3): e60. 2006.
2. Laboratoire Signalisation et morphogenèse des diatomées (CNRS / Ecole Normale Supérieure joint lab).


Contacts :

Chris Bowler
Ecole Normale supérieure, Paris.
cbowler@biologie.ens.fr


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