Tiny geometric algae, called diatoms, produce nearly a quarter of the world’s organic matter by photosynthesis. In the microscopic marine universe, diatoms coexist with both harmful and helpful bacteria.

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Source: Oregon State University

A Thalassiosira pseudonana diatom oogonium (egg cell) beginning to expand through the cell wall.

A new study, published March 23 in mBio, describes how a recently identified species of marine bacteria targets diatoms based on growth phase and nutrient availability.

Growing diatoms can resist bacterial attacks, but when growth ceases, the bacteria modulate their gene expression patterns to become aggressive — first swimming and releasing compounds that damage the diatom and then clustering around them to feed. Bacteria can also overcome the diatom’s defenses in nutrient-rich environments.

These findings highlight the dynamic relationship between bacteria and algae in the lab. Moving forward, researchers will explore what, if anything, changes in a more complex environment.

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