Motile epipelic diatoms exhibit dynamic aggregation behaviour altered under oxidative perturbation

Epipelic diatoms, known for their ability to move within sediments, display a complex pattern of aggregation that is influenced by environmental factors. Researchers placed a natural mix of Pleurosigma strigosum and Gyrosigma balticum in filtered water and observed their behavior under two conditions: a dark control with no changes, and a treatment with hydrogen peroxide (H2O2) initially at a concentration of 400 micromoles per liter.

After the initial exposure, the experimental group was left in the water for an additional 48 hours.

Using time-lapse photography and detailed image analysis, the scientists found that the diatoms quickly clumped together to form intricate, three-dimensional networks. In the dark control, the number of aggregates decreased from 11,767 to 3,237 over the course of 72 hours, while the surface coverage by the diatoms dropped from 24.4% to 10.3%. These changes were marked by frequent ups and downs.

However, when exposed to H2O2, the diatoms exhibited a more predictable and less fluctuating pattern of aggregation. Fewer clumps formed, and the remaining networks maintained their structure even after the H2O2 was removed. The researchers conclude that this dynamic behavior of diatom aggregation may play a role in the formation and stability of biofilms, although they do not differentiate whether this is a direct response or an emergent property of the cells interacting with a collective matrix.