Molecular Biology and Physiology

Algal Surface Adhesion Regulated by Light

Researchers at the Gottingen Max Planck Institute have discovered that the green algae used in biofuel bioreactors can be kept from forming opaque films on the reactors’ glass tubing by blocking the white and blue light that cues surface adherence.  Until now, no one knew what caused the algae to make their flagella stick to any surface they were near (including the surfaces of ponds, water treatment tanks, and garden furniture), but the German team, led by Oliver Baumchen and Christian Kreis, found out that light regulated the process.

White and blue light also make photosynthesis possible, and the scientists hypothesized that the reason adherence is cued by the same drivers is that most algae live in wet, dark soils.

“We believe that light-switchable adhesiveness may be a product of evolution,” said Kreis.  “If [algae in soils are close to] surfaces that are exposed to sunlight, this clever mechanism enable the algae to latch onto them and start carrying out photosynthesis.”

Using the green alga Chlamydomonas, the team also discovered that red light kept algal biofilms from forming, but exposing bioreactors to red light only was not an effective strategy because it stopped the photosynthesis that made biofuel production possible.

The researchers are currently working with microbiologists to determine which blue light photoreceptors in algae are essential for adherence and which are essential for photosynthesis.  They hope to create algal strains with modified blue-light photoreceptors that can support photosynthesis but block the formation of light-stopping biofilms.  Kreis is carrying things a step further and is trying to find other ways to prevent biofilm formation, such as weak electrical charges on essential surfaces.

Caption: Green algae can switch their ability to adhere to surfaces on and off by means of light. In light, their two fine hairs, called flagella, stick to a surface, whereas in the dark, the algae swim through the water using a sort of breast-stroke movement.
Credit: Oliver Bäumchen, MPIDS, Göttingen / Thomas Braun, Heidelberg
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For more information, go to the September 25 issue of Nature Physics;  DOI: 10.1038/nphys4258.