AsianScientist (Sep. 2, 2014) – Cyanobacteria may have once changed the entire atmosphere of the Earth with their photosynthetic activity, making it the oxygen-rich environment that it is today. Now, scientists have uncovered how light causes lifestyle changes in cyanobacteria, inducing the transition from a solitary planktonic existence to a social sessile one. This research has been published in the Journal of Biological Chemistry.
Cyanobacteria are a type of microalgae highly suitable for biomass production and biotechnology research. Cyanobacteria perform oxygenic photosynthesis as do plants, but in addition are equipped with advanced light receptors that sense the light essential for the photosynthetic reaction and a signal transduction mechanism to regulate intracellular processes.
In particular, while it is known that photoreceptors called cyanobacteriochromes are capable of detecting a wide range of light from near-ultraviolet to red light by a variety of mechanisms, in most cases their physiological roles remain unclear.
In the present study, a research group led by Professor Masahiko Ikeuchi at the University of Tokyo including first author graduate student Gen Enomoto, characterized a cyanobacteriochrome, SesA. They found that SesA is activated by blue light to synthesize a signaling molecule known as c-di-GMP. The authors proposed that the binding of c-di-GMP to the cellulose synthase enzyme results in the production of cellulose.
As cellulose begins to accumulate outside the cyanobacteria, this results in cell aggregation, transforming the cyanobacteria from single planktonic cells to stationary clusters. This aggregation is known to protect the cells from light-induced damage to the photosynthetic machinery. However, when the SesA protein was mutated, blue light was unable to cause cell aggregation.
With a deeper understanding of this signaling mechanism it may become possible to develop an efficient cell harvester method for use in photosynthetic biomass production, for example by inducing cell aggregation by irradiation with light of a particular color.
The article can be found at: Enomoto et al. (2014) Cyanobacteriochrome SesA is a Diguanylate Cyclase that Induces Cell Aggregation in Thermosynechococcus.
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Source: University of Tokyo.
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