Finding photosynthesis

The accidental discovery of a new form of chlorophyll has challenged expert’s understanding of the limits of photosynthesis. While studying cyanobacteria-built stromatolites, chlorophyll f was discovered, which uses lower light energy than any other known chlorophyll.

Chlorophyll allows plants, algae and some bacteria to convert carbon dioxide into sugar and oxygen by using the energy of sunlight, however until recently it was thought that this only occurred at wavelengths between 400 nm and 700 nm. In 1996 chlorophyll d was discovered to be capable of using light in the infrared region, 710 nm, but a study published in Science found chlorophyll f can absorb light as low as 720 nm.¹

Dr Min Chen from the School of Biological Sciences, University of Sydney, Australia explains: “I was actually looking for chlorophyll d, which we knew could be found in cyanobacteria living in low light conditions.” The team cultured a cyanobacterial sample at 720 nm, expecting to ensure only chlorophyll d survived. However when high performance liquid chromatography was performed on the cultured sample it not only revealed chlorophyll d but also a new chlorophyll not seen before. “Discovering this new chlorophyll has completely overturned the traditional notion that photosynthesis needs high energy light,” said Dr Chen. “Whatever happens next, the fact that we have discovered a cyanobacterium that exploits a tiny modification in its chlorophyll molecule to photosynthesize in light that we cannot see, opens our mind to the seemingly limitless ways that organisms adapt to survive in their environment.”

1. M. Chen et al., Science, on-line 19 August 2010.

This story originally appeared in The Column. Click here to view that issue.