Photosynthesis in the dark


Photo: Lars Behrendt

Scientists at Uppsala University have in collaboration with researchers in Denmark, Switzerland, Great Britain, USA and Australia have found cyanobacteria that can photosynthesize in the dark. The bacteria live in caves found in New Mexico, USA and can use light with long wavelengths, called Far-Red light, reflected by the cave walls for their photosynthesis.

The scientists studied bacteria in four different cave, all located in the Carlsbad Caverns National Park in New Mexico, USA. They investigated the composition of bacteria at different levels of light beginning at the entrance where the light is brightest and then moved further into the cave where it is darker.

Cyanobacteria use chlorophyll for photosynthesis, just like plants do. The most common variant of chlorophyll is Chlorophyll-a, which is used by most plants and give the leaves their green colour. Cyanobacteria living in the darker parts of the cave use other variants of chlorophyll, Chlorophyll-d and f. This enables them to use Far-Red light for their photosynthesis. The cave walls consist of limestone, which reflects Far-Red light better than visible light.

The study was published in Environmental Microbiology and an article about the study was also published in Forbes. 

Behrendt, L. , Trampe, E. L., Nord, N. B., Nguyen, J. , Kühl, M. , Lonco, D. , Nyarko, A. , Dhinojwala, A. , Hershey, O. S. and Barton, H. (2019), Life in the dark: far‐red absorbing cyanobacteria extend photic zones deep into terrestrial caves. Environ Microbiol. doi:10.1111/1462-2920.14774