Oxygenic photosynthesis in desert environments driven by far-red light

Photosynthesis provides all food and most energy resources on Earth. Photoautotrophic cyanobacteria and algae contribute the vast majority of primary productivity in aquatic environments, with higher plants performing the majority on land [1]. Plants and marine oxygenic phototrophs use chlorophylls (Chls) a and b to harvest visible wavelengths of light to power this carbon fixation. In 2010, a cyanobacterium inhabiting a stromatolite was discovered using a new pigment, Chl f, allowing it to harvest far-red wavelengths that penetrate these microbial fossils and permit oxygenic photosynthesis in the absence of visible light [2]. Subsequently, cyanobacteria synthesising Chl f and performing far-red photosynthesis have been discovered in diverse shaded terrestrial environments (microbial mats, soils, rock), underpinning food webs in these niches [3]. Deserts are predominantly devoid of plant life, but our recent sampling of arid, below-surface desert/sabkha environments in Western Sahara, completely shaded from visible light, revealed an incredible abundance and diversity of cyanobacteria. We aim to estimate the contribution of below-surface photosynthesis to global primary productivity and ecosystem function, via a detailed study of the microorganisms involved.

Objectives

Isolate and sequence axenic strains of cyanobacteria from our samples, revealing taxonomic diversity

Develop desert crust and salt pan analogues for studying far-red photosynthesis

Perform comprehensive pigment analysis to identify novel far-red absorbing pigments

Estimate global primary production occurring below the surface of desert environments.