Abstract EANA2024-53

M-dwarf stars are common in the Milky Way and live long enough to potentially allow life evolution. However, they are far less luminous than the Sun and emit only a minority of the light in the Visible (VIS, 400–700 nm) and most of it is in the far red (FR, λ > 750 nm). This poses a challenge for oxygenic photosynthetic organisms, which primarily absorb visible light. It is not clear yet if oxygenic photosynthesis, the most prominent biological process that shaped life evolution on our planet, is feasible under an M-dwarf spectral environment. This fundamental biological process generates atmospheric and surface biosignatures, making it an ideal focus for studying the detectability of life in other stellar systems. The capability to cope with different light regimes is a crucial factor influencing the growth potential of cyanobacteria, the simplest and most adaptable oxygenic photosynthetic organisms. Several cyanobacteria evolved for this reason fine photo-acclimations, termed Chromatic Acclimations (CA), to optimize the capture of incident wavelengths through their photosynthetic pigments. Through CA, some cyanobacteria modulate the relative ratio of visible-absorbing pigments to maximize VIS absorption, while others can perform complex reorganizations of the photosynthetic apparatus and/or synthesize novel, far-red-absorbing chlorophylls to absorb FR efficiently [1]. In nature, these strains can hence perform oxygenic photosynthesis in water, soil and subsurface environments, some characterized by low luminosity and/or enriched in FR light. Recently, we demonstrated that some of these cyanobacteria could survive and grow when exposed to a simulated M-dwarf light spectrum. We also investigated the physiological and molecular acclimation responses that underpin their growth in these conditions. [2–4]. The proposed talk will provide an overview of some of the cyanobacterial acclimation strategies to low-luminosity, FR-enriched and simulated M-dwarf light spectra. It will also highlight our recent discoveries regarding Synechococcus sp. PCC7335, capable of multiple CA (for low, VIS and FR light absorption), and highlight their importance for evaluating the feasibility of oxygenic photosynthesis on exoplanets orbiting M-dwarfs.

[1] Sanfilippo, J. E. et al. Annu. Rev. Microbiol. 73, 407–433 (2019)
[2] Claudi, R. et al. Life 11, 10 (2020)
[3] Battistuzzi, M. et al. Front. Plant Sci. 14, (2023)
[4] Battistuzzi, M. et al. Front. Plant Sci. 14, (2024)