Dark blue-green: Cave-inhabiting cyanobacteria as a model for astrobiology

Abstract

Subterranean environments on Earth serve as an analog for the study of microbes on other planets, which has become an active area of research. Although it might sound contradictory that photosynthetic cyanobacteria thrive in extreme low light environments, they are frequent inhabitants of caves on Earth. Throughout the phylum these cyanobacteria have developed unique adaptations that cannot only be used for biotechnological processes but also have implications for astrobiology. They can, for example, both accommodate for the low light conditions by producing specific pigments that allow photosynthesis in near-infrared (IR) radiation/far-red light, and they can synthesize bioplastic compounds and calcium carbonate sheaths which represent valuable resources during human colonization of other planets or rock bodies. This article will highlight the potential benefits of cave-inhabiting cyanobacteria and will present a suitable bioreactor technique for the utilization of these special microbes during future space missions.

Lethal Surface Ozone Concentrations Are Possible on Habitable Zone Exoplanets

“…A new metric quantifying the photoabsorption rate of photosynthetic pigments around different stars suggests that M8V stars could activate photosynthesis (Marcos-Arenal et al 2022). Moreover, cyanobacteria can survive and photosynthesize in caves and under low-light conditions (Hanelt et al 1997;Behrendt et al 2020;Jung et al 2023). Regardless of the possibility of photosynthesis on M dwarfs, O 2 production needs to surpass O 2 sinks in order to produce an oxygenated atmosphere (Lehmer et al 2018).…”

Growth and Photosynthetic Efficiency of Microalgae and Plants with Different Levels of Complexity Exposed to a Simulated M-Dwarf Starlight

“…On independent places on Earth, a restricted number of cyanobacteria have been shown to be able to utilize FR light alone or in addition to VIS light to carry oxygenic photosynthesis via the so-called Far-Red Light Photoacclimation (FaRLiP) [ 23 , 24 ]. FaRLiP cyanobacteria were deemed ideal model organisms when considering the possibility of oxygenic photosynthesis on exoplanets orbiting M-dwarfs as well as in caves and lava tubes [ 25 ], given their lighting environments [ 20 , 26 ]. We, thus, investigated the survival, growth, acclimation capabilities, and photosynthetic capacities of several strains of cyanobacteria exposed to a simulated M-dwarf starlight, demonstrating that cyanobacteria cannot only survive but even efficiently harvest the M-dwarf light spectrum, regardless of their ability to utilize specific FR light acclimation strategies [ 19 , 20 ].…”