Isolation of Novel Extreme-Tolerant Cyanobacteria from a Rock-Dwelling Microbial Community by Using Exposure to Low Earth Orbit

Abstract

Many cyanobacteria are known to tolerate environmental extremes. Motivated by an interest in selecting cyanobacteria for applications in space, we launched rocks from a limestone cliff in Beer, Devon, United Kingdom, containing an epilithic and endolithic rock-dwelling community of cyanobacteria into low Earth orbit (LEO) at a height of approximately 300 kilometers. The community was exposed for 10 days to isolate cyanobacteria that can survive exposure to the extreme radiation and desiccating conditions associated with space. Culture-independent (16S rRNA) and culture-dependent methods showed that the cyanobacterial community was composed of Pleurocapsales, Oscillatoriales, and Chroococcales. A single cyanobacterium, a previously uncharacterized extremophile, was isolated after exposure to LEO. We were able to isolate the cyanobacterium from the limestone cliff after exposing the rock-dwelling community to desiccation and vacuum (0.7 ؋ 10 ؊3 kPa) in the laboratory. The ability of the organism to survive the conditions in space may be linked to the formation of dense colonies. These experiments show how extreme environmental conditions, including space, can be used to select for novel microorganisms. Furthermore, it improves our knowledge of environmental tolerances of extremophilic rock-dwelling cyanobacteria.

Exposure of phototrophs to 548 days in low Earth orbit: microbial selection pressures in outer space and on early earth

“…Anabaena cylindrica was grown in BG-11 medium (Rippka et al, 1979;Olsson-Francis et al, 2010) at 25 1C, under a natural sunlight and day/night cycle. The akinetes were induced by transferring log phase cells into an iron limited (no iron) BG-11 medium, followed by three washes in the same medium.…”

“…The phylogenetic trees were constructed using the neighbour-joining method in MEGA4 (Saitou and Nei, 1987;Tamura et al, 2007). Analysis of the cyanobacterial components of the rock was presented previously (Olsson-Francis et al, 2010).…”

“…In a previous experiment, biofilms of phototrophs were exposed to conditions in low Earth orbit (LEO) for 10 days (Olsson-Francis et al, 2010) to isolate extremophilic phototrophs of potential use in biomass or oxygen provision in space exploration. The experiment showed that one species of cyanobacterium survived the exposure conditions, but that all the other organisms were killed.…”

Nitrogen fixing cyanobacteria: their diversity, ecology and utilisation with special reference to rice cultivation

“…It could also be a reflection of their long ancestry originating from the primitive Earth, which was inhospitable to most life forms. These features that certain cyanobacteria show in common with other extremophilic microorganisms such as exposure to high light, tolerance to UV radiation, desiccation, the ability to withstand very high to freezing temperatures and tolerance to acidity and alkalinity make them ideal candidates for Astrobiological studies (Seckbach, 2006;Francis et al, 2010;Billi et al, 2013) and in the search for novel…”

Cyanobacteria from Extreme Deserts to Space

“…The first space experiment with rock-dwelling microbial communities was carried out in 2007, during the ESA BIOPAN 6 mission; after 10 days of permanence in space a single Gloeocapsa-like cyanobacterium was selected within a sample from coastal limestone cliff in Beer, Devon (UK) initially composed of Pleurocapsales, Oscillatoriales and Chroococcales [41]. During the same space mission the endurance of resting-state cells of cyanobacteria, the akinetes, dried onto rocks was tested; after return to Earth only samples exposed to vacuum with filtered UV radiation retained their germination capability [42].…”