On the growth dynamics of the cyanobacterium Anabaena sp. PCC 7938 in Martian regolith

Abstract

The sustainability of crewed infrastructures on Mars will depend on their abilities to produce consumables on site. These abilities may be supported by diazotrophic, rock-leaching cyanobacteria: from resources naturally available on Mars, they could feed downstream biological processes and lead to the production of oxygen, food, fuels, structural materials, pharmaceuticals and more. The relevance of such a system will be dictated largely by the efficiency of regolith utilization by cyanobacteria. We therefore describe the growth dynamics of Anabaena sp. PCC 7938 as a function of MGS-1 concentration (a simulant of a widespread type of Martian regolith), of perchlorate concentration, and of their combination. To help devise improvement strategies and predict dynamics in regolith of differing composition, we identify the limiting element in MGS-1 – phosphorus – and its concentration-dependent effect on growth. Finally, we show that, while maintaining cyanobacteria and regolith in a single compartment can make the design of cultivation processes challenging, preventing direct physical contact between cells and grains may reduce growth. Overall, we hope for the knowledge gained here to support both the design of cultivation hardware and the modeling of cyanobacterium growth within.

Effects of atmospheric pressure, and of the partial pressures of CO2 and N2, on the growth rates of Anabaena sp. PCC 7938: Assessment and implications for cyanobacterium cultivation on Mars

“…If cyanobacteria are grown using resources naturally available on Mars, factors unrelated to atmospheric conditions are likely to limit growth. These may, for instance, be the presence of toxic compounds (e.g., perchlorates) in the liquid phase and the limited availability of elements leached from regolith 4 . For the sake of resource efficiency, N2 and CO2 could then be provided at the lowest partial pressures which can sustain the growth rates supported by the other factors.…”

“…Bioproduction systems that rely on diazotrophic, rock-weathering cyanobacteria for in situ resource utilization (ISRU) have been proposed as means of increasing the sustainability of crewed missions to Mars 1 . According to this proposal, cyanobacteria would be fed with water mined from the ground; carbon and nitrogen sourced from the atmosphere 2 ; and the local regolith, from which it has been argued that they could extract the other necessary nutrients 3,4 . They would produce various consumables directly, such as dioxygen and dietary supplements, but also support the growth of secondary producers (e.g., plants 5 or microorganisms 2,6,7 ).…”

“…The determination of this resource-efficiency is hindered by a lack of knowledge on cyanobacterium responses to the factors which are expected to limit their productivity on Mars. One of these factors pertains to the suitability of Mars's regolith as feedstock, which is the object of a separate line of work 4 . Another is the behaviour of cyanobacteria under atmospheric conditions that differ from Earth-ambient.…”

Microbial biomanufacturing for space-exploration—what to take and when to make

“…Although a great deal of progress has been made to adapt these organisms to utilization of single-carbon feedstocks 81 , 82 , they are still outclassed by organisms naturally capable of these functions 83 – 85 . Therefore, species with nutritional modes and metabolism uniquely suited to leverage resources available through LC and ISRU must be considered for development of ISM systems, basing their selection on application (feedstock/product pairing, scale, continuity, and responsiveness of the respective process) and scenario-specific criteria (environmental parameters) 34 , 86 , 87 . Specifically, organisms with the ability to assimilate single-carbon compounds alongside organics (mixotrophy) are most suitable.…”

Resource-efficiency of cyanobacterium production on Mars: Assessment and paths forward

“…One strategy proposed to feed these organisms lies in using selected species of diazotrophic, rock-weathering cyanobacteria as primary producers (12). An expanding body of work suggests that these could be fed with local resources: water mined from the ground and atmosphere; carbon and nitrogen sourced from the atmosphere as CO2 and N2 (13,14); and other nutrients leached from the local regolith (the Martian soil) (15)(16)(17). The cultivated cyanobacteria could then produce various consumables directly, such as O2, dietary proteins or biomaterials (18,19), but also be used for feeding heterotrophic microorganisms (13,20,21), plants (22), or other secondary producers.…”