Competitive Growth Assay of Mutagenized Chlamydomonas reinhardtii Compatible With the International Space Station Veggie Plant Growth Chamber

Abstract

A biological life support system for spaceflight would capture carbon dioxide waste produced by living and working in space to generate useful organic compounds. Photosynthesis is the primary mechanism to fix carbon into organic molecules. Microalgae are highly efficient at converting light, water, and carbon dioxide into biomass, particularly under limiting, artificial light conditions that are a necessity in space photosynthetic production. Although there is great promise in developing algae for chemical or food production in space, most spaceflight algae growth studies have been conducted on solid agar-media to avoid handling liquids in microgravity. Here we report that breathable plastic tissue culture bags can support robust growth of Chlamydomonas reinhardtii in the Veggie plant growth chamber, which is used on the International Space Station (ISS) to grow terrestrial plants. Live cultures can be stored for at least 1 month in the bags at room temperature. The gene set required for growth in these photobioreactors was tested using a competitive growth assay with mutations induced by short-wave ultraviolet light (UVC) mutagenesis in either wild-type (CC-5082) or cw15 mutant (CC-1883) strains at the start of the assay. Genome sequencing identified UVC-induced mutations, which were enriched for transversions and nonsynonymous mutations relative to natural variants among laboratory strains. Genes with mutations indicating positive selection were enriched for information processing genes related to DNA repair, RNA processing, translation, cytoskeletal motors, kinases, and ABC transporters. These data suggest that modification of DNA repair, signal transduction, and metabolite transport may be needed to improve growth rates in this spaceflight production system.

Moonshot: Affordable, Simple, Flight Hardware for the Artemis-1 Mission and Beyond

“…Liquid cultures of these "space-hardy" strains of Chlamydomonas could be propagated for production purposes using NASA growth hardware, such as VEGGIE (https://www. nasa.gov/content/veggie-plant-growth-system-activated-oninternational-space-station) being developed for plants (Zhang et al, 2020).…”

Molecular Pharming to Support Human Life on the Moon, Mars, and Beyond

“…Exceptional to the typical culture-based system vulnerabilities, microbial, oxygenic photoautotrophic cultures (i.e. microalgae 76,77 and cyanobacteria 78,79 ) represent a promising subset of culture-based systems that may be better equipped for supporting human life in space. They share many of the same benefits of molecular pharming; these organisms are able to use available in situ resources (i.e.…”

Application of ionizing radiation as an elicitor to enhance the growth and metabolic activities in Chlamydomonas reinhardtii

“…In contrast, novel mixotrophic fed-batch cultivation, including systematic feeding of acetic acid and nutrients, is considered a commercially viable strategy applicable to high-density Chlamydomonas cultures, increasing biomass density, productivity, and the total amount of recombinant proteins ( Fields et al., 2018 ). Genes related to DNA repair, signal transduction, and metabolite transport may contribute to the increased growth and biomass yield of Chlamydomonas cells, as suggested by a spaceflight production system using breathable plastic tissue culture bags ( Zhang et al., 2020 ). In addition, two chemical compounds, WD10784 and WD30030, are synthetic inducers to increase lipid synthesis and storage in Chlamydomonas cells without restricting growth or biomass yield ( Wase et al., 2019 ).…”