Pressurized Martian-Like Pure CO2 Atmosphere Supports Strong Growth of Cyanobacteria, and Causes Significant Changes in their Metabolism

Abstract

Surviving of crews during future missions to Mars will depend on reliable and adequate supplies of essential life support materials, i.e. oxygen, food, clean water, and fuel. The most economical and sustainable (and in long term, the only viable) way to provide these supplies on Martian bases is via bio-regenerative systems, by using local resources to drive oxygenic photosynthesis. Selected cyanobacteria, grown in adequately protective containment could serve as pioneer species to produce life sustaining substrates for higher organisms. The very high (95.3 %) CO2 content in Martian atmosphere would provide an abundant carbon source for photo-assimilation, but nitrogen would be a strongly limiting substrate for bio-assimilation in this environment, and would need to be supplemented by nitrogen fertilizing. The very high supply of carbon, with rate-limiting supply of nitrogen strongly affects the growth and the metabolic pathways of the photosynthetic organisms. Here we show that modified, Martian-like atmospheric composition (nearly 100 % CO2) under various low pressure conditions (starting from 50 mbar to maintain liquid water, up to 200 mbars) supports strong cellular growth. Under high CO2 / low N2 ratio the filamentous cyanobacteria produce significant amount of H2 during light due to differentiation of high amount of heterocysts.

Wet season cyanobacterial N enrichment highly correlated with species richness and <i>Nostoc</i> in the northern Australian savannah

“…Atmospheric N 2 transformed to organic N through biological fixation by cyanobacteria has δ 15 N values close to zero (Aranibar et al, 2004;Nadelhoffer and Fry, 1994). Across 7 months of active N fixation, isotopic N values averaged 0.9 ‰, indicating cyanobacteria were likely the primary source of bioavailable N (Evans and Ehleringer, 1994).…”

“…It has also been demonstrated that N enrichment was associated with Gloeocapsa (Wyatt and Silvey, 1969), Porphyrosiphon (Prasanna et al, 2000) and Schizothrix (Berrendero et al, 2016). Indeed, many cyanobacteria obtain N by scavenging from mutually shared EPS (Rossi et al, 2017) or have multiple mechanisms for N fixation either in the dark (Lüttge, 1997), through O 2 inhibition (Stal, 1995), in anaerobic circumstances (Murukesan et al, 2016) or aquatic cyanobacterial mats when submerged under water (Berrendero et al, 2016;Stewart, 1980).…”

“…There is a tight link between rainfall, soil moisture, bioavailable N and EPS excretion that in turn trigger a range of metabolic processes (Chen et al, 2014;Rossi and De Philip-pis, 2015). C and N fixation in cyanobacteria are closely interconnected as N fixation is energy demanding and dependent on carbohydrates provided by photosynthesis (Murukesan et al, 2016). It has been reported that diazotrophic growth by cyanobacteria occurs when the N to C balance is 1 to 1.5, and the EPS is used as a sink for excess C when the C : N ratio is unbalanced (Otero and Vincenzini, 2004) with C assimilation and diversion to EPS favoured over N fixation (Murukesan et al, 2016;De Philippis et al, 1996;Rossi and De Philippis, 2015).…”

Sustainable life support on Mars – the potential roles of cyanobacteria

“…In the Mars Direct plan (Baker & Zubrin 1990;Zubrin et al 1991;Zubrin & Wagner 2011) ) under a 99% argon (Ar), 1% CO 2 atmosphere . Recently, levels of about 25 µmol mg Chl a −1 h −1 were also reached with A. cylindrica cultures under high CO 2 /low N conditions (Murukesan et al 2015). With a concentration of 50 mg Chl a ml…”

“…5). Later results showed that an increase in CO 2 concentration (at least up to 20%, even though growth rates started to decrease after 10% for the 1-bar samples) under either 1 bar or 100 hPa leads to higher growth rates than ambient air composition at the corresponding pressure (Murukesan et al 2015;unpublished data). Thus, this strain seems to benefit from higher-than-usual pCO 2 , with a saturation about 4 hPa, at which level an around 3.5-fold increase in growth rates is observed for cells previously grown in ambient terrestrial atmosphere.…”