Potential Microbial Processes In An Ancient Martian Environment, An Investigation Into Bio-Signature Production And Community Ecology

Curtis-Harper, Elliot (2017). Potential Microbial Processes In An Ancient Martian Environment, An Investigation Into Bio-Signature Production And Community Ecology. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000cc45

Abstract

This work investigated whether the River Dee estuary can be considered as an martian environmental analogue and examined the whether an understanding of microbial processes could inform future life detection missions on Mars.

The subsurface environment of the River Dee estuary, UK, and its microbial community, was characterised and compared to the palaeolake at Gale Crater, Mars. Similarities were identified in pH, temperature and Total Organic Carbon measurements, as well as potential bioessential element availability (based on comparative mineralogy of the two sites). The microbial community at the River Dee site was also characterised, indicating that a diverse bacterial community thrived there, alongside a single dominant archaeal group. This provided key insight into potential microbial communities on Mars, and associated processes that may inform future Mars research.

Since the diversity and attributes of microorganisms is directly linked to their environment, the microbial community of the River Dee estuary was used to investigate potential martian geomicrobiological processes and community dynamics within a simulated martian experimental environment. Concentrations of the bioessential elements Fe, Mg and K were seen to increase in the biological experiments when compared with abiotic controls, leading to, for example, a 143 μmol L-1 difference in the concentration of Fe during the stationary phase. One bacterial group, the Acidobacteria Gp9, dominated the microbial community for 400 hr during the stationary phase, accounting for ~58 % of the microbial community at its peak.

For a subsequent experiment, five bacterial species were isolated from the simulated martian environment, and characterised in order to demonstrate their growth optima and tolerance to relevant environmental extremes. Clostridium amygdalinum was found to be a model organism for survival within environments like the palaeolake at Gale Crater, and is proposed as a useful biological analogue for future investigations of the potential of life in such environments on Mars.

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