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Fluctuation Analysis of Redox Potential to Distinguish Microbial Fe(II) Oxidation
1Department of Earth Sciences, University of Toronto , Toronto, Canada .
Astrobiology
|November 10, 2016
Summary
We developed a novel method using redox potential time series data to distinguish between biological and abiotic iron oxidation. This technique shows promise for detecting life in extraterrestrial environments like Mars.
Area of Science:
- Geochemistry
- Microbiology
- Astrobiology
Background:
- Distinguishing between biological and abiotic iron oxidation is crucial for understanding geochemical cycles.
- Iron oxidation plays a significant role in both terrestrial and extraterrestrial environments.
- Current methods for differentiating iron oxidation pathways can be complex and time-consuming.
Purpose of the Study:
- To develop a novel, portable method for distinguishing abiotic from biological iron oxidation using oxidation-reduction (redox) potential time series data.
- To assess the efficacy of detrended fluctuation analysis (DFA) in characterizing redox potential data for biological versus abiotic systems.
- To evaluate the potential application of this method in astrobiological contexts.
Main Methods:
- Utilized a platinum (Pt) electrode with a silver-silver chloride (Ag-AgCl) reference electrode to measure redox potential time series.
- Applied detrended fluctuation analysis (DFA) to analyze the root mean square fluctuation behavior of the redox potential data.
- Tested the method in situ on an active iron-oxidizing biofilm and in abiotic controls (killed sample, chemical control) from a groundwater discharge zone.
Main Results:
- Detrended fluctuation analysis revealed distinct average root mean square fluctuation behaviors between live (biological) and abiotic iron oxidation systems.
- The calculated scaling exponents (α values) from DFA were significantly different (p < 0.001) for biological versus abiotic pathways.
- The developed method successfully distinguished between live and abiotic chemical reaction pathways based on redox potential time series.
Conclusions:
- Time series analysis of electrode response data, specifically using DFA, can reliably distinguish between biological and abiotic iron oxidation.
- The simplicity, portability, and small size of the developed instrument make it suitable for field applications.
- This method holds significant potential for characterizing extraterrestrial environments, such as Mars and Europa, where water and iron are present.
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