Renaissance for magnetotactic bacteria in astrobiology

Creators: Shen, Jianxun; Paterson, Greig A.; Wang, Yinzhao; Kirschvink, Joseph L.¹; Pan, Yongxin; Lin, Wei

1. California Institute of Technology

Abstract

Capable of forming magnetofossils similar to some magnetite nanocrystals observed in the Martian meteorite ALH84001, magnetotactic bacteria (MTB) once occupied a special position in the field of astrobiology during the 1990s and 2000s. This flourish of interest in putative Martian magnetofossils faded from all but the experts studying magnetosome formation, based on claims that abiotic processes could produce magnetosome-like magnetite crystals. Recently, the rapid growth in our knowledge of the extreme environments in which MTB thrive and their phylogenic heritage, leads us to advocate for a renaissance of MTB in astrobiology. In recent decades, magnetotactic members have been discovered alive in natural extreme environments with wide ranges of salinity (up to 90 g L⁻¹), pH (1–10), and temperature (0–70 °C). Additionally, some MTB populations are found to be able to survive irradiated, desiccated, metal-rich, hypomagnetic, or microgravity conditions, and are capable of utilizing simple inorganic compounds such as sulfate and nitrate. Moreover, MTB likely emerged quite early in Earth's history, coinciding with a period when the Martian surface was covered with liquid water as well as a strong magnetic field. MTB are commonly discovered in suboxic or oxic-anoxic interfaces in aquatic environments or sediments similar to ancient crater lakes on Mars, such as Gale crater and Jezero crater. Taken together, MTB can be exemplary model microorganisms in astrobiology research, and putative ancient Martian life, if it ever occurred, could plausibly have included magnetotactic microorganisms. Furthermore, we summarize multiple typical biosignatures that can be applied for the detection of ancient MTB on Earth and extraterrestrial MTB-like life. We suggest transporting MTB to space stations and simulation chambers to further investigate their tolerance potential and distinctive biosignatures to aid in understanding the evolutionary history of MTB and the potential of magnetofossils as an extraterrestrial biomarker.

Copyright and License

© The Author(s) 2023. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Acknowledgement

We thank Runjia Ji, Mengling Kang, and Zhe Wang from the Institute of Geology and Geophysics, Chinese Academy of Sciences, for taking electron micrographs of magnetotactic bacteria, and Kathie Thomas-Keptra of the NASA Johnson Space Center & Jacobs Engineering for helpful suggestions on the manuscript. This work was supported by the National Natural Science Foundation of China (NSFC) grants (T2225011, 42293293, and 42202339), the China Postdoctoral Science Foundation grant (2023M733478), the Key Research Programs of the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS-201904 and IGGCAS-202102), and the Nautral Environment Research Council (NERC), UK (NE/P017266/1).

Contributions

JS and WL wrote the paper, with input from all authors. All authors revised the manuscript and approved the final version.

Data Availability

Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.

Conflict of Interest

The authors declare no competing interests.

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