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Bacterial utilisation of aliphatic organics: is the dwarf planet Ceres habitable?

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posted on 2023-05-21, 07:52 authored by Jayasinghe, SA, Fraser KennedyFraser Kennedy, Andrew McMinnAndrew McMinn, Martin, A
The regolith environment and associated organic material on Ceres is analogous to environments that existed on Earth 3–4 billion years ago. This has implications not only for abiogenesis and the theory of transpermia, but it provides context for developing a framework to contrast the limits of Earth’s biosphere with extraterrestrial environments of interest. In this study, substrate utilisation by the ice-associated bacterium Colwellia hornerae was examined with respect to three aliphatic organic hydrocarbons that may be present on Ceres: dodecane, isobutyronitrile, and dioctyl-sulphide. Following inoculation into a phyllosilicate regolith spiked with a hydrocarbon (1% or 20% organic concentration wt%), cell density, electron transport activity, oxygen consumption, and the production of ATP, NADPH, and protein in C. hornerae was monitored for a period of 32 days. Microbial growth kinetics were correlated with changes in bioavailable carbon, nitrogen, and sulphur. We provide compelling evidence that C. hornerae can survive and grow by utilising isobutyronitrile and, in particular, dodecane. Cellular growth, electron transport activity, and oxygen consumption increased significantly in dodecane at 20 wt% compared to only minor growth at 1 wt%. Importantly, the reduction in total carbon, nitrogen, and sulphur observed at 20 wt% is attributed to biotic, rather than abiotic, processes. This study illustrates that short-term bacterial incubation studies using exotic substrates provide a useful indicator of habitability. We suggest that replicating the regolith environment of Ceres warrants further study and that this dwarf planet could be a valid target for future exploratory missions.

Funding

Australian Research Council

Australian National University

Curtin University

University of Canberra

University of Melbourne

University of New South Wales

University of South Australia

University of Western Australia

History

Publication title

Life

Volume

12

Issue

6

Article number

821

Number

821

Pagination

1-17

ISSN

2075-1729

Department/School

Institute for Marine and Antarctic Studies

Publisher

MDPIAG

Place of publication

Switzerland

Rights statement

Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons 4.0 International (CC BY 4.0) license (https://creativecommons.org/licenses/by/4.0/).

Repository Status

  • Open

Socio-economic Objectives

Expanding knowledge in the biological sciences

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