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Main Title: Bacterial Growth in Chloride and Perchlorate Brines: Halotolerances and Salt Stress Responses of Planococcus halocryophilus
Author(s): Heinz, Jacob
Waajen, Annemiek C.
Airo, Alessandro
Alibrandi, Armando
Schirmack, Janosch
Schulze-Makuch, Dirk
Type: Article
Is Part Of: 10.14279/depositonce-8847
Language Code: en
Abstract: Extraterrestrial environments encompass physicochemical conditions and habitats that are unknown on Earth, such as perchlorate-rich brines that can be at least temporarily stable on the martian surface. To better understand the potential for life in these cold briny environments, we determined the maximum salt concentrations suitable for growth (MSCg) of six different chloride and perchlorate salts at 25°C and 4°C for the extremotolerant cold- and salt-adapted bacterial strain Planococcus halocryophilus. Growth was measured through colony-forming unit (CFU) counts, while cellular and colonial phenotypic stress responses were observed through visible light, fluorescence, and scanning electron microscopy. Our data show the following: (1) The tolerance to high salt concentrations can be increased through a stepwise inoculation toward higher concentrations. (2) Ion-specific factors are more relevant for the growth limitation of P. halocryophilus in saline solutions than single physicochemical parameters like ionic strength or water activity. (3) P. halocryophilus shows the highest microbial sodium perchlorate tolerance described so far. However, (4) MSCg values are higher for all chlorides compared to perchlorates. (5) The MSCg for calcium chloride was increased by lowering the temperature from 25°C to 4°C, while sodium- and magnesium-containing salts can be tolerated at 25°C to higher concentrations than at 4°C. (6) Depending on salt type and concentration, P. halocryophilus cells show distinct phenotypic stress responses such as novel types of colony morphology on agar plates and biofilm-like cell clustering, encrustation, and development of intercellular nanofilaments. This study, taken in context with previous work on the survival of extremophiles in Mars-like environments, suggests that high-concentrated perchlorate brines on Mars might not be habitable to any present organism on Earth, but extremophilic microorganisms might be able to evolve thriving in such environments.
Issue Date: 6-Aug-2019
Date Available: 28-Aug-2019
DDC Class: 520 Astronomie und zugeordnete Wissenschaften
570 Biowissenschaften; Biologie
Subject(s): brines
Sponsor/Funder: EC/FP7/339231/EU/Habitability of Martian Environments: Exploring the Physiological and Environmental Limits of Life/HOME
Journal Title: Astrobiology
Publisher: Mary Ann Liebert
Publisher Place: New York
Volume: 20
Issue: 2
Publisher DOI: 10.1089/ast.2019.2069
EISSN: 1557-8070
ISSN: 1531-1074
Appears in Collections:Zentrum für Astronomie und Astrophysik » Publications

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