The SPORES experiment of the EXPOSE-R mission:<i>Bacillus subtilis</i>spores in artificial meteorites

Panitz, Corinna; Horneck, G.; Rabbow, Elke; Rettberg, Petra; Moeller, Ralf; Cadet, Jean; Douki, Thierry; Reitz, Guenther

doi:10.1017/s1473550414000251

Cited by 31 publications

(18 citation statements)

References 24 publications

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“…Bacterial spores are well-established models for astrobiology, due to their resistance to multiple factors, including desiccation and UV irradiation. Spores of Bacillus pumilus and Bacillus subtilis, for example, have already been exposed and tested for their survival under true space conditions (Horneck et al 2012;Panitz et al 2015). Recently, Khodadad et al (2017) directly exposed desiccated spores of B. pumilus to the stratosphere (above 30 km of altitude).…”

Section: Discussionmentioning

confidence: 99%

Surviving in hot and cold: psychrophiles and thermophiles from Deception Island volcano, Antarctica

et al. 2018

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Polar volcanoes harbor unique conditions of extreme temperature gradients capable of selecting different types of extremophiles. Deception Island is a marine stratovolcano located at Maritime Antarctica that is notable for its pronounced temperature gradients over very short distances, reaching values up to 100 °C in the fumaroles, and subzero temperatures next to the glaciers. Due to these characteristics, Deception can be considered an interesting analogue of extraterrestrial environments. Our main goal in this study was to isolate thermophilic and psychrophilic bacteria from sediments associated with fumaroles and glaciers from two geothermal sites in Deception Island, comprising temperatures between 0 and 98 °C, and to evaluate their survivability to desiccation and UV-C radiation. Our results revealed that culturable thermophiles and psychrophiles were recovered among the extreme temperature gradient in Deception volcano, which indicates that these extremophiles remain alive even when the conditions do not comprise their growth range. The viability of culturable psychrophiles in hyperthermophilic environments is still poorly understood and our work showed the importance of future studies about their survival strategies in high temperatures. Finally, the spore-forming thermophilic isolates which we found have displayed good survival to desiccation and UV-C irradiation, which suggests their potential to be further explored in astrobiological studies.

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Section: Discussionmentioning

confidence: 99%

Surviving in hot and cold: psychrophiles and thermophiles from Deception Island volcano, Antarctica

et al. 2018

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“…Recently, Bacillus subtilis spores were used in the European Space Agency's EXPOSE-R mission (5,6), in which spores were exposed to selected parameters of outer space, including space vacuum. Temperature fluctuations during a long journey in space were measured, thereby mimicking the interplanetary transfer of life via impactejected rocks, and spore survival was measured.…”

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confidence: 99%

Germination, Outgrowth, and Vegetative-Growth Kinetics of Dry-Heat-Treated Individual Spores of Bacillus Species

Chen

Wang

et al. 2018

Appl Environ Microbiol

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DNA damage kills dry-heated spores of , but dry-heat-treatment effects on spore germination and outgrowth have not been studied. This is important, since if dry-heat-killed spores germinate and undergo outgrowth, toxic proteins could be synthesized. Here, Raman spectroscopy and differential interference contrast microscopy were used to study germination and outgrowth of individual dry-heat-treated and spores. The major findings in this work were as follows: (i) spores dry-heat-treated at 140°C for 20 min lost nearly all viability but retained their Ca-dipicolinic acid (CaDPA) depot; (ii) in most cases, dry-heat treatment increased the average times and variability of all major germination events in spore germination with nutrient germinants or CaDPA, and in one nutrient germination event with spores; (iii) spore germination with dodecylamine, which activates the spore CaDPA release channel, was unaffected by dry-heat treatment; (iv) these results indicate that dry-heat treatment likely damages spore proteins important in nutrient germinant recognition and cortex peptidoglycan hydrolysis, but not CaDPA release itself; and (v) analysis of single spores incubated on nutrient-rich agar showed that while dry-heat-treated spores that are dead can complete germination, they cannot proceed into outgrowth and thus not to vegetative growth. The results of this study provide new information on the effects of dry heat on bacterial spores and indicate that dry-heat sterilization regimens should produce spores that cannot outgrow and thus cannot synthesize potentially dangerous proteins. Much research has shown that high-temperature dry heat is a promising means for the inactivation of spores on medical devices and spacecraft decontamination. Dry heat is known to kill spores by DNA damage. However, knowledge about the effects of dry-heat treatment on spore germination and outgrowth is limited, especially at the single spore level. In the current work, Raman spectroscopy and differential interference contrast microscopy were used to analyze CaDPA levels in and kinetics of nutrient- and non-nutrient germination of multiple individual dry-heat-treated and spores that were largely dead. The outgrowth and subsequent cell division of these germinated but dead dry-heat-treated spores were also examined. The knowledge obtained in this study will help understand the effects of dry heat on spores both on Earth and in space, and indicates that dry heat can be safely used for sterilization purposes.

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“…As already outlined in the previous paper of the authors, it was attributed to the fact of evaporation of residual water from the samples (especially in the space vacuum conditions of BOSS experiment), minimizing UV radiation-generated reactive oxygen species. On the other hand, shielding by upper cell layers (stack arrangements) or in multi-cellular structures (biofilms in general) and by dust layers of only 0.5-1 mm in thickness (comparable to the SVT with sulfatic Mars regolith simulant [S-MRS]) can provide sufficient protection (Rettberg et al, 2004;Panitz et al, 2015;Frösler et al, 2017). The lower survival of the same samples of the MGR test is currently being examined more closely and will be verified after the receipt of a corresponding mission-based final calculation report at sample site by Redshift.…”

Section: Effect Of Space Vacuum or Martian Atmosphere And Pressure Comentioning

confidence: 99%

Tolerances ofDeinococcus geothermalisBiofilms and Planktonic Cells Exposed to Space and Simulated Martian Conditions in Low Earth Orbit for Almost Two Years

et al. 2019

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Fossilized biofilms represent one of the oldest known confirmations of life on the Earth. The success of microbes in biofilms results from properties that are inherent in the biofilm, including enhanced interaction, protection, and biodiversity. Given the diversity of microbes that live in biofilms in harsh environments on the Earth, it is logical to hypothesize that, if microbes inhabit other bodies in the Universe, there are also biofilms on those bodies. The Biofilm Organisms Surfing Space experiment was conducted as part of the EXPOSE-R2 mission on the International Space Station. The experiment was an international collaboration designed to perform a comparative study regarding the survival of biofilms versus planktonic cells of various microorganisms, exposed to space and Mars-like conditions. The objective was to determine whether there are lifestyledependent differences to cope with the unique mixture of stress factors, including desiccation, temperature oscillations, vacuum, or a Mars-like gas atmosphere and pressure in combination with extraterrestrial or Marslike ultraviolet (UV) radiation residing during the long-term space mission. In this study, the outcome of the flight and mission ground reference analysis of Deinococcus geothermalis is presented. Cultural tests demonstrated that D. geothermalis remained viable in the desiccated state, being able to survive space and Mars-like conditions and tolerating high extraterrestrial UV radiation for more than 2 years. Culturability decreased, but was better preserved, in the biofilm consortium than in planktonic cells. These results are correlated to differences in genomic integrity after exposure, as visualized by random amplified polymorphic DNA-polymerase chain reaction. Interestingly, cultivation-independent viability markers such as membrane integrity, ATP content, and intracellular esterase activity remained nearly unaffected, indicating that subpopulations of the cells had survived in a viable but nonculturable state. These findings support the hypothesis of long-term survival of microorganisms under the harsh environmental conditions in space and on Mars to a higher degree if exposed as biofilm.

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The SPORES experiment of the EXPOSE-R mission:Bacillus subtilisspores in artificial meteorites

Cited by 31 publications

References 24 publications

Surviving in hot and cold: psychrophiles and thermophiles from Deception Island volcano, Antarctica

Surviving in hot and cold: psychrophiles and thermophiles from Deception Island volcano, Antarctica

Germination, Outgrowth, and Vegetative-Growth Kinetics of Dry-Heat-Treated Individual Spores of Bacillus Species

Tolerances ofDeinococcus geothermalisBiofilms and Planktonic Cells Exposed to Space and Simulated Martian Conditions in Low Earth Orbit for Almost Two Years

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