Metallosphaera sedula on a Mission – mimicking Mars in frames of the Tanpopo 4 mission

With future long-term space exploration and life detection missions on Mars, understanding the microbial survival beyond Earth as well as the identification of past life traces on other planetary bodies becomes increasingly important. The series of the Tanpopo space mission experiments target a long-term exposure (one to three years) of microorganisms on the KIBO Module of the International Space Station (ISS) in the low Earth orbit (LEO) (Kawaguchi et al., 2020; Ott et al., 2020). In the search for possible past and/or present microbial life on Mars, metallophilic archaeal species are of a special interest due to their inherent extraordinary characteristics. Chemolithotrophic archaea (e.g., from the order Sulfolobales) employ a number of ancient metabolic pathways to extract energy from diverse inorganic electron donors and acceptors. Metallosphaera sedula, an iron- and sulfur-oxidizing chemolithotrophic archaeon, which flourishes under hot and acidic conditions (optimal growth at 74°C and pH 2.0), was cultivated on genuine extraterrestrial minerals (Milojevic et al., 2019; Milojevic et al., 2021) as well as synthetic Martian materials (Kölbl et al., 2017). In all cases, M. sedula cells were able to utilize given mineral materials as the sole energy source for cellular growth and proliferation. During the growth of M. sedula cells on these materials, a natural mineral impregnation and encrustation of microbial cells was achieved, followed by their preservation under the conditions of desiccation (Kölbl et al. 2020). Our studies indicate that this archaeon, when impregnated and encrusted with minerals, withstand long-term desiccation and can be even recovered from the dried samples to the liquid cultures (Kölbl et al., 2020). The achieved preservation of desiccated M. sedula cells facilitated our further survivability studies with this desiccated microorganism under simulated Mars-like environmental conditions and during the Tanpopo-4 space exposure experiment. [...

Advances in the Space Station

A space station is a spacecraft capable of supporting a human crew in orbit for an extended period of time, and is therefore a type of space habitat. It lacks major propulsion or landing systems. An orbital station or an orbital space station is an artificial satellite (i.e. a type of orbital spaceflight). Stations must have docking ports to allow other spacecraft to dock to transfer crew and supplies. The purpose of maintaining an orbital outpost varies depending on the program. Space stations have most often been launched for scientific purposes, but military launches have also occurred. As of 2022, there are two fully operational space stations in low Earth orbit (LEO) – the International Space Station (ISS) and China's Tiangong Space Station (TSS). While the ISS has been permanently inhabited since October 2000 with the Expedition 1 crews, the TSS will do so with the Shenzhou 14 crews in June 2022. The ISS is used to study the effects of spaceflight on the human body, as well as to provide a location to conduct a greater number and longer length of scientific studies than is possible on other space vehicles. China's Tiangong Space Station is scheduled to finish its phase 1 construction by the end of 2022 with the addition of two lab modules. India has also proposed to build a space station in the coming decades. There have been numerous decommissioned space stations, including USSR's Salyuts, Russia's Mir, NASA's Skylab, and China's Tiangong 1 and 2

Exploring Fingerprints of the Extreme Thermoacidophile Metallosphaera sedula Grown on Synthetic Martian Regolith Materials as the Sole Energy Sources

The biology of metal transforming microorganisms is of a fundamental and applied importance for our understanding of past and present biogeochemical processes on Earth and in the Universe. The extreme thermoacidophile Metallosphaera sedula is a metal mobilizing archaeon, which thrives in hot acid environments (optimal growth at 74°C and pH 2.0) and utilizes energy from the oxidation of reduced metal inorganic sources. These characteristics of M. sedula make it an ideal organism to further our knowledge of the biogeochemical processes of possible life on extraterrestrial planetary bodies. Exploring the viability and metal extraction capacity of M. sedula living on and interacting with synthetic extraterrestrial minerals, we show that M. sedula utilizes metals trapped in the Martian regolith simulants (JSC Mars 1A; P-MRS; S-MRS; MRS07/52) as the sole energy sources. The obtained set of microbiological and mineralogical data suggests that M. sedula actively colonizes synthetic Martian regolith materials and releases free soluble metals. The surface of bioprocessed Martian regolith simulants is analyzed for specific mineralogical fingerprints left upon M. sedula growth. The obtained results provide insights of biomining of extraterrestrial material as well as of the detection of biosignatures implementing in life search missions

Molecular repertoire of Deinococcus radiodurans after 1 year of exposure outside the International Space Station within the Tanpopo mission

Background: The extraordinarily resistant bacterium Deinococcus radiodurans withstands harsh environmental conditions present in outer space. Deinococcus radiodurans was exposed for 1 year outside the International Space Station within Tanpopo orbital mission to investigate microbial survival and space travel. In addition, a groundbased simulation experiment with conditions, mirroring those from low Earth orbit, was performed. Methods: We monitored Deinococcus radiodurans cells during early stage of recovery after low Earth orbit exposure using electron microscopy tools. Furthermore, proteomic, transcriptomic and metabolomic analyses were performed to identify molecular mechanisms responsible for the survival of Deinococcus radiodurans in low Earth orbit. Results: D. radiodurans cells exposed to low Earth orbit conditions do not exhibit any morphological damage. However, an accumulation of numerous outer-membrane-associated vesicles was observed. On levels of proteins and transcripts, a multi-faceted response was detected to alleviate cell stress. The UvrABC endonuclease excision repair mechanism was triggered to cope with DNA damage. Defense against reactive oxygen species is mirrored by the increased abundance of catalases and is accompanied by the increased abundance of putrescine, which works as reactive oxygen species scavenging molecule. In addition, several proteins and mRNAs, responsible for regulatory and transporting functions showed increased abundances. The decrease in primary metabolites indicates alternations in the energy status, which is needed to repair damaged molecules. Conclusion: Low Earth orbit induced molecular rearrangements trigger multiple components of metabolic stress response and regulatory networks in exposed microbial cells. Presented results show that the non-sporulating bacterium Deinococcus radiodurans survived long-term low Earth orbit exposure if wavelength below 200 nm are not present, which mirrors the UV spectrum of Mars, where CO₂ effectively provides a shield below 190 nm. These results should be considered in the context of planetary protection concerns and the development of new sterilization techniques for future space missions

Scanning electron microscopy images of dehydrated cells of <i>D</i>. <i>radiodurans</i> deposited on aluminum plates and used in experimental set up of Tanpopo mission.

<p>(<b>A</b>, <b>B</b>) Scanning electron microscopy images, showing upper surface and inner content of multilayers of dehydrated <i>D</i>. <i>radiodurans</i> cells deposited on aluminum plates. (<b>C</b>, <b>D</b>) Higher magnification images displaying upper surface of multilayers of dehydrated cells of <i>D</i>. <i>radiodurans</i>. (<b>E</b>, <b>F</b>) Magnified images of tetracocci and diplococci of <i>D</i>. <i>radiodurans</i> taken from the inner part of dehydrated multilayers. (<b>A</b>, <b>C</b>, <b>E</b>) control cells of <i>D</i>. <i>radiodurans</i>; (<b>B</b>, <b>D</b>, <b>F</b>) cells of <i>D</i>. <i>radiodurans</i> exposed to UVC-vacuum conditions.</p

Heatmap of metabolites, which were considered different between cells of <i>D</i>. <i>radiodurans</i> exposed to UVC/vacuum and non-exposed control cells.

<p>Eucledian distance was used for calculating the dendrogram. *Identification was based on database research and not on a reference substance.</p

First two levels of gene ontology annotations of all proteins of <i>D</i>. <i>radiodurans</i>, which were identified in at least three out of four replicates in at least one condition.

<p>First two levels of gene ontology annotations of all proteins of <i>D</i>. <i>radiodurans</i>, which were identified in at least three out of four replicates in at least one condition.</p

Molecular response of <i>D</i>. <i>radiodurans</i> experienced under UVC and vacuum conditions.

<p>First two levels of molecular pathways are represented which are affected by UVC irradiation under vacuum conditions.</p

Bar plot of KEGG categories (x-axis) with corresponding enrichment factors (y-axis).

<p><b>Categories with a minimum enrichment factor of two for either UVC/vacuum (blue) treated or control (red) conditions are mapped.</b> An enrichment factor of zero means that not a single protein in this category was upregulated in the displayed condition.</p