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A special issue of Life (ISSN 2075-1729). This special issue belongs to the section "Microbiology".

Deadline for manuscript submissions: closed (31 January 2023) | Viewed by 33126

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Special Issue Editors

Dr. Luis Zea

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Guest Editor

BioServe Space Technologies, Aerospace Engineering Sciences, University of Colorado Boulder, Boulder, CO, USA
Interests: space microbiology; biofilms; biomining; space life sciences

Dr. Sergio Santa María

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Guest Editor

Fully Integrated Lifecycle Mission Support Services (FILMSS), Space Biosciences Research Branch, NASA Ames Research Center, CA 94035, USA
Interests: space radiation; yeast; DNA repair

Dr. Marta Cortesao

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Guest Editor

German Aerospace Center (DLR), Institute of Aerospace Medicine, Radiation Biology, Linder Hoehe, 51147 Cologne, Germany
Interests: space biology; biotechnology; Aspergillus; microgravity; biomining; astronaut health
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Special Issue Information

Dear Colleagues,

Different microbial responses to microgravity have been observed during the first 60 years of space microbiology research. These include changes in growth dynamics, horizontal gene transfer, susceptibility or resistance to antibiotics, cell size, envelope characteristics, formation of membrane vesicles, cellular aggregation, biofilm formation, virulence, gene expression, and metabolite synthesis, to name a few. Increased access to powerful omics tools, devices to simulate certain aspects of reduced gravity environments (e.g., clinostats and rotating wall vessels), and new research platforms for reduced gravity are allowing for novel and comprehensive investigations to take place both on and off Earth. Furthermore, new space exploration programs such as Artemis will enable space microbiology research beyond lower Earth orbit (LEO) and outside Earth’s Van Allen belts. This Special Issue is open for submissions of research papers and review articles on topics including but not limited to:

Experimental microbiology performed under simulated reduced gravity on Earth (low-shear modeled microgravity), in reduced gravity platforms (drop towers, parabolic and suborbital flights), or in spaceflight (International Space Station, Tiangong Space Station, and sortie flights);
Plans for microbiological research and applications beyond LEO including biomining, biology-based in situ resource utilization (ISRU), bioremediation of regolith, bioconcrete production, and myco-architecture;
Technologies enabling novel microbial research and applications in space, including bio-regenerative life support systems, bioreactors, microbial biomanufacturing, and microfluidic devices and data acquisition systems for telemetry-based microbiology;
Microbe–plant and microbe–animal interactions;
Microbiome of the built environment in space and analogs;
Microbial evolution;
Nutritional applications of microbes in space;
Synthetic, systems, and computational microbiology.

Dr. Luis Zea
Dr. Sergio Santa María
Dr. Marta Cortesao
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Life is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

simulated microgravity
low-shear modeled microgravity
biology-based in situ resource utilization (ISRU)
enabling technologies
microbe–plant interactions
microbe–animal interactions
microbiome of the built environment
synthetic, systems, and computational microbiology

Published Papers (9 papers)

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Research

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28 pages, 32710 KiB

Open AccessEditor’s ChoiceArticle

Morphology of Penicillium rubens Biofilms Formed in Space

by Megan Hupka, Raj Kedia, Rylee Schauer, Brooke Shepard, María Granados-Presa, Mark Vande Hei, Pamela Flores and Luis Zea

Life 2023, 13(4), 1001; https://doi.org/10.3390/life13041001 - 13 Apr 2023

Cited by 2 | Viewed by 2816

Abstract

Fungi biofilms have been found growing on spacecraft surfaces such as windows, piping, cables, etc. The contamination of these surfaces with fungi, although undesirable, is highly difficult to avoid. While several biofilm forming species, including Penicillium rubens, have been identified in spacecraft, the effect of microgravity on fungal biofilm formation is unknown. This study sent seven material surfaces (Stainless Steel 316, Aluminum Alloy, Titanium Alloy, Carbon Fiber, Quartz, Silicone, and Nanograss) inoculated with spores of P. rubens to the International Space Station and allowed biofilms to form for 10, 15, and 20 days to understand the effects of microgravity on biofilm morphology and growth. In general, microgravity did not induce changes in the shape of biofilms, nor did it affect growth in terms of biomass, thickness, and surface area coverage. However, microgravity increased or decreased biofilm formation in some cases, and this was incubation-time- and material-dependent. Nanograss was the material with significantly less biofilm formation, both in microgravity and on Earth, and it could potentially be interfering with hyphal adhesion and/or spore germination. Additionally, a decrease in biofilm formation at 20 days, potentially due to nutrient depletion, was seen in some space and Earth samples and was material-dependent. Full article

(This article belongs to the Special Issue Gravitational Microbiology Research and Applications)

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13 pages, 4309 KiB

Open AccessArticle

Bacterial Virulence and Prevention for Human Spaceflight

by Hakim Ullah Wazir, Pooja Narang, Giulia Silvani, Christine Mehner, Kate Poole, Catherine Burke and Joshua Chou

Life 2023, 13(3), 656; https://doi.org/10.3390/life13030656 - 27 Feb 2023

Viewed by 2091

Abstract

With the advancement in reusable rocket propulsion technology, space tourist trips into outer space are now becoming a possibility at a cost-effective rate. As such, astronauts will face a host of health-related challenges, particularly on long-duration space missions where maintaining a balanced healthy microbiome is going to be vital for human survival in space exploration as well as mission success. The human microbiome involves a whole list of micro-organisms that reside in and on the human host, and plays an integral role in keeping the human host healthy. However, imbalances in the microbiome have been directly linked to many human diseases. Research findings have clearly shown that the outer space environment can directly affect the normal microbiome of astronauts when the astronaut is exposed to the microgravity environment. In this study, we show that the simulation of microgravity on earth can mimic the outer space microgravity environment. Staphylococus aureus (S. aureus) was chosen for this study as it is an opportunistic pathogen, which is part of the normal human skin microflora and the nasal passages. This study’s results show that S. aureus proliferation was significantly increased under a microgravity environment compared to Earth’s gravity conditions, which complements previous work performed on bacteria in the outer space environment in the International Space Station (ISS). This demonstrates that this technology can be utilised here on Earth to mimic the outer space environment and to study challenging health-related questions. This in return saves us the cost on conducting experiments in the ISS and can help advance knowledge at a faster rate and produce countermeasures to mitigate the negative side effects of the hostile outer space environment on humans. Full article

(This article belongs to the Special Issue Gravitational Microbiology Research and Applications)

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17 pages, 3264 KiB

Open AccessArticle

Simulated Micro-, Lunar, and Martian Gravities on Earth—Effects on Escherichia coli Growth, Phenotype, and Sensitivity to Antibiotics

by Lily A. Allen, Amir H. Kalani, Frederico Estante, Aaron J. Rosengren, Louis Stodieck, David Klaus and Luis Zea

Life 2022, 12(9), 1399; https://doi.org/10.3390/life12091399 - 8 Sep 2022

Cited by 7 | Viewed by 2497

Abstract

Bacterial behavior has been studied under microgravity conditions, but very little is known about it under lunar and Martian gravitational regimes. An Earth-based approach was designed and implemented using inclined clinostats and an in-house-developed code to determine the optimal clinorotation angular speed for bacterial liquid cultures of 5 RPM. With this setup, growth dynamics, phenotypic changes, and sensitivity to antibiotics (minimum inhibitory concentration (MIC) of two different classes of antibiotics) for three Escherichia coli strains (including uropathogenic) were examined under simulated micro-, lunar, and Martian gravities. The results included increased growth under simulated micro- and lunar gravities for some strains, and higher concentrations of antibiotics needed under simulated lunar gravity with respect to simulated micro- and Martian gravities. Clinostat-produced results can be considered suggestive but not determinative of what might be expected in altered gravity, as there is still a need to systematically verify these simulation devices’ ability to accurately replicate phenomena observed in space. Nevertheless, this approach serves as a baseline to start interrogating key cellular and molecular aspects relevant to microbial processes on the lunar and Martian surfaces. Full article

(This article belongs to the Special Issue Gravitational Microbiology Research and Applications)

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17 pages, 2901 KiB

Open AccessArticle

Enabling Clonal Analyses of Yeast in Outer Space by Encapsulation and Desiccation in Hollow Microparticles

by Simon Ng, Cayden Williamson, Mark van Zee, Dino Di Carlo and Sergio R. Santa Maria

Life 2022, 12(8), 1168; https://doi.org/10.3390/life12081168 - 31 Jul 2022

Cited by 3 | Viewed by 2850

Abstract

Studying microbes at the single-cell level in space can accelerate human space exploration both via the development of novel biotechnologies and via the understanding of cellular responses to space stressors and countermeasures. High-throughput technologies for screening natural and engineered cell populations can reveal cellular heterogeneity and identify high-performance cells. Here, we present a method to desiccate and preserve microbes in nanoliter-scale compartments, termed PicoShells, which are microparticles with a hollow inner cavity. In PicoShells, single cells are confined in an inner aqueous core by a porous hydrogel shell, allowing the diffusion of nutrients, wastes, and assay reagents for uninhibited cell growth and flexible assay protocols. Desiccated PicoShells offer analysis capabilities for single-cell derived colonies with a simple, low resource workflow, requiring only the addition of water to rehydrate hundreds of thousands of PicoShells and the single microbes encapsulated inside. Our desiccation method results in the recovery of desiccated microparticle morphology and porosity after a multi-week storage period and rehydration, with particle diameter and porosity metrics changing by less than 18% and 7%, respectively, compared to fresh microparticles. We also recorded the high viability of Saccharomyces cerevisiae yeast desiccated and rehydrated inside PicoShells, with only a 14% decrease in viability compared to non-desiccated yeast over 8.5 weeks, although we observed an 85% decrease in initial growth potential over the same duration. We show a proof-of-concept for a growth rate-based analysis of single-cell derived colonies in rehydrated PicoShells, where we identified 11% of the population that grows at an accelerated rate. Desiccated PicoShells thus provide a robust method for cell preservation before and during launch, promising a simple single-cell analysis method for studying heterogeneity in microbial populations in space. Full article

(This article belongs to the Special Issue Gravitational Microbiology Research and Applications)

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21 pages, 3964 KiB

Open AccessArticle

CAMDLES: CFD-DEM Simulation of Microbial Communities in Spaceflight and Artificial Microgravity

by Rocky An and Jessica Audrey Lee

Life 2022, 12(5), 660; https://doi.org/10.3390/life12050660 - 29 Apr 2022

Cited by 1 | Viewed by 3187

Abstract

We present CAMDLES (CFD-DEM Artificial Microgravity Developments for Living Ecosystem Simulation), an extension of CFDEM^®Coupling to model biological flows, growth, and mass transfer in artificial microgravity devices. For microbes that accompany humans into space, microgravity-induced alterations in the fluid environment are likely to be a major factor in the microbial experience of spaceflight. Computational modeling is needed to investigate how well ground-based microgravity simulation methods replicate that experience. CAMDLES incorporates agent-based modeling to study inter-species metabolite transport within microbial communities in rotating wall vessel bioreactors (RWVs). Preexisting CFD modeling of RWVs has not yet incorporated growth; CAMDLES employs the simultaneous modeling of biological, chemical, and mechanical processes in a micro-scale rotating reference frame environment. Simulation mass transfer calculations were correlated with Monod dynamic parameters to predict relative growth rates between artificial microgravity, spaceflight microgravity, and 1 g conditions. By simulating a microbial model community of metabolically cooperative strains of Escherichia coli and Salmonella enterica, we found that the greatest difference between microgravity and an RWV or 1 g gravity was when species colocalized in dense aggregates. We also investigated the influence of other features of the system on growth, such as spatial distribution, product yields, and diffusivity. Our simulation provides a basis for future laboratory experiments using this community for investigation in artificial microgravity and spaceflight microgravity. More broadly, our development of these models creates a framework for novel hypothesis generation and design of biological experiments with RWVs, coupling the effects of RWV size, rotation rate, and mass transport directly to bacterial growth in microbial communities. Full article

(This article belongs to the Special Issue Gravitational Microbiology Research and Applications)

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Review

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18 pages, 601 KiB

Open AccessReview

Prospective Use of Probiotics to Maintain Astronaut Health during Spaceflight

by Sahaj Bharindwal, Nidhi Goswami, Pamela Jha, Siddharth Pandey and Renitta Jobby

Life 2023, 13(3), 727; https://doi.org/10.3390/life13030727 - 8 Mar 2023

Cited by 2 | Viewed by 4333

Abstract

Maintaining an astronaut’s health during space travel is crucial. Multiple studies have observed various changes in the gut microbiome and physiological health. Astronauts on board the International Space Station (ISS) had changes in the microbial communities in their gut, nose, and skin. Additionally, immune system cell alterations have been observed in astronauts with changes in neutrophils, monocytes, and T-cells. Probiotics help tackle these health issues caused during spaceflight by inhibiting pathogen adherence, enhancing epithelial barrier function by reducing permeability, and producing an anti-inflammatory effect. When exposed to microgravity, probiotics demonstrated a shorter lag phase, faster growth, improved acid tolerance, and bile resistance. A freeze-dried Lactobacillus casei strain Shirota capsule was tested for its stability on ISS for a month and has been shown to enhance innate immunity and balance intestinal microbiota. The usage of freeze-dried spores of B. subtilis proves to be advantageous to long-term spaceflight because it qualifies for all the aspects tested for commercial probiotics under simulated conditions. These results demonstrate a need to further study the effect of probiotics in simulated microgravity and spaceflight conditions and to apply them to overcome the effects caused by gut microbiome dysbiosis and issues that might occur during spaceflight. Full article

(This article belongs to the Special Issue Gravitational Microbiology Research and Applications)

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21 pages, 1056 KiB

Open AccessReview

Euglena, a Gravitactic Flagellate of Multiple Usages

by Donat-P. Häder and Ruth Hemmersbach

Life 2022, 12(10), 1522; https://doi.org/10.3390/life12101522 - 29 Sep 2022

Cited by 5 | Viewed by 5638

Abstract

Human exploration of space and other celestial bodies bears a multitude of challenges. The Earth-bound supply of material and food is restricted, and in situ resource utilisation (ISRU) is a prerequisite. Excellent candidates for delivering several services are unicellular algae, such as the space-approved flagellate Euglena gracilis. This review summarizes the main characteristics of this unicellular organism. Euglena has been exposed on various platforms that alter the impact of gravity to analyse its corresponding gravity-dependent physiological and molecular genetic responses. The sensory transduction chain of gravitaxis in E. gracilis has been identified. The molecular gravi-(mechano-)receptors are mechanosensory calcium channels (TRP channels). The inward gated calcium binds specifically to one of several calmodulins (CaM.2), which, in turn, activates an adenylyl cyclase. This enzyme uses ATP to produce cAMP, which induces protein kinase A, followed by the phosphorylation of a motor protein in the flagellum, initiating a course correction, and, finally, resulting in gravitaxis. During long space missions, a considerable amount of food, oxygen, and water has to be carried, and the exhaled carbon dioxide has to be removed. In this context, E. gracilis is an excellent candidate for biological life support systems, since it produces oxygen by photosynthesis, takes up carbon dioxide, and is even edible. Various species and mutants of Euglena are utilized as a producer of commercial food items, as well as a source of medicines, as it produces a number of vitamins, contains numerous trace elements, and synthesizes dietary proteins, lipids, and the reserve molecule paramylon. Euglena has anti-inflammatory, -oxidant, and -obesity properties. Full article

(This article belongs to the Special Issue Gravitational Microbiology Research and Applications)

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16 pages, 342 KiB

Open AccessReview

The Impacts of Microgravity on Bacterial Metabolism

by Gayatri Sharma and Patrick D. Curtis

Life 2022, 12(6), 774; https://doi.org/10.3390/life12060774 - 24 May 2022

Cited by 20 | Viewed by 4793

Abstract

The inside of a space-faring vehicle provides a set of conditions unlike anything experienced by bacteria on Earth. The low-shear, diffusion-limited microenvironment with accompanying high levels of ionizing radiation create high stress in bacterial cells, and results in many physiological adaptations. This review gives an overview of the effect spaceflight in general, and real or simulated microgravity in particular, has on primary and secondary metabolism. Some broad trends in primary metabolic responses can be identified. These include increases in carbohydrate metabolism, changes in carbon substrate utilization range, and changes in amino acid metabolism that reflect increased oxidative stress. However, another important trend is that there is no universal bacterial response to microgravity, as different bacteria often have contradictory responses to the same stress. This is exemplified in many of the observed secondary metabolite responses where secondary metabolites may have increased, decreased, or unchanged production in microgravity. Different secondary metabolites in the same organism can even show drastically different production responses. Microgravity can also impact the production profile and localization of secondary metabolites. The inconsistency of bacterial responses to real or simulated microgravity underscores the importance of further research in this area to better understand how microbes can impact the people and systems aboard spacecraft. Full article

(This article belongs to the Special Issue Gravitational Microbiology Research and Applications)

19 pages, 22757 KiB

Open AccessReview

Effect of Space Flight Factor on Dormant Stages in Aquatic Organisms: A Review of International Space Station and Terrestrial Experiments

by Victor R. Alekseev, Jiang-Shiou Hwang and Margarita A. Levinskikh

Life 2022, 12(1), 47; https://doi.org/10.3390/life12010047 - 29 Dec 2021

Cited by 2 | Viewed by 2205

Abstract

This work is a review of the experiments carried out in the Russian segment of the ISS (inside and outside) from 2005 to 2016 on the effect of the space flight factor on the resting stages of organisms. In outer space, ultraviolet, a wide range of high and low temperatures, cosmic radiation, altered gravity, modified electromagnetic field, vacuum, factors of technical origin, ultrasound, microwave radiation, etc. and their combination determine the damaging effect on living organisms. At the same time, biological dormancy, known in a wide range of bacteria, fungi, animals and plants, allows them to maintain the viability of their dormant stages in extreme conditions for a long time, which possibly allows them to survive during space flight. From 2005 to 2016, the resting stages (propagules) of micro- and multicellular organisms were tested on the ISS to assess their ability to survive after prolonged exposure to the conditions of open space and space flight. Among the more than 40 species studied, about a third were dormant stages of aquatic organisms (eggs of cyprinodont fish, daphnia embryos, resting eggs of fairy shrimps, tadpole shrimps, copepods and ostracods, diapausing larvae of dipterans, as well as resting cysts of algae). The experiments were carried out within the framework of four research programs: (1) inside the ISS with a limited set of investigated species (Akvarium program); (2) outside the station in outer space without exposure to ultraviolet radiation (Biorisk program); (3) under modified space conditions simulating the surface of Mars (Expose program); and (4) in an Earth-based laboratory where single-factor experiments were carried out with neutron radiation, modified magnetic field, microwave radiation and ultrasound. Fundamentally new data were obtained on the stability of the resting stages of aquatic organisms exposed to the factors of the space environment, which modified the idea of the possibility of bringing Earth life forms to other planets with spacecraft and astronauts. It also can be used for creating an extraterrestrial artificial ecosystem and searching for extraterrestrial life. Full article

(This article belongs to the Special Issue Gravitational Microbiology Research and Applications)

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