Microorganisms are essential to maintain our health, environment and the sustainability of buildings in which we live and work, both on Earth and during space exploration. Given that there are more microbial cells in and on our bodies than our own cells, it stands to reason that wherever humans travel, microbes will follow — including on space missions.
As human space missions that carry both professional and citizen astronauts continue to rapidly expand in duration and distance from our planet, including the moon and Mars, understanding the impact of spaceflight on microbial responses is of increasing importance.
During past spaceflight missions, microorganisms have caused serious illness as well as failure of onboard life-support systems and other essential spacecraft operations. However, microorganisms also have many beneficial aspects that are critical for the success of human space missions. These include generating building materials using planetary resources; sustaining human, plant and environmental microbiomes; food production; improving methods for waste recovery; and planetary protection (preventing microbial contamination between Earth and other planetary bodies).
Accordingly, a key objective for future human exploration missions is to understand and control the impact of the spaceflight environment on interactions between microbes, their hosts and their habitat.
As outlined in a new article for the journal Nature Microbiology, Cheryl Nickerson and her colleagues report their vision for the future of spaceflight microbiology for human health and habitat sustainability. In this commentary, they outline key elements needed to ensure a better understanding of microbial responses to spaceflight and next-generation tools needed to successfully perform this research.
The authors stress that a successful path forward to enable applications for crew health and habitat sustainability requires an in-depth understanding of the spaceflight-induced mechanisms that underlie unexpected microbial characteristics, many of which differ from those observed when the same organisms are grown on Earth. These include changes in microbial virulence (disease-causing ability), physiology, gene expression, microbiome diversity, biofilm formation, ability to degrade spaceflight materials, antibiotic resistance, host-pathogen and host-commensal interactions (commensal microbes can be beneficial or benign to the hosts they inhabit).
The authors also note that future space missions would benefit greatly from the design and development of genetically engineered microorganisms and microbial communities for new applications in biotechnology to sustain human activities during the unique conditions of spaceflight. However, this effort will also require understanding how microbes adapt and respond to the unique conditions of the spaceflight environment.
Knowledge gained from this research could also include novel in-flight production of pharmaceuticals, probiotics, gut-brain strategies to maintain health, oxygen generation and carbon dioxide recovery. In addition, as evidenced by previous work from Nickerson’s team, such studies could provide new insight into ways to improve human health and environmental sustainability on Earth.
Nickerson is a researcher in the Biodesign Center for Fundamental and Applied Microbiomics and professor in ASU’s School of Life Sciences. She and her team are pioneers in spaceflight microbiology, having flown numerous experiments on the space shuttle, SpaceX and the International Space Station. The results from their interdisciplinary studies have advanced the fields of infectious disease and environmental microbiology and laid the foundation for use of the microgravity research platform for modern microbiological research in spaceflight.
Nickerson’s team, composed of academic, government and commercial collaborators, continues to work closely with NASA to study the effect of the microgravity environment of spaceflight on microbial responses, especially those that are important for causing infectious disease in astronauts and biofouling environmental life-support systems. Using both spaceflight and NASA ground-based spaceflight analog technology, Nickerson and her colleagues have conducted a series of groundbreaking experiments aimed at improving our understanding of microbial responses to the spaceflight environment, their effects on astronauts and their impact on the habitability of spacecraft and function of onboard life-support systems.
Among the changes that microbes experience during spaceflight is reduced gravity, which can decrease the force created by the extracellular fluid flowing over cell surfaces. This decrease in the physical force of fluid flow (or shear) can trigger a range of microbial responses in some pathogens, from increased virulence to modulations of antimicrobial resistance and immune system avoidance. Nickerson’s team was the first to identify that physical forces in a microbe’s environment affect its ability to cause disease, leading to the concept called “mechanobiology of infectious disease," a rapidly growing research field that is providing a better understanding of ways to prevent disease on Earth.
"As humans live and work for longer periods in space, including exploration missions to the moon, Mars and beyond, it is critical to understand how microbes change their characteristics in response to spaceflight, as they have both beneficial and adverse effects on our health and that of our habitats," Nickerson said. "Knowledge gained from characterizing microbe-host-habitat interactions in space is essential to reduce risks to crew health and improve the design, efficiency and lifetime of the space habitat and its environmental life-support systems."
Microorganisms are impressive in their adaptability. They are incessantly receiving cues from their environmental surroundings and fine-tuning their behavior accordingly. The spaceflight environment, which represents a significant departure from conditions on Earth, induces a range of microbial adaptations that Nickerson and her colleagues have been investigating for many years. Some of the highlights of this ongoing research are described in the new paper and serve as a blueprint to enable future investigations.
Nickerson also acknowledges that the experimental design and implementation of spaceflight biological experiments is inherently challenging, in part due to limitations in power, volume and crew time, as well as unpredictable launch delays. However, even with these challenges, spaceflight research must be held to the same high scientific standards as terrestrial research, especially considering the uniqueness of the research platform and the large investment of time and money that these experiments demand.
She and her team further note that future space exploration approaches to microbiological research require a new paradigm for the design of next-generation spaceflight hardware (instrumentation) that is required to conduct the level of sophisticated biological experiments needed to ensure mission success.
In the Nature Microbiology article, Nickerson is joined by ASU colleagues Jennifer Barrila and George Poste, in the Biodesign Center for Fundamental and Applied Microbiomics and the Complex Adaptive Systems Initiative, respectively, as well as Audrie A. Medina-Colorado, at KBR in Houston, and Mark Ott, at the NASA Johnson Space Center.
While research to date has provided tantalizing clues concerning microbial responses to spaceflight and their role in human health and habitat sustainability, the number of microorganisms subjected to fractional gravity conditions has been limited. Accordingly, a far more comprehensive characterization of diverse organisms is needed, including commensal and pathogenic microbes.
In their collective vision, the authors lay out critical goals for microbiology space research and translational applications that must be addressed to gain the knowledge needed for the success of future human space exploration missions. These goals include understanding microbial response mechanisms to enable translational applications, advancing spaceflight analog culture systems on Earth, streamlining and simplifying processes for spaceflight experiments, synergizing engineering and biology approaches, increasing investigator resources (e.g., larger funding commitments, more astronaut time, routine access to spaceflight platforms), and developing multifunctional spaceflight hardware with the appropriate analytical precision and accuracy.
The rapidly increasing commercialization of spaceflight for the general public, coupled with an ambitious agenda for future deep-space exploration missions for professional astronauts, will expedite the need for advancements in space microbiological research. The authors’ new commentary article offers a vision and blueprint for a next-generation approach that will lead to translational applications to ensure the health of space travelers and the integrity of their habitat environment.
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