By all appearances, the universe beyond Earth is a vast, lonely, and sterile
space. Yet, wherever humans may travel, an abundance of microbial life will
follow.
In a first study of its kind, lead author Jiseon Yang at the Arizona State
University Biodesign Institute, Center for Fundamental and Applied
Microbiomics, and her colleagues characterized different bacterial
populations isolated over time from potable (drinking) water from the
International Space Station (ISS).
While historical monitoring of the ISS potable water system has focused on
identifying microbial species that are present through both
culture-dependent and independent (genome sequencing) methods, it is
challenging for microbial identification approaches alone to faithfully
predict the function of microbial communities. Understanding microbial
function is critical to safeguard the integrity of mission-critical
spacecraft life support systems and astronaut health.
The current study by Yang and her team investigated key functional
properties of waterborne bacterial isolates from the ISS potable water
system that were collected over the course of many years. The aim of this
study was to expand our knowledge of how microbial characteristics that are
important for astronaut health and space habitat integrity may change during
long duration exposure to the microgravity environment of spaceflight. This
is a critical issue to address, as microbial adaptations to microgravity
been shown to dramatically alter bacterial characteristics, including their
ability to form dense bacterial aggregates known as biofilms in the ISS
potable water system that could threaten mission success.
Investigations of the function and behavior of mixed microbial populations
are gaining traction in the scientific community, as these types of studies
provide insight into how microorganisms interact with each other and their
environment in practical settings. Such research can help provide crucial
guidelines for the assessment of microbial risk to water systems in space as
well as on Earth.
"Polymicrobial interactions are complex and may not be stable over time,"
Yang says. "Our study provides in-depth phenotypic analyses of single- and
multi-species bacterial isolates recovered from the ISS water system over
multiple years to understand long-term microbial interactions and adaptation
to the microgravity environment. The results from our study may improve
microbial risk assessments of human-built environments in both space and on
Earth."
Yang is joined by ASU colleagues Jennifer Barrila, Olivia King and Cheryl
Nickerson, who led the Biodesign team, as well as co-authors Robert JC
McClean of Texas State University, and Mark Ott and Rebekah Bruce from the
NASA Johnson Space Center, Houston.
The group's findings appear in the current issue of the journal npj Biofilms
and Microbiomes.
Life's liquid
Water is a life-giving and indispensable substance, on Earth and in space.
During spaceflight, a supply of clean water is essential for drinking and
basic hygiene, but the challenges of reliably supplying it to astronauts are
formidable, with every drop carefully managed.
According to NASA, without the ability to recycle water on the ISS, ~40,000
pounds of water per year would need to be transported from Earth to resupply
just four crewmembers at an exorbitant cost for the full duration of their
stay aboard the ISS.
The water purification system on the ISS, known as the Environmental Control
and Life Support System, is used to cleanse wastewater in a three-step
process. After initial filtration to remove particles and debris, the water
passes through multi-filtration beds containing substances that remove
organic and inorganic impurities. Finally, a catalytic oxidation reactor
removes volatile organic compounds and kills microorganisms.
Although sophisticated life-support systems of this kind are designed to
prevent contamination of this vital resource, bacterial communities have
shown enormous resourcefulness in thwarting many preventive measures, with
some forming biofilms throughout the ISS water recovery system.
In the current study, microbial activity was examined in the NASA-archived
bacterial isolates collected from the ISS potable water system over multiple
years. Bacterial species were profiled for antibiotic resistance, biofilm
structure and composition, metabolism, and hemolysis (ability to lyse red
blood cells).
Tiny and determined
Despite the diminutive size of individual bacteria, which are unable to be
seen by the naked eye, they are a force to be reckoned with. In addition to
their individual abilities to cause a range of infectious diseases in
humans, bacteria often clump together on surfaces to form dense multispecies
aggregates known as biofilms, which are inherently resistant to being
cleared by antimicrobials.
Bacterial biofilms have a major global socioeconomic impact and cause a
myriad of health and industrial problems, resulting in annual economic
losses in the billions of dollars on Earth. These problems include fouling
oil and chemical process lines, encrusting invasive medical stents, causing
infectious disease, and contaminating water resources. In addition, biofilms
can also cause aggressive corrosion to a broad range of materials, including
the capacity to degrade stainless steel, which is the material used in the
ISS water system.
For these reasons, control of bacteria in complex microbial ecosystems and
management of biofilm formation are vital challenges, made particularly
acute during spaceflight.
Aboard the ISS, the NASA water recovery system continuously generates
potable water from recycled urine, wastewater and condensation through
distillation, filtrations, catalytic oxidation, and iodine treatment.
Despite these efforts, in-flight analysis of water samples from the ISS
potable water system have shown microbial levels that exceed NASA
specifications for potable water. The sources of this contamination are
primarily due to environmental flora embedded in the water system itself.
Sky-high risk management
While many of the same microbes found in drinking water on Earth are also
found in the ISS samples, there is a concern that the space environment may
act to heighten the potential threats these organisms pose in this unique
environment. Of particular interest are the conditions of microgravity,
which members of this same research group have previously shown can enhance
the virulence and stress resistance of some infectious microbes, alter their
gene expression profiles, and encourage biofilm formation.
Compounding these issues is the fact that astronauts suffer aspects of
immune suppression from spending time in the space environment, potentially
leaving them more vulnerable to infection from microorganisms.
The results of the current study indicated that the ISS waterborne bacterial
isolates exhibited resistance to multiple antimicrobial compounds, including
antibiotics, as well as distinct patterns of biofilm formation and carbon
utilization. In addition, one of the bacterial isolates, known as
Burkholderia, displayed hemolytic activity, singling it out as a microbe of
potential concern for astronaut health.
Observation of bacterial species interactions in this study also revealed
distinct patterns of behavior, some of which were dependent on whether the
samples were collected during the same year or over the course of different
years, suggesting that adaptive processes were at work over time in the
microgravity environment. Importantly, the dynamic phenotypes observed in
this polymicrobial study would not have been fully predicted using
sequencing technologies alone.
The findings from this study will help overcome the formidable challenges of
ensuring safe drinking water for spaceflight missions, particularly those of
longer duration. In addition, this study may provide information to improve
the functionality of engineered water systems on Earth for industrial
benefit and safety of the general public.
Reference:
Jiseon Yang, Jennifer Barrila, C. Mark Ott, Olivia King, Rebekah Bruce,
Robert J. C. McLean, Cheryl A. Nickerson.
Longitudinal characterization of multispecies microbial populations
recovered from spaceflight potable water.
npj Biofilms and Microbiomes, 2021; 7 (1)
DOI: 10.1038/s41522-021-00240-5
No comments:
Post a Comment