Manned space missions bring with them a plethora of
challenges to keep astronauts alive and healthy, especially on long-
duration space missions. Astronauts need to breathe, eat, drink, excrete
their food and drink, and be kept free of infections to stay healthy
enough to do their job. The key to an astronauts' wellbeing has been
found, somewhat contradictorily, to be a group of tiny organisms --
bacteria.
You might think of space as a germ-free environment, but microbes
can be carried to space inside human gut flora as well as in food and
water and once up there, can be expelled by humans in their breath.
According to NASA, immune systems weaken during space flight,
making the impact of infection even greater.
What's more, the greater radiation levels and the weightless
microgravity environment of space alter bacteria as they grow. Recent
work at NASA by Cheryl Nickerson and her team from Arizona State
University discovered that certain bacteria become more virulent in
space, meaning they become better at infecting us.
"Salmonella bacteria become more potent, virulent
and are more able to cause disease," says Nickerson.
"They also become more resistant to factors such as
the acid in your stomach." Nickerson's group is
investigating a range of bacteria found in food, water
and our gut flora, including Salmonella typhimurium,
a common cause of food poisoning and diarrhea, and
Pseudomonas aeruginosa, which is a known water
contaminant.
'War with microorganisms'
As astronauts spend longer periods of time in space, their increased
exposure to recycled air and water is likely to affect their risk of
infection
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Mark Nott is one the people in charge of crew health at NASA and
focuses on keeping microbes at bay. "We're at a constant war with
microorganisms because they adapt," he says. "The stressful
environment of spaceflight affects them and under stress your immune
system also functions less effectively and we have to take precautions
for this." Reduced immunity can cause some bacteria, such as
Pseudomonas aeruginosa, to cause illness despite normally being
carried by many of us with no effect.
"However, not all microorganisms are bad and so the key is to
understand how they change and impact us," explains Nott, who also
found that the infectious bacteria Staphylococcus aureus, which causes
a range of symptoms from boils to food poisoning, becomes benign in
microgravity.
By understanding the changes in salmonella and other disease-causing
bacteria in microgravity Nickerson hopes to not only keep crew healthy
but also help humans down on Earth through the development of drugs
and vaccines.
"Infections are becoming harder to treat; we have no vaccine for
salmonella food poisoning and it remains [one of] the leading cause of
bacterial food-borne illness worldwide," states Nickerson.
Spaceflight opens up a new world of research that can't take place on
Earth and Nickerson has unmasked key changes in the behaviour of
genes in the bacteria which aren't usually seen under gravity. "Vaccines
are about identifying targets and in microgravity the bacteria have
unmasked themselves and revealed secrets to help develop
therapeutics."
Sustaining life in space
The research is in its early stages but it's just one
example of how bacteria are being investigated by
space agencies. Far from just a health hazard,
bacteria could be used to help sustain astronauts in
space, as a source of food and oxygen.
"The major advantage to using bacteria is the size of
them," explains Christophe Lasseur, coordinator of life
support research and development at the European
Space Agency (ESA). "For space missions the mass
of oxygen, food, and water is high and not compatible
with current launch technologies. A crew of six to
Mars would need over 30 tons."
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Lasseur directs the MELLiSSA programme at ESA, which aims to
develop a regenerative life-support ecosystem for use on board
spacecraft. "We need to recycle everything for an ecosystem that can
sustain human life," says Lasseur. The team wants to recycle 80% of
all mass on board, including carbon dioxide, which can become toxic if
allowed to build up.
Key algae and bacteria can mop up carbon dioxide and in turn release
oxygen to enable astronauts to breathe. "We have approached this
molecule by molecule, first oxygen, then water and now food, which is
more complex," says Lasseur.
The chosen range of bacteria not only utilize carbon dioxide but can
also harness other human waste products, such as urine and feces -- a
win-win given their growth results in food for the astronauts.
Eating bacteria grown on urine may not sound like a delicacy, and it
isn't, which is why psychology also comes into play. "Our most
advanced work is using spirulina as this has been used as a protein
source for many centuries and in many countries, making it much more
psychologically acceptable," explains Lasseur. Spirulina is a
cyanobacterium found in many salt water lakes and is consumed
readily by lake communities. The edible bacterium is also marketed as
a health supplement.
In the search for bacteria that feed on our food waste, Lasseur's team
discovered a hidden gem that has an additional medical benefit --
helping to fight cholesterol.
"We were looking for bacteria which use a lot of carbon and nitrogen as
there's a lot of this in waste disposal," states Lasseur. The resulting
use of Rhodospirillum rubrum led to a nutritious product found to
produce significantly lower levels of cholesterol in mice and will soon
be marketed by spin-off company EzCOL BV, which is in talks with big
pharma. This bacterium has been by-passed in favor of more
nutritious alternatives for consumption by astronauts but the research
to get there has borne beneficial fruit for those of us not venturing up
into space.
As for the astronauts, Mars missions could be a reality in the, albeit
distant, future. And when the day comes, crews could depart feeling
confident of reaching the red planet well fed, watered and free of
infection.
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