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Persistent Bacteria On Spacecraft May Complicate Search For Alien Life

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Researchers have found how super-hardy microbes on spacecraft persist, shedding light on new ways that can prevent them from impeding the search for extraterrestrial life.

What Is Planetary Protection?

The search for life in outer space is one of the biggest quests modern humans have decided to undertake. However, NASA does not want to complicate this quest by accidentally injecting life that comes from Earth into other worlds.

This is why it takes the concept of planetary protection seriously. NASA does not want to find false-positives of signs of life on other planets. In fact, it is bound by international law to keep Earth-dwelling microbes from reaching other celestial bodies by hanging on for a ride on one of its spacecraft.

To ensure this does not happen, NASA practices a wealth of measures to keep its spacecraft and facilities clean. For instance, all surfaces are sprayed with an alcohol solution to kill all surface-dwelling microbes. For any surface to be considered biologically clean, there must not be more than 300,000 microbial spores on it.  

Unfortunately, NASA's alcohol solution is not strong enough to deal with a 20-year-old bacterial problem.

Microbes On Spacecraft

The problem of microbes lurking in spacecraft is not new. Analysis of the surfaces of various spacecraft, including the International Space Station, has shown that a diverse microbiome of bacteria, fungi, and archaea exist on spacecraft.

Of particular interest is Acinetobacter, an extremely hardy bacteria known to contaminate hospitals, nursing homes, and health care facilities. The World Health Organization ranks Acinetobacter as one of the most dangerous bacteria in the world.  

A team of researchers at the California State Polytechnic University has set out to find out what keeps Acinetobacter alive even in the cleanest of rooms.

After collecting isolated strains of Acinetobacter from various sources, including the Odyssey and Phoenix missions to Mars and the exterior of the ISS, the team subjected the strains to a diet composed of cleaning agents, namely ethanol, isopropyl alcohol, and a floor detergent called Kleenol 30.

Why Spacecraft Bacteria Endure

They found that this particularly persistent breed of bacteria does not just subsist on nothing but cleaning agents; it actually thrives on them.

Acinetobacter survived solely on ethanol as an energy source, also while remaining resistant to oxidative stress. This is important since the harsh environment of Mars can be a primary source of oxidative stress for any forms of life that may live there.

The bacteria also used ethanol as a source of carbon for making DNA, proteins, and other molecules that sustain life.

Although the particular strains used for the study were not able to use isopropyl alcohol and Kleenol 30 for food, they could break them down, meaning they could be used as energy sources for other microbes.

Acinetobacter was also found to be resistant to hydrogen peroxide, which is found in disinfectants, bleaches, and detergents. It can also withstand radiation, high pressure, and temperatures as high as 176 degrees Fahrenheit.

"You can clean the rooms out and sterilize them," says study lead author and chemistry professor Rakesh Mogul. "To be a bit Jurassic Park about it: Life will find a way."  

Mogul believes the study can help the planetary protection community come up with more stringent cleaning measures to keep hardy microbes in check. The use of different cleaning agents in rotation could keep a community of persistent microbes from invading spacecraft and potentially taking over new worlds.  

Details of the study are published in the journal Astrobiology.

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