No sign space station microbes are turning nasty

There is no evidence that bacteria living onboard the International Space Station are mutating into forms dangerous to humans, researchers say.

A study led by environmental engineer Erica Hartmann from Northwestern University in the US concludes that genetic changes found in colonies of common bacteria living in the ISS are adaptations to harsh conditions. There is no indication that they are becoming pathogenic.

Concerns about the orbiting microbes were raised late last year when scientists led by Nitin Singh and Daniela Bezdan from the Biotechnology and Planetary Protection Group at the Jet Propulsion Laboratory of the California Institute of Technology, US, sequenced samples of the bacterium Enterobacter recovered from the ISS.

The results showed that all the samples belonged to a single species, E. bugandensis, but matched only a single very rare strain found just three times on Earth.{%recommended 6904%}

All the ISS samples contained genes associated with drug-resistance and while there was no indication the bacteria were harmful, their discovery was enough for the researchers to sound a warning.

“Given the multi-drug resistance results for these ISS E. bugandensis genomes and the increased chance of pathogenicity we have identified, these species potentially pose important health considerations for future missions,” says Singh.

The latest research examines two other common bacterial species recovered from the ISS – Staphylococcus aureus and Bacillus cereus.

Analysis showed that the strains were changing – a not unusual, even inevitable, evolutionary process in microorganisms that cycle through multiple generations in short periods of time – but there was no indication that they were becoming more pathogenic or virulent.

“There has been a lot of speculation about radiation, microgravity and the lack of ventilation and how that might affect living organisms, including bacteria,” says Hartmann. 

“These are stressful, harsh conditions. Does the environment select for superbugs because they have an advantage? The answer appears to be ‘no’.”

The research is published in the journal mSystems.