Microbes in space: concerns raised about bacteria in the ISS

Researchers find strains inside the space station have the potential to endanger astronaut health. Andrew Masterson reports.

Toilets are hotbeds for bacteria – even, it seems, on the International Space Station.

Toilets are hotbeds for bacteria – even, it seems, on the International Space Station.

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Five strains of the bacterium Enterobacter recovered from areas on board the International Space Station (ISS) have been identified, with researchers urging further careful research to determine whether continuous exposure to microgravity could induce potentially dangerous mutations.

In a paper published in the journal BMC Microbiology, a team 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, detail genomic analyses of Enterobacter gathered from the toilet and gym areas of the space station.

The bacterial genus is widespread on Earth, and associated with a range of sometimes serious human conditions, including septic arthritis, osteomyelitis, skin and soft tissue damage and lower respiratory tract infections. Some strains exhibit multiple antibiotic resistance.

Sequencing of the ISS samples revealed that all five strains belonged to a single species, E. bugandensis.

The members of the Enterobacter genus have been widely studied and sequenced, leading to a library of 1291 full genomes.

When Bezdan and colleagues ran the numbers on the space station microbes, however, they found that they were similar to only three – and rare ones, at that. They report similarities with strains found to date only once – one recovered from neonatal blood in a Tanzanian patient, another from a neonatal urine sample in the US, and the third from a 72-year-old woman with multiple health problems.

In total, the researchers report, the eight strains thus “formed a unique ecotype”.

The ISS strains all contained genes associated with drug-resistance. They did not, however, contain combinations associated with high infection rates. Nevertheless, the results are 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.

“However, it is important to understand that the strains found on the ISS were not virulent, which means they are not an active threat to human health, but something to be monitored.”

The authors predicted using computer analyses that there was a 79% probability that the bacteria may potentially cause disease under the right circumstances.

There is also, they note, a degree of uncertainty regarding the development of the strains because of the highly unusual conditions in which they live.

“Whether or not an opportunistic pathogen like E. bugandensis causes disease and how much of a threat it is, depends on a variety of factors, including environmental ones,” says co-author Kasthuri Venkateswaran.

“Further in vivo studies are needed to discern the impact that conditions on the ISS, such as microgravity, other space, and spacecraft-related factors, may have on pathogenicity and virulence.”

  1. https://bmcmicrobiol.biomedcentral.com/articles/10.1186/s12866-018-1325-2
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