Shapeshifting bacteria in space pose problem for astronauts

Bacteria cultured in space and then treated with a common antibiotic were more resistant to treatment than a control group on Earth.
By Clint Huston | Sep 16, 2017
Researchers who designed an experiment to culture a common bacteria on the International Space Station (ISS) and treat it with a common antibiotic have learned that, in a near-weightless environment, the bacterial cells displayed a talent for shapeshifting that helped them survive treatment.

The findings, which have implications for both astronauts who become sick in space and earthlings, are published in the journal Frontiers in Microbiology.

"We knew bacteria behave differently in space and that it takes higher concentrations of antibiotics to kill them," said lead author Luis Zea, at the University of Colorado at Boulder's BioServ Space Technologies, in a university statement. "What's new is that we conducted a systematic analysis of the changing physical appearance of the bacteria during the experiments."

The team's experiments involved the culture of E. coli bacteria on ISS and then treatment with several different concentrations of the antibiotic gentamicin sulfate, which is effective in killing E. coli on Earth. Compared to an Earth control group, the cultured bacteria responded with a 13-fold increase in cell numbers and a 73 percent reduction in cell volume size, the statement said.

Because gravity-driven forces like buoyancy and sedimentation are absent in space, the only way bacteria on the space station can ingest drugs is through natural diffusion, Zea explained, adding that the substantial decrease of the bacterial cell surface reduces the rate of molecule-cell interaction.

The bacterial cell wall and outer membrane also grew thicker, boosting protection against the antibiotic, while some of the E. coli cells produced outer membrane vesicles, which act as messenger cells that can start the infection process.

"Both the increase in cell envelope thickness and in the outer membrane vesicles may be indicative of drug resistance mechanisms being activated in the spaceflight samples," said Zea. "And this experiment and others like it give us an opportunity to better understand how bacteria become resistant to antibiotics here on Earth."


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