Protected with an antimicrobial door ESA

Killing bacteria in space is surprisingly hard. Space missions have been plagued by bacterial biofilms that have coated surfaces and corroded equipment.

Now, an antimicrobial metal surface that explodes bacteria on contact has been tested on the International Space Station (ISS), and it may be used in future missions to keep astronauts healthy.

Elisabeth Grohmann at the Beuth University of Applied Sciences Berlin and her colleagues tested an antimicrobial coating called AGXX, which consists of thin layers of the metals silver and ruthenium treated with vitamin C.


They affixed metal sheets to a contamination-prone surface: the ISS’s bathroom door. Taking swabs at six, 12, and 19 months, the team found that compared with sheets of stainless steel and silver, the AGXX surface had a significantly reduced number of bacteria.

Pop those bugs

AGXX works via a redox reaction between the silver and ruthenium, producing free radicals that damage bacterial cell membranes. “They really explode the bacteria,” says Grohmann.

Over time, some bacteria grew, but by 19 months there were 80 per cent fewer strains on the AGXX than on the steel. No serious illness-causing bugs were found, says Grohmann, but most strains found were resistant to at least three antibiotics.

Spacecraft are ripe environments for bacterial resistance, partly because there isn’t the normal competition between the human-associated bacteria and bugs from environment. Certain strains develop thicker cell walls and others multiply faster in microgravity.

Astronauts on the ISS aren’t allowed to use aerosol cleaning agents, or liquids containing flammable alcohol, so new antimicrobial fixes are in high demand.

The study concluded in 2015, and since then the antimicrobial properties of AGXX have been improved, says Grohmann. The coating will next be tested in a joint isolation mission between NASA and Russia’s Institute of Biomedical Problems.

Journal reference: Frontiers in Microbiology, DOI: 10.3389/fmicb.2019.00543