The plugs in the International Space Station’s water recovery systems were backed up so heavily that the hoses had to be sent back to Earth to be cleaned and replenished. This is thanks to the accumulation of biofilms: collections of microorganisms that stick together, and often also to surfaces – for example, the interiors of water recovery pipes. These microbial or fungal growths can clog filters in water treatment systems and make astronauts sick.
So space, like Earth, has a germ problem — so what? Because biofilms can impair integrity and damage equipment, including spacesuits, recycling units, radiators, and water treatment facilities, it can cost space agencies money to replace damaged materials. For all of 2023, NASA has budgeted a whopping $1.3 billion as part of its budget to resupply its cargo missions to the International Space Station. Preventing microbial growth on encapsulated space missions will be especially critical for long-distance trips to places like the Moon or Mars, where a quick return to Earth to repair or treat sick astronauts would be less feasible.
In a mutual collaboration between researchers at the University of Colorado, MIT, and NASA Ames Research Center, researchers studied samples from the space station using a well-defined and well-understood species of Gram-negative bacteria. The scientists also joined forces with experts at LiquiGlide, a company run by MIT researcher Kripa Varanasi that specializes in “the elimination of friction between solids and liquids.” The multidisciplinary study found that covering surfaces with a thin layer of nucleic acids inhibited the growth of bacteria in samples exposed to the International Space Station.
The scientists concluded that these acids carry a slight negative electrical charge that prevents microbes from sticking to surfaces. It should be noted, however, that the bacteria faced a unique physical barrier as well as a chemical one: the test surfaces were etched into the “nanograss”. These silicone screws, which look like little forests, were then coated with silicone oil, creating a slippery surface that biofilms struggled to stick to.
Application of this specific method of coating surfaces with nucleic acids to prevent biofilm build-up showed that in terrestrial samples, microbial composition was reduced by about 74 percent. Surprisingly, the space station samples showed an even greater decrease, about 86 percent. However, one of the recommendations the team made, based on these preliminary findings, is that long-term testing should be carried out in a future mission. “We don’t know how long we’ll be able to maintain this performance,” Pamela Flores, a University of Colorado microbiologist who was involved in the study, said in a statement. “So we definitely recommend a longer incubation period and also, if possible, continuous analysis, not just endpoints.”