Space mutations might help target antibiotic-resistant bacteria.

A PLOS Biology paper reports that bacteriophages evolved on the International Space Station developed mutations that made them more effective at killing certain antibiotic-resistant urinary tract infection bacteria when returned to Earth.

A team led by Srivatsan Raman at the University of Wisconsin–Madison published a PLOS Biology paper reporting results from an experiment that sent bacteriophages and bacteria to the International Space Station. The experiment was launched in September 2020 with logistical help from Rhodium Scientific and used cryovials designed to maintain about -80°C. The researchers sent a library of 1,660 pre-modified phage variants and kept identical control samples on Earth. They later compared how the phages and bacteria evolved in microgravity with how they evolved under normal laboratory conditions. Key findings: - Phages flown to space took longer to kill their bacterial hosts than the Earth controls, a difference the authors attribute to reduced convection in microgravity and a greater reliance on diffusion. - Space-grown E. coli developed mutations in the mlaA gene that led to phospholipids flipping to the cell surface, altering the bacterial membrane where phages attach. - Phages that prevailed in space acquired hydrophobic substitutions in their receptor binding proteins, which the paper suggests may have increased tail-fiber flexibility or stability for attaching to altered membranes. - When returned to Earth, the space-evolved phages were more effective against certain antibiotic-resistant bacteria that cause urinary tract infections than the Earth-evolved variants. - The authors note that stresses in the human urinary tract may resemble some space-induced stresses, and the article mentions a potential commercial case for producing space-evolved “superphages,” while also noting that scaling would require facilities larger than the ISS and more research. Summary: The study shows that microgravity-related stresses can lead to different phage–bacteria evolutionary outcomes and that space-evolved phages in this experiment were better at killing some antibiotic-resistant urinary tract infection strains when tested on Earth. The authors and the article indicate this result points to a possible role for space-based phage development, but they also say further work and larger-scale facilities would be needed before practical or commercial applications could be evaluated.