See Niggli et al., mBio
Polymicrobial infections are widespread and pathogenoc interaction potentially trigger evolutionary dynamics with pathogens adapting to each other. In this work, the Kümmerli group explored the potential of Staphylococcus aureus to adapt to its competitor Pseudomonas aeruginosa. Experimental evolution experiments with three different S. aureus strains showed that S. aureus rapidly becomes resistant to inhibitory compounds secreted by P. aeruginosa. Three main factors contribute to strain-specific resistance evolution: (i) overproduction of a molecule that protects against oxidative stress; (ii) the formation of small colony variants that also protect against oxidative stress; and (iii) changes in membrane transporters that may reduce toxin uptake. Taken together, this work shows that species interactions can change over time, potentially favoring species coexistence, which in turn could influence disease progression and treatment options.