Pyochelin biotransformation shapes bacterial competition

It has become evident that numerous infections are polymicrobial and Pseudomonas aeruginosa and Staphylococcus aureus are among the most frequently isolated co-infecting bacterial species. We applied mass spectrometry guided interaction studies to determine how chemical interaction shapes the fitness and community structure during co-infection of these two pathogens. We demonstrate that S. aureus is equipped with an elegant mechanism, inactivation of pyochelin via the yet uncharacterized methyltransferase Spm (staphylococcal pyochelin methyltransferase), to increase its survival during in vivo competition with P. aeruginosa. Methylation of pyochelin abolishes the siderophore activity of pyochelin and significantly lowers pyochelin-mediated intracellular ROS production in S. aureus. In a murine wound co-infection model, a S. aureus mutant unable to metyhlate pyochelin shows significant lower fitness compared to its parental strain. ### Competing Interest Statement The authors have declared no competing interest.