Pyochelin biotransformation by Staphylococcus aureus shapes bacterial competition with Pseudomonas aeruginosa in polymicrobial infections

Abstract

Pseudomonas aeruginosa and Staphylococcus aureus are among the most frequently isolated bacterial species from polymicrobial infections of cystic fibrosis patients and chronic wounds. 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 to inactivate pyochelin via the yet uncharacterized methyltransferase Spm (staphylococcal pyochelin methyltransferase). 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 methylate pyochelin shows significantly lower fitness as compared to its parental strain. Thus, Spm mediated pyochelin methylation is a novel mechanism to increase S. aureus survival during in vivo competition with P. aeruginosa.