Light Modulates Important Pathogenic Determinants And Virulence In 2 Acinetobacter Baumannii, Pseudomonas Aeruginosa And Staphylococcus Aureus Eskape Pathogens

Light sensing has been extensively characterized in the human pathogen Acinetobacter baumannii at environmental temperatures. However, the influence of light on the physiology and pathogenicity of human bacterial pathogens at temperatures found in warm-blooded hosts is still poorly understand. In this work, we show that ESKAPE priority pathogens, such as Staphylococcus aureus, Pseudomonas aeruginosa, and Acinetobacter spp., which have been recognized by the WHO and the CDC as critical, can also sense and respond to light at temperatures found in human hosts. Most interestingly, in these pathogens light modulates important pathogenicity determinants as well as virulence in an epithelial infection model, which could have implications in human infections. In fact, we found that a-toxin-dependent hemolysis, motility and growth under iron deprived conditions are modulated by light in S. aureus. Light also regulates persistence, metabolism and the ability to kill competitors, in some of these microorganisms. Finally, light exerts a profound effect on the virulence of these pathogens in an epithelial infection model, though the response is not the same in the different species: virulence was enhanced by light in A. baumannii and S. aureus, while in A. nosocomialis and P. aeruginosa it was reduced. Neither the BIsA photoreceptor nor the type VI secretion system (T6SS) are involved in virulence modulation by light in A. baumannii. Overall, this fundamental knowledge highlights the potential use of light to control pathogen's virulence, either directly or by manipulating the light regulatory switch towards the lowest virulence/persistence configuration.