Modelling host–pathogen interactions: Galleria mellonella as a platform to study Pseudomonas aeruginosa response to host-imposed zinc starvation

Nutritional immunity, a key component of the vertebrate innate immune response, involves the modulation of zinc availability to limit the growth of pathogens. Pseudomonas aeruginosa counteracts host- imposed zinc starvation through metabolic adaptations, including reprogramming of gene expression and activating efficient metal uptake systems. To unravel how zinc shortage contributes to the complexity of bacterial adaptation to the host environment, it is critical to use model systems that mimic fundamental features of P. aeruginosa- related diseases in humans. Among available animal models, Galleria mellonella has recently emerged as a promising alternative to mammalian hosts. This study aims to evaluate whether G. mellonella can recapitulate the zinc- related nutritional immunity responses observed in mammalian infections. Our results show that, upon P. aeruginosa infection, the larvae upregulate several zinc transporters, suggesting an active redistribution of the metal in response to the pathogen. Additionally, P. aeruginosa colonizing the larvae induces Zn uptake regulator- controlled genes, consistent with bacterial adaptation to zinc starvation. Disruption of bacterial zinc uptake capability significantly reduces P. aeruginosa virulence, underscoring the importance of zinc acquisition in pathogenesis also within this model host. As a proof of concept, we also demonstrate that this in vivo model can serve as a viable preliminary screening tool to unveil novel players involved in P. aeruginosa response to zinc starvation, offering valuable insights into the host-pathogen battle for micronutrients.