Exploring the spatial distribution of biomolecules in Pseudomonas aeruginosa biofilms formed on PDMS and lung explants by mass spectrometry imaging.

Bacterial biofilms constitute a form of collective organization that enhances bacterial tolerance to both antibiotics and immune defences. Among bacteria, Pseudomonas aeruginosa (P. aeruginosa) is a major opportunistic pathogen, with marked biofilm-forming capacity, highly implicated in chronic pulmonary infections. Understanding the metabolic and structural dynamics of P. aeruginosa biofilms is thus essential for the development of new therapeutic strategies. In this work, we investigated the formation of P. aeruginosa biofilm and its molecular composition on two different substrates of importance in public health. The first model is a synthetic polydimethylsiloxane (PDMS) surface, an inert model commonly used to simulate biomedical devices, and the second is a murine lung explant which offers a more physiologically relevant context to study lung infection. Using these models, mass spectrometry imaging (MSI), specifically MALDI-MSI technology, was used to map the spatial distribution of biofilm-produced compounds without prior labelling. This approach enabled the detection of multiple molecular families involved in the regulation, communication and structural organization of biofilm. The technique provides additional information on differences in the distribution of these molecules, particularly phenazine derivatives, within the models. Indeed, biofilms formed on lung explants show increased production of pyocyanin, invading lung tissue. These results highlight the power of MSI to explore the spatial metabolism of bacterial biofilms. It opens interesting perspectives for the microbiology of chronic infections by enabling visualization of chemical interactions between pathogens and their host environment.