Introduction:

Stenotrophomonas maltophilia is an opportunistic pathogen causing various infections. Its prevalence has increased, especially in cystic fibrosis patients, and its multidrug resistance poses challenges in treatment. The bacterium forms multispecies biofilms with other pathogens and is known for its role in pathogenicity in infected lungs.

Goals:

Our goal is to understand the biofilm characteristics of S. maltophilia in single und multispecies biofilms as well as the differential gene expression patterns within these biofilms.

Materials and methods:

In this study over 200 clinical isolates of S. maltophilia as well as chromosomally labeled fluorescent strains of S. maltophilia K279a, P. aeruginosa PA01, S. aureus SH1000 and C. albicans SC5314 were used. Biofilms were formed in flow and static settings and were used for RNA seq analysis. Additionally, promotor fusion constructs of selected genes were generated and were further analyzed.

Results:

Our analysis revealed strain-specific variability in biofilm formation and architecture among S. maltophilia isolates. RNA seq analysis of these isolates identified shared and strain-specific genes, with iron uptake being a key factor in biofilm metabolism. CLSM imaging showed that species interactions affect the structural composition of multispecies biofilms. S maltophilia showed alteration in lactate metabolism, propionate degradation and a switch in cytochrome oxidases in our biofilm models. The expression of virulence factors, QS signaling and cyclic diGMP was decreased in PA01 in coculture with K279a.

Summary:

Our data show that isolates of S. maltophilia are highly diverse on a phenotypic and genotypic level. Common genes were identified to play a crucial role in the biofilm formation of S. maltophilia. CLSM imaging has shown a distinct distribution and layer formation of different species within multispecies biofilms. RNA seq analysis and the application of reporter fusion constructs showed specific and different expression patterns for each species as compared to single species biofilms, suggesting that each species acknowledge and respond to the presence of others.