Microbiological and rheological dynamics of mixed biofilms formed by bacteria and eukaryotic virus

Biofilms are structured microbial communities embedded within an extracellular matrix that confers protection against environmental stresses. In both natural and clinical settings, biofilms are rarely composed of a single species and may also involve interactions with bacteriophages or even eukaryotic viruses. Since both biofilms and viruses are ubiquitous, and viruses remain among the neglected components of the microbiome, understanding their interactions is essential. In hospitalized patients, catheter colonization by biofilms markedly increases the risk of bacteremia and septicemia, and biofilm formation is almost inevitable during long-term catheterization. In this study, we investigated biofilm-forming capacities of uropathogenic Escherichia coli (UPEC) and clinical strains associated with catheter-related systemic infections. Selected strains were further examined to evaluate the influence of the ubiquitous mammalian reovirus on bacterial biofilm formation and to evaluate biofilm entrapment of viral particles and its impact on viral infectivity. Bacterial growth, survival and biofilm production were measured in the presence or absence of the virus. While reovirus exhibited no bactericidal effects and biofilm biomass remained largely unchanged, rheological and microscopic analyses revealed strain-specific alterations in biofilm properties. Remarkably, reovirus retains infectivity after release from biofilms, indicating that bacterial biofilms may serve as reservoirs or shelters for eukaryotic viruses.