Microrheological evolution of mono- and dual-species Pseudomonas aeruginosa– Staphylococcus aureus biofilms

Pseudomonas aeruginosa and Staphylococcus aureus are common pathogens in chronic infections. Therapeutic challenges arise from the biofilm’s resilience to the human immune system and antibacterial treatments. Here, we aim to understand the early-stage mechanical development of P. aeruginosa and S. aureus biofilms as well as their growth kinetics. Mono- and dual-species cultures at various ratios were monitored for 24 hours using video particle-tracking microrheology to determine the evolving viscoelasticity. Biofilm kinetics and the total growth were evaluated using phase-contrast and confocal microscopy. Enhanced biomass and increased viscosity were observed in all dual-species biofilms, with the most noticeable increase in samples with an initially equal ratio. Transition times marking distinctive stage of the local microenvironment are identified. These findings suggest population-associated factors influence the development of P. aeruginosa - S. aureus biofilms.