Periodic Spatial Disturbances Alter the Expression of Quorum Sensing Virulence Factors in Pseudomonas aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen known to cause a variety of severe diseases and is a leading cause of mortality among immunocompromised patients. Current therapeutic interventions that rely heavily on antibiotics are no longer able to adequately combat bacterial infections due to the emergence of drug-resistant strains and the effectiveness of bacterial cooperation mechanisms, such as quorum-sensing (QS). Pathogenic bacteria, such as P. aeruginosa, employ this density-dependent mechanism to coordinate bacterial behaviors needed for host colonization, biofilm formation, antibiotic neutralization, and exotoxin secretion. As such, there is a growing interest in the development of novel non-antibiotic-based approaches to mitigate P. aeruginosa pathogenicity and disrupt the functionality of the QS system. Previous studies suggest that periodic disturbances to the spatial structures of QS-bacteria uncouples the distribution of bacteria and autoinducer, altering the expression of QS-regulated genes; but this has yet to be explored in P. aeruginosa. As such, we examined the effect of periodic spatial disturbances on the expression of QS regulated virulence genes in P. aeruginosa. qRT-PCR analysis suggests that periodic disturbances downregulate expression of QS-transcription regulators and QS-virulence effectors across major QS systems in planktonic-state cells compared to an undisturbed control. We also found that amplitude of disturbance dictated the range of frequencies at which expression of QS-transcription regulators was reduced; at an intermediate amplitude of 0.3mm, gene expression was reduced over a wider range of shaking frequencies relative to smaller and larger amplitudes. These results suggest that an optimal combination of physical forces favor this reduction in expression at intermediate shaking amplitudes. Overall, these results establish that disrupting P. aeruginosa biofilm structure affects the expression of QS-regulated genes. As such, our results suggest that combining physical disruption forces could lead to novel non-antibiotic-based approaches to mitigate pathogenesis of P. aeruginosa.