AUTHOR=Subramoni Sujatha , Muzaki Muhammad Zulfadhly Bin Mohammad , Booth Sean C. M. , Kjelleberg Staffan , Rice Scott A. 

TITLE=N-Acyl Homoserine Lactone-Mediated Quorum Sensing Regulates Species Interactions in Multispecies Biofilm Communities

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=11

YEAR=2021

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2021.646991

DOI=10.3389/fcimb.2021.646991

ISSN=2235-2988

ABSTRACT=<p>Bacterial biofilms are important medically, environmentally and industrially and there is a need to understand the processes that govern functional synergy and dynamics of species within biofilm communities. Here, we have used a model, mixed-species biofilm community comprised of <italic>Pseudomonas aeruginosa</italic> PAO1, <italic>Pseudomonas protegens</italic> Pf-5 and <italic>Klebsiella pneumoniae</italic> KP1. This biofilm community displays higher biomass and increased resilience to antimicrobial stress conditions such as sodium dodecyl sulfate and tobramycin, compared to monospecies biofilm populations. <italic>P. aeruginosa</italic> is present at low proportions in the community and yet, it plays a critical role in community function, suggesting it acts as a keystone species in this community. To determine the factors that regulate community composition, we focused on <italic>P. aeruginosa</italic> because of its pronounced impact on community structure and function. Specifically, we evaluated the role of the N-acyl homoserine lactone (AHL) dependent quorum sensing (QS) system of <italic>P. aeruginosa</italic> PAO1, which regulates group behaviors including biofilm formation and the production of effector molecules. We found that mixed species biofilms containing <italic>P. aeruginosa</italic> QS mutants had significantly altered proportions of <italic>K. pneumoniae</italic> and <italic>P. protegens</italic> populations compared to mixed species biofilms with the wild type <italic>P. aeruginosa</italic>. Similarly, inactivation of QS effector genes, e.g. <italic>rhlA</italic> and <italic>pvdR</italic>, also governed the relative species proportions. While the absence of QS did not alter the proportions of the two species in dual species biofilms of <italic>P. aeruginosa</italic> and <italic>K. pneumoniae</italic>, it resulted in significantly lower proportions of <italic>P. aeruginosa</italic> in dual species biofilms with <italic>P. protegens</italic>. These observations suggest that QS plays an important role in modulating community biofilm structure and physiology and affects interspecific interactions.</p>