Pseudomonas aeruginosa alginate overproducing mucoid strain displayed dominancy in mixed community biofilms.

Pseudomonas aeruginosa is an opportunistic pathogen that causes chronic respiratory infections in cystic fibrosis (CF) patients. Mucoid strains are characterized by over-production of alginate and make significant contributions to the severity of lung infection in CF patients. In addition to the clinical significance of alginate production, alginate is also known to facilitate biofilm production by P. aeruginosa. Alginate production in P. aeruginosa was first reported in 1966, and has been well studied in terms of its role in lung infection and biofilm formation. However, there are no current reports on the role of alginate and its mucoid phenotype within mixed (dual or triple species) community biofilms. Interaction behaviours of over-producing alginate mucoid strain were hence studied under planktonic and continuous-culture flow cell biofilm. In this study, it was observed that the mucoid strain was able to not only co-exist with, but also to out-compete and dominate in the mixed community against Pseudomonas protegens, and Klebsiella pneumonia. In contrast, the wild-type, non-mucoid P. aeruginosa comprised a minor component,