Studying the effect of alginate overproduction on pseudomonas aeruginosa biofilm by atomic force microscopy

Abstract

Pseudomonas aeruginosa is the most impor tant pathogen in cystic fibrosis patients and forms biofilms in the lung. P. aeruginosa strains isol lated fe r rom the lungs of the patients have a mucoid phenotype overproducing alginate. The phenotype forms highly structured biofilms which are more resistant to antibiotics than biofilms for med by its nonmucoid phenotype. Conversion to the alginate-overproducing phenotype occurs through a mutation in rpoNgene in the strains. The biofilms formed by the alginate-overproducing phenotype are highly sticky, but their stickiness has not been measured. Herein, the stickiness of biofilms formed by the rpoN mutant was measured by atomic force microscopy (AFM). Confocal laser scanning microscopy showed that the biofilms formed by the slowly-growing rpoN mutant were more structured than those formed by the wild-type strain. AFM analysis indicated that the biofilms formed by the rpoN mutant were stickier than those formed by the wild type strain during the attachment and establishment stages, but the difference in stickiness was greatly reduced during the maturation stage possibly due to the cytosolic contents released from dead cells in the biofilms formed by the wild type. These results suggest that the alginate overproduction greatly affects the physical properties (topography and stickiness) of P. aeruginosa biofilms as well as the physiological properties (cell death and growth) of the bacterial cells inside the biofilms. Copyright © 2011 American Scientific Publishers All rights reserved.