Question

Pseudomonas aeruginosa is able to colonize the respiratory mucosa and cause recurring pneumonia in cystic fibrosis patients. The following experiments were performed to determine how P. aeruginosa can colonize mucous membranes. 0.1 mL broth culture was added to 0.4 mL serum and incubated for 1 hour; 0.1 mL of the same broth culture was added to 0.4 mL isotonic saline and incubated for 1 hour. Plate counts were performed on 1-mL samples to determine the number of bacteria. Immunoelectrophoresis was then used to compare normal serum to the serum incubated with Serratia and Pseudomonas.

Please a possible explanation for the ability of Pseudomonas to colonize mucous membranes.

Answer 1

Pseudomonas aeruginosa move through water and mucous by using its polar flagellum and chemotaxis and make contact with body's mucous membranes. Then they use pili and adhesins to attach to the epithelial cells of the mucous membrane. Attachment activates signalling and quorum sensing genes to eventually them to start synthesising an alginate biofilm. While the biofilm grows, bacteria lose their flagella to become nonmotile and secrete a variety of enzymes that enable them to derive nutrients from the host cells. Eventually, the biofilm develops water channels to deliver water and nutrients to all the bacteria within the biofilm. As the biofilm begins to get too crowded with bacteria, quorum sensing enables some of the Pseudomonas to produce flagella again, escape the biofilm, and colonise a new location.