Pseudomonas aeruginosa is able to colonize the respiratory mucosa and cause recu

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.

What is the purpose of the saline in the above experiment? The more detailed the answer, the better.

Explanation / Answer

The purpose of saline addition to the broth is to maintain the isotonicity of the solution. If we want to compare the number of bacteria in the test and control, we certaonly dont want to loose any cells due to tonicity difference. So the control has been mixed with saline water so that cells are placed in isotonic solution. If the cells are placed in normal water the cells will absorb water and burst out.

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