The Bacteria Diet

How Pseudomonas proves so tenacious, and why it acts so differently in Cystic fibrosis-afflicted lungs than in normal human lungs, are puzzles that Whiteley has been working to solve for more than a decade.

The relationship between Pseudomonas aeruginosa, a common bacteria that’s harmless to normal lungs, and Cystic fibrosis, a rare hereditary disease that affects the mucus glands of the lungs, is a simple one for the people who have Cystic fibrosis.

Pseudomonas infections, more than any other single cause, are responsible for killing them.

“It’s a chronic infection,” says Marvin Whiteley, an assistant professor of molecular genetics and microbiology. “If you have Cystic fibrosis, you get a Pseudomonas infection, typically, between 3-7 years old, and you maintain it for the rest of your life.

“You never get rid of it. No matter how many antibiotics you use, or how frequently you use them, you don’t eradicate the infection, and that’s ultimately what the patient succumbs to. The lungs just quit functioning.”

How Pseudomonas proves so tenacious, and why it acts so differently in Cystic fibrosis-afflicted lungs than in normal human lungs, are puzzles that Whiteley has been working to solve for more than a decade.

The answers involve, among other elements, the bacteria’s ability to merge into a “biofilm” that attaches to the surface of the lung and is resistant to antiobiotics, as well as its ability to communicate with itself, via “quorum sensing,” to know when a lung is susceptible to infection.

Whiteley’s investigation of Pseudomonas aeruginosa, which has won him numerous awards, has also taken a turn into the past. He’s trying to answer questions that were being asked by the French scientist Louis Pasteur more than a hundred years ago.

“Every bacterium that causes an infection has to eat something,” says Whiteley. “What are the bacteria growing on? What are the nutrient sources? What’s amazing is that Pasteur was asking these questions about poly-microbial infections in the late 1800s, but no one has worked on it. It’s been completely ignored.”

Learning as much as possible about what the bacteria use as a nutrient source is important, among other reasons, because the dramatic increase of certain nutrients in the mucus of the CF-afflicted lung is what likely triggers Pseudomonas aeruginosa to turn virulent in the first place.

“There are, we believe, two amino acids in particular that Pseudomonas bacteria really like,” he says. “In their presence the bacteria become very virulent much more quickly than they normally would.”

If the Pseudomonas aeruginosa bacteria can be tricked into seeing lower levels of these amino acids, says Whiteley, infection could be prevented. Even if it’s not prevented forever, there’s evidence that a delay in infection could significantly prolong the lifespan of people with Cystic fibrosis.

“Even if we prevent a Pseudomonas infection, it doesn’t mean that there’s not another bacterium in there that would take its place, but most of the other ones we can treat,” he says. “This one is intrinsically resistant to antibiotics.”