Scientist have begun to realize that many types of bacteria often live together as a complex community, and the investigators wish to apply that idea to the bacteria in the respiratory system of people with Cystic Fibrosis (CF). It is possible that the survival of the many millions of bacteria in the CF lung depends on the production of special chemicals that might be made only by very few types of bacteria. If that is true, medicines that interfere with those chemicals could treat the lung infections that cause trouble for nearly all people with CF. The investigators wish to study the production of several potentially critical chemicals by the respiratory bacteria and to examine the effect of those chemicals on the makeup of the entire community of bacteria. To detect all the bacteria in that community, the investigators will use new methods that use bacterial genetic information and can detect hundreds of different types of bacteria in respiratory samples of individual CF patients.