Substances produced by a harmful bacterium in the lungs of cystic fibrosis patients may enhance the growth of other bacteria that, in turn, inhibit the harmful bacterium’s biofilm, according to new research published in PLOS Pathogens.

To better understand the role of streptococci in cystic fibrosis, Jessica Scoffield of the University of Alabama at Birmingham and colleagues grew several biofilms in dishes and in fruit flies. Each biofilm consisted of a P. aeruginosa strain and a streptococcus strain. The researchers used molecular and microscopy techniques to observe interactions between the bacteria.

The scientists found that a carbohydrate substance known as alginate, produced by a particular strain of P. aeruginosa known as FRD1, promotes the biofilm of the streptococcus species Streptococcus parasanguinis. At the same time, biofilm formation by S. parasanguinis restricts biofilm formation by P. aeruginosa—in line with previous studies.