Streptococcus pneumoniae is a main cause of bacterial pneumonia worldwide. It can also cause ear and sinus infections and, in more severe cases, meningitis or sepsis. It shares the human respiratory tract with many closely related bacterial species. Among them is Streptococcus mitis, a common member of the microbiome that can remain with us for a long time without causing harm. A new study, published in the mBio journal, shows that these bacteria do not simply coexist, they actively compete.