S100A9 and pneumococcal pneumonia: Here we show that S100A8/A9 plays an important role in lowering concentrations of divalent metal ions in defined pneumococcal growth experiments in vitro, and that deficiency of S100A9 (and thus of heterodimeric S100A8/A9) was accompanied by increased levels of divalent metal ions in pneumococcal pneumonia, leading to bacterial outgrowth.