Mixed sample of bacterial cells from F. tularensis tularensis (ATCC 6223) and F. tularensis subsp. holarctica LVS (ratio 100:1). Contamination lower than 1% could be identified using appropriate probe sets. (A: FISH staining with probe EUB338-6-FAM for staining of all bacteria in liquid samples. B: Specific staining of F. tularensis subsp. holarctica).