Vital dye reaction and granule localization in periplasm of Escherichia coli.
Tetrazolium salts are widely used in biology as indicators of metabolic activity - hence termed vital dyes - but their reduction site is still debated despite decades of intensive research.The prototype, 2,3,5- triphenyl tetrazolium chloride, which was first synthesized a century ago, often generates a single formazan granule at the old pole of Esc