Bifidobacterium sp. bacteria stained with the ViaGram™ Red+ Bacterial Gram Stain and Viability Kit (Cat. No. V7023). While all cells exhibit a red-fluorescent surface stain (gram-positive), live cells exhibit blue-fluorescent internal staining and dead cells with compromised membranes exhibit yellow-green–fluorescent internal staining. This image was obtained by taking multiple exposures through bandpass optical filter sets appropriate for DAPI, fluorescein and Texas Red® dye.