Also see Figures S1, S2 and Table S3. (A) Cellular targets of the fluorescent dyes. The nucleic acid dye Pi enters cells with compromised membranes; DiBAC binds to intracellular lipid-containing material of depolarized cells; and SybrGreen stains the nucleic acids of all bacteria irrespective of their membrane status, identifying two clusters of cells: the low- (LNA) and high- (HNA) nucleic acid containing cells. (B) Average proportions of damaged cells (Pi+ and DiBAC+) and cells with a low (LNA) or high nucleic acid content (HNA) in three unrelated individuals (n=5–10 samples/individual). Values are mean±sem. (C) SybrGreen and Pi dual-staining in 3 unrelated individuals. Pi- cells are in grey, Pi+ cells are in pink, with the HNA (solid) and LNA (stripes) subsets indicated. (D) Pi and DiBAC dual-staining in the same individuals. Pi- cells are in grey, Pi+ cells are in purple, with the DiBAC- (stripes) and DiBAC+ (solid) fractions indicated.