Representative whole-cell rRNA-targeted FISH micrographs depicting major bacterial and archaeal lineages observed in production water samples from the Cook Inlet basin. (A) Members of Bacteria (green) and members of Archaea (red) in sample CIB-1. (B) Methanolobus spp. (orange) and other members of Archaea (green) in CIB-1. (C) Members of the Firmicutes (yellow-orange) and other members of Bacteria (green) in CIB-1. (D) Methanosarcina spp. (orange) and other members of Archaea (green) in CIB-2. (E) Acetobacterium spp. (red-orange) and other members of Bacteria (green) in CIB-2. (F) Members of Archaea (red) and members of Bacteria (green) in CIB-3. Probe specificities: EUBmix, all Bacteria; ARCH915, most Archaea; DAPI, general DNA stain; Mlob828, genus Methanolobus; SRB385, some Firmicutes; SARCI551, genus Methanosarcina; Aceto828, genus Acetobacterium.