Detection of bacteria by acridine orange and FISH in Cladonia arbuscula (diagonal sections of inner surface, CLSM images). (a) Acridine orange: bacterial cells are yellow-orange particles. (b) EUB338MIX-Cy3 and HGC236-Cy5 bacterial FISH probes: Actinobacteria are yellow objects, and other bacterial cells are red. Scale bars are 15 μm.