FIG. 10.

Detection of microorganisms within environmental samples by fluorescent dye labeling. (A) Bacillus subtilis in soil labeled with violet-fluorescent wheat germ agglutinin Gram-positive-specific cell wall stain. (B) Arctic biofilm (predominantly Thiomicrospira) stained with SYTO-9, a bacterial stain for nucleic acids. The green is the SYTO-9; the yellow matrix represents sulfur minerals. (C) Microorganisms in a gypsum endolith labeled with carboxyfluorescein diacetate, a probe for esterase activity that does not label dead cells. (D) Green-fluorescent wheat germ agglutinin labeling fungal hyphae in a Mojave Desert endolith. The red fluorescence is chlorophyll autofluorescence from photosynthetic cyanobacteria within this microbial community.