The Nikon MicroscopyU confocal microscopy image gallery was created with a PCM-2000 confocal scanning system interfaced to a Nikon Eclipse E600 upright microscope. Images were recorded in successive z-axis serial sections with C-Imaging Systems software with excitation illumination provided by an argon-ion and/or a helium-neon laser.

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View a second confocal sequence of lichen thallus.

Lichen is an organism that results from intimate cooperation between two distinct life forms, fungi and algae. This tough and hardy partnership can live where nothing else will grow -- even on bare rock. Lichens can actually eat stones, survive severe cold or hot climates, and remain dormant for long periods of time without harm. Although each organism is able to thrive independently, certain types of inhospitable environments require that they cooperate in a mutually beneficial relationship in order to survive. The resulting intertwined life support system allows lichens to be the first to colonize harsh exposed areas such as solidified lava flows, dry rock surfaces, and the polar regions. The partnership created by fungi and algae is sometimes joined by a species of blue-green bacteria (known as cyanobacterium) that has photosynthetic ability.

Although unable to directly convert sunlight into food, fungi are able to absorb water and minerals. This is accomplished through the vast system of thread-like filaments that form extensive networks referred to as mycelium. In addition to secreting enzymes to break down organic matter, some species of fungi produce acids that release minerals from rock. Rootless algae, however, contain chlorophyll cells and are able to manufacture useful carbohydrates in the process of photosynthesis. The fungus receives much of its nutrient requirement from the algae. In return, the fungus spreads to envelop the algae cells between interlacing fibrous networks that provide the algae with moisture and protection from evaporation.

The cells of the algae and the fungus remain distinct and do not intermix genetic material, however, without the their combined efforts, each would cease to exist in harsh environments. The species of fungus, and not the algae, determines the shape and appearance of the resulting lichen.