Lichens are extraordinary symbiotic organisms that survive where each of their composite species wouldn’t survive on their own. The dominant species is a fungus – a consumer or decomposer organism – that partners with algae or cyanobacteria (sometimes both). Most lichens grow very, very slowly – often less than a millimeter per year, and some lichens are thought to be among the oldest living things on Earth. This article has more information about lichens: Lichen biology
Another type of symbiosis has recently been discivered between cacti and bacteria, that enables the cactus to survive in some of the earth’s harshest environments. These cacti can colonise sheer rock faces due to the presence of bacteria that release rock-dissolving chemicals.
How cacti become rock busters