Microcolonial Fungi Adapt to Extreme Conditions

a bright orange peel fungi grows on a tree trunk

Biological Strategy

Ascomycota

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Protect From Temperature

Many living systems function best within specific temperature ranges. Temperatures higher or lower than that range can negatively impact a living system’s physiological or chemical processes, and damage its exterior or interior. Living systems must manage high or low temperatures using minimal energy, which often requires controlling responses along incremental temperature changes. To do so, living systems use a variety of strategies, such as avoiding high or low temperatures, removing excess heat, and holding heat in. Insulation is a well-known example of managing low temperatures by retaining heat using thick layers of hair, fur, or feathers to hold warm air next to the skin.

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Fungi

Kingdom Fungi: Mildews, molds, mushrooms, rusts, smuts, and yeasts

Once thought to be more closely related to plants, fungi have been found to contain chitin in their cell walls, indicating a closer evolutionary relationship to animals. Fungi are decomposers, using digestive enzymes to break down their surroundings, making them an essential part of ecosystems worldwide, as new soil is formed from rotting matter. Almost all fungi reproduce through spores (mushrooms, molds) or asexual budding (some yeast). There are estimated to be more than 2 million species, but only about 140,000 have been described. Fungi have great importance in culture, food, and medicine (including being the source of penicillin) worldwide.

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Free-living ascomycetes growing in colonies can spread into the extremely hostile environments including deserts because they possess extracellular polymeric substances and other adaptations.

“Rock-inhabiting MCF [microcolonial fungi] endure sudden changes in the environment by rapidly adapting their metabolic activity, life style and survival structures to the new conditions. Ultrastructural peculiarities of these fungi suggest spore-like metabolism and protection (Fig. 6) although MCF do not propagate sexually (Gorbushina, 2003; Gorbushina et al., 2003). Relevant characteristics of poikilo-tolerant MCF include: (i) the capacity to survive long periods of suspended metabolism. In this way, they can remain as colonies made up of pseudo tissue-like microcolonies comprising 100–500 cells for several decades until conditions favourable to further growth return; (ii) the ability to re-organize internally by constantly replacing dying or dead cells with new buds (Gorbushina et al., 2003) and Fig. 6C; (iii) the ability to form filamentous hyphae that develop from clump-like colonies (Fig. 5E) to penetrate deep into rocks thus protecting themselves from environmental stresses. In this sense, the visible portion of melanized MCF is like the tip-of-the-iceberg, because the hyphae can rapidly penetrate several mm to cm into hard rocks in search of more protected environments and; (iv) the ability to create a multitude of varnish-like coatings, skins and shells that arise from the impregnation of the extracellular matrix and melanin layers with minerals (Dragovich, 1984; 1993; 1998; Gorbushina, 2003).” (Gorbushina 2007:1619-1620)