5.5 Lichens
3 min read•june 18, 2024
Lichens are fascinating examples of in nature. These organisms, formed by fungi and algae or living together, showcase the power of cooperation in the microbial world.
Lichens demonstrate how different species can work together to thrive in harsh environments. They play important roles in ecosystems, from helping create soil to cleaning the air, and even have potential uses in medicine and environmental cleanup.
Lichens
Relevance of lichens in microbiology
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Top images from around the web for Relevance of lichens in microbiology
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- Lichens classic example of symbiosis, key concept in microbiology
- Symbiosis close, long-term interaction between two or more different biological species (fungi and algae or cyanobacteria)
- Lichens demonstrate principles of mutualistic symbiosis
- type of symbiotic relationship in which both organisms benefit from interaction (protection and nutrients)
- Studying lichens helps understand complex interactions between microorganisms (fungi, algae, cyanobacteria)
- Lichens showcase adaptability and diversity of microorganisms in various ecosystems (arctic tundra, deserts, forests)
Symbiosis in lichen structures
- Lichens composed of two main components: fungal partner () and photosynthetic partner ()
- Photobiont can be either algae () or cyanobacteria ()
- Fungal partner provides protective structure called
- Thallus shields photobiont from environmental stressors like UV radiation and (drying out)
- Photobiont, either algae or cyanobacteria, performs photosynthesis
- Photosynthesis produces organic compounds that serve as food source for fungal partner (glucose, other sugars)
- Fungal partner absorbs minerals (nitrogen, phosphorus) and water from environment, which benefits photobiont
- Mutualistic relationship allows lichens to thrive in diverse and often harsh environments (rock surfaces, tree bark)
Lichen morphology and reproduction
- Lichens exhibit various growth forms:
- have a leaf-like appearance with distinct upper and lower surfaces
- form a crust-like layer tightly adhered to the substrate
- have a shrub-like or hanging structure
- Some lichens develop specialized structures:
- are hollow, upright structures found in certain lichens, often bearing reproductive structures
- Lichens reproduce through various methods:
- are small clusters of algal cells wrapped in fungal hyphae, used for asexual reproduction
- Isidia are small, coral-like outgrowths on the surface, also used for asexual reproduction
- The fungal component of most lichens belongs to the phylum , which produce spores in sac-like structures
Ecological impact of lichens
- Lichens important bioindicators of air quality
- Sensitive to air pollution, particularly sulfur dioxide and nitrogen oxides (from fossil fuel combustion)
- Presence or absence of certain species can indicate level of air pollution in an area (, )
- Lichens play crucial role in nutrient cycling in ecosystems
- Contribute to weathering of rocks, aiding in soil formation (through secretion of )
- Lichens fix atmospheric nitrogen, making it available for other organisms (especially in nutrient-poor environments)
- Lichens serve as food source and habitat for various animals, including invertebrates (mites, springtails) and mammals (reindeer, caribou)
- Some lichen species used in traditional medicine for their antimicrobial and anti-inflammatory properties (, )
- Lichens have potential applications in
- Can accumulate heavy metals (lead, cadmium) and other pollutants, helping to clean up contaminated sites (abandoned mines, industrial areas)
Key Terms to Review (38)
Ascomycetes: Ascomycetes are a class of fungi that produce spores within a sac-like structure called an ascus. They are the largest and most diverse group of fungi, known for their important roles in ecosystems, agriculture, and industry.
Bioindicator: A bioindicator is an organism or a community of organisms that provides information about the environmental conditions of a particular habitat or ecosystem. These organisms are sensitive to changes in their environment and can be used to monitor the overall health and quality of an ecosystem.
In the context of lichens, bioindicators are particularly useful in assessing air quality and pollution levels, as lichens are highly sensitive to various environmental stressors.
Bioremediation: Bioremediation is the use of living organisms, such as microbes or plants, to degrade, transform, or remove environmental contaminants from a polluted site. It is a natural process that harnesses the metabolic capabilities of these organisms to clean up and restore contaminated ecosystems.
Cetraria islandica: Cetraria islandica, commonly known as Iceland moss, is a lichen species that belongs to the genus Cetraria. Lichens are composite organisms formed by a symbiotic relationship between a fungus and an algae or cyanobacteria. Cetraria islandica is a foliose lichen, meaning it has a leaf-like, flattened growth form.
Cortex: The cortex is the outermost layer of a lichen's thallus, providing protection and structural support. It is typically composed of tightly packed fungal hyphae.
Crustose: Crustose refers to a type of lichen growth form that appears as a thin, flat, and tightly adhering crust on the surface of rocks, tree bark, or other substrates. Crustose lichens are considered the most primitive and simplistic growth form among lichens.
Crustose lichens: Crustose lichens are a type of lichen characterized by their crust-like, tightly adhering growth form. They grow flat against their substrate, such as rocks or tree bark, making them difficult to remove without damaging the substrate.
Cyanobacteria: Cyanobacteria are a group of photosynthetic, gram-negative bacteria found in various aquatic environments. They play a significant role in oxygen production and nitrogen fixation.
Dermatophytes: Dermatophytes are a group of fungi that cause infections in keratinized tissues such as skin, hair, and nails. They are responsible for common fungal infections like athlete's foot and ringworm.
Desiccation: Desiccation refers to the process of extreme drying or dehydration, where an organism or material loses a significant amount of its water content. This term is particularly relevant in the context of lichens and physical methods for controlling microorganisms.
Epiphytes: Epiphytes are plants that grow on other plants, deriving moisture and nutrients from the air, rain, and sometimes debris accumulating around them. They do not parasitize their host plant.
Foliose: Foliose is a term used to describe a specific type of lichen growth form that resembles a leaf or foliage. These lichens have a flattened, leaf-like appearance and are typically attached to the substrate by a central point or short stalk.
Foliose lichens: Foliose lichens are a type of lichen with a leaf-like, flat structure that grows parallel to the substrate. They have distinct upper and lower surfaces and can often be seen loosely attached to their substrate.
Fruticose: Fruticose refers to a type of lichen growth form that is characterized by a shrub-like, branched, or tufted appearance. These lichens have a distinct, three-dimensional structure that protrudes from the substrate, often resembling miniature trees or bushes.
Fruticose lichens: Fruticose lichens are a type of lichen characterized by their bushy, branched, and often shrub-like appearance. They attach to substrates at a single point and can grow vertically or pendulously.
Hypogymnia physodes: Hypogymnia physodes, also known as the monk's hood lichen, is a foliose lichen species that is commonly found growing on the bark of trees and on rocks. It is a symbiotic relationship between a fungus and an algae, forming a unique organism with distinctive features.
Isidium: An isidium is a small, coralloid, or granular outgrowth from the surface of a lichen thallus that can function as a means of vegetative reproduction. Isidia are specialized structures that allow lichens to propagate and spread without the need for sexual reproduction.
Lecanora conizaeoides: Lecanora conizaeoides is a species of lichen that is commonly known as the 'pollution lichen' due to its ability to thrive in areas with high levels of air pollution. As a lichen, it is a symbiotic relationship between a fungus and an algae or cyanobacteria.
Lichen: Lichens are symbiotic associations between a fungus and a photosynthetic partner, usually algae or cyanobacteria. They play crucial roles in ecosystems as bioindicators and pioneers in soil formation.
Lichen: Lichens are composite organisms that form a symbiotic relationship between a fungus and an algae or cyanobacteria. They are found in a wide variety of habitats and play important ecological roles.
Lichen Acids: Lichen acids are a diverse group of secondary metabolites produced by lichens, which are symbiotic organisms composed of a fungus and an algae or cyanobacteria. These acids play crucial roles in the ecology and physiology of lichens.
Medulla: The medulla is the innermost layer of a lichen's thallus, consisting of loosely packed fungal hyphae. It plays a crucial role in nutrient storage and water retention.
Mutualism: Mutualism is a type of symbiotic relationship where both organisms involved benefit from the interaction. In microbiology, mutualistic relationships often involve microorganisms and their hosts providing essential nutrients or protection.
Mutualism: Mutualism is a type of symbiotic relationship in which both organisms involved derive a clear benefit from the interaction, often through the exchange of resources or services. This mutually beneficial relationship is essential in various ecological contexts, including prokaryote habitats, lichen formation, and the normal microbiota of the urogenital tract.
Mycobiont: The mycobiont is the fungal component of a lichen, a symbiotic association between a fungus and a photosynthetic partner, typically an alga or cyanobacterium. The mycobiont provides the structural framework and protection for the lichen, while the photosynthetic partner supplies the mycobiont with carbohydrates produced through photosynthesis.
Nostoc: Nostoc is a genus of cyanobacteria, also known as blue-green algae, that are found in a wide variety of environments. These photosynthetic microorganisms play important roles in both the topics of Nonproteobacteria Gram-Negative Bacteria and Phototrophic Bacteria, as well as Lichens.
Parasitism: Parasitism is a symbiotic relationship where one organism (the parasite) benefits at the expense of another organism (the host). This interaction often leads to harm or disease in the host.
Photobiont: A photobiont is a photosynthetic partner in a symbiotic relationship, such as the one found in lichens. It is the component of the lichen that is responsible for producing food through photosynthesis, providing the other partner, the mycobiont, with essential nutrients.
Podetia: Podetia are the stalk-like structures that support the reproductive structures in certain lichens. These elongated, often branched structures emerge from the main body of the lichen, known as the thallus, and serve as platforms for the development and dispersal of the lichen's spores.
Rhizines: Rhizines are root-like structures found in lichens that anchor the thallus (body) to the substrate. They do not absorb water or nutrients but provide stability.
Ringworm: Ringworm is a common fungal infection of the skin caused by dermatophytes. It presents as a red, circular rash with clearer skin in the middle.
Sabouraud’s agar: Sabouraud's agar is a specialized fungal growth medium used to cultivate dermatophytes and other types of fungi. It has a slightly acidic pH, which inhibits bacterial growth while promoting fungal development.
Soredia: Soredia are small, powdery dispersal units found on the surface of some lichens. They consist of a bundle of algal cells surrounded by fungal hyphae, allowing the lichen to reproduce asexually and colonize new substrates.
Symbiosis: Symbiosis refers to the close and often long-term interaction between two or more different organisms, where at least one organism benefits from the relationship. This term is central to understanding the complex relationships that exist among various microorganisms, as well as between microbes and their host organisms, in the context of the topics 1.3 Types of Microorganisms, 4.1 Prokaryote Habitats, Relationships, and Microbiomes, 5.3 Fungi, and 5.5 Lichens.
Thallus: A thallus is a plant body that lacks true roots, stems, and leaves, and is typically undifferentiated into distinct organs. It is a characteristic feature of certain groups of organisms, such as algae and lichens.
Trebouxia: Trebouxia is a genus of green algae that forms a symbiotic relationship with fungi to create lichens. As the photobiont partner in this symbiosis, Trebouxia provides the photosynthetically produced carbohydrates that the fungus relies on for nutrition and growth.
Trichophyton rubrum: Trichophyton rubrum is a dermatophytic fungus that causes common skin infections such as athlete's foot, jock itch, and ringworm. It thrives in warm, moist environments and primarily affects keratinized tissues like skin, nails, and hair.
Usnea barbata: Usnea barbata, commonly known as old man's beard, is a species of lichen that belongs to the Parmeliaceae family. It is a fruticose lichen, meaning it has a shrubby, branching growth form, and is often found hanging from the branches of trees in temperate and boreal forests.