Structural Components of Lichen

The symbiotic association found in lichens is classified as a controlled parasitism. In this relationship, the fungal partner benefits by obtaining nutrients, while the photosynthetic alga or cyanobacterium is harmed or restricted in its growth.

Lichen Symbiotic Relationship

Lichens play crucial ecological and practical roles despite being nonpathogenic to humans. Ecologically, they act as early colonizers that break down rock to produce soil, stabilize desert soils, and serve as a vital winter food source for caribou. In some lichens, cyanobacterial partners fix nitrogen, enriching the environment. Humans utilize slow-growing, long-lived lichens in food, as dyes, as environmental indicators of pollution due to their sensitivity, and to extract antibacterial compounds that hold potential medical value.

Ecological and Human Roles of Lichens

Lichens are taxonomically classified as fungi, and their fungal components predominantly belong to the phyla Ascomycota and Basidiomycota.

Fungal Partners of Lichens

Lichens are categorized into three primary growth forms based on their morphology: crustose lichens, which are tightly attached to their substrate and have a crust-like appearance; foliose lichens, which feature leaf-like lobes and are attached at a single point; and fruticose lichens, which have rounded, branched structures.

Types of Lichens

Lichens are symbiotic associations between a fungus and a photosynthetic partner, which can be either an alga or a cyanobacterium. They are characteristically slow-growing organisms that can survive for centuries in a variety of habitats.

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Fungi are a diverse group of saprotrophic eukaryotic organisms with cell walls containing chitin. They can be unicellular or multicellular, with some forms (such as yeasts and reproductive spores) being microscopic, while others are large and conspicuous.

Fungi

Historically, protists have been informally categorized into three distinct groups based on their characteristics: the animal-like protozoans, the plant-like algae, and the fungus-like protists (such as water molds).

Groups of Protists

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Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

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Fungus


A mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground, on soil, or on its food source.

The standard for the name "mushroom" is the cultivated white button mushroom, Agaricus bisporus; hence the word "mushroom" is most often applied to those fungi (Basidiomycota, Agaricomycetes) that have a stem (stipe), a cap (pileus), and gills (lamellae, sing. lamella) on the underside of the cap.

Mushroom

Mycology

- Hyphae
- Pseudophyphae
- Dimorphic Fungi
-  Chitin

Physical Characteristics of Different Fungi

Fungi can reproduce both sexually and asexually. The specific reproductive types and mechanisms they employ are key characteristics used to distinguish different fungal groups.

Reproduction of Fungi

Fungi is a diverse kingdom that can be broken down into seven phyla:
- Ascomycota
- Basidiomycota
- Blastocladiomycota
- Chytridiomycota
- Glomeromycota
- Microsporidia
- Neocallimastigomycota

Fungal Diversity 

Yeasts are a type of unicellular fungi that are included in the study of microbiology. There are over $${}1000$$ known species that exist in a wide variety of environments, ranging from the deep sea to the human body. While some yeasts have beneficial applications, such as causing bread to rise and facilitating beverage fermentation, they can also cause food spoilage and lead to human diseases, such as oral thrush and vaginal yeast infections.

Yeasts

Molds are multicellular fungi consisting of long filaments that combine to form visible colonies. They are ubiquitous in diverse environments, such as soil, rotting food, and damp indoor spaces, and they serve an essential ecological role in decomposing dead plants and animals. While some molds can cause allergies or produce disease-causing metabolites called mycotoxins, others have critical pharmaceutical uses, such as the production of the antibiotic penicillin and the immunosuppressant cyclosporine used to prevent organ rejection.

Molds

Fungi play vital roles as environmental decomposers and are critical for the production of certain foods, such as cheeses.

Human and Ecological Importance of Fungi

Fungi are included in the field of microbiology because, despite the existence of macroscopic structures like mushrooms and molds, many unicellular yeasts and the reproductive spores of macroscopic fungi are microscopic.

Fungi in Microbiology

Fungi have significant medical relevance; while some pathogenic species cause mycoses, others are opportunistic pathogens that lead to infections primarily when the host's immune system is compromised. Conversely, fungi are also medically beneficial as major sources of antibiotics, such as penicillin.

Medical Relevance of Fungi

Urediniomycetes is a class of fungi that includes plant rusts, which form reddish masses on plants and can cause significant economic damage by reducing crop yields.

Urediniomycetes

Ustilagomycetes is a class of fungi that includes plant smuts, which form dark masses on plants and can cause substantial economic loss by reducing crop yields.

Ustilagomycetes

Lichens

Protozoans are nonphotosynthetic, motile, unicellular eukaryotic organisms that inhabit diverse aquatic and terrestrial environments. While many live independently as free-living organisms, others are parasitic pathogens that cause disease in hosts, or beneficial symbionts that assist their hosts with metabolic functions.

"Animal-Like" Protozoans

Algae are autotrophic protists, existing as either unicellular or multicellular organisms, that play a key ecological role by producing approximately 70% of the oxygen and organic matter in aquatic environments.

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