Fungi: Diversity and Systematics

Fungi from Different Environments

• Fungi are diverse and found in various environments.
• Diverse types of fungi are shown in images.

Fungi Systematics

• Fungi are typically categorized into five divisions.
• Glomeromycota, Chytridiomycota, Zygomycota, Ascomycota, and Basidiomycota are the main divisions.
• Anamorphic fungi represent a group of fungi that lack sexual reproduction and are not considered formal taxonomic divisions. This group encompasses fungi that have lost their ability for sexual reproduction.
• The diverse characteristics of these fungi categorize them as a separate group.

Fungi Practical Section

• Fungi are eukaryotic, non-motile organisms.
• Their cell walls are composed of chitin; they lack chlorophyll, and reproduce through spores.
• Spores may be formed in either sexual or asexual processes.
• Most fungi are saprophytes, breaking down organic matter.
• These organisms play a crucial role in waste decomposition.
• A minority of fungi can cause diseases in plants and animals.
• Among the vast array of fungal species, only a limited number cause human infections.

Characteristic Features of Fungi

• Fungi emerged roughly 800 million years ago.
• They are eukaryotic and heterotrophic, including saprophytes, parasites, and symbionts.
• Fungi cells contain nuclei, mitochondria, Golgi apparatus, and reserve substances such as glycogen and fats.
• Fungi are ubiquitous, inhabiting various environments like air, water, soil, skin, and plant debris.

Additional Characteristic Features of Fungi

• Fungi thrive in aerobic and some anaerobic conditions (like yeasts), mostly existing as mesophiles (optimum growth at 25-30°C).
• However, their growth spans a temperature range from -12°C to +68°C.
• The water content in their substrate for growth is critical, within 11% to 14%.
• They typically favor a pH range of 5-6, though some can tolerate a wider range of 1-10.
• Osmotic pressure above 10% in the growth substrate also influences their growth.
• Light has little impact on fungal growth, although some exhibit phototropism (as in Mucor and Rhizopus).
• Fungi may occasionally produce mycotoxins like aflatoxin B1.

Characteristic Features: Morphology

• Fungi exhibit two main morphological forms: yeast (unicellular) and molds (filamentous).
• Molds usually have a mycelium, which is made up of a network of hyphae.

Characteristic Features: Cell Wall

• Fungi cell walls predominantly consist of polysaccharides like β-glucans and cellulose, along with aminopolysaccharides, chitin, and chitosan.
• Proteins and lipids are structurally linked with these polysaccharides.
• Cell wall pigments vary in color, from colorless to black.
• Cell walls also contain various enzymes involved in substrate decomposition and synthesis.

Characteristic Features: Types of Mold Mycelium

• Mold mycelium can be categorized into two types: air mycelium (used for reproduction) and nutrient mycelium (used for absorption of nutrients).

Typical Microbiome of Polish Soil

• Common fungal types include Penicillium, Aspergillus, Trichoderma, Rhizopus, Mucor, Beauveria, Gliocladium, Humicola, Acremonium, Myrothecium, Paecilomyces, Trichothecium, Fusarium, Alternaria, Rhizoctonia, and Botrytis, among others.

Glomeromycota - Mycorrhizal Fungi

• Glomeromycota form arbuscular mycorrhizae, which are symbiotic structures that increase plant nutrient uptake. Mycorrhizal fungi have their hyphae enter the cortical cells of the plant roots.
• They are typically symbionts, lacking in sexual reproduction, and primarily reproducing through thick-walled chlamydospores.

Zygomycota - Rhizopus sp.

• Rhizopus is a group of saprophytic (decomposers) and pathogenic (disease-causing) fungi that are common in the family Rhizopodaceae.
• Members of this genus are often used in various industrial processes.
• Rhizopus oryzae plays a role in producing lactic acid, bio-absorbing heavy metals, generating enzymes like chitinase and lipase, creating surfactants, and performing alcoholic fermentation.
• This species also produces fumaric acid and biotin.

Rhizopus sp. - Reproduction

• Rhizopus reproduction involves both asexual and sexual stages.
• Asexual reproduction creates sporangiospores; sexual reproduction forms a zygospore via the process of plasmogamy, karyogamy, and meiosis.

Ascomycota - Penicillium and Aspergillus

• These are filamentous fungi known for widespread distribution.
• Many species are well-known saprophytes. Some also act as pathogens.
• Certain species produce antibiotics (like penicillin) and toxic compounds (mycotoxins).
• These fungi are used in biotechnology processes, including cheese-making, antibiotic production, and organic acid production. They also participate in degrading organochlorine compounds and producing helpful enzymes.

Ascomycota - Trichoderma sp.

• Trichoderma are soil-borne, green spore-producing fungi, widely adapted.
• Trichoderma fungi are known for their role in diverse environments and rapid growth traits, making them useful for research.
• Trichoderma exhibit natural resistance to various harmful compounds, production of enzymes, and generation of antimicrobial compounds.

Interaction of Trichoderma & Penicillium

• Trichoderma and Penicillium have interaction in nature, which can be seen in a petri dish experiment. Growth of fungi can be assessed to demonstrate interactions.

Ascomycota - Reproduction

• Ascomycota fungi show two types of reproduction: asexual and sexual.
• Asexual methods involve the creation of conidiospores from conidiophores for reproduction.
• Sexual reproduction occurs via specialized structures to produce ascospores inside asci.

Ascomycota - Yeasts

• Certain yeasts belong to Ascomycota, exhibiting single-celled morphology with round shapes.
• Yeast cell walls are often made of hemicellulose.

Saccharomyces cerevisiae (yeast)

• Saccharomyces cerevisiae is a crucial yeast, used in fermentation (alcohol production), baking, and diverse dietary supplements.
• This species is a significant model organism in biological research because its genome shares similarities with the human genome. This species is also used to manufacture medications like insulin and vaccines, and it is a prominent model in analyzing neurodegenerative disorders.
• S. cerevisiae is also a useful probiotic used in certain health treatments.

Saccharomyces cerevisiae - Reproduction

• S. cerevisiae primarily reproduces asexually via budding, where a new cell develops as a bud from the mother cell.
• Sexual reproduction occurs with the formation of the ascus containing ascospores through the process of fusion, karyogamy, and meiosis.

Anamorphic Fungi

• Anamorphic fungi are a heterogeneous group of fungi characterized solely by asexual reproduction. These fungi reproduce through conidia and chlamydospores.
• The majority of these fungi display mycelium organization that is divided into three groups, namely Hyphomycetes, Agnomycetes, and Coelomycetes.
• Many species fulfill roles like decomposition (saprophytes), plant parasitism, or human and animal disease induction.

Anamorphic Fungi - Geotrichum candidum

• Geotrichum candidum is a soil-borne fungus that is found in association with humans.
• It is a saprophyte that occurs in a variety of locations, including soil, fruits, vegetables, and the digestive or respiratory tracts of humans.
• This species produces enzymes, like lipase, and acts as a cheesemaking component (e.g., in Camembert cheese).

Anamorphic Fungi - Fusarium sp.

• Fusarium species are widely distributed in soil and frequently associated with plant life.
• As saprophytic fungi, some species cause plant diseases.
• Fusarium species are recognized for the production of mycotoxins.
• Macroconidia have a distinct shape and structure, playing a role in Fusarium identification.

Meaning of Fungi

• Fungi participate in various essential ecological and industrial processes.
• These organisms break down organic matter in soil, enhancing nutrient cycling.
• Fungi also have significant industrial applications, including antibiotic production, organic acid generation, cheese manufacturing, and alcohol production.

Additional Roles of Fungi

• Fungi engage in symbiotic relationships such as mycorrhizae, enhancing nutrient absorption in plants or aiding in animal digestion.
• Some fungi are parasites, causing infections in both plants and animals, which are known as mycoses. This can lead to spoilage of food products, like milk and other perishable products.

Explore the fascinating world of fungi found in different environments and their systematic classification. This quiz covers the five main divisions of fungi, their unique characteristics, and their ecological roles. Test your knowledge on their structure, reproduction, and significance in waste decomposition.