Fungal Biodiversity
Prof. Dr. Kalaivani Nadarajah • The characteris+cs of fungi • The evolu+on of the fungi • Fungal classifica+on • Fungal life cycles
The Characteris,cs of Fungi • Body form – unicellular – filamentous (tube-‐like strands called hypha (singular) or hyphae (plural) – mycelium = aggregate of hyphae – sclero,um = hardened mass of mycelium that generally serves as an overwintering stage. – mul,cellular, such as mycelial cords, rhizomorphs, and fruit bodies (mushrooms)
fruiting bodies
both are composed of hyphae
mycelium
The Characteris,cs of Fungi • Heterotrophy -‐ 'other food' – Saprophytes or saprobes -‐ feed on dead ,ssues or organic waste (decomposers) – Symbionts -‐ mutually beneficial rela,onship between a fungus and another organism – Parasites -‐ feeding on living ,ssue of a host. • Parasites that cause disease are called pathogens.
Heterotrophic by Absorp,on • • • •
Fungi get carbon from organic sources Hyphal ,ps release enzymes Enzyma,c breakdown of substrate Products diffuse back into hyphae
Nucleus hangs back and “directs”
Product diffuses back into hypha and is used
Hyphae • Tubular • Hard wall of chi,n • Crosswalls may form compartments (± cells) • Mul,nucleate • Grow at ,ps
Hyphal growth • Hyphae grow from their ,ps • Mycelium = extensive, feeding web of hyphae • Mycelia are the ecologically ac,ve bodies of fungi This wall is rigid
Only the tip wall is plastic and stretches
Modifica,ons of hyphae
Fungi as Saprobes and Decomposers
Fungi as Symbionts (Mutualism)
Mycorrhizae • “Fungus roots” • Mutualism between: – Fungus (nutrient & water uptake for plant) – Plant (carbohydrate for fungus)
• Several kinds – Zygomycota – hyphae invade root cells – Ascomycota & Basidiomycota – hyphae invade root but don’t penetrate cells
• Extremely important ecological role of fungi!
“Ecto”mycorrhizae
Russula mushroom mycorrhizas on Western Hemlock root
Fungal hyphae around root and between cells
Mycorrhiza cross sections
Lichens • “Mutualism” between – Fungus – structure – Alga or cyanobacterium – provides food • Three main types of lichens: – Crustose lichens form flat crusty plates. – Foliose lichens are leafy in appearance, although lobed or branched structures are not true leaves. – Fru+cose lichens are even more finely branched and may hang down like beards from branches or grow up from the ground like ,ny shrubs.
Lichen internal structure
Lichens are nature’s biological monitors of pollution and air quality • Thalli act like sponges • Some species more sensitive to pollution • Which species are present can indicate air quality • Most resistant species can also be analyzed for pollutants, including bioaccumulation of heavy metals and radioactive isotopes
Lobaria
Fungi as Parasites & Pathogens
Fungi are Spore-‐ific!!! • Spores -‐ asexual (product of mitosis) or sexual (product of meiosis) in origin. • Purpose of Spores – Allows the fungus to move to new food source. – Resistant stage -‐ allows fungus to survive periods of adversity. – Means of introducing new gene,c combina,ons into a popula,on
Reproduce by spores • Spores are reproduc,ve cells – Sexual (meio,c in origin) – Asexual (mito,c in origin)
• Formed: – Directly on hyphae – Inside sporangia – Frui,ng bodies
Penicillium hyphae with conidia Pilobolus sporangia Amanita fruiting body
Hyphal growth from spore
germinating spore mycelium
• Mycelia have a huge surface area
The Characteris,cs of Fungi • Fungus is oZen hidden from view. It grows through its food source (substratum), excretes extracellular diges,ve enzymes, and absorbs dissolved food. • Indeterminate clonal growth. • Vegeta,ve phase of fungus is generally sedentary.
The Characteris,cs of Fungi Cell wall present, composed of cellulose and/or chi,n. Food storage -‐ generally in the form of lipids and glycogen. Eukaryotes -‐ true nucleus and other organelles present. All fungi require water and oxygen (no obligate anaerobes). Fungi grow in almost every habitat imaginable, as long as there is some type of organic ma^er present and the environment is not too extreme. • Diverse group, number of described species is somewhere between 69,000 to 100,000 (es,mated 1.5 million species total). • • • • •
Generalized Life Cycle of a Fungus
Evolution of the fungi
asci zygosporangia motile spores
basidia
Classification & Phylogeny
Chytridiomycota – “chytrids” • Simple fungi • Produce mo,le spores -‐ zoospores • Mostly saprobes and parasites in aqua,c habitats • Could just as well be Pro,sts
Chytridium growing on spores
Chytriomyces growing on pine pollen
Zygomycota – “zygote fungi” Rhizopus on strawberries
• Sexual Reproduc,on -‐ zygosporangia • Asexual reprod. – common (sporangia – bags of asexual spores) • Hyphae have no cross walls • Grow rapidly • Decomposers, pathogens, and some form mycorrhizal associa,ons with plants
Rhinocerebral zygomycosis
Sexual zygsporangium with one zygospore
Asexual sporangium with spores inside
Life cycle of Rhizopus
Ascomycota – “sac fungi” • Sexual Reproduc,on – asci (sing. = ascus) • Asex. Reprod. – common • Cup fungi, morels, truffles • Important plant parasites & saprobes • Yeast -‐ Saccharomyces • Decomposers, pathogens, and found in most lichens A cluster of asci with spores inside
Sac fungi diversity
Basidiomycota – “club fungi” • Sexual Reproduc,on – basidia • Asexual reprod – not so common • Long-‐lived dikaryo+c mycelia • Rusts & smuts –plant parasites • Mushrooms, polypores, pugalls, boletes, bird’s nest fungi • Enzymes decompose wood, leaves, and other organic materials • Decomposers, pathogens, and some form mycorrhizal associa,ons with plants
SEM of basidia and spores
Hyphal fusion mycelium and fruiting body are dikaryotic of haploid mycelia
haploid mycelium
Mushroom Life Cycle N Meiosis
2N
N+N Nuclear fusion in basidium
young basidia - the only diploid cells
Bioluminescence in Mycena
Some fungi have more than one scien,fic name – Why? • Teleomorph: the sexual reproduc,ve stage (morph), typically a frui,ng body (e.g., Morchella esculenta, Agaricus brunescens). • Anamorph: an asexual reproduc,ve stage (morph), oZen mold-‐like (e.g. Aspergillus flavus, Fusarium solani). When a single fungus produces mul,ple morphologically dis,nct anamorphs, they are called synanamorphs. • Holomorph: the whole fungus, including all anamorphs and the teleomorph.
Deuteromycota – Form Phylum “Imperfect Fungi” • Fungi that seldom or never reproduce sexually. • Asexual reproduc,on by vegeta,ve growth and produc,on of asexual spores common.
Yeasts • Single celled fungi • Adapted to liquids – Plant saps – Water films – Moist animal ,ssues
Saccharomyces
Candida
Molds • Rapidly growth • Asexual spores • Many human importances – Food spoilage – Food products – An,bio,cs, etc.
Noble Rot - Botrytis
HUMAN-‐FUNGUS INTERACTIONS • Beneficial Effects of Fungi – Decomposi,on -‐ nutrient and carbon recycling. – Biosynthe,c factories. Can be used to produce drugs, an,bio,cs, alcohol, acids, food (e.g., fermented products, mushrooms). – Model organisms for biochemical and gene,c studies.
• Harmful Effects of Fungi – Destruc,on of food, lumber, paper, and cloth. – Animal and human diseases, including allergies. – Toxins produced by poisonous mushrooms and within food (e.g., grain, cheese, etc.). – Plant diseases.