Kingdom Fungi

Introduction to Fungi Look similar to a plant but also have much in common with animals. Mushrooms, toadstools, mildews, yeasts and moulds are all members of this kingdom. Some unicellular fungi, but most are multicellular.

Fungi Morphology Multicellular species have ‘bodies’ made up of hyphae, a network of fine filaments You can’t see these as clearly in mushrooms because they are so densely packed together in a tight mass The mushroom part you see is only one part of the complex fungus. The majority of the organism is contained underground in the form of a loose branching network of hyphae called mycelium

Morphology Some species have hyphae (hypha) that are divided into cells by cross walls called septa (septum) Each individual cell has one or more nuclei The septa are porous and allow for the movement of cytoplasm to flow through the hyphae from cell to cell In cells without septa, each hypha looks like one big cell with many nuclei and undivided cytoplasm. The cell walls of fungi are made of chitin, which is also found in the exoskeletons of insects.

Feeding The majority are saprotrophs, which means they break down decaying matter and play a big role in the recycling of nutrients. As hyphae grow across a food source, they release digestive enzymes that break down large organic molecules into smaller organic molecules

Feeding It is extracellular digestion because it happens outside the body The small molecules diffuse across the fungus for growth and repair The more extensive the mycelium the more space for absorbing nutrients

Parasitic Fungi Some fungi are parasites and can cause diseases such as athlete’s foot and ringworm. They are specialized and produce hyphae called haustoria which penetrates host’s cells without killing them (Dutch Elm Disease) Cordyceps myrmecophila (ant-loving) invades and kills ants by absorbing the ant’s internal cavity through its growing hyphae.

Symbiotic Fungi Many fungus live in symbiotic relationships with plants or animals Remember that a symbiotic relationship is a relationship that is beneficial to both species. An example is that most trees have mycorrhiza in close contact with their roots. The hyphae of these fungi enter the cells of the roots and help provide the roots with nutrients. The fungus also improves air and water flow through the soil. The fungus benefits by absorbing organic nutrients from the plant.

Fungal Reproduction Most fungi have both asexual and sexual methods of reproduction The simplest asexual way is fragmentation, in which pieces of the hyphae are broken off and grow into new mycelia. This happens if something breaks the mycelium, like a gardener, for instance…

Fungal Reproduction The majority of fungi live on land and therefore produce spores, which are windblown reproductive cells that help the fungi disperse to new locations. The spores are produced in great number to help increase the chances of dispersal and survival. A puffball can produce as many as one trillion spores!

Classifying Fungi Original ancestors of fungi are not known. They may have evolved separately from more than one origin. Four subgroups…

1) Zygospore Fungi (Zygomycotes) Include bread moulds and other saprotrophs, as well as a few parasites of protists and small invertebrate animals. Keep sexual reproduction in reserve for unfavourable times During this sexual reproduction, they produce zygospores which give this group their name.

2) Club Fungi (Basidiomycotes) Include mushrooms that grow on lawns, bracket fungi on dead tree trunks and the puffballs and stinkhorns found on woodland floors. All these parts are called basidiocarps, which are reproductive structures or ‘fruiting bodies’.

2) Club Fungi (Basidiomycotes) The parasitic types do not form fruiting bodies and are called ‘smuts’ or ‘rusts’ and can cause lots of damage on crop plants. The largest part of the club fungi is a vast sprawling network of hyphae that spread underground. Complex reproductive cycle. Usually reproduce sexually.

Club Fungi Examples

3) Sac Fungi (Ascomycotes) Include powdery mildews on leaves, morals and truffles Largest group of fungi Identified by small fingerlike sacs called asci (ascus), which they develop during sexual reproduction Most are saprotrophs that break down the hard to digest materials in wood and bone Other species are parasites of plants producing leaf curl, chestnut blight Usually reproduce asexually Produce spores at the tips of modified hyphae exposed to air

4) Imperfect Fungi (Deuteromycotes) Only reproduce asexually Do not have a sexual phase of reproduction, hence the term ‘imperfect fungi’. Develop mycelium from spores called conidia

4) Imperfect Fungi (Deuteromycotes) Very diverse group containing very important members such as: the mould, penicillin, which grows on mouldy fruit and is an important antibiotic, cyclosporin is obtained from a fungus that lives in the soil, it is a drug that is used after transplant to help suppress the rejection of the transplanted organ. Others are used to make soy sauce and blue cheese.