Kingdom Fungi 2Group 4

Common Characteristics of Fungi

Mycologists, scientists who specialize in the study of fungi, believe there are a million or more species of fungi. Scientists believe they have identified only 5% of all fungi.

Heterotrophic FungiFungi can obtain nutrients by

absorption

Saprophytic FungiFungi secretes enzymes to break

down dead organic matter in recycling

Parasitic FungiFungi obtain their nutrients from

living hosts.

Fungi cell walls are made mostly of the carbohydrate chitin.

Fungi can reproduce sexually and asexually.

Kingdom Fungi is more related to Kingdom Animalia than Kingdom Plantae.

Kingdom Fungi & Kingdom Animalia probably diverged from a common ancestor some 0.6 billion years ago.

Fungi cell walls are made mostly of the carbohydrate chitin.

Chitin can be found also in exoskeleton insects

The storage carbohydrate of fungi is called glycogen.

Glycogen can be found also in muscles.

Fungi ReproductionDikaryotic Stage – the

coexistence of two different mating types of nuclei which is unique to fungi.

Plasmogamy is a stage in the sexual reproduction of fungi

. In this stage, the cytoplasm of two parent mycelia fuse together without the fusion of nuclei, as occurs in higher terrestrial fungi. After plasmogamy occurs, the secondary mycelium forms. The secondary mycelium consists of dikaryotic cells, one nucleus from each of the parent mycelia. It is the fusion of protoplasm between two motile or non-motile gametes. It involves the union of two protoplast bringing two haploid nuclei close together in the same cell...

KaryogamyKaryogamy is the fusion of pronuclei of two cells,

as part of syngamy, fertilization, or true bacterial conjugation.

It is one of the two major modes of reproduction in fungi. In fungi that lack sexual cycles, it is an important source of genetic variation through the formation of somatic diploids.

The term comes for the Greek karuo- (from karuon) meaning nut and -gamos meaning marriage.It is mainly found in fungal phylum ascomycetes. Species that use this mode of reproduction is responsible for causing ringworm.

Four groups of fungi according to their molecular structures and sexual reproduction:

ChytridsZygomycetesAscomycetes Basidiomycetes

ChytridiomycetesMembers of the fungi phylum are

considered to be the most primative fungi and probably appeared about 500 million years ago.

Chytrids, as member of this group are known, are found anywhere.

ChytridsMicroscopic and differ from other

fungi phyla because chytrids produce motile spores called zoospores.

Synthesize and release digestive enzymes that break down molecules in the protective covers of other organisms.

Anaerobic chytrids are chytrids that do not need oxygen.

ZygomycetesInclude a variety of fungi. The

black bread mold is a common zygomycetes. It decomposes bread, fruits, vegetables, and decaying animals, and produces a fuzzy, black growth within the substance

All the fungi assigned to this group (which probably does not represent a single clade) form spores in a sporangium. Some notable examples:the bread mold, Rhizopus stolonifera

Rhizopus oryzae, used to make sake, the rice wine of Asia. Can also infect humans, especially if they are immunosuppressed (e.g., AIDS patients, transplant recipients).

Another species of Rhizopus is used in the commercial production of glucocorticoids.

Many mycorrhizal fungi belong to this group.

AscomycetesCommonly called “sac fungi” or “cup

fungi” for the cup-shaped fruiting bodies of many ascomycetes, this group includes many delicious, edible fungi.

There are some 30,000 known ascomycetes, about 500 species of which we called yeast. Yeasts reproduce asexually by budding. Most yeasts are singled-celled but some are multi-cellular.

Ascomycetes produce two kinds of spores:asexual spores called conidia ascospores produced following sexual reproduction. Four or eight ascospores

develop inside a saclike ascus (the group is commonly called sac fungi). Some notable examples:Saccharomyces cerevisiae one of the budding yeasts.

It ferments sugar to ethanol and carbon dioxide [Discussion] and thus is used◦ to make alcoholic beverages like beer and wine

◦ to make ethanol for industrial use

◦ in baking (it is often called baker's yeast). Here, it is the carbon dioxide that is wanted (to make bread and cakes "rise" and have a spongy texture).

Yeast is also used◦ in the commercial production of some vitamins.

◦ in the production — using recombinant DNA technology — of some human therapeutic proteins.

Neurospora crassa, another favorite "model" organism in the laboratory. The fungal partner in most lichens is an ascomycete. Powdery mildews that attack ornamental plants The chestnut blight, which in a few decades killed almost all of the mature

American chestnut trees in the Appalachians of North America. The Dutch elm disease, which has killed many of the American elms in the United

States. Pneumocystis jirovecii, which is a major cause of illness in immunosuppressed

people, e.g., patients with AIDS. The truffle and the morel, both highly-prized food delicacies. The photo (courtesy

of the French Embassy Press & Information Division) shows a farmer from the Périgord (in southwestern France) admiring a truffle. Truffles establish a symbiotic relationship with the roots of such trees as oaks.

BasidiomycetesMost mushrooms, shelf fungi, and

puffballs belong to the fungi phylum called basidiomycetes.

Basidiomycetes are the most familiar of the fungi. Also called “club fungi”, they account for about a third of all identified fungi.

Almost 25,000 basidiomycete species have been identified.

Basidiomycetes include mushrooms, shelf fungi, puffballs, rusts, and smuts. They are dispersed by spores borne at the tips of basidia (giving rise to the name for the group).

Mushrooms are masses of interwoven hyphae growing up from the main mass of the mycelium growing underground. The basidia develop on the undersides and release their spores (four from each basidium) into the air.

A single mycelium may expand outward year after year as its hyphae grow into new terrain. In some species, mushrooms are sent up once a year at the periphery producing a circle known since medieval times as a "fairy ring".

Some notable basidiomycetes:Armillaria bulbosa. A single specimen in northern Michigan (USA) was found to have spread over 37 acres (15 hectares) of the forest floor. RFLP analysis of samples taken from many different locations within this area showed that all the samples were from a single clone. Assuming the normal rate of vegetative growth for this species, it must have taken 1500 years to spread to that size.

the cultivated, edible mushroom that finds its way into pizza, soups, etc. Amanita muscaria. Forms a beautiful mushroom but deadly when eaten. Smuts. Parasites of important crops like wheat, oats, and rye. Rusts. Some, such as

◦ wheat black stem rust (Puccinia graminis) and◦ white pine blister rust

are serious pests. Both have complicated life cycles during which they pass through a second plant host (barberry plants for wheat black stem rust, gooseberries or wild currants for the white pine blister rust).

Most of the fungi body is mycelium, the mass of hyphae that contains the vegetative part of a fungus.

It reproduce asexually by fragmentation and conidia spore formation.

LichensLichens are fungi that live in a symbiotic association

with an autotrophic green alga or cyanobacterium (the "photobiont") or — in some cases — both.

The fungal partner (the "mycobiont") in most lichens (98% of them) is an ascomycete. Zygomycetes make up the remainder.

The relationship is often characterized as mutualistic; that is, both partners benefit. But recent evidence (e.g. in British soldier) suggests that while the fungus is dependent on its autotrophic partner, the photobiont is often perfectly content to live alone.

Lichens secrete a variety of unusual chemicals; some of these probably assist in the breakdown of rock substrates like the one shown here.

The biggest organism is…The largest living thing on earth

(as of the year 2000) is a 2400-year old Armillaria ostoyae, commonly known as a “honey mushroom”. This specimen was found in Oregon whereits underground mycelium spreads from tree root covering 2,200 acres.

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