Fungi

Fungi

Chapter 26

Characteristics

• Fungi are eukaryotic, heterotrophic and most are multicellular, but some can have unicellular stages

• Yeast cells are unicelluar and the fungus best known for making bread rise; mushrooms, mold and mildew are also fungi

• The study of fungi is called mycology• There are three main phyla of fungi: Zygomycota,

Ascomycota and Basidiomycota

Nutrients

• Fungi get their nutrients by absorbing organic molecules from the environment

• Instead of ingesting food and digesting the nutrients inside of the cells, fungi secrete digestive enzymes out of their cells and absorb the digested nutrients into their cell walls

• Some fungi are saprophytic, meaning they get their organic nutrients from dead materials

Structure

• Fungi have filaments called hyphae and cell walls that contain chitin– Chitin is a polysaccharide that also makes up the

exoskeletons of insects, crustaceans and other arthropods

• Multiple hyphae that form the body of a fungus are called mycelium– Some species have hyphae that are divided, but

some species do not

Reproduction

• Fungi can reproduce both asexually and sexually

• Asexual Reproduction:– Produce identical haploid spores– Different types of fungi produce different types of

spores: sporangiospores or conidiophores– These spores are different due to whether they

have divisions in their mycelia or not

Sexual Reproduction

• Many, but NOT ALL, species can reproduce sexually, creating genetic variation

• Fungi are neither male nor female; instead we say that fungi are either plus or minus– Only + and – can mate with each other, NOT + and +

or – and – • In sexual reproduction, the hyphae of a + wil

fuse with the hyphae of a – and their nuclei will combine their genetic information

Zygomycota

• Most of these are terrestrial and found in soil• Mycelia of zygomycetes are not divided

(coenocytic)• Bread mold is included in this phylum• Zygomycetes can reproduce both asexually

and sexually• Sexual spore of zygomycetes is called a

gametangium (2n)

Basidiomycota

• Often called club fungi because of their clublike sexual reproductive structures (basidia)

• The basidiocarp are the structures like mushrooms that have spores in their gills

• Most members of basidiomycota are mushrooms, but not all of them

Ascomycota

• These are known as sac fungi because of their sexually reproducing forms

• Some members of this phyla are called cup fungi because of the structures that hold the sacs of spores (asci)

• Many yeast species are ascomycetes– These are fungi that help bread rise and ferment

grapes into wine

Mycorrhizae & Lichens• Mycorrhizae have a symbiotic relationship with

plant roots– Found on more than 80% of vascular plants– Helps the plant take up nitrogen, phosphates and

other ions– All three fungal phyla can form mycorrhizae

• Lichens have a symbiotic relationship with a photosynthetic partner (usually green algae)– Most of these are ascomycota– The fungi provide shelter, while the photosynthesizer

provides sugars

Fungi and Humans

• Fungi can interact with humans by causing disease, they are used in industry and we eat them occasionally

• Each phyla can contribute to disease and industry

• Food fungi mostly come from Basidiomycota (mushrooms)

Diseases

• Common fungal infections:– Ringworm– Athlete’s foot– Candida albicans

• Other fungal infections– Histoplasma capsulatum, Paracoccidioides

immitis, and Blastomyces dermatitidis– All of these cause respiratory illnesses and can be

inhaled from soil and bird feces

Industry

• Fungi can be used in nonfood industries, such as pharmaceuticals and genetic engineering

• The antibiotic penicillin is created from the fungi in the genus Penicillium

• Cortisone cream is made from chemicals from the genus Rhizopus

• Saccharomyces cerevisiae has been vital in genetic engineering: vaccine for Hep B and production of ethanol for automobile fuel

Food

• Many species of fungi either aid in the production of food or are food themselves

• Yeast (S. cerevisiae) is an important nutritional supplement because it contains vitamins, minerals and other nutrients

• Many mushrooms species are found in grocery stores for consumption

• Some fungi can damage foods: bread and fruit mold in the kitchen, corn and wheat smut in fields