Fungi Biology 342

Fungi Cells  Kingdom: Fungi  Fungi are eukaryotic single or multicellular organisms  Fungi membranes have chitin to add rigidity  Most fungi lack flagella thus immobile gametes  Microstructure consists of two forms: thread-like hyphae and branch- like Mycelium

Classification History of fungi  Fungi were first described as plants in 1729 in a publication “Nova plantarum genera”.  Fungi were considered a type of plant for nearly 250 years.  1729 – 1975 : fungi were placed in Kingdom Plantae  : structural and molecular work began to raise questions…  1993 : Fungi firmly in its own Kingdom: Fungi  DNA sequencing demonstrates that fungi are more closely related to animals than to plants.

Interesting facts  The oldest fossil fungi – a chytrid is from the late Precambrian (550 million yrs ago).  Fungi are primary decomposers of dead plant and animal tissue releasing back into the atmosphere billions of tons of carbon each year.  Fungi are immobile so disperse around the world with spores riding on air currents.  Fungi feed by the absorption of nutrients released by secreted digestive enzymes.  Fungi can reproduce asexually and sexually.  Fungi are genetically and chemically very similar to animals making fungal diseases difficult to treat.

Kingdom Fungi: Divisions  Chytridiomycota – Chytrids  Zygomycota – bread molds  Ascomycota – Yeasts and Sac fungi  Basidiomycota – Club fungi

Basidiomycota  Mushrooms, puffballs and shelf fungus  Many types are consumed as delicacies, others are poisonous  Cryptococcus is a human yeast pathogen found in bird droppings – when inhaled can cause meningitis and encephalitis

Zygomycota  Molds of bread and fruits  Mycorrhizal fungi – live on roots of vascular plants – take-up phosphate ions from soil – forms a network that connects individual plants together – sharing water and nutrients  Parasites of plants, insects and other small animals

Chytridiomycota  All are aquatic  Only fungi with flagellated gametes  Parasites of plants and insects, no direct impact on humans  Chytridiomycosis – emerging infectious disease of Amphibians spreading world wide contributing to their global decline

Ascomycota  Yeasts, molds, and sac fungi  Cultivated by leaf-cutter ants  White-nose Syndrome – an emergent infectious disease in bats killing millions, bat declines in the NW US at 80%  Candida skin infections in humans  Valley fever, Coccidiodes immitis in people  Aspergillus on peanuts generates Aflatoxin which damages livers and is carcinogenic  Ergotism in people

Spreading Fungal Diseases  Coccidioidomycosis (valley fever) caused by Coccidiodes immitis.  Human Pathogenic Yeast (Fungal meningitis) caused by Cryptococcus spp.  Chytridiomycosis (Amphibian disease) caused by Batrachochytrium dendrobatidis.  White-nose Syndrome (bat disease) caused by Pseudogymnoascus destructans.

Ergotism  Rye Ergot fungus, Claviceps purpurea  Fungus grows on cereal plants, especially rye but also triticale, wheat and barley  Produces an alkaloid called ergotamine that when ingested by humans and other mammals causes the disease known as Ergotism  Symptoms include hallucinations, stomach cramps, burning sensations in limbs referred to as “Saint Anthony’s Fire”.

Salem Witch Trials  In the winter of in Salem, Massachusetts 140 people were arrested and 20 women were hanged for witchcraft.  The “witches” where accused of hexing a dozen young girls that exhibited violent fits, convulsions, incoherent ranting, strange burning sensations on their skin and then going into trances.  Rye bread was a major part of the girls winter diet.

Emerging Infectious Disease Chytridiomycosis = Chytrid Amphibian enzootic  Fugal parasite of frogs and salamanders in the old world – first observed early1900’s.  African clawed frog is unaffected by infection.  Today the fungus has spread world wide- the Americas, Australia, Europe, Caribbean….  Today 30% of global amphibian populations are affected – with catastrophic declines of local populations - some disappearing from a location in a single year.  100% mortality in some populations with no way to control the chytrid fungus

Chytrid fungus  First case in NA – 1978  African Clawed frogs (Xenopus laevis) imported WW for pregnancy testing, laboratory research and for the pet trade – breeding programs shipped 20,000/yr. in 1970’s.  American Bullfrog (Rana catesbeiana) shipped worldwide for food in high-end restaurants.  Both these frog species escaped or were released and have become established everywhere– both are unaffected carriers of chytrid fungus.  Chytrid is widespread in California – N. leopard frog

White-Nose Syndrome  Fungal growth around the muzzles and wings of hibernating bats – first observed in US in  From one cave in New York it has spread to 25 states and five Canadian Provinces.  It kills > 90% of bats within 5 years of invading a hibernacula – there is no known treatment.  It is estimated to have killed from 6 to 7 million bats since its invasion of North America.  Bats consume tons of insects which is beneficial to agriculture and public health

Emerging Infectious Disease White-nose – bat enzootic  The fungus is cold-loving and will not grow above 68 degrees F.  In winter when bats are hibernating the fungus grows on their skin causing lesions and waking them during their torpor – expending fat reserves and they die before summer.