Lecture 21 Outline
The fungus among us (human fungal diseases, mildews)
Asperigllus infection foot bones
Aspergillus embolism in artery
Aspergillus infection of the eye
Aspergillus infection of the lung
Chronic blastomycosis on the nose
Candida infection between fingers
Candida infection on tongue (thrush)
Grotesque coccidiomycosis on face
Cryptococcal infection of lung
Hand with hand, foot and mouth disease
Histoplasmosis evidence on gums
Penicillium rare skin infection
Penny Black first use on cover
Role in nature
in the environment, fungi are critical to the breakdown and decay of biological materials
fungi can eat almost anything
thus, the detritus or leftovers from decay are foods for fungi
like in a compost pile, heterotrophic bacteria eat the 'tasty' parts of the organic debris
the less digestible portions of the rotting material, like the lignin in wood, is degraded by fungi
the decay process is critical for returning nutrients and minerals to the soil
images were presented showing various wood rots, rotting fruit and bread molds
another important environmental role of fungi is in association with plants
mycorrhizal fungi live in the soil on the surface of or within plant roots
most plants have mycorrhizal fungi associated with their roots
the fungi have a large surface area and help in the transport of mineral nutrients and water to the plants
the plants provide fixed carbon compounds to the fungi as their contribution to this symbiotic relationship
Plant pathogens
many fungi are harmful to plants and must be controlled in agricultural settings
powdery mildews are obligate parasites that grow on roses, squashes, and cucumber leaves
the powdery mildews cannot be cultured in the laboratory unless grown on plant leaves
study is difficult and few good fungicides exist for use in agriculture
smut on corn is caused by Ustilago and can be very harmful to corn crops
rice blast disease is caused by Pyricularia and can affect leaves or stems
rice is a major staple crop worldwide and rice blast destroys a large portion of each year's crops
there are very active research programs into control of rice blast through agrichemicals
rusts on leaves constitute another class of pathogenic fungi
these are often seen of fruit crops and give the leaves a rusty color
Ergot on wheat and rye produces hallucinogenic compounds similar to LSD
there is some evidence that the witch hunts in Salem were induced by Ergot contaminated grains
post-harvest fruit is susceptible to fungal pathogens
some 40% of all fruit harvested is consumed by fungi
commercial fungicides are difficult to discover because of selectivity issues
fungi are closely related to animals cells and thus compounds that kill fungi often kill animals
bacterial protein synthesis and cell wall biosynthesis differ from similar processes in animals and make good targets for antibiotics
fungal protein synthesis is too much like animal protein synthesis to make it a good target for a fungicide
many of the commercial fungicides block sterol biosynthesis in fungi
sterols are required for cell membrane functioning
compounds in the azole class, like fenpropidin and fenpropimorph, are commonly used as fungicides
Positive fungi
many fungi are beneficial to man, in addition to their environmental roles
antibiotics like penicillin and cephalosporin are fungal products
fungi are used in the production of beer, wine, blue cheese, soy sauce, bread and other food products
fungi are used to produce commercial products like specific alcohols, organic acids, and vitamins
Human pathogens
fungal infections of humans are called mycoses
there are really three classes: cutaneous non-invasive, subcutaneous, and systemic
cutaneous non-invasive mycoses attack the non-living portion of skin tissue
the outer layer of skin is mainly dead cells, keratin, sebaceous (sweat) solids
the fungi colonize the skin and eat the keratin and other dead cell materials
Tineas and Ringworm diseases are caused by organisms like Trichophyton, Microspurum, and Epidermophyton
tineas are transmissible via human-human, animal-human, and soil-human contact
the tineas grow in circles where the edges are red and scaly, thus the term ringworms
tinea pedis - athlete's foot grows in the moist dark areas between the toes
when it spreads to the toenails (tinea unguium) it can be very difficult to get rid of
tinea cruris - jock itch grows in the male groin area - again a warm moist dark environment
tinea capitis - found on the scalp, generally in children leading to hair loss
tinea manum is on the hand and tinea barbae (barber's itch) under the beard
some infections are opportunistic and arise when the immune system is damaged by illness, transplant surgery or age
Candida causes candidiasis, often found in the mouth and called thrush
thrush is common in infants and AIDS patients and can infect the blood and be lethal
Candida is also the causative agent of vaginal "yeast infections"
Cryptococcus is found in bird droppings and can infect skin abrasions and the respiratory tract
it can cause fever, move to the brain or bones and in some cases cause death
Aspergillus is the most common fungus in the environment and very pervasive in soil
in immunocomprimised people it can infect the lungs causing necrosis (death) of lung tissue
the ensuing pneumonia can be fatal and the fungi can infect the brain, heart and other organs
Systemic infections
Histoplasmosis - Ohio Valley Fever - some 80-90% of people in the Ohio Valley region show signs of previous infection with histoplasmosis
it may be the causative agent of the "mummy's curse" from Tut's tomb
there are 500,000 cases annually in the US, thousands hospitalized and some deaths
the histoplasma fungi are common in soil and bird guano (droppings)
the fungal cells can grow within phagocytes and thus evade the immune response
symptoms can be mild fungal flus to severe diseases that can infect many organs
Coccidioidomyces - San Joaquin Valley Fever - a soil fungus that can produce cold-like respiratory disease
it can also grow in the lung and lead to rapid, explosive and deadly infections
Blastomyces - Chicago disease - often found in decaying wood and abandoned buildings
can produce flu symptoms, but can lead to abscesses in the lung
often it is seen as a chronic skin infection that erodes the skin surface
when the infection is systemic and in the blood, it can lead to death
Subcutaneous infections are below the skin surface
Sporotrichosis - Rose-gardener's disease - commonly transmitted by a prick from a rose thorn
basketweavers are also at risk
the disease can spread from the skin infection to the lymph nodes
Mycetoma - complex disfiguring syndrome - often contracted through a small injury by a thorn, leaf edge or wood sliver
leads to local abscesses in the skin
this can spread to the bones and muscles
often the disease is insidious and difficult to cure
Review of Exam 2
