Eukaryotic Microorganisms: The Fungi Chapter 17 Eukaryotic Microorganisms: The Fungi

17.1 The Kingdom Fungi Includes the Molds and Yeasts Fungi share a combination of characteristics. Fungi lack chlorophyll Fungal walls contain chitin Most fungi are not truly multicellular Fungi are heterotrophic as saprophytes or decomposers Molds grow as long, tangled filaments of cells in visible colonies. Yeasts are unicellular fungi. Some are dimorphic Figure 17.02B: Fungal Colonies.

Figure 17.02A: Hypha Structure. Fungal life cycles involve a growth phase and reproductive phase. Most fungi (except yeasts) exist as hyphae. A mycelium is a thick mass of hyphae. In many species, septa divide the cytoplasm into separate cells. Hyphae containing many nuclei are considered coenocytic. Figure 17.02A: Hypha Structure. © Dr. Dennis Kunkel/Visuals Unlimited

Fungal growth is influenced by several factors. Fungi take up nutrients through absorption. Most fungi are aerobic. Most fungi grow best at around room temperature. - Psychrophilic fungi grow in the refrigerator. Many fungi thrive at slightly acidic pH (pH 5-6). © Dennis Kunkel Microscopy, Inc./Visuals Unlimited/Corbis. Figure 17.04: Roquefort cheese. Figure 17.03: Hypha structure. © Jones and Bartlett Publishers. Photographed by Kimberly Potvin

Mycorrhizae live in mutualistic symbiosis with plant roots. Figure 17.05A: Mycorrhizae and Their Affect on Plant Growth. © Dr. Gerald Van Dyke/Visuals Unlimited Mycorrhizae live in mutualistic symbiosis with plant roots. They help take up water and minerals. Fungal endophytes live in plant tissue, particularly leaves. Courtesy of Dr. A. Elizabeth Arnold, Assistant Professor & Curator, Gilbertson Mycological Herbarium, Department of Plant Sciences, University of Arizona Figure MF 17.02: Endophytes in cacao leaves.

Figure 17.06A: Sporangia of bread mold. Reproduction in fungi involves spore formation. Sporulation occurs in fruiting bodies Asexual reproductive structures develop at the ends of specialized hyphae. Many asexual spores (sporangiospores) develop in sacs called sporangia. Others produce unprotected spores (conidia) on conidiophores. Figure 17.06A: Sporangia of bread mold. © Andrew Syred/Photo Researchers, Inc.

Figure 17.09: A Typical Fungal Life Cycle of a Mold. Fragmentation of hyphae yields arthrospores. In budding, a blastospore develops from the parent cell. Fungi can also reproduce sexually. Opposite mating types come together and fuse into a heterokaryon. © Medical-on-Line/Alamy Images Figure 17.07: Yeast budding. Figure 17.09: A Typical Fungal Life Cycle of a Mold.

17.2 Fungi Have Evolved into a Variety of Forms Fungi can be classified into several major groups The newly discovered Cryptomycota don’t have chitin in their cell walls Microsporidia are unicellular parasites in protists and animals, have chitin but lack true mitochondria Chytridiomycota They are primarily aquatic. They have flagellated reproductive cells. The Glomeromycota are a group of mycorrhizae that live in over 80% of plants’ roots. Figure 17.10: A Phylogeny for the Kingdom Fungi.

Zygomycetes are terrestrial fungi that grow as mold on bread and produce. During sexual reproduction, they form a heterokaryotic, diploid zygospore. Figure 17.11: Mold Growing on a Tomato. © Jones and Bartlett Publishers. Photographed by Kimberly Potvin Figure 17.12: Sexual Reproduction in the Zygomycota. © Carolina Biological Supply Company/Phototake/Alamy Images

Figure 17.13B: Morel mushroom. Ascomycetes account for 75% of known fungi, including: Baker’s yeast. The fungus that produces aflatoxin. The edible morel. The mold that produces penicillin. Candida albicans, the cause of thrush, diaper rash, and vaginitis. Figure 17.13A: Yeast cells. © Dr. John D. Cunningham/Visuals Unlimited Figure 17.13B: Morel mushroom. © Liane Matrisch/Dreamstime.com Figure 17.13C: Moldy orange. Courtesy of Jeffrey Pommerville

Figure 17.14A: Ascocarp on apple leaf. Ascomycetes can produce: conidia through asexual reproduction. ascospores through sexual reproduction. Figure 17.14B: Asci. © Dr. John D. Cunningham/Visuals Unlimited Figure 17.14A: Ascocarp on apple leaf. © Biodisc/Visuals Unlimited

Figure 17.15C: Typical lichen growing. Lichens are a mutualistic association between a fungus (frequently an ascomycete) and a photosynthetic organism. Figure 17.15C: Typical lichen growing. Courtesy of Jeffrey Pommerville Figure 17.15A: Lichens.

Basidiomycetes are club fungi, including mushrooms and puffballs. Some form mycorrhizae. Others are plant pathogens. Basidia on the gills of a mushroom cap contain sexually-produced basidiospores. Courtesy of Jeffrey Pommerville Figure 17.16A: Amanita muscaria. Figure 17.17A: Mushroom gills. Courtesy of Jeffrey Pommerville

Figure 17.18: The Sexual Reproductive Cycle of a Typical Basidiomycete.

Yeasts represent a term for any single-celled stage of a fungus. Saccharomyces is a fungus that can ferment sugars. S. cerevisiae is a model eukaryotic organism. They are used in bread backing and alcohol production.

17.3 Some Fungi cause Intoxications Fungal toxins are called mycotoxins. Some fungi can be poisonous or deadly when consumed. Aspergillus flavus and A. parasiticus produce carcinogenic aflatoxins which contaminate many agricultural products. Ergotism is caused by Claviceps purpurea, which grows on grains. Ergot deposited in the grain can cause: numbness. hot and cold sensations seizures paralysis of nerve endings Lysergic acid diethylamide (LSD) is a derivative of an alkaloid in ergot.

Some mushrooms produce mycotoxins. Mushroom poisoning or mycetism - Mimic acetylcholine, affecting peripheral nervous system - Causes hallucinations - Produces intoxication Amanita causes about 90% of deaths from mushroom ingestion. - Produces cramping, vomiting, and diarrhea - In a week, leads to liver and kidney failure Figure 17.19A: Amanita phalloides. © Niels-DK/Alamy Images

17.4 Some Fungi Can Invade the Skin Dermatophytosis is an infection of the body surface Tinea infections/ringworm, athletes foot, on the skin, hair or nails. They can be transmitted by contact with: domestic animals. fomites like floors, mats or towels. Symptoms include blister-like lesions with a thin fluid discharge. Treatment often involves changing the skin environment (moisture, pH, etc.). Figure 17.20B: Ringworm. Courtesy of CDC

Figure 17.21A: Candida albicans. Candidiasis often is a mild, superficial infection. Candida albicans can cause candidiasis when: the immune system is compromised or microbial populations in the body change. Vulvovaginitis, often called a “yeast infection,” involves: itching, burning, reddening. swelling, discharge. Figure 17.21A: Candida albicans. Courtesy of Dr. Godon Roberstad/CDC

Figure 17.21B: Oral candidiasis. Excessive antibiotic use may decrease protective bacteria in the vagina and intestine, allowing C. albicans to flourish. Oral candidiasis (thrush) involves white curd-like growth on the mucous membranes of the mouth. Onychia involves hardening, browning, and distortion of fingernails. Figure 17.21B: Oral candidiasis. Courtesy of CDC

Figure 17.22B: Sporotrichosis lesions. Sporotrichosis is an occupational hazard. Sporotrichosis can occur in people who work with: wood. wood products. soil. Infection with spores can cause pus-filled lesions. Figure 17.22A: Sporothrix schenckii. © E. Gueho - CNRI/Photo Researchers, Inc. Figure 17.22B: Sporotrichosis lesions. © Everett Beneke/Visuals Unlimited

17.5 Many Fungal Pathogens Cause Lower Respiratory Tract Diseases Cryptococcosis usually occurs in immunocompromised individuals. It is caused by Cryptococcus neoformans. C. neoformans is found in urban soil and pigeon droppings. Inhaled cells penetrate to the air sacs of lungs. Cells can (rarely) pass into the bloodstream, infecting the brain and meninges. Courtesy of Dr. Leanor Haley/CDC Figure 17.23A: TEM of C. neoformans. © Scott Camazine/Alamy Figure 17.23B: Cryptococcus in lungs of AIDS patient.

Histoplasmosis can produce a systemic disease. It is caused by Histoplasma capsulatum. It is found in dry, dusty soil, chicken coops, and bat caves. Most people suffer only mild influenza-like symptoms. Becomes serious in AIDs patients Figure 17.24: H. capsulatum. © Science Source/Photo Researchers, Inc.

Blastomycosis usually is acquired via the respiratory route. It is caused by Blastomyces dermatitidis. It is associated with dusty soil and bird droppings. It can cause lung and skin infections. Inhalation causes: lung lesions. persistent cough. chest pains. It can cause chronic pneumonia and may disseminate to other organs in AIDS patients.

Figure 17.25: The Life Cycle of Coccidioides immitis. Coccidioidomycosis can become a potentially lethal infection. It is caused by Coccidioides immitis. Called “Valley Fever” in desert valleys of the SW U.S. Inhalation of arthrospores causing: a dry, hacking cough. chest pains. high fever. Rarely, infection disseminates to tissues such as internal organs and meninges of the spinal cord. Figure 17.25: The Life Cycle of Coccidioides immitis.

Pneumocystis pneumonia (PCP) can cause a lethal pneumonia. It is caused by Pneumocystis jiroveci. It is a common infection in AIDS patients. P. jiroveci has a complex life cycle in the alveoli. It is usually transmitted through respiratory droplets.

Other fungi also cause mycoses. In aspergillosis, conidia enter the body and grow as a mycelium. It is commonly caused by Aspergillus fumigatus. Disease usually occurs in immunosuppressed hosts Surgery may be necessary to remove an aspergilloma from the lungs. Disseminated Aspergillus can affect the heart or brain causing meningitis.