2The Significance of Fungi Decompose dead organisms and recycle their nutrientsForm associations with roots of vascular plants, which help plants absorb water and mineralsUsed for food, in religious ceremonies, and in manufacture of foods and beveragesProduce antibioticsServe as important research tools30% cause diseases of plants, animals, and humansCan spoil fruit, pickles, jams, and jellies
3Nutrition of Fungi Acquire nutrients by absorption Most are saprobes Some trap and kill microscopic soil-dwelling nematodesHaustoria allow some to derive nutrients from living plants and animalsMost are aerobic; some are anaerobic; many yeasts are facultative anaerobes
4The Kingdom of the Fungae MyceteaeGreat variety and complexityApproximately 100,000 speciesMajority are unicellular or colonial
5The Kingdom of the Fungae Can be divided intothree groups:YeastsMoldsMacroscopic Fungi
6The Kingdom of the Fungae Can be divided intothree groups:YeastsRound or oval shapeUnique mode of asexual reproductionSome form pseudohyphae (false filaments)
7The Kingdom of the Fungae Can be divided intothree groups:MoldsLong, threadlike cellsFilamentous arrangement (hyphae)Some are dimorphic (yeast-like and filamentous forms exist)
8The Kingdom of the Fungae Macroscopic fungiMushrooms, toad stoolsBracket fungiStink horns
9Fungi CHARACTERISTICS Parasitic or Saprophytic Eukaryotic Form Filaments termed hyphaeHyphae form mycelium septate or aseptateCell wall composed of chitinor celluloseSlow to propagateMost are aerobicpH acidic
10FungiFUNGUS: multicellular, spore bearing, achlorophyllous organism which multiply sexually or asexually and whose usually filamentous somatic structure are septate or aseptate (coenocytic). The nutritional need of a fungus are facilitated by the enzymes cellulase and/or chitinase.
11Fungi*All molds are fungi but all fungi are not molds-- yeasts are fungi but they are unicellular and produce no aerial mycelium molds filamentous fungi that produce aerial mycelium
12Fungi Somatic Structures Hyphae: the tubelike filaments that constitute a mycelium.Mycelia: The somatic hairlike structures of a fungus. A mass of hyphae produced by some fungi.
13Groups of Fungi LOWER FUNGI Aseptate mycelia Aseptate myceliaused to be called Phycomycetes Saprophytic or parasiticMost primitive fungiFound mostly in soil, water, leavesCoenocytic = AseptateProduce asexual spore in sporangium
14Groups of Fungi Oomycetes The oomycetes develop biflagellated zoospores with oppositely directed flagella. The mycelia is well developed, branched, aseptate or coenocytic. Sexual reproduction is oogamous. Some species are plant parasites of commerical crops such as grapes and potatoes. Some species are fish parasites.Characteristic of Oomycetes:water moldsSome portion of life cycle is flagellatedCause fish disease and disease of commercial cropsPlasmoparaPhytophthora infestations--potato blight Saplonegia fish infections
15Water Molds Differ from fungi in the following ways Have tubular cristae in their mitochondriaCell walls are of cellulose instead of chitinSpores have two flagella – one whiplike and one tinsel- likeHave true diploid thalli
16Groups of Fungi Zygomycetes Zygomycetes have well developed mycelia in which the hyphae are usually aseptate; however, septa may form in older portions of the mycelia. Asexual spores are produced in sporangium. Sexual spores are produced after fusion of two gametes formed at hyphal tips.Characteristics of Zygomycetes-predominantly terrestrialBreakdown organic molecules and are important in recyclingSome are human pathogensLife cycle include both sexual and asexual reproductioncharacterized by zygospores
17Groups of FungiChytridiomycetes responsible for recycling of nutrients in aquatic habitats.
18Groups of FungiTrichomycetes are major parasites of insects.
19Groups of FungiHIGHER FUNGI contain septate mycelia
20Groups of FungiAscomycetes possess septate hyphae and produce ascospores in sac- like structures known as asci. Karyogamy and meiosis occur in the developing ascus resulting in four haploid cells. These cells become ascospores. Mitosis occurs after meiosis and produces usually eight ascospores per ascus. Produces asexual conidiospores.Two stages:1. Sexual or ascospore stage2. Asexual or conidial stageCharacteristics of Ascomycetes:Sac fungi also known as Perfect fungiMostly plant pathogensCell wall composed mostly of chitinproduce sexual (ascospores) and asexual spores (conidiospores)
22Groups of Fungi Basidiomycetes: Produce basidia, club-like structures in which karyogamy and meiosis occur. At maturity, two or four haploid basidiospores are produced on a basidium. The hyphae are septate and contain clamp connections. Include mushrooms, toadstools, rust, smuts, bracket fungi, puff balls, and birds nest fungi.Basidiocarppileus capstipe stemlamellae gills
23Groups of Fungi Deuteromycetes: Include fungi whose sexual reproductive stages have never been observed. These fungi produce asexual conidia in abundance. The hyphae are septate.Characteristic of DeuteromycetesFungi imperfect: most clinically importantonly reproduce asexually by conidiosporesmycelium septatemost pathogenic fungi in this groupeither had sexual stage and lost it or it has not been describedall yeast that reproduce only be budding
24Asexual Spores Sporangiospores Formed by successive cleavages within the sporangiumSporangium attached to the sporangiophoreReleased when the sporangium rupturesConidiosporesaka conidiaFree sporesDevelop either by pinching off the tip of fertile hypha or by segmentation of a vegetative hypha
26Deuteromycetes Pathogens Histoplasmosis, also known as Darling's disease, is a disease caused by the fungus Histoplasma capsulatum. Symptoms of this infection vary greatly, but the disease primarily affects the lungs.
27Deuteromycetes Pathogens HistoplasmosisOccasionally, other organs areaffected; this is calleddisseminated histoplasmosis,and it can be fatal if untreated.Histoplasmosis is commonamong AIDS patients because oftheir lowered immune system.Found in soil and associated withpoultry feces and bat guano.
28Deuteromycetes Pathogens Sporothrix schenckii is the causative agent of Sporotrichosis or rose-handler's disease. Sporotrichosis is a subcutaneous infection and it starts following entry of the infecting fungus through the skin via a minor injury and may affect an otherwise healthy individual. Following entry, the infection may spread via the lymphatic route (nodular lymphangitis may develop). Patients infected with Sporothrix schenckii may be misdiagnosed as pyoderma gangrenosum due to the large ulcerations observed during the course of sporotrichosis.
29Deuteromycetes Pathogens Coccidioides immitis is apathogenic fungust hat residesin the soil in certain parts ofthe southwestern United States.It can cause a disease calledcoccidioidomycosis (Valley Fever), and itis a rare cause of meningitis, mostly inImmunocompromised persons. It hasbeen declared a select agent by boththe U.S. Department of Health andHuman Services and the U.S.Department of Agriculture and isconsidered a biosafety level 3 pathogen.Infects lungs and skinmainly.
30Deuteromycetes Pathogens Blastomyces s a fungal genus responsible for the medical condition blastomycosis. The most well known species of the genus is Blastomyces dermatitidis. B. dermatitidis is a dimorphic fungal pathogen, found primarily in the Mid-West and Northern United States and Canada. It exists in the soil in a filamentous form that produces spores directly upon the wall of the hyphae, lacking any kind of fruiting body to aid in aerosolization/dissemination of the spores. The natural reservoir of this organism in the environment is not clearly defined, but it seems to be associated with rivers and lakes. Blastomyces is endemic to the Mississippi and Ohio river valleys and the vicinity of the Great Lakes. Outbreaks of blastomycosis are often associated with disruptions of the soil that might lead to the artificial elevation of spore and/or hyphal fragments in the air.
31Deuteromycetes Pathogens These agents infect human and animal hosts when they are inhaled. At the elevated temperature of 37°C in a host, the fungus undergoes a phase transition to the pathogenic yeast form. Yeast form cells multiply in the lung and may cause disease in immuno-competent hosts, sometimes disseminating to the skin, central nervous system and bones.
32Dimorphism Some fungi exhibit different morphologies--grow as filamentousforms in soil and media, but in a suitableanimal host form yeast. May displaydimorphism just by changing environmentand/or nutritional conditions.Histoplasma capsulatum - mold on media atroom temperature, yeast at 37CCandida albicans: yeast at room temperature,pseudohyphae in body1. Dimorphism is advantageous because it allows them to reproduce more rapidly2. Fends off immune response (encapsulate)3. Allow them to obtain nutrition more rapidly
33Opportunistic Pathogens - Ringworm Ringworm is a fungal infection of the skin in humans and domestic animals such as sheep and cattle. Those that cause parasitic infection (dermatophytes) feed on keratin, the material found in the outer layer of skin, hair, and nails. These fungi thrive best on skin that is warm and moist.
42Sick Building Syndrome Causative agents Stachybotrysis Cladiosporium Toxins produces by the fungi produce the clinical symptoms.
43Sick Building Syndrome Causative agents Water leaks lead to contamination
44Fungi in Symbiosis – the Lichens [INSERT FIGURE 12.27]
45Fungi are Friends and Foes Not only involved in infectionsAllergiesPoisoningAgricultural damageBenefits of fungiDecomposing organic matter and returning essential minerals to the soilMycorrhizae increase the ability of plant roots to absorb water and nutrientsProduction ofAntibioticsAlcoholOrganic acidsVitaminsFood flavorings