I. FUNGI (Mycology) u Diverse group of heterotrophs. u Many are ecologically important saprophytes(consume dead and decaying matter) Chapter 12: u Others are parasites. Fungi, Algae, Protozoa, and u Most are multicellular, but yeasts are unicellular. u Most are aerobes or facultative anaerobes. Parasites u Cell walls are made up of chitin (polysaccharide). u Over 100,000 fungal species identified. Only about 100 are human or animal pathogens. u Most human fungal infections are nosocomial and/or occur in immunocompromised individuals (opportunistic infections). u Fungal diseases in plants cause over 1 billion dollars/year in losses. CHARACTERISTICS OFFUNGI (Continued) CHARACTERISTICS OFFUNGI 2. Molds and Fleshy Fungi 1. Yeasts u Multicellular, filamentous fungi. u Unicellular fungi, nonfilamentous, typically oval or u Identified by physical appearance, colony characteristics, spherical cells. Reproduce by mitosis: and reproductive spores. u Fission yeasts: Divide evenly to produce two new cells u Thallus: Body of a mold or fleshy fungus. Consists of many (Schizosaccharomyces). hyphae. u Budding yeasts: Divide unevenly by budding (Saccharomyces). u Hyphae (Sing: Hypha): Long filaments of cells joined together. Budding yeasts can form pseudohypha, a short chain of u Septate hyphae: Cells are divided by cross-walls (septa). undetached cells. u Coenocytic (Aseptate) hyphae: Long, continuous cells that are not divided by septa. Candida albicans invade tissues through pseudohyphae. Hyphae grow by elongating at the tips. u Yeasts are facultative anaerobes, which allows them to Each part of a hypha is capable of growth. grow in a variety of environments. u Vegetative Hypha: Portion that obtains nutrients. u Reproductive or Aerial Hypha: Portion connected with u When oxygen is available, they carry out aerobic respiration. reproduction. u When oxygen is not available, they ferment carbohydrates to produce u Mycelium: Large, visible, filamentous mass made up of many ethanol and carbon dioxide. hyphae. Mycelium: Large, Visible Mass of Hyphae Characteristics of Fungal Hyphae: Septate versus Coenocytic 1 LIFECYCLEOFFUNGI CHARACTERISTICS OFFUNGI (Continued) u Filamentous fungi can reproduce asexually by Dimorphic Fungi fragmentation of their hyphae. u Can exist as both multicellular fungi (molds) and yeasts. u Fungal spores are formed from aerial hyphae and are u Many pathogenic species. used for both sexual and asexual reproduction. u Mold form produces aerial and vegetative hyphae. 1. Asexual spores: Formed by the aerial hyphae of one organism. u Yeast form reproduces by budding. New organisms are identical to parent. u Dimorphism in pathogenic fungi typically depends on u Conidiospore: Unicellular or multicellular spore that is not temperature: enclosed in a sac. u At 37oC: Yeast form. u Chlamydospore: Thick-walled spore formed within a hyphal segment. u At 25oC: Mold form. u Sporangiospore: Asexual spore formed within a sac u Dimorphism in nonpathogenic fungi may depend on other (sporangium). factors: Carbon dioxide concentration. 2. Sexual spores: Formed by the fusion of nuclei from two opposite mating strains of the same species. New organisms are different from both parents. IMPORTANT DIVISIONS OF FUNGI Opportunistic Infection by Candida 1. Deuteromycota albicans in an AIDS Patient u Not known to produce sexual spores. u Reproduce asexually. u Catch-all category for unclassified fungi: u Pneumocystis carinii: Causes pneumonia in AIDS patients. Leading cause of death in AIDS patients. Originally classified as a protozoan. u Candida albicans : Causes yeast infections of vagina in women. Opportunistic infections of mucous membranes in AIDS patients. Source: Atlas of Clinical Oral Pathology, 1999 IMPORTANT DIVISIONS OF FUNGI Life Cycle of a Zygomycete : Black Bread Mold (Rhizopus) Reproduces Asexually and Sexually 2. Zygomycota (Conjugation Fungi) u Also known as bread molds. u Saprophytic molds with coenocytic hyphae (lack septa). u Asexual Reproduction: Used most of the time. Sporangiospore: Asexual spore enclosed within a sporangium or sac at the end on an aerial hypha. u Sexual Reproduction: Occurs through conjugation, the joining of hypha of two different strains (plus and minus). Zygospores: Sexual spores which are enclosed in a thick, resistant wall. u Generally not pathogens. u Rhizopus nigricans: Common black bread mold. May cause opportunistic infections in diabetes patients 2 Reproductive Structures of Zygomycete (Rhizopus) IMPORTANT DIVISIONS OF FUNGI Sporangia (asexual) and Zygospore (sexual) 3. Ascomycota (Sac Fungi) u Molds with septate hyphae and some yeasts. u Asexual Reproduction: Conidiospores not enclosed in a sac. Become airborne easily. Form chains (broom-like structures). u Sexual Reproduction: Ascospores enclosed in a sac-like structure (ascus). u Include common antibiotic producing fungi and yeasts, and several human pathogens. u Penicillium notatum (Produces penicillin) u Saccharomyces(Brewer’s yeast) u Trychophyton(Athlete’s foot) u Aspergillus (Carcinogenic aflatoxin in peanuts), u Blastomyces(Respiratory infections) u Histoplasma capsulatum (Respiratory and systemic infections) Life Cycle of Eupenicillium (Ascomycete) Reproduces Asexually and Sexually Severe nail infection with Trichophyton rubrum in a 37-year-old male AIDS patient. Source: Intern. J. Dermatol. 31(1992): 453. IMPORTANTDIVISIONS OFFUNGI 4. Basidiomycota (Club Fungi) u Have septate hyphae. u Include mushrooms, toadstools, rusts, and smuts. u Sexual Reproduction: Produce basidiospores: Spores formed externally on a club shaped sexual structure or base called basidium. u Asexual Reproduction: Through hyphae. u Examples: u Cryptococcus: Causes opportunistic respiratory and CNS infections in AIDS patients. Disseminated Histoplasma capsulatum, skin infection. u Amanita: Mushroom produces lethal toxins to humans. Source: Microbiology Perspectives, 1999. u Claviceps purpurea: Produces ergot toxin in wheat and rye. 3 Life Cycle of a Basidiomycete NUTRITIONAL ADAPTATIONS OFFUNGI Mushrooms are Produced Sexually Fungi absorb their food, rather than ingesting it. u Fungi grow better at a pH of 5, which is too acidic for most bacteria. u Almost all molds are aerobic. Most yeasts are facultative anaerobes. u Fungi are more resistant to high osmotic pressure than bacteria. u Fungi can grow on substances with very low moisture. u Fungi require less nitrogen than bacteria to grow. u Fungi can break down complex carbohydrates (wood, paper), that most bacteria cannot. FUNGAL DISEASES Systemic Mycosis: Histoplasmosis Mycosis: Any fungal disease. Tend to be chronic because fungi grow slowly. Mycoses are classified into the following categories: I. Systemic mycoses: Fungal infections deep within the body. Can affect a number if tissues and organs. u Usually caused by fungi that live in the soil and are inhaled. Not contagious. u Examples: u Histoplasmosis (Histoplasma capsulatum): Initial infection in lungs. Later spreads through blood to most organs. Disseminated Histoplasma capsulatum,lung infection. u Coccidiomycosis (Coccidioides immites): Resembles tuberculosis. Source: Microbiology Perspectives, 1999. FUNGAL DISEASES (Continued) Cutaneous Mycosis II.Cutaneous mycoses: Fungal infections of the skin, hair, and nails. u Secrete keratinase, an enzyme that degrades keratin. u Infection is transmitted by direct contact or contact with infected hair (hair salon) or cells (nail files, shower floors). u Examples: u Ringworm(Tinea capitis and T. corporis) u Athlete’s foot(Tinea pedis) u Jock itch(Tinea cruris) Ringworm skin infection: Tinea corporis Source: Microbiology Perspectives, 1999 4 Cutaneous Mycosis FUNGAL DISEASES (Continued) III. Subcutaneous mycoses: Fungal infections beneath the skin. u Caused by saprophytic fungi that live in soil or on vegetation. u Infection occurs by implantation of spores or mycelial fragments into a skin wound. u Can spread to lymph vessels. IV. Superficial mycoses: Infections of hair shafts and superficial epidermal cells. Prevalent in tropical climates. Candida albicans infection of the nails. Source: Microbiology Perspectives, 1999. ECONOMIC IMPORTANCE OF FUNGI FUNGAL DISEASES (Continued) u 25-50% of harvested fruits and vegetables are damaged Opportunistic mycoses: Caused by organisms that are by fungi. generally harmless unless individual has weakened u Fungal infections of plants are commonly called rots, defenses: rusts, blights, wilts, and smuts. u AIDS and cancer patients u Phytophthora infestans: Caused great potato famine in mid- u Individuals treated with broad spectrum antibiotics 1800s. Over 1 million people died from starvation in Ireland. u Very old or very young individuals (newborns). Many immigrated to the U.S. u Examples: u Beneficial fungi: u Aspergillosis: Inhalation of Aspergillus spores. u Candida oleophila: Prevents fungal growth on harvested fruits. u Yeast Infections orCandidiasis: Caused mainly by Candida u Saccharomyces cerevisiae: Used to make bread and wine. albicans. Part of normal mouth, esophagus, and vaginal flora. u Genetically engineered yeast strains are used to make proteins (Hepatitis B vaccine). u Taxomyces: Produces anticancer drugtaxol. u Trichoderma: Produces cellulase. Used to make fruit juice. II. ALGAE II. ALGAE u Simple eucaryotic photosynthetic autotrophs. u Vegetative Structures of multicellular algae: u Unicellular or multicellular. Kingdom Protista. u Thallus: Body. Lacks conductive tissue. u Most are found in the ocean or other bodies of water. u Holdfasts: Anchor alga to rock.