survey of eukaryotic microbes
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Survey of Eukaryotic Microbes• Fungi
• Algae
• Lichens
Chapters 5 & 22TalaroFoundations in Microbiology
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Kingdom Fungi• 100,000 species divided into 2 groups
– macroscopic fungi – microscopic fungi
• Heterotrophic none are autotrophic on their own• Majority are harmless saprobes living off dead and decaying plants & animals• Some are parasites, but none are obligate
– Mycoses• Optimal growth temperature generally mesophilic 20o - 40oC but many can grow at 4oC• Extremely widespread distribution in many habitats• Reproduce through spores formed on special reproductive hyphae
– Asexual reproduction • Spores are formed through budding or conidia formation
– Sexual reproduction • Spores are formed following fusion of male & female strains & formation of
sexual structure• Sexual spores are one basis for classification
• Mycology – the study of fungi
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Conidiumasexual spore
hypha
Septumcrosswall
Aseptate or coenocytic
MyceliumA mass of hyphae
Body of Mold
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Four Main Divisions
• Zygomycetes
• Ascomycetes
• Basidiomycetes
• Deuteromycetes• No sexual spores• Called by many the Fungi Imperfecti
•Plasmogamy - haploid nucleus of donor cell (+) penetrates cytoplasm of recipient cell (__)
• Karyogamy - (+) and (__) nuclei fuse to form a diploid zygote nucleus
• Meiosis - diploid nuclei gives rise to haploid nuclei
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Unicellular Fungi - Yeast• Two general classes - budding and fission yeast
• Cell division distinguishes two classes
• Budding yeast do not divide evenly
• Fission yeast divide evenlySaccharomyces cerevisiae
Schizosaccharomyces pombe
Ascomycetes with aninfrequent sexual stage
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Fungi as Infectious Agents
• Molds & yeasts are widely distributed in air, dust, fomites & normal flora
• Humans are relatively resistant• Fungi are relatively nonpathogenic except to
immunosupressed patients• Only 300 have been linked to disease in animals,
of the 100,000 fungal species • Human mycoses are caused by true pathogens and
opportunistic pathogens
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Fungal Infection• Systemic Mycoses
• Deep infection, usually multiple organs affected, not transferable from organism to organism
• Subcutaneous Mycoses• Infection beneath surface of skin, requires implantation of hyphae or spores via puncture wound
• Cutaneous Mycoses • Caused by dermatophytes (infect epidermis, hair or nails), secrete keritinase, human to human transmission
• Superficial Mycoses• Localized along hair shafts and superficial (surface) epithelial cells
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Antifungal Compounds• Antifungals are placed into 3 categories based on their
mode of action– Azoles
• Inhibit the synthesis of ergosterol, the main fungal sterol in the plasma membrane
• e.g., Miconazole– Polyenes
• Interact with fungal membrane sterols and creates pores in the plasma membrane
• e.g., Amphotericin B– 5-fluorocytosine
• Cytosine analog• Inhibits nucleic acid synthesis• Fungal infections of the blood, lungs, heart & CNS and urinary tract
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Systemic Mycoses caused by True Pathogens
• Histoplasma capsulatum
• Coccidioides immitis
• Blastomyces dermatitidis
• Paracoccidioidomycosis brasiliensis
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Histoplasma capsulatum• Histoplasmosis• Typically dimorphic• Distributed worldwide, most prevalent in eastern & central
regions of US• Grows in moist soil high in nitrogen content• Inhaled conidia produce primary pulmonary infection that may
progress to systemic involvement of a variety of organs & chronic lung disease
• Amphotericin B– Polyene
• Ketoconazole– Azole
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Subcutaneous Mycoses• Mycetoma or Eumycetoma• Madurella mycetomatis • Agricultural workers• Ketoconale
– Azole
• Itraconazole– Azole
• Amputation
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Cutaneous Mycoses• Infections strictly confined
to keratinized epidermis (skin, hair, nails) are called dermatophytoses - ringworm & tinea
• 39 species in the genera Trichophyton, Microsporum, Epidermophyton
• Communicable among humans, animals, & soil
• Infection facilitated by moist, chafed skin
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• Ringworm of scalp (tinea capitis) affects scalp & hair-bearing regions of head; hair may be lost
• Ringworm of body (tinea corporis) occurs as inflamed, red ring lesions anywhere on smooth skin
• Ringworm of groin (tinea cruris) “jock itch” affects groin & scrotal regions
• Ringworm or foot & hand (tinea pedis & tinea manuum) is spread by exposure to public surfaces; occurs between digits & on soles
• Ringworm of nails (tinea unguium) is a persistent colonization of the nails of the hands & feet that distorts the nail bed
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Ringworm Treatment
• Ointments containing – Tolnaftate
• Azole
– Miconazole• Azole
– Lamisil • Azole
– Griseofulvin• Inhibits fungal microtubules
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Superficial Mycoses• Tinea versicolor
causes mild scaling, mottling of skin
• White piedra is whitish or colored masses on the long hairs of the body
• Black piedra causes dark, hard concretions on scalp hairs
Opportunistic MycosesOpportunistic fungal pathogen
Host’s defense must be impaired.
Fungus has a weak or nonexistent virulence in a host with a normal functioning immune system.
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Candida albicans• Normal flora of oral cavity, genitalia, large intestine or
skin of humans• Account for 80% of nosocomial fungal infections• Account for 30% of deaths from nosocomial infections• Thrush
– Occurs as a thick, white, adherent growth on the mucous membranes of mouth & throat
• Vulvovaginal yeast infection– Painful inflammatory condition of the female genital region
that causes ulceration & whitish discharge• Cutaneous candidiasis
– Occurs in chronically moist areas of skin and burn patients
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Cryptococcus neoformans
• A widespread encapsulated yeast that inhabits soils around pigeon roosts
• causes Cryptococcosis• Common infection of AIDS, cancer or diabetes
patients• Infection of lungs leads to cough, fever, & lung
nodules• Dissemination to meninges & brain can cause
severe neurological disturbance & death
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Pneumocystis carinii• A small, unicellular fungus that causes pneumonia (PCP)
– The most prominent opportunistic infection in AIDS patients• This pneumonia forms secretions in the lungs that block
breathing & can be rapidly fatal if not controlled with medication
• Pentamidine – Mode of action is unclear– Investigations indicate that the drug inhibits the synthesis of
DNA, RNA, phospholipids and proteins• Cotrimoxazole
– Folate inhibitor– Azole
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Aspergillus• Very common airborne soil
fungus• 600 species
– 8 involved in human disease
• Inhalation of spores causes fungus balls in lungs and invasive disease in the eyes, heart, & brain
• Amphotericin B – Polyene
• Nystatin– Polyene
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Zygomycosis
• Zygomycetes are extremely abundant saprobic fungi found in soil, water, organic debris, & food
• Genera most often involved are Rhizopus, Absidia, & Mucor
• Usually harmless air contaminants invade the membranes of the nose, eyes, heart, & brain of patients with either diabetes or malnutrition with severe consequences.
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Alga / Algae• Photosynthetic protists
– Some biologists refer to them as algae
• Photoautotrophic– Contain chloroplasts with chlorophyll & other pigments– Produce large proportion of atmospheric O2
• Provide basis of food web in most aquatic habitats• Not classified as plants
– Lack many plant structures • Cuticle, vascular tissues, cell wall primarily composed of cellulose
• Cell wall– Contains cellulose, unique polysaccharides & variety of glycoproteins
• May or may not have flagella• Microscopic forms are unicellular, colonial, filamentous• Macroscopic forms are colonial & multicellular• Most are free-living in fresh and marine water• Some inhabit soil or trees• Water required for all aspects of life
– Cellular support, reproduction, and nutrient acquisition
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Algae• Classified
according to types of pigments & components of the cell wall
• Must use pigment that absorbs light that has not been filtered out
Littoral zone is defined as the area between the high water and
low water marks
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Dinoflagellates• Unicellular algae - plankton• Interlocking cellulose plates embedded in plasma membrane, structural integrity• Two flagella, propel by spinning through water
• Photosynthetic, uses conventional chlorophyll, also accessory pigments
• Some exist in as endosymbionts
• Jellyfish, corals & mollusks• Provide food to host organism through photosynthesis, host organism protects dinoflagellate from environment
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• Some produce toxins and cause of PARALYTIC SHELLFISH POISONING
• Paralytic shellfish poisoning side affect of RED TIDE
• Toxins produced by dinoflagellates accumulate in shellfish
• Toxin harmless to shellfish, very harmful (sometimes fatal) to other life
• Eating poorly prepared contaminated shellfish (oysters on the half shell) causes paralytic disease
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Diatoms• Phytoplankton• Unicellular or chains• Silica cell wall• Two symmetrical sides• Marine, freshwater & soil• Two halves• Carbon cycle• Silicon cycle
Progressivelysmaller
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Brown Algae • Kelp • Brown algae include the largest protists • Macroscopic - can reach lengths of 50 m (Macrocystis pyrifera)• Rapid growth rate - 20 cm/day• Many commercial uses
•Thickener for cooking, rubber tires, hand lotions
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Red Algae / Rhododphyta• Occupy greater depths than other algae• Red pigment allows algae to absorb blue light• Source of agar
• Bacteriological growth medium• Source of carrageenan
• Thickening agent• Evaporated milk, ice cream
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Green Algae• Many plant like characteristics
• Cellulose cell wall, chlorophyll a and b, starch for energy storage
• Hypothesized ancestors of terrestrial plants• Either unicellular or multicellular• Most are microscopic
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Lichens• Combination of fungus and photosynthetic organisms
• photobiont or phycobiont• Green algae, cyanobacterium• Yellow green algae or brown algae• There are some examples of a lichens containing both green
algae and cyanobacteria • Placed in kingdom fungi, classified based on fungal partner
• Ascomycetes & Basidiomycetes• Symbiotic relationship benefits both partners
• Harshes environments• Deserts to Antartica• Primary colonists – require water• Resistant to dessication
• Obligatory for the fungus• Relationship is typically not obligatory for the photobiont
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SorediumSoredium spread bywind
Algal cells are not endosymbiontsThere is one example of the cyanobacteria as true endosymbionts
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• Lichens are not plants and do not have roots • Grown on the surface of rocks, soil, sand, walls,
roofs and monuments• Lichens also grow as epiphytes on other plants
– Trunks and branches of trees
• Secrete organic acids which breaks down substratum– Part of nutrient cycling
• Very slow growing organisms• Important food source for reindeer• Bioindicator species
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