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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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Asexual spores on aerial mycelia

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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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Zygomycetes

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Ascomycetes

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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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Basidomycetes

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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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Dimorphic Fungi

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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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Histoplasma capsulatum

25 ºCHyphal growth

Histoplasmosis!!

36 ºCYeast like colony

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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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Tinia Capitis

Tinea Corporis

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Ringworm of the extremities

Tinia unguium

Trichophyton

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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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Candida albicans

Candida

Cryptococcus

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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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Cryptococcus neoformans

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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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Pneumocystis cariniiFungal cysts in lung tissue

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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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community.iexplore.com/photogallery/ www.anta.canterbury.ac.nz/

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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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Fructicose

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Reproduce by fragmentation

A few algal cells surroundedby fungal hyphae