Survey of Eukaryotic Microbes
• Fungi
• Algae
• Lichens
Chapters 5 & 22
Talaro
Foundations in Microbiology
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Kingdom Fungi
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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
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Mycology – the study of fungi
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Septum
crosswall
Aseptate or coenocytic
Conidium
asexual spore
hypha
Mycelium
A mass of hyphae
Body of Mold
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Asexual spores on aerial mycelia
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Four Main Divisions
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Zygomycetes
Ascomycetes
Basidiomycetes
Deuteromycetes
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•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
No sexual spores
Called by many the Fungi Imperfecti
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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 evenly
Saccharomyces cerevisiae
Ascomycetes with an
infrequent sexual stage
Schizosaccharomyces pombe
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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
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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
36 ºC
25 ºC
Hyphal growth Yeast like colony
Histoplasmosis!!
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Subcutaneous Mycoses
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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 & hairbearing 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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Trichophyton
Ringworm of the extremities
Tinia unguium
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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
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Opportunistic Mycoses
Opportunistic fungal pathogen
Host’s defense must be impaired.
Fungus has a weak or nonexistent
virulence in a host with a normal
functioning immune system.
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 carinii
Fungal 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
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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
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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
l 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
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Phytoplankton
Unicellular or chains
Silica cell wall
Two symmetrical sides
Marine, freshwater & soil
Two halves
Carbon cycle
Silicon cycle
Progressively
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smaller
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
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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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Soredium
Soredium spread by
wind
Algal cells are not endosymbionts
There 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 surrounded
by fungal hyphae
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