I. I. FUNGI (Mycology)FUNGI (Mycology) Diverse group of heterotrophs.Diverse group of heterotrophs.

Many are ecologically important Many are ecologically important saprophytessaprophytes (consume dead and (consume dead and decaying matter)decaying matter)

Others are parasites. Others are parasites.

Most are multicellular, but yeasts are unicellular.Most are multicellular, but yeasts are unicellular. Most are aerobes or facultative anaerobes.Most are aerobes or facultative anaerobes. Cell walls are made up of Cell walls are made up of chitinchitin (polysaccharide). (polysaccharide). Over 100,000 fungal species identified. Only Over 100,000 fungal species identified. Only

about 100 are human or animal pathogens.about 100 are human or animal pathogens. Most human fungal infections are nosocomial and/or occur in Most human fungal infections are nosocomial and/or occur in

immunocompromised individuals (opportunistic infections).immunocompromised individuals (opportunistic infections).

Fungal diseases in plants cause over 1 billion Fungal diseases in plants cause over 1 billion dollars/year in losses.dollars/year in losses.

CHARACTERISTICSCHARACTERISTICS OFOF FUNGI FUNGI

1. Yeasts1. Yeasts

Unicellular fungi, nonfilamentous, typically oval or Unicellular fungi, nonfilamentous, typically oval or

spherical cells. Reproduce by mitosis:spherical cells. Reproduce by mitosis: Fission yeastsFission yeasts: Divide evenly to produce two new cells : Divide evenly to produce two new cells

((SchizosaccharomycesSchizosaccharomyces).).

Budding yeastsBudding yeasts: Divide unevenly by budding (: Divide unevenly by budding (Saccharomyces)Saccharomyces)..

Budding yeasts can form Budding yeasts can form pseudohyphapseudohypha, a short chain of , a short chain of

undetached cells.undetached cells.

Candida albicans Candida albicans invade tissues through pseudohyphae.invade tissues through pseudohyphae.

Yeasts are facultative anaerobes, which allows them to Yeasts are facultative anaerobes, which allows them to

grow in a variety of environments.grow in a variety of environments. When oxygen is available, they carry out aerobic respiration.When oxygen is available, they carry out aerobic respiration.

When oxygen is not available, they ferment carbohydrates to produce When oxygen is not available, they ferment carbohydrates to produce

ethanol and carbon dioxide.ethanol and carbon dioxide.

CHARACTERISTICSCHARACTERISTICS OFOF FUNGI (Continued)FUNGI (Continued)

2. Molds and Fleshy Fungi2. Molds and Fleshy Fungi Multicellular, filamentous fungi.Multicellular, filamentous fungi. Identified by physical appearance, colony characteristics, Identified by physical appearance, colony characteristics,

and reproductive spores.and reproductive spores. ThallusThallus: Body of a mold or fleshy fungus. Consists of many : Body of a mold or fleshy fungus. Consists of many

hyphae.hyphae. HyphaeHyphae (Sing: Hypha): Long filaments of cells joined together. (Sing: Hypha): Long filaments of cells joined together.

Septate hyphae:Septate hyphae: Cells are divided by cross-walls (septa). Cells are divided by cross-walls (septa). Coenocytic (Aseptate) hyphaeCoenocytic (Aseptate) hyphae: Long, continuous: Long, continuous cells that cells that

are not divided by septa.are not divided by septa.Hyphae grow by elongating at the tips.Hyphae grow by elongating at the tips.Each part of a hypha is capable of growth.Each part of a hypha is capable of growth.

Vegetative HyphaVegetative Hypha: Portion that obtains nutrients.: Portion that obtains nutrients. Reproductive or Aerial HyphaReproductive or Aerial Hypha: Portion connected with : Portion connected with

reproduction.reproduction. MyceliumMycelium: Large, visible, filamentous mass made up of many : Large, visible, filamentous mass made up of many

hyphae.hyphae.

Characteristics of Fungal Hyphae:Septate versus Coenocytic

Mycelium: Large, Visible Mass of Hyphae

CHARACTERISTICSCHARACTERISTICS OFOF FUNGI (Continued)FUNGI (Continued)

Dimorphic FungiDimorphic Fungi

Can exist as both multicellular fungi (molds) and yeasts.Can exist as both multicellular fungi (molds) and yeasts.

Many pathogenic species.Many pathogenic species. Mold form produces aerial and vegetative hyphae.Mold form produces aerial and vegetative hyphae.

Yeast form reproduces by budding.Yeast form reproduces by budding.

Dimorphism in pathogenic fungi typically depends on Dimorphism in pathogenic fungi typically depends on

temperature:temperature: At 37At 37ooC: Yeast form.C: Yeast form.

At 25At 25ooC: Mold form.C: Mold form.

Dimorphism in nonpathogenic fungi may depend on other Dimorphism in nonpathogenic fungi may depend on other

factors: Carbon dioxide concentration.factors: Carbon dioxide concentration.

LIFELIFE CYCLECYCLE OFOF FUNGIFUNGI Filamentous fungi can reproduce asexually by Filamentous fungi can reproduce asexually by

fragmentation of their hyphae.fragmentation of their hyphae.

Fungal sporesFungal spores are formed from aerial hyphae and are are formed from aerial hyphae and are

used for both sexual and asexual reproduction. used for both sexual and asexual reproduction.

1. Asexual spores1. Asexual spores: Formed by the aerial hyphae of one organism. : Formed by the aerial hyphae of one organism.

New organisms are identical to parent.New organisms are identical to parent.

ConidiosporeConidiospore: Unicellular or multicellular spore that is not : Unicellular or multicellular spore that is not

enclosed in a sac.enclosed in a sac.

ChlamydosporeChlamydospore: Thick-walled spore formed within a hyphal : Thick-walled spore formed within a hyphal

segment.segment.

SporangiosporeSporangiospore: Asexual spore formed within a sac : Asexual spore formed within a sac

(sporangium).(sporangium).

2. Sexual spores2. Sexual spores: Formed by the fusion of nuclei from two opposite : Formed by the fusion of nuclei from two opposite

mating strains of the same species. New organisms are different mating strains of the same species. New organisms are different

from both parents.from both parents.

IMPORTANTIMPORTANT DIVISIONSDIVISIONS OFOF FUNGIFUNGI

1. Deuteromycota1. Deuteromycota Not known to produce sexual spores. Not known to produce sexual spores.

Reproduce asexually.Reproduce asexually.

Catch-all category for unclassified fungi:Catch-all category for unclassified fungi: Pneumocystis cariniiPneumocystis carinii: Causes pneumonia in AIDS : Causes pneumonia in AIDS

patients. Leading cause of death in AIDS patients. patients. Leading cause of death in AIDS patients.

Originally classified as a protozoan.Originally classified as a protozoan.

Candida albicansCandida albicans: Causes yeast infections of vagina in : Causes yeast infections of vagina in

women. Opportunistic infections of mucous women. Opportunistic infections of mucous

membranes in AIDS patients.membranes in AIDS patients.

Opportunistic Infection by Candida albicans in an AIDS Patient

Source: Atlas of Clinical Oral Pathology, 1999

IMPORTANTIMPORTANT DIVISIONSDIVISIONS OFOF FUNGIFUNGI

2. Zygomycota (Conjugation Fungi)2. Zygomycota (Conjugation Fungi) Also known as bread molds. Also known as bread molds. Saprophytic molds with Saprophytic molds with coenocyticcoenocytic hyphae (lack septa). hyphae (lack septa). Asexual ReproductionAsexual Reproduction: Used most of the time. : Used most of the time.

SporangiosporeSporangiospore: Asexual spore enclosed within a : Asexual spore enclosed within a sporangiumsporangium or sac at the end on an aerial hypha. or sac at the end on an aerial hypha.

Sexual ReproductionSexual Reproduction: Occurs through : Occurs through conjugationconjugation, the , the joining of hypha of two different strains (plus and minus).joining of hypha of two different strains (plus and minus).

Zygospores:Zygospores: Sexual spores which are enclosed in a thick, Sexual spores which are enclosed in a thick, resistant wall. resistant wall.

Generally not pathogens.Generally not pathogens. Rhizopus nigricansRhizopus nigricans: Common black bread mold. May cause : Common black bread mold. May cause

opportunistic infections in diabetes patientsopportunistic infections in diabetes patients

Life Cycle of a Zygomycete: Black Bread Mold (Rhizopus)Reproduces Asexually and Sexually

Reproductive Structures of Zygomycete (Rhizopus)Sporangia (asexual) and Zygospore (sexual)

IMPORTANTIMPORTANT DIVISIONSDIVISIONS OFOF FUNGIFUNGI3. Ascomycota (Sac Fungi)3. Ascomycota (Sac Fungi) Molds with septate hyphae and some yeasts.Molds with septate hyphae and some yeasts.

Asexual ReproductionAsexual Reproduction: : ConidiosporesConidiospores notnot enclosed in a enclosed in a

sac. Become airborne easily. Form chains (broom-like sac. Become airborne easily. Form chains (broom-like

structures).structures).

Sexual ReproductionSexual Reproduction: : AscosporesAscospores enclosed in a enclosed in a sac-likesac-like

structure (structure (ascusascus).). Include common antibiotic producing fungi and yeasts, Include common antibiotic producing fungi and yeasts,

and several human pathogens.and several human pathogens. Penicillium notatumPenicillium notatum (Produces penicillin)(Produces penicillin) SaccharomycesSaccharomyces (Brewer’s yeast)(Brewer’s yeast) TrychophytonTrychophyton (Athlete’s foot)(Athlete’s foot) AspergillusAspergillus (Carcinogenic aflatoxin in peanuts)(Carcinogenic aflatoxin in peanuts),, BlastomycesBlastomyces (Respiratory infections)(Respiratory infections) Histoplasma capsulatumHistoplasma capsulatum (Respiratory and systemic infections)(Respiratory and systemic infections)

Life Cycle of Eupenicillium (Ascomycete)Reproduces Asexually and Sexually

Severe nail infection with Trichophyton rubrum ina 37-year-old male AIDS patient.Source: Intern. J. Dermatol. 31(1992): 453.

Disseminated Histoplasma capsulatum, skin infection.Source: Microbiology Perspectives, 1999.

IMPORTANTIMPORTANT DIVISIONSDIVISIONS OFOF FUNGIFUNGI

4. Basidiomycota (Club Fungi)4. Basidiomycota (Club Fungi) Have septate hyphae.Have septate hyphae.

Include mushrooms, toadstools, rusts, and smuts.Include mushrooms, toadstools, rusts, and smuts.

Sexual ReproductionSexual Reproduction: Produce : Produce basidiosporesbasidiospores: Spores : Spores

formed externally on a club shaped sexual structure or formed externally on a club shaped sexual structure or

base called base called basidiumbasidium. .

Asexual ReproductionAsexual Reproduction: Through hyphae.: Through hyphae.

Examples:Examples: Cryptococcus: Cryptococcus: Causes opportunistic respiratory and CNS Causes opportunistic respiratory and CNS

infections in AIDS patients.infections in AIDS patients.

Amanita: Amanita: Mushroom produces lethal toxins to humans.Mushroom produces lethal toxins to humans.

Claviceps purpurea:Claviceps purpurea: Produces ergot toxin in wheat and rye. Produces ergot toxin in wheat and rye.

Life Cycle of a BasidiomyceteMushrooms are Produced Sexually

NUTRITIONALNUTRITIONAL ADAPTATIONSADAPTATIONS OFOF FUNGIFUNGI

Fungi Fungi absorbabsorb their food, rather than ingesting it. their food, rather than ingesting it.

Fungi grow better at a pH of 5, which is too Fungi grow better at a pH of 5, which is too acidicacidic for for

most bacteria.most bacteria.

Almost all molds are Almost all molds are aerobicaerobic. Most yeasts are . Most yeasts are facultative facultative

anaerobes.anaerobes.

Fungi are more Fungi are more resistantresistant to to high osmotic pressurehigh osmotic pressure than than

bacteria.bacteria.

Fungi can grow on substances with very Fungi can grow on substances with very low moisturelow moisture..

Fungi require less nitrogen than bacteria to grow.Fungi require less nitrogen than bacteria to grow.

Fungi can break down complex carbohydrates (wood, Fungi can break down complex carbohydrates (wood,

paper), that most bacteria cannot.paper), that most bacteria cannot.

FUNGALFUNGAL DISEASESDISEASES

Mycosis:Mycosis: Any fungal disease. Tend to be chronic because Any fungal disease. Tend to be chronic because

fungi grow slowly. fungi grow slowly.

Mycoses are classified into the following categories:Mycoses are classified into the following categories:

I. SystemicI. Systemic mycosesmycoses: Fungal infections deep within the : Fungal infections deep within the

body. Can affect a number if tissues and organs.body. Can affect a number if tissues and organs.

Usually caused by fungi that live in the soil and are Usually caused by fungi that live in the soil and are

inhaled. Not contagious.inhaled. Not contagious.

Examples:Examples: HistoplasmosisHistoplasmosis ( (Histoplasma capsulatumHistoplasma capsulatum): Initial infection in ): Initial infection in

lungs. Later spreads through blood to most organs.lungs. Later spreads through blood to most organs.

CoccidiomycosisCoccidiomycosis ( (Coccidioides immitesCoccidioides immites): Resembles tuberculosis.): Resembles tuberculosis.

Systemic Mycosis: Histoplasmosis

Disseminated Histoplasma capsulatum, lung infection.Source: Microbiology Perspectives, 1999.

FUNGALFUNGAL DISEASES (Continued)DISEASES (Continued)

II. CutaneousII. Cutaneous mycosesmycoses: Fungal infections of the skin, hair, : Fungal infections of the skin, hair,

and nails. and nails.

Secrete keratinase, an enzyme that degrades keratin.Secrete keratinase, an enzyme that degrades keratin.

Infection is transmitted by direct contact or contact with Infection is transmitted by direct contact or contact with

infected hair (hair salon) or cells (nail files, shower infected hair (hair salon) or cells (nail files, shower

floors).floors).

Examples:Examples: RingwormRingworm ( (Tinea capitisTinea capitis and and T. corporisT. corporis))

Athlete’s footAthlete’s foot ( (Tinea pedisTinea pedis))

Jock itchJock itch ( (Tinea crurisTinea cruris))

Cutaneous Mycosis

Ringworm skin infection: Tinea corporisSource: Microbiology Perspectives, 1999

Cutaneous Mycosis

Candida albicans infection of the nails.Source: Microbiology Perspectives, 1999.

FUNGALFUNGAL DISEASES (Continued)DISEASES (Continued)

III. SubcutaneousIII. Subcutaneous mycosesmycoses: Fungal infections beneath the : Fungal infections beneath the

skin. skin.

Caused by saprophytic fungi that live in soil or on Caused by saprophytic fungi that live in soil or on

vegetation. vegetation.

Infection occurs by implantation of spores or mycelial Infection occurs by implantation of spores or mycelial

fragments into a skin wound. fragments into a skin wound.

Can spread to lymph vessels. Can spread to lymph vessels.

IV. Superficial mycosesIV. Superficial mycoses: Infections of hair shafts and : Infections of hair shafts and

superficial epidermal cells. Prevalent in tropical climates.superficial epidermal cells. Prevalent in tropical climates.

FUNGALFUNGAL DISEASES (Continued)DISEASES (Continued)

Opportunistic mycosesOpportunistic mycoses: Caused by organisms that are : Caused by organisms that are

generally harmless unless individual has weakened generally harmless unless individual has weakened

defenses:defenses: AIDS and cancer patientsAIDS and cancer patients

Individuals treated with broad spectrum antibioticsIndividuals treated with broad spectrum antibiotics

Very old or very young individuals (newborns).Very old or very young individuals (newborns).

Examples:Examples: AspergillosisAspergillosis: Inhalation of : Inhalation of AspergillusAspergillus spores. spores.

Yeast Infections or Candidiasis:Yeast Infections or Candidiasis: Caused mainly by Caused mainly by Candida Candida

albicansalbicans. Part of normal mouth, esophagus, and vaginal flora.. Part of normal mouth, esophagus, and vaginal flora.

ECONOMIC IMPORTANCE OF FUNGIECONOMIC IMPORTANCE OF FUNGI 25-50% of harvested25-50% of harvested fruits and vegetables are damaged fruits and vegetables are damaged

by fungi.by fungi.

Fungal infections of plants are commonly called rots, Fungal infections of plants are commonly called rots,

rusts, blights, wilts, and smuts.rusts, blights, wilts, and smuts. Phytophthora infestansPhytophthora infestans: Caused great potato famine in mid-: Caused great potato famine in mid-

1800s. Over 1 million people died from starvation in Ireland. 1800s. Over 1 million people died from starvation in Ireland.

Many immigrated to the U.S.Many immigrated to the U.S.

Beneficial fungi:Beneficial fungi: Candida oleophilaCandida oleophila: Prevents fungal growth on harvested fruits.: Prevents fungal growth on harvested fruits.

Saccharomyces cerevisiaeSaccharomyces cerevisiae: Used to make bread and wine. : Used to make bread and wine.

Genetically engineered yeast strainsGenetically engineered yeast strains are used to make proteins are used to make proteins

(Hepatitis B vaccine).(Hepatitis B vaccine).

TaxomycesTaxomyces: Produces anticancer drug taxol.: Produces anticancer drug taxol.

TrichodermaTrichoderma: Produces cellulase. Used to make fruit juice.: Produces cellulase. Used to make fruit juice.