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KINGDOM FUNGI
Introduction to FungiA large and diverse group ranging from a single-celled yeast or filamentous mold to a fleshy mushroom
Include some of the most important organisms, in terms of ecological and economic roles
Their ability to breakdown dead organic material allow continuation of the cycle of nutrients through ecosystem
Introduction to FungiSymbiotic fungi, which inhabit plant roots, supply essential nutrients to most vascular plants
Mycology
The branch of microbiology that studies fungi
General Characteristics of FungiHeterotrophic
Use organic compounds as carbon source
Nonphototrophic
Do not use light as energy source
Absorptive
Take up nutrients in solution
Saprophytic
Obtain nutrients by decomposing deal organic matter
Morphology of FungiYeasts
Single-celled form of fungusDo not have chlorophyllAble to reproduce by buddingSometimes, the bud remains with the mother cell and produces a pseudohyphaForm round, pasty or mucoid colonies with a pleasant odor, when on solid media
Morphology of FungiMolds
Highly branched and loosely intertwined hyphae that form a myceliumMycelia form woolly growth on damp and decaying material in nature and fuzzy spreading colonies on solid culture media
Morphology of FungiMycelium
A mass of hyphaecoenocytic--undividedsepta--incomplete divisionsThallus
body of the fungus Consists of long interconnected filamentsHyphae
individual filaments
FUNGAL HYPHAE
Coenocytic (undivided) hypha
Septate hypha
septum
Morphology of FungiDimorphism
Fungi are able to grow either as a mold or as a yeast
In pathogenic fungi, it is temperature-dependentYeastlike at 37CMoldlike at 25CMucor sp.
Morphology of FungiFleshy fungi
Form the fruiting structures Consist of tightly intertwines hyphaeEx: mushrooms, truffles or shelf fungi
Reproduction of FungiAssexual
elongation and fragmentationbuddingasexual spores Formed by the hyphae of one organismGenetically identical to the parent
Sexual
sporesResult from the fusion of nuclei from two opposite mating strains of the same species of fungus
Types of Asexual SporesConidia
Uni- or multicellular spores that are not enclosed in a sacEx. Aspergillus
Arthrospores
Formed by the fragmentation of a septate hypha into single, slighlty thickened cellsEx. Coccidioides immitis
Blastoconidia
Consists of buds coming off the parent cellEx. Candida albicans and Cryptococcus
Types of Asexual Spores
Chlamydospores
Thick-walled spores formed by rounding and enlargement within a hyphal segmentEx. Yeast form of C. albicans
Sporangiospores
Formed within a sac (sporangium)Each sporangium can contain hundred of sporangiosporesEx. Rhizopus
Sexual reproductionSexual spores results from sexual reproduction, consisting of three phases:
PlasmogamyHaploid donor cell nucleus (+) penetrates cytoplasm of recipient cell ()
Karyogamy+ and nuclei fuse
MeiosisDiploid nucleus produces haploid nuclei (sexual spores)
Sexual SporesZygospore
Fusion of haploid cells produces one zygospore
Ascospore
Formed in a sac (ascus)
Basidiospore
Formed externally on a pedestal (basidium)
Divisions of FungiThe Lower Fungi
All are coenocytic and lack septaChytridiomycetes and Zygomycetes
The Higher Fungi
All are septated, terrestrial, and have nonmotile conidia and gametesAscomycetes, Basidiomycetes and Deuteromycetes
Basis for ClassificationSexual reproduction
Shape and internal structure of the sporangia
The structure which produce the sporesMost useful characteristic for identification
LOWER FUNGI
ChytridiomycetesWater molds with uniflagellated sporangiospores and gametesGrow as fuzzy, whitish masses on organic materials in streams or pondsSometimes classified under Protista
Ex. Allomycesgrows in tropical ponds and streamsproduce beautiful bright orange sporangia
OomycetesForm the cottony masses on dead algae and animals in freshwaterFunction as decomposersAsexually, resemble the zygomycete fungi
Produce nonmotile female gametes and sexual spores (zoospores)Produce biflagellate sporangiospores and male gametes
Traditionally classified under fungi due to its structure
However, Its cellulose cell wall and DNA analysis confirmed its close relation to other algae
OomycetesSaprolegnia sp.
Parasite of fishesPhytophthora infestans
Causative agent of the great potato blight of Ireland
ZygomycetesTerrestrial molds
Able to complete their life cycle with minimal moisture Produce nonmotile sporangiospores and zygospores
Rhizopus (black mold)
Usually develops on stale bread Has a life cycle typical of ZygomycetesCauses zygomycoses, which attack immunocompromised individuals
HIGHER FUNGI
Ascomycetes
Produce sexual spores called ascosporesThe spores undergo several meiotic division producing haploid ascospores within an ascus
Morchella spp. (Morel)
Mushrooms with globular heads on stalkKnown for its delicious taste
Aspergillus
Causes opportunistic and systemic mycosesBlastomyces dermatitidis, Histoplasma capsulatum
Causes systemic mycosesMicrosporum, Trichophyton
Causes cutaneous mycosesMorchella sp.
Basidiomycetes
Produce sexual spores called basidiosporesUsually form basidiocarpsCommonly known as club fungi, mushrooms, puffballs or shelf fungiHave unique phase in their life cycle called dikaryon
A mycelium that contains two different kinds of nuclei (one from each parent)
DeuteromycetesDo not produce sexual sporesProduce conidia onlyGrow as molds or yeastsAlso known as Fungi Imperfecti
Due to lack of sexual stageMany species can cause human diseases
Blastomyces, Cryptococcus, Histoplasma, and CandidaAspergillusPenicillium
MycosesAny fungal infectionGenerally chronic infection due to the slow growth of fungi
Classification of mycoses is based according to:
Degree of tissue involvement Mode of entry into the host
Four groups of mycoses
Systemic, Subcutaneous, Cutaneous, Opportunistic
Systemic MycosesFungal infection deep within the bodyCan affect a number of tissues and organsUsually caused by terrestrial fungiTransmission is through inhalation of sporesInfection typically starts in the lungs, then spread to other body tissues
Ex. Coccidioidomycosis, Histoplasmosis
Coccidioidomycosiscocci, desert fever, desert rheumatism, desert bumps
Etiologic agent: Coccidioides immitisA dimorphic fungusAsexual spores: arthrosporesSexual spores: endospores
Endemic in southwestern United States, and Central and South AmericaConsidered as a potential biological weapon
Histopath showing endospore
CoccidioidomycosesThree clinical forms:
Primary pulmonarySigns and symptom: flu-like with rashes (erythema multiforme)If the disease does not progress, the individual develops resistance for 20 years to a lifetime
Benign formHallmark: development of well-defined lung cavitationMay be subclinical for years
Disseminated formDevelops in very few individualsSpread to various internal organs, including the brain
HistoplasmosisEtiologic agent:
Histoplasma capsulatum
A dimorphic fungusMycelial form:
produces microconidia (spores)
Found worldwideMode of transmission:
inhalation of spores Yeast formMycelial form
HistoplasmosisThree clinical forms:
Primary acuteMay be asymptomatic or may develop flu-like symptomsOther symptoms: chest pain, shortness of breath, hoarseness
Chronic cavitaryRelatively large pulmonary lesions developWith little signs and symptomsOften mistaken for tuberculosis
Severe disseminatedOccur most often in immunocompromised patientsOften fatal
Subcutaneous MycosesFungal infection beneath the skin caused by saprophytic fungi that live in soil and on vegetation
Infection occurs by direct implantation of spores or mycelial fragments into a puncture wound in the skin
Sporothrichosis
Gardeners diseaseA chronic subcutaneous mycosis with eventual lymphatic involvementIf untreated, may become a generalized infection involving bones, joints and other internal organsA relatively common disease with predilection to horticultural workers
Subcutaneous MycosesSporothrichosis
Etiologic agent: Sporothrix schenckiiA dimorphic fungus that commonly inhabits the soil and the epidermis of plantsAcquired through a scratch from a thorny plant, forcing the fungus into the subcutaneous tissues
Clinical presentation:From a small, movable, subcutaneous nodule, it spread to the lymph vessels of arm Open lesions are prone to secondary bacterial infection
Cutaneous Mycoses (Dermatomycoses)Fungi that infect only the epidermis, hair and nailsKnown as dermatophytes, which secrete keratinaseTransmission is from human to human or from animal to human by direct contact Transmission also by contact with infected hairs and epidermal cells
Causative agents:
Microsporum, Epidermophyton, TrichophytonMonomorphic fungi cultures at room temperture using Sabourauds mediumIdentification is based on gross and microscopic morphology of the colony
Some Clinical Forms of DermatomycosesTinea capitisTinea barbaeTinea ungiumTinea corporisTinea pedisTinea cruris
MicrosporumInfect hair and skin onlyForm both macro- and microconidia on short conidiophoresMacroconidia:
Multiseptate, fusiform, spindle- to oval shaped, cell walls vary in thickness and textureImportant for species identificationMicroconidia:
Single-celled, pyriform and smooth-walled, and are not diagnostic for any species
Common species
M. canis causes ectothrix hair and skin infectionM. ferrugineum causes tinea capitis; its branching hyphae has prominent cross walls, which gives it the characteristic bamboo hyphaeM. gypseum causes tinea barbae, ectothrix infectionM. canisM. ferrugineumM. gypseum
EpidermophytonInfect skin and nails only
Epidermophyton floccosum
the only species that infect man
Cause infection of the groin, body, feet and nailsMacroconidia:
club-shaped; singly or in clumps of 2 or 3; smooth cell wall; with 2-5 septaNo microconidia are formed
TrichophytonInfects the skin, hair or nailsInfect man and other animalsCharacterized by smooth-walled macro- and microconidia
Only a few species form macroconidia
Macroconidia are mostly directly attached on hyphae and fusiform in shape
Microconidia
Mostly spherical to pyriform or of irregular shape
Common species of TrichophytonT. concentricum
Commonly produce characteristic circular skin lesions tinea umbricata, a form of tinea corporisChlamydoconidia (in old culture) show typical balloon-shape
T. mentagrophytes
Cause of athletes footAlso cause tinea capitis, tinea corporis, tinea barbae and tinea crurisForm numberous, round microconidia, often in grape-like clusters
Common Species of TrichophytomT. rubrum
cause long-established foot and toenail infection, which is difficult to eradicateMay also cause tinea corporis and tinea capitisMicroconidia are thin-walled, cigar-shaped
T. tonsurans
Causes endothrix hair infections The entire hair shaft seems to be filled with sporesCauses tinea capitis, tinea corporis and tinea pedisMicroconidia are abundant, club-shaped and attached on the hyphae
Opportunistic PathogensMode of transmission:
Spores inhaled by people with debilitating lung diseases or cancerA granulomatous, necrotizing disease of the lungs, which often disseminate hematogenously to various organsMicroscopic exam:
Hyaline, septate hyphae with dichotomous branchingNo yeast observedGenerally harmless, but can become pathogenic in immunocompromised host
AspergillosisCausative agent: Aspergillus fumigatus
Opportunistic PathogensMucormycosis
phycomycosis or zygomycosisCaused mostly by Rhizopus and MucorInfection occurs mostly in patients with diabetes mellitus, leukemia or those undergoing immunosuppressive therapyMicroscopic exam: Large, hyaline, coenocytic hyphae
Candidiasis
moniliasis, mycotic vulvovaginitis, thrushCaused by Candida albicansA normal flora of the GI tract, vagina and oral areasIn room temperature, favors yeast form, which reproduce by buddingInside the human body, may develop a pseudohyphaeFrequently occurs in newborn, AIDS patient and those on broad-spectrum antibiotic
Cryptococcosisacute or chronic, pulmonary, systemic or meningeal mycosis genus: Cryptococcus (C. neoformans)Encapsulated yeastGrows in soil; from pigeon droppings no.2 cause of deaths in AIDS in ThailandMonomorphic
ToxinsSome fungi produce toxins that are hallucinogenic or poisonous
Muscarin
Produced by Amanita muscaria mushroomHighly hallucinogenicConsumed as part of the religious rites of people native to the northern rim of the Pacific Ocean
Phalloidin and amanitin
Produced by A. phalloides mushroom (death cap)Highly poisonousIngestion of a small queantity can cause death from irreversible liver failureA. muscariaA. phalloides
ToxinsErgot
Produced by Claviceps purpureaA mold that grows on rye which produces highly toxic ergotSt. Anthonys fire (ergot poisoning)Manifested by disorientation, hallucination, gangrene, abortion or deathErgot derivative drugs include methergine
ToxinsAflatoxin
Produced by Aspergillus flavusFrom not properly dried crops, such as peanuts and cereal grainscan cause severe liver damage and deathEven low levels may be carcinogenic
Black mold toxin
sick building syndromeStachybotrys chartarum in damp buildingscan manifest as headaches, dermatitis and general malaise