Mycology Mod 1-3

Medical mycology

is the branch of microbiology that deals with the study of fungi causing disease in humans.

Pitryiasis vesicolot

Tinea nigra

Superficial fungal infections

Dermatophytosis

are fungal infections of the skin and nails caused by several different fungi and classified by the location on the body.

Tinea corporis

Tinea cruris

Tinea pedis

Dermatophytosis of nails, skin hair

Chromycosis

Sporotrichosis

Subcutaneous fungal infections

Histoplasmosis

Blastomycosis

Cryptococcosis

Systemic candidiasis

Aspergilosis

Coccidoidomycosis

Systemic fungal infections

Fungal taxonomy

is the science of naming, describing, and classifying fungi based on their structural, biochemical, genetic, and reproductive characteristics

molecular phylogenetics

Historically, fungi were grouped based on morphology and spore formation, but modern taxonomy integrates ______ to provide a more accurate classification system.

Morphology

reproductive mode

Biochemical features

Genetic markers

Key criteria used in fungal taxonomy include:

Mitosis

Some unicellular fungi can reproduce by

Budding

Yeast cells reproduce by a process called

budding

a process in which part of the cell pinches itself off to produce small offspring

Kingdom Fungi

is a diverse group of eukaryotic organisms distinct from plants, animals, and bacteria.

They are heterotrophic, possess chitin in their cell walls, and reproduce by spores.

Fruiting body

Diploid nuclei

Spores released

Germination of spores and growth of mycelia

Fusion of two hyphae of compatible mating types

Growth of dikaryotic mycelium

Secual reproduction of fungi

Phylum Asccomycota (Sac Fungi)

Phylum Basidiomycota (Club Fungi)

Phylum Zygomycota (Zygomycetes)

Other Relevant Groups

Phylum Glomeromycota, Phylum Chytridiomycota, Deuteromycetes (Fungi Imperfecti)

Medically important fungi are distributed among several phyla:

Phylum Ascomycota (Sac Fungi)

✓ Largest phylum of fungi; reproduce sexually via asci and ascospores.

✓ Includes many important yeasts and molds.

Candida albicans

Aspergillus fumigatus

Histoplasma capsulatum

Examples of Phylum Ascomycota (Sac Fungi)

Candida albicans

common cause of mucocutaneous and systemic candidiasis.

Aspergillus fumigatus

causes aspergillosis.

Histoplasma capsulatum

– dimorphic fungus causing histoplasmosis

Phylum Basidiomycota (Club Fungi)

▪ Sexual reproduction via basidia and basidiospores.

▪ Includes mushrooms and some yeasts.

Cryptococcus neoformans

Malassezia spp.

Examples of Phylum Basidiomycota (Club Fungi)

Cryptococcus neoformans

encapsulated yeast causing cryptococcosis.

Malassezia spp.

lipophilic yeasts causing tinea versicolor.

Phylum Zygomycota (Zygomycetes)

▪ Produces zygospores during sexual reproduction.

▪ Rapid-growing, environmental molds.

Rhizopus, Mucor, Lichtheimia

Examples of Phylum Zygomycota (Zygomycetes)

Rhizopus, Mucor, Lichtheimia

agents of mucormycosis.

Mucoromycota and Zoopagomycota

Zygomycota is now largely reclassified into _____ and _____ based on molecular data.

Phylum Glomeromycota

Phylum Chytridiomycota

Deuteromycetes (Fungi Imperfecti)

Other Relevant Groups

Phylum Glomeromycota

mostly arbuscular mycorrhizal fungi, not pathogenic.

Phylum Chytridiomycota

– includes primitive fungi; mostly non-pathogenic to humans

Deuteromycetes (Fungi Imperfecti)

– an artificial group of fungi with no known sexual stage, including many pathogenic asexual forms (now reassigned based on molecular data).

1. Yeasts (unicellular, e.g., Candida, Cryptococcus)

2. Molds (filamentous, e.g., Aspergillus, Rhizopus)

3. Dimorphic fungi (mold in environment, yeast in host, e.g., Histoplasma, Blastomyces)

Medical mycology focuses on genera/species associated with human disease.

These fungi are classified as:

• Candida albicans, Candida auris

• Cryptococcus neoformans, Cryptococcus gattii

Yeasts:

• Aspergillus fumigatus, A. flavus

• Rhizopus, Mucor (Zygomycetes)

• Dermatophytes: Trichophyton, Microsporum, Epidermophyton

Molds:

• Histoplasma capsulatum

• Blastomyces dermatitidis

• Coccidioides immitis/posadasii

• Paracoccidioides brasiliensi

Dimorphic fungi:

• Malassezia spp. (superficial infections)

• Pneumocystis jirovecii (opportunistic pneumonia; formerly classified as a protozoan)

Other pathogens:

▪ International Mycological Association (IMA)

▪ International Society for Human and Animal Mycology (ISHAM)

▪ Mycobank and Index Fungorum

Modern fungal taxonomy is dynamic, with regular updates based on phylogenetic studies. Mycological societies such as:

international Mycological Association

IMA

International Society for Human and Animal Mycology

ISHAM

Mycobank and Index Fungorum

online repositories for fungal names and classifications ...provide updated taxonomic guidelines based on genomic data.

Eukaryotic

Fungi are ___ organisms with distinct structures adapted for survival, reproduction, and pathogenicit

Hyphae

are long, branching filamentous structures of a fungus. • They are the basic structural units of molds.

Septate hyphae

Aseptate (coenocytic) hyphae

Types of Hyphae

Septate hyphae

Types of hyphae

divided by cross -walls (septa); common in Ascomycota and Basidiomycota.

Aseptate hyphae

Types of hyphae

lack septa; typical of Zygomycota.

Mycelium

is a mass or network of hyphae.

▪ It forms the vegetative part of the fungus.

Vegetative mycelium

Aerial mycelium

Types of mycelium

Vegetative mycelium

Types of mycelium

penetrates the substrate for nutrient absorption.

Aerial mycelium

Types of mycelium

projects above the surface and may bear reproductive structures.

Spores

Fungi produce _____ for reproduction and dispersal

Yeast Cells

are unicellular fungi that reproduce primarily by budding or fission.

▪ They appear as round to oval cells, usually 3–15 µm in size.

Dimorphism

Some fungi can exist in two morphological forms—yeast and mold— depending on temperature or environment.

25-30 (room temp)

37 (body temp)

Dimorphism at what temp.

Mold form

Yeast form

Histoplasma capsulatum, Blastomyces dermatitidis, Coccidioides immitis, Sporothrix schenckii

Examples of dimorphic fungi

Polymorphism

Refers to fungi that can exhibit multiple forms (e.g., hyphae, pseudohyphae, and yeast cells) simultaneously.

Candida albicans

Prime example of polymorphism

Asexual reproduction

Common in most pathogenic fungi. ▪ Involves mitotic division of a single parent.

• Conidia (produced by conidiophores)

• Sporangiospores (produced inside sporangia)

• Blastoconidia (budding from yeast cells)

Forms asexual spores, such as:

Sexual reproduction

Involves genetic recombination between two compatible mating types. ▪ Less common in medical fungi.

• Ascospores (in Ascomycota)

• Basidiospores (in Basidiomycota)

• Zygospores (in Zygomycota)

Produces sexual spores, such as:

fission of somatic cell

budding of somatic cell

fragmentation or disjoining of hyphae

asexual spore formation

Asexual reproduction in fungi

Plasmogamy

Karyogamy

Meiosis

The process of sexual reproduction involves three phases:

Plasmogamy

fusion of protoplasm

Karyogamy

fusion of nucleus

Meiosis

reductional nuclear division

A. Gametic copulation

B. Gamete-gametangial copulation

C. Gametangial copulation

D. Somatic copulation

E. Spermatization

Various methods by which compatible nuclei are brought together in plasmogamy. ▪ Some are:

Gametic copulation

Fusion of two naked gametes, one or both of them are motile ➢ Isogamous, Anisogamous, Oogamous

Isogamous

Anisogamous

Oogamous

Types of Sexual Reproduction Based on Gamete Morphology

Isogamous

▪ Involves fusion of morphologically similar gametes.

▪ Gametes are equal in size and shape, but differ physiologically (e.g., mating type + and −).

▪ Common in primitive fungi and algae.

Example: Rhizopus species.

Anisogamous

▪ Involves fusion of dissimilar gametes in size or form.

▪ Both gametes are motile, but the male is smaller and the female is larger.

Seen in some algae and lower fungi.

Oogamous

▪ A specialized form of anisogamy.

▪ Large, non-motile female gamete (egg) fuses with a small, motile male gamete (sperm).

▪ Common in higher plants and animals; rare in fungi.

Gamete-gametangial copulation

▪ Male and female gametangia comes into contact but do not fuse.

▪ A fertilization tube formed from where male gametangium enters the female gametangium and male gamete passes through this tube

Gametangial copulation

Two gametangia or their protoplast fuse and give rise to zygospore

Somatic copulation

▪ Also known as somatogamy.

▪ In this process fusion of somatic cell occurs

▪ This sexual fusion of undifferentiated vegetative cell results in dikaryotic hyphae, so the process is also called dikarotization

Spermetization

▪ It is a union of special male structure called spertatium with a female receptive structure.

▪ Spermatium empties its content into receptive hyphae during plasmogamy

Ascospore

Basidiospore

Zygospore

Oospore

Types of sexual spores

Ascospore

It is usually single celled produced in a sac called ascus (plural: asci) and usually there are 4-8 ascospore in an ascus but the number may vary from species to species • The ascospore are usually arranged in a linear order. In some case ascospores are long, narrow and are arranged in parallel order.

Basidiospore

• It is a reproductive spore produced by basidiomycetes. • This single celled spores are born in a club shaped structure called basidium • These basidiospore aerves as main air dispersal unit for the fungi

Zygospore

are thick-walled spores formed when two sexually compatible hyphae or gametangia of certain fungi fuse together. ▪ In suitable condition, zygospore germinates to produce a single vertical hyphae which forms a aporangium and releases its spore

Oospore

These are formed within a special female structure called Oogonium. ▪ Fertilization of egg by male gamete in female sex organ give rise to oospoes. ▪ There are one or more oospores in each oogonium

Conidia

Sporangia

Blastocondia

Specialized Structures

Conidia

▪ Asexual, non-motile spores formed externally on conidiophores. ▪ Common in Aspergillus, Penicillium, and Dermatophytes. ▪ Useful for microscopic identification.

Sporangia

▪ Sac-like structures containing sporangiospores. ▪ Found in Zygomycetes (e.g., Rhizopus, Mucor). ▪ Sporangia burst to release spores

Blastocondia

▪ Budding cells seen in yeasts like Candida. ▪ May appear as single or multiple buds from the mother cell. ▪ Also involved in pseudohyphae formation

Nutritional needs

Growth condition

Media used

Growth Requirements and Fungal Nutritio

Rquires carbon

Nutritional needs

Sabouraud dextrose agar (SDA)

Brain-heart infusion (BHI)

Chromogenic agar

Media Used

Sabouraud dextroase agar (SDA)

Media

widely used for fungal culture

Brain Heart Infusion (BHI)

Media

used for dimorphic fungi

Chromogenic agar

Media

differentiates candida species