Fungi Morphology and Reproduction

• Fungi are morphologically divided into mushrooms, yeasts, and molds.
• Some, called dimorphic fungi, can grow as yeasts in tissues at 37°C or as molds in natural environments and labs at 25°C.
• Fungi can grow with or without oxygen.
• They can be multicellular (hyphae) or unicellular organisms.
• Hyphae with cross-walls (septa) are called septate hyphae.
• Hyphae lacking septa are called coenocytic hyphae.
• Fungi reproduce asexually via budding or sexually via genetic recombination.
• Lichens consist of hyphae and cyanobacteria or green algae.

Asexual Spores

• Sporangiospores are spores inside a sac (sporangium).
• Conidia (or conidiospores) are spores not enclosed by a sac.

Types of Conidia

• Arthrospores are rectangular spores.
• Chlamydospores are spherical spores.
• Blastospores are buds from a parent cell.
• Phialospores bud from the mouth of a vase-shaped cell.
• Microconidia and macroconidia are spores formed by the same fungus under different conditions; microconidia are one-celled, while macroconidia have two or more cells.
• Porospores grow out through small pores.

Pathogenic Fungi: Mycoses

• I. Superficial Mycoses (Cutaneous Mycoses) affect the surface.

Dermatomycoses

• Also known as Tinea or ringworm, these include:
• Trichophyton: Affects hair, skin, and nails.
• Epidermophyton: Affects skin and nails.
• Microsporum: Affects hair and skin.
• Specific conditions include:
  • Tinea capitis (scalp)
  • Tinea corporis (body)
  • Tinea cruris (jock itch)
  • Tinea unguium (nails)
  • Tinea pedis (athlete's foot)
  • Tinea versicolor (skin discoloration)

Other Superficial Mycoses

• Sporotrichosis is caused by Sporothrix schenckii.
• Candidiasis is caused by Candida albicans and can result from immunosuppression.
• Candidiasis can manifest as vaginal yeast infections, diaper rash in infants, or oral thrush.

Deep Mycoses

• Examples include infections caused by:
• Aspergillus
• Candida
• Blastomyces
• Histoplasma
• Cryptococcus
• Coccidioides
• Paracoccidioides

Algae

• Algae are photosynthetic, aquatic organisms that reproduce asexually and sexually.

Classification of Algae

• Chlorophyta: Green algae.
• Rhodophyta: Red algae (cell wall contains agar).
• Phaeophyta: Brown algae.
• Chrysophyta: Golden & yellow-green algae & diatoms; cell walls contain silica.
• Diatoms are a major source of the world's oxygen.

Protozoans

• Protozoans are eukaryotes, unicellular, and lack a cell wall.
• Most are motile and require a moist environment.
• Trophozoite: The motile, active, feeding form
• Cyst: The dormant form, which is important for survival in unfavorable environments.

Life Cycle of Protozoans

• Asexual reproduction occurs via schizogony, where the nucleus divides multiple times before the cell divides.

Important Protozoans

• Trichomonas vaginalis lacks a cyst stage and requires quick transfer from host to host.
• Giardia lamblia has a cyst stage.
• Microspora causes diseases in HIV patients.
• Balantidium coli is found in water.
• Trypanosoma is a flagellated protozoan.
• Entamoeba histolytica is found in soil and water and has pseudopods.
• Apicomplexa have complex life cycles involving multiple hosts; examples include Plasmodium, Toxoplasma gondii, and Cryptosporidium.

Helminths

• Helminths have a microscopic infective stage (egg or larva).
• Their life cycle includes fertilized egg, larva, and adult stages.

Classification of Helminths

• I. Platyhelminths (flatworms)
  • A. Trematodes (flukes) are named by the definite host tissue (e.g., lung fluke, liver fluke, blood fluke).
  • B. Cestodes (tapeworms) are intestinal parasites like Taenia solium and Taenia saginata.
• II. Nematodes (roundworms)
  • A. Enterobius vermicularis: pinworms
  • B. Ascaris lumbricoides