Untitled Quiz

• Fungi were discovered before bacteria and viruses
• Mushrooms were the first microorganisms known
• Fungi mostly caused skin or cosmetic infections, while bacteria/viruses caused fatal diseases so there was little interest in studying them
• In ancient Greece, Hippocrates recognized that people with oral thrush (Candida albicans) were already weakened by other diseases
• In the Middle Ages, children in Europe were infected with favus, a fungal disease of the scalp, smooth skin and nails, due to Trichophyton schoenleinii
• Most fungal diseases are non-communicable, but exceptions exist like dermatophytes
• Debilitated means weakened

Immunocompetence

• Immunocompromised means having a weakened immune system
• Immunocompetent means having a strong immune system

Dermatophytes

• Include 3 genera: Epidermophyton, Trichophyton, and Microsporum

Focus on Fungi

• In the 1980s, HIV/AIDS spread and weakened immune systems, making individuals susceptible to fungal infections, leading to respiratory infections like Pneumocystis pneumonia

Non-Communicable Fungi

• Refers to fungal infections that cannot easily be transmitted from one person to another
• Exist in the environment or within the host and cause disease under specific conditions, often affecting individuals with weakened immune systems

Microscopic Fungi

• Classified by the type of vegetative growth, either as yeasts or molds

Yeast

• Single-celled
• Budding example: Candida albicans
• Fission example: Schizosaccharomyces pombe

Yeast Production

• Blastoconidia (buds) like Candida
• Hyphae that fragment into arthroconidia like Trichosporon
• Pseudohyphae

Ablasto Condition

• Blasto conidia is an asexual holo blaste conidia formed through the blowing out of budding process of yeast cell

Arthrocndidi

• A type of fungal spore typically produced by segmentation of pre-existing fungal hyphae
• Example: Arthrocndidi of coccidioides immitis

Molds

• Filamentous, often branching cells called hyphae (singular, hypha)
• A mass of hyphae is termed mycelium
  • Mycelial means the mass of hypha
  • Hypha is singler

Dimorphism

• Having two forms
• An important characteristic of certain fungal pathogens
• 1-yeast form
• 2-mycelial form

YM Shift

• The transition of dimorphic fungi between yeast form in the host and the mold form in the environment, triggered by environmental changes
• Example: H. capsulatum
• This conversion is temperature sensitive
  • Yeast form happens at 37°c
  • Mycelial form happens at 25°c

Dimorphism

• Aids fungal survival and pathogenesis
• H. capsulatum yeast form survives inside macrophages
• Raises pH in vacuoles to resist destruction
• Produces a-(1-3)-D-glucan to avoid phagocytosis
• Travels via bloodstream to organs like the spleen and liver

Fungi Taxonomic Classification

• Based on:

  • Mode of sexual reproduction (meiosis)
  • Morphology
  • Life cycle
  • Physiology
  • Cladistic analysis

• If no sexual reproductive cycle is observed, the fungi are referred to as mitosporic and are further classified by cladistics analysis

• Phylogenetic refers to classification of organisms according to their evolutionary sequence, reflecting genetic relationships

• Sporagiospore are spores that are produced in an enclosed sac-like structure called a sporangium at the end of the sporangiophores

• The largest category of fungi pathogenic for humans is the Subkingdom Dikarya, consisting of two phyla: Ascomycota and Basidiomycota

Familiar Phylum

• Zygomycota is not considered a valid taxon because it is not monophyletic
• Monophyletic is a group or clade comprised of a single common ancestor and all the descendants of that ancestor
• Fungal pathogens previously classed in the zygomycota are now found in subphylum Mucoromycotina and subphylum Entomophthoromycotina

Mucoromycotina

• Identified by the production of:
  • Non-septate hyphae (coenocytic)
  • Sporangia and sporangiospores
  • Zygospore (sexual spore) formed by the fusion of two gametangia
  • Example: Rhizopus, Mucor

Ascomycota

• Sac fungi
• Accounts for about 75% of all described fungi
• Includes yeasts and molds
• Reproduce sexually after plasmogamy, followed by karyogamy and meiosis within a sac or ascus
• Asci are either naked, e.g., yeasts, or are formed within fruiting bodies
• Each ascus usually contains 8 ascospores
• The most important order in Ascomycota is Onygenales
• This order contains five families
• Some members of this order can degrade keratin, the principal protein of epidermis, hair, and nails
• This order contains the most medically important genera

Basidiomycota

• Reproduces sexually by basidiospores produced on the outside of the spore-mother cell called a basidium
• Doli Pore septa are specialized dividing walls between cells (septa) and found in almost all species of fungi in the Phylum Basidiomycota
• Aclamp connection is a hook-like structure formed by growing hy Phal cells of certain