Micropara 2f

• Fungi


  A diverse group of spore-producing eukaryotic organisms that is found almost everywhere on Earth and feed on organic matter, including molds, yeast, mushrooms

  
• Fungi are NOT PLANTS because they have no chlorophyll, hence they can't photosynthesize
• Fungi may cause disease in plants and animals especially on immunocompromised hosts
• Mycology


  The study of fungi

  
• Types of fungi based on source of food

  • Saprophytic fungi
  • Parasitic fungi
  • Beneficial fungi
• Saprophytic fungi


  Their main source of food is dead and decaying organic matter, they act as "garbage disposers" / "recyclers" by secreting digestive enzymes onto the dead plant and animal matter, decomposing this material and absorbing the nutrients
• Parasitic fungi


  Living on and within animals and plants; cannot make its own food so it is dependent on its host
• Beneficial fungi


  Attributed to the production of cheeses, beer, wine, and other foods and drugs
• Fungi can be microscopic or macroscopic (mushroom) organisms
• Types of microscopic fungi

  • Unicellular fungi
  • Multicellular fungi
• Unicellular fungi


  Only few are unicellular like yeasts, can perform all the activities efficiently on its own, still contains membrane-bound organelles, their cell wall is made up of chitin, capable of asexual reproduction through spores (budding), Pseudohyphae - chains of easily disrupted fungal cells marked by constrictions rather than septa at the junctions
• Multicellular fungi


  Cell wall is made up of a rigid polysaccharide called chitin, Hyphae - elongated, tubular filaments that contain the organelles and nucleus of the fungi, most fungi perform extracellular digestion by secreting digestive enzymes into the environment where there is availability of food to break down complex components into simpler ones for absorption, Mycelium - a branched network of hyphae or a collection of hyphae that intertwine, Spores - capable of sexual or asexual reproduction of fungi, function like seeds that can land where there is moisture and food and grow (germinate) to produce hyphae
• Comparison: Fungi vs Bacteria

  • Nucleus (Eukaryotic vs Prokaryotic)
  • Organelles (Present & membrane-bound vs few are absent and not membrane-bound)
  • Cell wall content (Chitin vs Peptidoglycan)
  • Spores (Reproduction & survival)
• Septate hyphae


  Contains septa, which are cross walls that divide the hypha into cells, allow passage and exchange of fluids and nutrients from one cell to another
• Aseptate hyphae


  Without septum, protoplasm is continuous
• Fungal spores are very resistant structures that are carried great distances by wind. They are resistant to heat, cold, acids, bases, and other chemicals
• Types of fungal reproduction

  • Asexual Reproduction - production of asexual spores / conidia through simple cell division or mitosis and not by the fusion of gametes
  • Sexual Reproduction - production of sexual spores done by the fusion of two gametes or simply the fusion of two nuclei

  
• Yeasts


  Eukaryotic single-celled (unicellular) organisms that lack mycelia, reproduce by budding which is a form of asexual reproduction, found in wine, beer, and alcoholic beverages, soil and water, skin of fruits and veggies
• Common examples of yeasts


  • Saccharomyces cerevisiae (baker's yeast) - ferments sugar to alcohol, breaks down simple sugars to carbon dioxide and water
  • Candida albicans - an opportunistic yeast that lives harmlessly on the skin and mucous membranes, can cause superficial / systemic yeast infections when conditions cause a reduction in the number of indigenous bacteria
• Molds


  Fungi often seen in water and soil and on food, multicellular and grow in the form of hyphae, reproduction is by spore formation, either sexually or asexually, great commercial importance: Penicillium (Penicillin) the first antibiotic
• Dimorphic fungi


  Can live either as yeasts or as molds, at body temperature (37 °C) exist as unicellular yeasts, at room temperature (25°C) exist as molds, example: Histoplasma capsulatum which causes histoplasmosis

  
• Fleshy fungi


  Commonly encountered in forests, Mushrooms are a class of true fungi consisting of a network of filaments (mycelium) that grow in the soil
• Major modes of transmission for fungal infections

  • Direct skin contact with infected host
  • Indirect contact with contaminated fomite such as hair brushes, clothing, caps, bed linens, towels
  • Inhalation of fungal spores

  
• Fungi do not secrete toxins, tissue damage associated with fungal infections results primarily from direct invasion of tissue, with subsequent displacement and destruction of vital structures plus toxic effects of the inflammatory response
• Classification of fungal diseases

  • Superficial mycoses - affect the outermost areas of the human body: hair, fingernails, toenails, the dead, outermost layers of the skin (the epidermis), the living layers of skin (dermis)
  • Subcutaneous mycoses - more severe type, fungal infections of the tissues underlying the dermis, grotesque in appearance
  • Systemic mycoses - fungal infections of internal organs of the body affecting two or more different organ systems simultaneously, most common instance is when respiratory system and the bloodstream are both affected

  
• Specific types of superficial mycoses (tinea infections)

  • Tinea capitis (ringworm of the scalp)
  • Tinea corporis (ringworm of the body)
  • Tinea barbae (ringworm of the beard)
  • Tinea faciei (ringworm of the face)
  • Tinea manuum (ringworm of the hand)
  • Tinea cruris (jock itch)
  • Tinea pedis (athlete's foot)
  • Tinea unguium (nail fungus)

  
• Pityriasis versicolor / Tinea versicolor


  Caused by Malassezia furfur, results in hypo or hyperpigmentation on the skin usually on the back or chest, common in puberty age and in tropical areas
• Sporotrichosis


  Also known as "rose gardener's disease", caused by the dimorphic fungus Sporothrix schenckii, usually occurs on a person's hand or the arm after touching contaminated plant matter, has the potential to disseminate and become systemic, presents as a small, painless bump that can develop after exposure to the fungus, the bump can be red, pink, or purple, and usually appears on the finger, hand, or arm where the fungus has entered through a break in the skin, the bump will eventually grow larger and may look like an open sore or ulcer that is very slow to heal
• Mycetomas


  Also known as "Madura foot", caused by the Eumycetoma mold, a chronic granulomatous infection that involves the feet (usually), hands, or other areas, causes firm, usually painless but debilitating masses under the skin that can eventually affect the underlying bone
• Pneumocystis pneumonia


  Caused by the opportunistic pathogen Pneumocystis jirovecii, commonly acquired by patients with weakened immune system (HIV/AIDS, corticosteroid therapy), extremely rare in healthy people, presents with fever, cough, dyspnea, chills
• Aspergillosis


  Caused by the opportunistic pathogen Aspergillus (mold), commonly acquired by patients with weakened immune system, presents with fever, cough, dyspnea, chills, aspergilloma (fungus ball)

  
• Specific Tinea infections: Tinea capitis


  ringworm of the scalp
• Specific Tinea infections: Tinea corporis


  ringworm of the body
• Specific Tinea infections: Tinea barbae 


  beard
• Specific Tinea infections: Tinea faciei


  face
• Specific Tinea infections: Tinea manuum


  hand
• Specific Tinea infections: Tinea cruris


  groin
• Specific Tinea infections: Tinea pedis


  foot
• Specific Tinea infections: Tinea unguium


  nail
• Sporotrichosis (subcutaneous)

  "rose gardeners disease"

  Fungi: Sporothrix schenckii