fungi and protozoa

• what are Fungi?

  Are Eukaryotes, nearly all multicellular. distinguished from other kingdoms by nutrition, structural organization, growth, and reproduction.
• 3 main types of fungal nutrition

  • Saprobes - absorb nutrients from dead organic material
  • Parasitic fungi - absorb nutrients from cells of living hosts, some are pathogenic
  • Mutualistic fungi - absorb nutrients from a host, but reciprocate to benefit the host
• Hyphae


  The basic structural unit of fungal vegetative body (mycelium)
• Hyphae

  Except for yeast, hyphae are organized around and within food source.

  Composed of tubular walls containing chitin.

  Provide enormous surface area: 10cm2 of soil may contain 1km of hyphae with 314cm2 surface area.
• Septate hyphae


  Hyphae of septate fungi are divided into cells by cross-walls called septa
• Aseptate hyphae


  Hyphae of aseptate fungi lack cross walls (coenocytic)
• Haustoria


  Modified hyphae of parasitic fungi that penetrate the host tissue but remain outside cell membrane
• Modes of fungal reproduction

  • Sexual (by meiosis)
  • Asexual (by mitosis)
• Spores


  The agent of dispersal responsible for geographic distribution of fungi
• Molds


  Rapidly growing fungus with no sexual stages, may develop into a sexual fungus
• Molds

  Molds with no known sexual stage are known as Deuteromycota or imperfect fungi:

  penicillium
• Modes of yeast reproduction

  • Asexual by budding
  • Sexual by producing asci or basidia
• Saccharomyces cerevisiae


  The most important domesticated fungus, used for baking and brewing, and as a model organism
• Lichens


  Symbiosis of algae with fungal hyphae
• Algae in lichens


  • Provides fungus with food
  • May fix nitrogen
• Fungus in lichens


  • Provides good environment for algae growth
  • Produces compounds that shield algae and prevent predation
• Lichen reproduction


  1. Fungi reproduce sexually (usually ascocarps)

  2. Algae reproduce asexually by cell division

  3. Symbiotic units reproduce asexually by fragmentation or formation of soredia
• Mycorrhizae


  Specific, mutualistic association of plant roots and fungi, increases absorptive surface of roots and exchanges soil minerals
• Ecosystems depend on fungi as decomposers and symbionts
• Some fungi are pathogens, e.g. athlete's foot, ringworm, Dutch elm disease, ergot
• Many animals, including humans, eat fungi, including cultivated and wild mushrooms, and truffles
• Nitrogen Cycle


  A biogeochemical process through which nitrogen is converted into many forms, consecutively passing from the atmosphere to the soil to organism and back into the atmosphere
• Stages of Nitrogen Cycle

  • Nitrogen fixation
  • Nitrification
  • Assimilation
  • Ammonification
  • Denitrification
• Nitrogen Fixation


  Atmospheric nitrogen (N2) is converted into the usable form - ammonia (NH3), deposited into soils from the atmosphere and surface waters, mainly through precipitation
• Nitrification


  Ammonia is converted into nitrate by the presence of bacteria in the soil, nitrites are formed by the oxidation of ammonia
• Assimilation


  Plants take in nitrogen compounds from the soil with the help of their roots, which are available in the form of ammonia, nitrite ions, nitrate ions or ammonium ions and are used in the formation of the plant and animal proteins
• Ammonification


  When plants or animal die, the nitrogen present in the organic matter is released back into the soil, decomposers convert the organic matter back into ammonium
• Denitrification


  Nitrogen compounds make their way back into the atmosphere by converting nitrate into gaseous nitrogen, occurs in the absence of oxygen, carried out by denitrifying bacterial species
• Mycoses


  Infections caused by fungi, classified based on the area affected: superficial, cutaneous, subcutaneous, systemic
• Tinea versicolor, Tinea nigra

  Superficial mycoses caused by Malassezia furfur and Phaeoannellomyces werneckii respectively
• Ringworm infections


  • Tinea capitis - head
  • Tinea corporis - body
  • Tinea barbae - beard
  • Tinea manuum - hand
  • Tinea unguium - nails
  • Tinea pedis - "athlete's foot" - feet
  • Tinea cruris - "jock itch" - groin
• Sporotrichosis


  Subcutaneous mycosis caused by Sporothrix schenckii
• Histoplasmosis


  Systemic mycosis caused by Histoplasma capsulatum, isolated in soil with bird or bat droppings, transmitted by airborne route
• Blastomycosis


  Systemic mycosis caused by Blastomyces dermatidis, begins as a respiratory infection and may spread to other sites
• Candidiasis


  Most frequently encountered opportunistic fungal infection, caused by Candida species, can colonize mucosal surfaces and enter the bloodstream
• Cryptococcosis


  Causes cryptococcal meningitis, most cases occur in people with weakened immune systems, Cryptococcus neoformans present in soil contaminated with bird droppings
• Protozoa


  Single-celled organisms, some are parasitic and cause disease, three main groups: ciliates, flagellates, amoebae
• Flagellates


  • Smallest of the protozoa, move by means of one to several flagella, lack of mitochondria suggests they may have evolved prior to endosymbiotic events
• Parabasalids


  Anaerobic and are obligate symbionts or parasites of insects and vertebrates
• Diplomonads


  Have two identical-sized nuclei located alongside each other, e.g. Giardia lamblia which multiplies in the small intestine and causes malabsorption syndrome