Hetttt

• Chapter 5 topics

  • Microbiology and Parasitology
  • Introduction
  • Algae
  • Protozoa
  • Fungi
  • Lichens
  • Slime Moulds
• Algae

  • Photosynthetic, eucaryotic organisms
  • Range in size from unicellular microorganisms to large, multi-cellular organisms
  • Produce energy by photosynthesis
  • May be arranged in colonies or strands
  • Found in fresh and salt water, wet soil, and on wet rocks
  • Cell walls contain cellulose
  • Classified as green, golden, brown, or red algae
  • Include diatoms, dinoflagellates, desmids, Spirogyra, Chlamydomonas, Volvox, and Euglena
  • Important source of food, iodine, fertilizers, emulsifiers, stabilizers, and gelling agents
• Protozoa


  • Nonphotosynthetic, eucaryotic organisms
  • Mostly unicellular and free-living
  • More animal-like than plant-like
  • Ingest whole algae, yeasts, bacteria, and smaller protozoa for nutrients
  • Do not have cell walls, but may possess a pellicle
  • Life cycle includes trophozoite and cyst stages
  • Some are parasites causing human diseases like malaria, giardiasis, and trypanosomiasis
  • Divided into groups based on method of locomotion
• Fungi


  • Study of fungi is mycology
  • Found everywhere
  • Diverse group of eucaryotic organisms including yeasts, moulds, and fleshy fungi
  • Not photosynthetic
  • Cell walls contain chitin
  • Some unicellular, some grow as hyphae forming mycelium
  • Hyphae can be septate or aseptate
  • Not plants, act as "garbage disposers" in nature
• Common Pond Water Algae and Protozoa

  • Amoeba sp.
  • Euglena sp.
  • Stentor sp.
  • Vorticella sp.
  • Volvox sp.
  • Paramecium sp.
• Prototheca, a genus of algae, is a rare cause of human infections
• Phycotoxins produced by algae can be poisonous to humans, fish, and other animals
• Ingesting phycotoxins from dinoflagellates causing "red tides" can lead to paralytic shellfish poisoning
• Protozoa are nonphotosynthetic, eucaryotic organisms that ingest whole algae, yeasts, bacteria, and smaller protozoa for nutrients
• Protozoa have a trophozoite (motile, feeding, dividing) and cyst (nonmotile, dormant) stage in their life cycle
• Some protozoa are parasites causing human diseases like malaria, giardiasis, and trypanosomiasis
• Protozoa are divided into groups based on their method of locomotion: Amebae, Ciliates, Flagellates, Sporozoa
• Fungi are eucaryotic organisms that include yeasts, moulds, and fleshy fungi, acting as "garbage disposers" in nature
• Fungal cell walls contain chitin and some fungi grow as hyphae forming mycelium
• Some fungi have septate hyphae while others have aseptate hyphae
• Fungi contain a polysaccharide called chitin
• Fungi


  • Some are unicellular, while others grow as filaments called hyphae
  • Hyphae intertwine to form a mass called a mycelium
  • Some have septate hyphae (divided into cells by cross walls)
  • Some have aseptate hyphae (without septa)
  • Whether a fungus has aseptate or septate hyphae is an important clue to its identification
• Fungi Reproduction


  1. Depending on the species, fungal cells can reproduce by budding, hyphal extension, or the formation of spores

  2. There are 2 general categories of spores: Sexual spores, Asexual spores (conidia)

  3. Some fungi produce both asexual and sexual spores

  4. Fungal spores are very resistant structures
• Fungi Classification


  • Based primarily on their mode of sexual reproduction and the type of sexual spore they produce
  • 5 phyla of fungi: Zygomycotina, Chytridiomycotina, Ascomycotina, Basidiomycotina, and Deuteromycotina
  • Deuteromycotina includes medically important moulds such as Aspergillus and Penicillium
• Yeasts are eukaryotic, unicellular organisms that lack mycelia
• Yeasts


  • Individual yeast cells can only be observed using a microscope
  • Yeasts usually reproduce by budding or occasionally by spore formation
  • A string of elongated buds is known as a pseudohypha
  • Some yeasts produce chlamydospores (thick-walled, spore-like structures)
• Yeasts are found in soil, water, and on the skins of fruits and vegetables
• Yeasts have been used for centuries to make wine, beer, and in baking
• Candida albicans is the yeast most frequently isolated from human clinical specimens
• Yeast colonies may be difficult to distinguish from bacterial colonies
• A simple wet mount can be used to differentiate yeast colonies from bacterial colonies
• Yeasts are larger than bacteria, oval-shaped, and often observed in the process of budding
• Moulds


  • Often seen in water, soil, and on food
  • Produce cytoplasmic filaments called hyphae
  • Reproduction is by spore formation, sexually or asexually
• Some moulds produce antibiotics and enzymes used commercially
• The flavor of certain cheeses is due to moulds that grow in them
• Fleshy Fungi


  • Include mushrooms, toadstools, puffballs, and bracket fungi
  • Consist of a network of filaments (mycelium) growing in soil or on rotting logs
  • Some mushrooms are edible, some are toxic
• A variety of fungi are of medical, veterinary, and agricultural importance due to the diseases they cause
• Infectious diseases caused by moulds in humans are called mycoses
• Superficial mycoses are fungal infections of the outermost areas of the human body, while cutaneous mycoses are infections of the living layer of the skin
• Superficial mycoses


  Fungal infections of the outermost areas of the human body - hair, nails, and epidermis
• Cutaneous mycoses


  Fungal infections of the living layer of the skin, the dermis
• Dermatophytes


  • Cause tinea ("ringworm") infections
• Note that "ringworm" infections have nothing to do with worms
• The yeast, Candida albicans, can cause cutaneous, oral, and vaginal infections
• Subcutaneous mycoses


  Fungal infections of the dermis and underlying tissues