L1-3 bacteria

• Bacteria are prokaryotic cells
• microbiology is the study of organisms too small to be seen clearly by the unaided eye
• microorganisms exists in populations:

  • mixed populations
  • bacteria interact with each other and with other organisms
  • alter their environment
  • most of biomass on earth is microbial
• infectious diseases are caused by _

  pathogens
• disease controlled by:

  • vaccinations
  • antibiotics
  • personal hygiene
  • control measures
• disease is still the major cause of death in many lower income countries
• impact of microorganisms on humans:

  • cannot exist with microorganisms
  • both beneficial and harmful to humans
  • most microorganisms are beneficial
• what are the 3 domains of life?


  Eukaryote, Bacteria, Archaea
• Eukaryotes:

  • consists of one or more cells, each with a nucleus
  • include all organisms except: bacteria, viruses, certain (blue-green) algae
  • include fungi, animals, and plants as well as some unicellular organisms
• Bacteria:

  • large domain of prokaryotic microorganisms
  • few micrometres in length
  • sphere, rods and spiral shape
• Archaea:

  • similar size to bacteria
  • tRNA and ribosomal RNAs
  • absence of peptidoglycan cell walls, (often replaced with proteinaceous coat)
  • ether linked lipids built from phytanyl chains
  • occur only in unusual habitats
• all bacteria have:

  • compartmentalization and metabolism
  • growth
  • evolved
• properties of some bacteria:

  • motility
  • differentiation
  • communication
• microbial cell size:


  virus<bacteria<eukaryotes<yeast<algae<protists
• smaller cells have higher surface area to volume ratio so have _ growth


  faster
• more cell growth so more mutations possible leading to :


  greater evolutionary possibilities
• bacterial cell structure:

  label

  A) capsule/slime layer

  B) cell wall

  C) cytoplasmic membrane

  
• S-layer is present in some bacteria (function unknown)
• bacterial cell membrane function:

  • barrier to separate cell from its environment
  • selectively permeable to control movement of molecules
  • site of respiration and photosynthesis
  • energy conservation
• cell wall of bacteria function:

  • determines and maintains shape of bacteria
  • protects cell from osmotic lysis
• diplococci occurs as _ cells

  2
• streptococci is a _ of cells

  link
• clump of cocci are cells in a _

  clump
• gram-positive cell contain a _ layer of peptidoglycan 


  thick
• gram-negative cell wall have a _ layer of peptidoglycan


  thin
• gram negative cell wall has:

  outer membrane composed of lipids, proteins and lipopolysaccharides

  thin layer of peptidoglycan surrounding outer membrane
• s layer consists of proteins or glycoproteins
• how to gram stain:

  1. stain with crystal violets
  2. add iodine (to form complex with crystal violet)
  3. wash with ethanol
  4. counterstain with safranin
• gram-positive is _


  purple
• gram-negative is _


  negative
• peptidoglycan:

  • only found in Bacteria
  • cell wall antibiotics prevent cell wall formation (bacteriolytic)
  • lysozyme breaks GM bonds to burst the cell
  • defence against bacteria
• external cell wall:

  • capsule is made of polysaccharides

  function of capsule:

  • protect from host defences such as phagocytosis
  • protect from harsh environment
  • attach to surfaces
• lysozymes and antibiotics don't kill archaea becuase they lack


  peptidoglycan
• fimbriae structure:

  • short
  • thin
  • hair-like
  • proteinaceous
• fimbriae function:

  • recognition and attachment to surfaces
• pili structure:

  • longer, thicker and less numerous than fimbriae
• pili function:

  • required for mating
• types of flagellum:

  • polar flagellum-> flagellum at end of cell
  • monotrichous->one flagellum
  • amphitrochous ->one flagellum at each end
  • lophotrichous -> cluster of flagella at one or both ends
  • peritrichous -> spread over entire surface of cell
• proton turbine (protons flow through motor proteins, causing forces on charges present in the ring, so the flagellum can spin)
• bacteria cytoplasm (gelatinous material) contains:

  • ribosomes
  • cellular inclusion
  • macromolecules
  • organic molecules
  • inorganic molecules