bacteria

• • Bacteria replicate via binary fission
  • They have large circular DNA and smaller plasmids
  • DNA and plasmids replicate first
  • Cell grows, DNA moves to opposite sides, plasmids are distributed randomly
  • Cytoplasm divides
  • New cell membrane and wall form
  • Two cells are produced
  • Binary fission allows rapid division in warm, nutrient-rich conditions
• • Bacteria can grow in artificial media
  • Different media are used for specific bacteria
  • Some contain bile salts or blood as food
  • limited
  • Indicators may signal color changes
  • Growth observed on petri dishes
  • Suitable for all growth phases
  • Slower, not real-time
  • Contamination detectable
• LIQUID GROWTH  way to grow bacteria

  → other way is liquid growth to grow bacteria 

  → grow the bacteria to large scale 

  → however is there is contamination you don't’ know what is responsible

  →  or if cloudiness is contamination 

  → has to be done under aseptic technique  to minimize contamination 
• MONITORING GROWTH WITH LIQUID GROWTH  spectrophotometry → one of the benefits of Liquid media is that you are able to see how quickly the bacteria grow

  → you can monitor using something called spectrophotometry 

  → looking at the cell optical density of the bacteria culture 

  → the more bacteria grow , the higher the concentration the more bacteria that will scatter the light 

  → thus we will have a higher absorbance reading on the Spectrometer   
• → This is what is supposed to look 

  → lag phase =  have this sort of bit of time when the bacteria get in, use their environment before they start growing. 

  → log phase/expensional phase = division accelerated 

  → stationary phase = nutrients reduced / oxygen depletion/PH reduction 

  → Death phase = life spa ends and start to die / recycle
• What do bacteria need to grow?

  The correct temperature

  •   Psychrophiles – cold – optimal growth 15°C or below
  • Mesophiles – middle range - optimal growth 25°C -40°C ( accustomed to e coli) 
  • Bacteria that likes to grow in high temperatures → PCR enzymes 
  • Thermophiles - optimal growth 50°C-60°C or below
• The correct pH

  • Most bacteria need neutral pH 6.5-7.5 
  • Acidophiles – less than pH 5.4
  • Neutrophiles pH 5.4-8.5
  • Alkaliphiles pH 7-12 or higher
• Potassium, magnesium, calcium and cofactors

  • Enzyme cofactors

  Oxygen

  • Obligate aerobes are an organism that requires oxygen to grow. 
  • Facultative anaerobes
  • Obligate anaerobe
  • Microaerophillic\
• Gram + positive = bacteria .peptidoglycan layer is much thicker with cytoplasmic membrane underneath. stains purple with gram stain

  does not havea outter membrane

  
• Gram - bacteria thin peptidoglycan layer between 2 membranes the cytoplasmic and outer membrane. stains pink with gram stain
• functions of bacterial cell envelope can attack, stress responses, makes biofilm, protective. Some bacteria will produce an extra layer like a capsule, some bacterial thicken their cell walls/ stop things going in and destroying them 

  →  also be used to shed their cell walls →  make these biofilms

  → allows bacteria to colonize surfaces in environments that allow them to thrive in

  → It adds a layer of protection and it keeps them stuck onto these walls
• Gram staining procedure: 1. prepare heat- fixed bacterial smear.2. cover smear with crystal violet then rinse with water.3. cover smear with gram's iodine then rinse.4. decolorise smear with acetone then rinse.5. cover smear with saffranin then rinse and dry.6. observe with oil immersion.
• theory of gram staining adding the decolourizer causes shrinking of the peptidoglycan layer. So the crystal violet iodide molecules can't escape the now smaller peptidoglycan pores. in gram - bacteria the remaining pores after decolourizing are still large so violet iodide can flow out.
• peptidoglycan structurecovalent bonds of amino acids form sheet like structure. crystal lattice.stabilises cytoplasmic membrane so they can withstand high internal osmotic pressures.
• surface structures - Fimbriae (attachment), pili (gene transfer), flagella (movement)
• prokaryotes

  Bacteria and Archaea
• Prokaryotes vs. Eukaryotes differences

  prokaryotes: no nucleus, smaller, no organelles, peptidoglycan cell wall, small ribosomes, single circular chromosome with no histones.

  eukaryotes: larger, has DNA, nucleus and cell wall
• brief binary fission steps

  1. replication of the circular chromosome.

  2. growth and circular chromosomes move to opposite poles.

  3. invagination of the cell wall once the cell has expanded enough.

  4. separation into two daughter cells.
• growing bacteria

  via artificial media e.g. agar jelly, nutrient broths, blood based media. In petri dishes or in test tubes (liquid growth).
• liquid media benefits

  very fast growth, can look at density of growth in spectrometry.
• liquid media cons

  - harder to see contamination and cannot differentiate between different types and strains. cannot measure death phase. can't see colonies or measure over time growth.
• Bacterial growth curve

  Lag phase: metabolic activity w/o division Log phase: rapid cell division Stationary phase: nutrient depletion slows growth. Spore formation in some bacteria. Death phase: prolonged nutrient depletion and build up of waste products leads to death.

  
• conditions for bacteria growth

  optimal temperature for that strain, optimum pH, carbon and oxygen source and enzyme cofactors.
• Gram + bacteria

  peptidoglycan layer is much thicker with cytoplasmic membrane underneath. stains purple with gram stain
• Gram - bacteria

  thin peptidoglycan layer between 2 membranes the cytoplasmic and outer membrane. stains pink with gram stain
• functions of bacterial cell envelope

  can attack, stress responses, makes biofilm, protective
• acid fast bacteria

  have myocolic acid in cell wall. A lipid that protects bacteria from many detergents and acids. Resistant to decolourisation by acid- alcohol staining.
• Gram staining procedure

  1. prepare heat- fixed bacterial smear.

  2. cover smear with crystal violet then rinse with water.

  3. cover smear with gram's iodine then rinse.

  4. decolorise smear with acetone then rinse.

  5. cover smear with saffranin then rinse and dry.

  6. observe with oil immersion.
• theory of gram staining

  adding the decolourizer causes shrinking of the peptidoglycan layer. So the crystal violet iodide molecules can't escape the now smaller peptidoglycan pores. in gram - bacteria the remaining pores after decolourizing are still large so violet iodide can flow out.
• peptidoglycan structure

  covalent bonds of amino acids form sheet like structure. crystal lattice.

  stabilises cytoplasmic membrane so they can withstand high internal osmotic pressures.
• bacterial capsules

  Well organized, not easily washed off. Made of polysaccharides. Help pathogenic bacteria resist phagocytosis. Looks like force field around cell. adhere to host tissue. Biofilm formation. exist in harsh conditions.
• surface structures

  Fimbriae (attachment), pili (gene transfer), flagella (movement)