Microbio

• In vitro


  Events that occur outside the biological environment
• Moisture


  • Water is essential for life
  • Cells are 70% to 95% water
  • Organisms can survive complete drying (desiccation) when dormant in cysts/spores
  • Organisms in moist, nutrient-rich environments will grow and reproduce
• Temperature


  • Every microorganism has an optimum growth temperature
  • Minimum temperature below which it ceases to grow
  • Maximum temperature above which it dies
• pH preferences of microorganisms

  • Most prefer a neutral or slightly alkaline growth medium (pH 7.0-7.4)
  • Acidophilic microbes (acidophiles) prefer a pH of 2 to 5
• Alkaliphiles


  Prefer an alkaline environment (pH 8.5) such as found inside the intestine and in soda lakes
• Osmotic Pressure


  Pressure exerted on a cell membrane by solutes both inside and outside the cell
• Solutes


  Substances dissolved in liquid
• Osmosis


  Movement of a solvent through a permeable membrane from a solution
• Diffusion


  Opposite of osmosis
• Crenation


  Loss of water causes the cell to shrink
• Plasmolysis


  Inhibiting cell growth and multiplication
• Plasmolysis in bacterial cells


  Cell membrane and cytoplasm shrink away from the cell wall
• Hypotonic


  Concentration outside is less than inside in which the cell is suspended
• Hemolysis (Erythrocytes)


  Increase in water within cell cause it to swell and if sufficient water enters the cell will burst (lyse)
• Isotonic


  Equal both inside and outside
• Isotonic environment


  Excess water neither leaves nor enters the cell and thus plasmolysis or plasmolysis occurs
• Halophilic


  Microbes that prefer salt environment
• Piezophiles


  Thrive in deep ocean and in oil well, where the atmosphere pressure is very high
• Obligate Aerobes


  Prefer the same atmosphere as humans
• Microaerophiles


  Require oxygen but reduced concentration of oxygen
• Obligate Anaerobe


  Killed by the media so then they can gather information that will enable identification at any pathogens that are present
• Hypertonic - Concentration inside is less than outside in which the cell is suspended
• Halo - salt
• Philic - love
• Halotolerant - tolerate high concentrations of salts
• Culture Medium: Nutrients prepared for Microbial Growth
• Sterile: No living microbes
• Inoculum: Introduction of microbes into medium
• Culture: Microbes growing in/on culture medium
• Agar:

  • Complex polysaccharide
  • Used as solidifying agent for culture media in petri plates, slants and deeps
  • Generally not metabolized by microbes
  • Liquefies at 100°C
  • Solidifies at -40°C
• Bacterial Growth - refers to an increase in the number of organisms rather than an increase in their size
• Binary fission - division into two daughter cells
• Generation time - times it takes a particular bacterial species to undergo binary fission
• Short generation time - rapid growers
• Long generation time - slow grower
• Liquid Media - bacteria grow producing turbidity/surface pellicle ( Vibrio & Bacillus )/ granular deposits (Streptococci)
• Solid Media - any liquid medium can be rendered solid by the addition of certain solidifying agents. Agar is the most commonly used solidifying agent.
• Agar - composed of two long chain polysaccharides ( 70% agarose and 30% agarapectin)
• Semi-solid media - reducing the amount of agar to 0.2% - 0.5% refers a medium semi-solid. Useful for bacterial motility
• Minimal requirements - non fastidious