rorome

• In vitro


  Events that occur outside the body
• In vivo


  Events that occur inside the body
• Growth


  • Orderly increase in the sum of all components of an organism
  • Replication of all cellular structures, organelles and components
• Microbial growth


  • Increase in the number of cells, not an increase in the size of the organism
  • Thousands of cells make up a bacterial colony, hence colonies are composed of billions of cells
• Bacterial growth


  Proliferation or multiplication of bacteria
• Nutritional requirements

  • Carbon
  • Nitrogen, sulfur & phosphorus
  • Inorganic ions
  • Growth factors
• Autotrophs/Lithotrophs


  Microorganisms that utilize inorganic compounds, salts and water as their sole source of carbon
• Autotrophs/Lithotrophs


  • Photolithotrophs
  • Chemolithotrophs
• Heterotrophs/Organotrophs


  Microorganisms that utilize organic substances like sugars/glucose as their carbon source
• Heterotrophs/Organotrophs


  • Photoorganotrophs
  • Chemoorganotrophs
• Approximately 14% of bacterial cells are nitrogen and about 4% are sulfur and phosphorus
• Magnesium


  • Stabilizes ribosomes, cell membranes & nucleic acids and serves as a co-factor for many enzymes
• Potassium


  • For the normal functioning & integrity of ribosomes and also for certain enzymatic activities
• Calcium


  • An important constituent of the cell walls of Gram-positive bacteria and contributes to the resistance of bacterial endospores against adverse environmental conditions
• Iron


  • Part of cytochrome and also functions as cofactor in enzymatic activities
• Trace elements are components of enzymes & function as cofactors
• Growth factors


  • Vitamin B complex
  • Amino acids
  • Purines
  • Pyrimidines
• Moisture/water


  The bacterial cell is composed mainly of water
• Oxygen classification of microbes

  • Aerobes
  • Obligate/strict anaerobes
  • Aerotolerant anaerobes
  • Microaerophilic anaerobes
  • Facultative organisms
• Strict aerobes


  • Strictly require oxygen for growth
• Obligate/strict anaerobes


  • Cannot survive in the presence of oxygen, lack enzymes like superoxide dismutase and catalase
• Aerotolerant anaerobes


  • Can resist exposure to oxygen and therefore are not killed by its presence
• Microaerophilic anaerobes


  • Able to grow at low oxygen tension but its rate of growth is diminished
• Facultative organisms


  • Can grow under both aerobic or anaerobic conditions
• Temperature requirements


  • Thermophiles
  • Mesophiles
  • Psychrophiles
• Thermophiles


  • Heat loving, grows best at an optimum temperature range of 50 - 60°C
• Hyperthermophiles (extreme thermophiles)


  • Favor temp above 100°C
• Pyrolobus Fumarii is a bacterium (archeon) found living at the highest temperature of around 113°C
• Mesophiles


  • Require an optimum temperature of 20 - 40°C
• Psychrophiles


  • Require an optimum temperature of 10 - 20°C, love cold temperatures and thrive in cold ocean water
• Psychroduric organisms


  Organisms able to endure very cold temperatures and can be preserved in the frozen state
• pH requirements


  • Alkalophiles (pH 8.4 – 9.0)
  • Neutrophiles (pH 7.5 – 8.0)
  • Acidophiles (pH 6.5 – 7.0)
• Most medically important bacteria grow best at pH of 6.7 – 7.5; considered neutrophiles
• Vibrio Cholerae, the causative agent of cholera, is the only human pathogen that grows well above pH 8
• Piezophiles


  Thrive deep in the ocean and in oil wells, where the atmospheric pressure is very high
• Halophiles


  Require high salt concentration for growth
• Osmophiles


  Require high osmotic pressure for growth
• Haloduric organisms


  Do not prefer to live in salty environments but are capable of surviving there
• Phases of bacterial growth curve

  • Lag phase
  • Logarithmic/Exponential/Log phase
  • Stationary phase
  • Death phase or Decline phase
• Lag phase


  • Bacteria absorb nutrients, synthesize enzymes & prepare for cell division
  • Bacteria do not increase in number but there is increase in size