MICROPARA

• Bacterial physiology


  The study of the physical and chemical requirements of bacteria
• Physical requirements of bacteria

  • Temperature
  • pH
  • Osmotic pressure
• Temperature


  • Degree at which the organism exhibit growth
• Temperature ranges for bacterial growth

  • Psychrophiles (0°C to 20°C, optimum 15°C)
  • Mesophiles (10°C to 45°C, optimum 35°C)
  • Thermophiles (40°C to 70°C, optimum 60°C)
  • Hyperthermophiles (75°C to 113°C, optimum 80°C)
• pH ranges for bacterial growth

  • Acidophiles (pH <6)
  • Neutrophiles (pH 6 to 8)
  • Alkalinophiles (pH >8)

  
• Osmophiles


  Organisms that require high osmotic pressure in order to survive
• Halophiles


  Require high levels of salt; can survive in salt water (marine) environment
• Chemical requirements of bacteria

  • Carbon source
  • Oxygen
  • Inorganic ions
• Autotrophs


  Microorganisms that utilize inorganic compounds (e.g., carbon dioxide) and inorganic salts as their sole carbon source
• Photolithotrophs


  Derive energy from light
• Chemolithotrophs


  Derive energy from oxidation of inorganic substances and molecules
• Heterotrophs


  Organisms that make use of organic substances like sugars or glucose as their carbon source
• Oxygen requirements

  • Obligate aerobes
  • Microaerophilic microbes
  • Obligate anaerobes
  • Facultative aerobes
  • Aerotolerant anaerobes
• Capnophiles


  Organisms that may require the addition of carbon dioxide (5-10%) to enhance their growth
• Bacterial growth cycle


  1. Lag phase

  2. Log/Exponential phase

  3. Stationary phase

  4. Death/Decline phase

  
• Lag phase


  • Little or no multiplication but enzymes are very active; a period of adjustment and adaptation
• Log/Exponential phase


  • Organisms grow at maximum; most metabolically active; most sensitive to antimicrobials
• Stationary phase


  • Growth ceases because nutrients are exhausted or toxic metabolic products have accumulated; number of living cells = number of dying cells
• Death/Decline phase


  • Rate of cell division stops completely; direct microscopic count may remain constant but viable count slowly decreases
• Microbial ecology


  Interrelationships between microorganisms and the world around them
• Symbiosis


  Living together or close association of two dissimilar organisms

  
• Types of symbiotic relationships

  • Neutralism
  • Commensalism
  • Mutualism
  • Parasitism
• Neutralism


  Neither symbiont is affected by the relationship
• Commensalism


  Beneficial to one symbiont, no consequence to the other organism
• Mutualism


  Beneficial to both symbionts
• Parasitism


  Beneficial to one symbiont, detrimental to the other
• Classes of biosafety cabinets

  • Class I
  • Class II
  • Class III

  
• Class I biosafety cabinet


  • Open front, utilizes a vacuum that pulls the air towards it, provides minimal personnel protection, does not protect work surface
• Class II biosafety cabinet


  • Laminar flow with variable sash opening, sterilizes the air inside and the air coming out, provides protection for worker and work surface
• Class III biosafety cabinet


  • Affords the most protection, equipped with glove compartments that confer minimum exposure to biological specimen, provides maximum protection
• Biosafety levels


  • Level 1 (Minimal risk)
  • Level 2 (Moderate risk)
  • Level 3 (High risk)
  • Level 4 (Extreme risk)
• Biosafety level 1


  Those not known to cause disease in healthy adults, used for laboratory teaching
• Biosafety level 2


  Being sought in clinical specimens, commonly isolated in association with disease
• Biosafety level 3


  Handling specimens known to contain viruses, not in routine clinical tests, causes zoonotic infections
• Bioterrorism - use of microorganisms to impose fear or harm to a population
• Microbial reservoirs

  • Living reservoirs (Humans, Animals, Insects)
  • Nonliving reservoirs (Environment, Food/water/milk, Fomites)
• Passive carriers


  Carry pathogens without ever having had the disease; no symptoms of illness
• Convalescent carriers


  Harbor pathogens and transmit the pathogen while in a period of recovery
• Active carriers


  Completely recover from the disease but continue to harbor the pathogen
• Modes of transmission

  • Contact
  • Airborne
  • Droplet
  • Vehicular
  • Vector-borne