microbiology lab midterm PT2

• Oxidase test


  Purpose: to determine the presence of cytochrome c

  Positive result: blue/purple

  Negative result: clear
• Citrate test


  Purpose: to determine if the organism uses carbon as energy source

  Positive result: blue

  Negative result: green
• Nitrate test


  Purpose: to determine the bacteria's ability to reduce nitrates

  Color change: Red if nitrite is present; add zinc if not red
• Aerobic


  Requires oxygen to occur
• Anaerobic


  Doesn't require oxygen
• Takahara's disease is caused by the inability to produce catalase
• Clostridium bacteria are obligate anaerobes, so they would not be expected to produce catalase as the catalase test requires oxygen
• Disruption of cytochrome c oxidase in Leigh's disease results in generalized weakness and loss of muscle tone because cytochrome c oxidase is essential for cellular respiration and energy production
• Nitrate reduction can occur in both aerobic and anaerobic processes, but would be expected to occur more often in the absence of oxygen
• Hyperthermophilic organisms can withstand the highest heat
• Dry heat


  Convection, e.g. hot air oven
• Moist heat


  Condensation, e.g. autoclaving
• UV light types


  UVC (200-290 nm) is the most lethal
• Effects of UV radiation

  Causes skin & DNA damage
• Repair mechanisms


  Light repair and dark repair
• Spores are less affected to UV damage due to their thick, resilient outer layers
• Carotenoids in bacteria provide protection against UV radiation and have antioxidant properties
• Bactericidal


  Causes death of bacteria
• Bacteriostatic


  Temporarily inhibits bacterial growth
• Disinfectants


  Chemical products used on surfaces
• Antiseptics


  Used on humans
• To measure bacteriostatic effects, the modified use-dilution experiment would not be diluted as much
• Zones of inhibition


  Circular area around an antibiotic where bacteria don't grow

  Larger zone = more resistant

  Smaller zone = less resistant
• Organisms are most sensitive to antimicrobial agents during the log phase of growth
• Normal microbiota


  Permanently present on/in the body
• Transient microbiota


  Temporarily present
• Normal and transient microbiota do not normally cause disease, but can under the right circumstances, so they need to be removed before surgery to reduce infection risk
• MSA was used to grow bacteria from the skin due to its high salt concentration
• Coagulase


  An enzyme that causes clotting of blood plasma, increasing the risk of pathogens