Microbio 150

• Explain why most human pathogens are mesophiles?

  Human pathogens are this because our body temperature is approx. 37°C and most bacteria resident in human body.
• List the components of the bacterial cell that are influenced by temperature changes.

  Ribosomes, enzymes and cell membranes are all affected by temperature.
• Explain the effect of temperature on Serratia marcescens

  At 22C the growth higher and there is adistinnction with the color as well it has pink.

  At 37C the growth still high however there is no pink color involved.
• Why is it not advisable to connect the data points for each organism in your graph

  Gaps are large that you need more data points to see real line of best fit
• In what ways could you adjust incubation temp. to grow an organism at less than its optimal growth rate?

  A way would be the decrease or increase the temp. through the optimal growth rate
• Why do different temp. produce diff growth rates?

  Because different bacteria can only survive and grow with a certain temp affect the enzymes and the shape
• What was the purpose of the Snyder test?

  To favor the growth of oral bacteria & discourage growth of other bacteria.

  Yellow- positive

  Green- negative
• Why the color of the medium changes from green to yellow

  Evidence of fermentation & highly suggestive of the presence of dental decay.
• What precautions do you need to do to avoid dental caries?

  mechanical disruption of the plaque biofilm

  chemical disruption of the plaque biofilm
• Ingredients of the snyder test

  Pancreatic digest, yeast extract. It digest because these both create enzymes to digest.
• What kinds of dietary items would likely increase the number of lactobacilli in saliva? (ST)


  Sugar & carbohydrates, sweets, honey.
• Why isn't the molten Snyder Test Agar allowed to solidify as a slant?

  -so you can mix the saliva in the medium

  -lactobacilli are facultative anaerobes

  -if we inoculate on a solid surface, the bacteria will grow aerobically and will not ferment the sugar
• Is UV light ionizing or non ionizing?

  Non-ionizing
• Which wavelength of UV light is most germicidal?

  Shorter wavelength
• How does UV light cause death of microbes?

  Due to its mutagenic properties that cause pyrimidine dimers
• What limited protection do cells have against the damaging effects of UV radiation?

  Bacteria cells have enzymes of the SOS system that can correct pyrimidine dimers in small areas
• How are endospores protected from the harmful effects of UV light?

  -Endospores are more resistant to UV light than vegitavie cells

  -DNA of endospores is protected by small acid-soluble proteins that bind to DNA and alter is conformation, thereby protecting it from photochemical damage
• What result was observed when the Petri dish was kept covered during exposure to UV light? Why was such a result observed?

  Growth all over dish, because UV light could NOT penetrate through
• Why was the cover used on the petri dishes?

  It was used to have it as a control part of it and to compare the result of the UV light.
• Which organism survived the longest exposure and why?

  B. subtilis survived the longest because of endospores.
• Why were you told to remove the plate covers prior to exposing them to UV?

  To prevent the plastic from blocking the UV light
• Identify the 3 types of hemolysis on the blood agar plate

  beta hemolysis-complete clear destruction

  
  

  alpha hemolysis-partial destruction producing greenish discoloration

  
  

  gamma hemolysis-non hemolysis and simple growth with no change to medium
• What type of hemolysis would the causative agent of strep throat produce?

  What type of hemolysis would the causative agent of pneumonia produce?

  Streptococcus pyogenes and beta hemolysis (group A strep)

  Streptococcus pneumoniae
• The kirby bauer method

  used to determine if an organism is susceptible or resistant to a selection of antimicrobial agents.
• Special culture medium used for the Kirby Bauer Method Test


  E.coli & S. epidermis
• What factors influence the size of the zone of inhibition for an antibiotic

  diffusibility of the agent, size of the inoculum and type of medium