the agar plate we use is covered by a lawn of bacteria.
a lawn of bacteria completely covers the surface of an agar plate.
it is usually created by spreading a suspension of bacteria evenly over the plate using a sterile spreader. 

15 lbs per inch *2

​121.5 degrees C

chemical control of microbes

 disc diffusion method
(Kirby-Bauer method)
 tests the effectiveness of disinfectants and antiseptics by placing paper discs soaked in the test agent on an agar plate inoculated with bacteria.

a zone of inhibition
around the disc indicates the agent's effectiveness

what is the purpose of the disc diffusion method?

 1. inoculation: an agar plate is inoculated with a lawn of the target bacteria. 
2. agent application: each disc is soaked with test disinfectant or antiseptic. 
3. disc placement: sterile filter paper discs are placed on the agar surface. 
4. incubation: the plate is incubated
5. zone of inhibition: a clear zone (zone of inhibition) around the disc indicates that the antimicrobial agent has inhibited the growth of the bacteria. 

antiseptics
kill or inhibit microorganisms on living tissues (skin, wounds, mucous membranes) 

ex: iodine, chlorhexidine, alcohol, diluted hydrogen peroxide 

autoclave uses
moist heat sterilization:
steam generated under pressure kills microbes

                           in today's lab
  we will assess the growth of four different bacterial species            exposed to incubation under different temperatures.
 question:
    what is the optimal growth temperature for each of these bacterial species?
 hypothesis:
    your educated guess using this information..
   
  1. M. luteus is a mesophile
  2. S. marcescens is a psychrotolerant mesophile 
  3. E. coli is a mesophile
​  4. B. stearothermophilus is a thermophile

disinfectants
kill or inhibit
​microorganisms on non-living surfaces
(think countertops, floors, and medical equipment)

ex: bleach, hydrogen peroxide, alcohol, glutaraldehyde 

review question:

What was the purpose of the lab where we exposed 4 different bacterial strains to 4 different temperatures? 

what is the meant by the zone of inhibition? how does this zone relate to the effectiveness of a disinfectant/antiseptic?