Lab exam 2 review with answers for Tues. 3/31

What are organisms grown on? agar
What is nutrient agar? Beef extract and peptone
What are the purposes of growth on agar? Colony morphology, amount, isolation in mixed culture
What is agar? Sea weed-kelp derivative
What is the best temperature for culture growth of most microbes? 37oC
What is sterilization of prepared agar? 121oC for 15 min
What are the two methods of agar inoculation? Loop dilution and streak method
Describe the two methods. Pour plate vs. streak plate
The streak method depends on inoculation into how many areas of the agar? 4 What is accomplished by using the streak method? To gradually dilute colonies What should be the outcome? Pure culture

What two methods of determination of bacterial populations were performed in class? Standard Plate Count/Serial dilutions and Turbidity
What are major differences between the two methods? Use of agar; use of spectrophotometer
How is the outcome of the standard count different from the turbidity method? Colony number versus turbidity reading
How does the spectrophotometer work? Light shown through specimen recorded by photodetector
What is the difference between turbidity ( absorbance) and percent transmission? Turbidity: light absorbed %P: light transmitted
As the percent transmission increases, what is observed about the organisms in the broth? Fewer numbers
Answer the same question for absorbance. More organisms
What is the optimum growth temperature for most bacteria? 37oC
What is room temperature? 25oC
At what temperatures, would you expect to have growth and in what amount? 5C: +-; 23C: +; 37C: ++; 42C: +\-
What happens when the concentration of solutes in the growth media exceeds that in the organism? Plasmolysis (hypertonic)
What if the solute is lower? hypotonic
What special medium was used for oxygen testing? Thioglycollate. What unique substance did it contain? Oxidation-reduction agent.
What is the thermal death point? Temp that kills in 10 min. What is thermal death time? Time to kill at particular temp.



What is the purpose of U.V light? sterilization How is the damage produced? Thymine dimers Can the damage be repaired? Yes What is the procedure for using U.V. light? In the petri dish, the U.V. light affects what? Colonies on plate

What is the difference between disinfectant and antiseptic? Inanimate Objects vs. skin Antiseptics lower concentration of bugs
Be able to recognize aerobic, anaerobic, facultative anaerobic and microaerophilic.
The pour-plate disk method produces results called the colony forming units/ml? How is the result determined? Colony count-number of colonies on plate times dilution factor.
What is the susceptibility testing method used in lab called? Disk diffusion-Kirby Bauer.
What is the medium used to perform antimicrobial susceptibility? Mueller Hinton
What values are used to determine the susceptibility result? Mm size of zone of inhibition How is it obtained? Measure zone of inhibition

Know how to perform a serial dilution. Know Absorbance and Percent Transmission. Know Thermal Death Point and Death Time. Know Growth in types of Oxygen environments and termperatures.
Know Osmolality Experiment: Hypertonic, hypotonic and plasmolysis
Know pour plate, streak plate and broth loop dilution tube plate
Know how to make a dilution