WORK Sheet Micro chapter 7 edited 9 19 PDF

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Chapter 7 (6) Worksheet Name: Maryann Cucina

Date: 9/17/19

1. Draw and label a standard bacterial growth curve. Make sure you label the axes, the stages and briefly explain in your own words what is occurring at each stage.

Log phase Stationary Death or decline phase

Logarithm of # of cells Lag phase

Time

2. What are 5 ways to measure bacterial growth? Indicate which ones measure viable cells with an *. a. Standard Plate Count b. Direct Microscopic Counts c. Most Probable Number d. Filtration e. Other Methods: Turbidity, Spectrophotometer

3. Most probable number (MPN) technique is a method used to A. Estimate the number of viable microbes in a water sample B. Count microbes that are dead or alive. C. Used the counting of CFU on agar plates to determine viable cell numbers D. Calculate the microbial biomass in a sample of water. 4. Name 3 groups of bacteria based on their growth pH requirement. 7: Alkaliphiles

5. Why does preserving food in a solution with a high salt concentration work? High concentrations of dissolved substances exert sufficient osmotic pressure to kill or inhibit microbial growth. 6. Why do bacteria produce exoenzymes? So they can split large molecules of carbohydrate, lipid, or protein into smaller ones so they can be absorbed. 7. Match the following microbial oxygen requirements with their descriptions. __B__ obligate aerobe

a. Carbon-dioxide loving organism

__F__ obligate anaerobe

b. Must have abundant oxygen

__E__ microaerophile

c. Can live in presence of oxygen, but don’t use it in their metabolism

__A__ capnophile __C__ aerotolerant anaerobe

d. Can use oxygen if it is present, but if oxygen is absent, they will shift to an anaerobic metabolism e. Do best in a small amount of oxygen f. Killed by free oxygen

8. Match the type of media with the correct description. __E__ defined __C__ complex __D__ selective __B__ differential __A__ enrichment

a. Contains special nutrients that allow “fussy” eaters to grow b. An example: potato dextrose agar made with real potatoes c. contains an ingredient that causes a change that can be observed when a particular reaction occurs d. encourages the growth of some organisms but suppresses the growth of others e. is a very specific medium with known chemicals with known amounts...