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CMB 201 Lab Exam 1

Terms in this set (22)

List two ways in which we use aseptic technique
1. Flame the loop
2. Work near flame at all times
3. Keep agar plates covered/test tubes with cotton in top
Diagram the procedure for streaking bacterial cells for isolation on a nutrient agar plate from a liquid culture in a test tube. List the steps of the procedure; don't forget to incorporate aseptic technique.
1. Flame the loop, dip it in your culture, drag it out in section 1
2. Flame the loop again, drag from section 1 to section 2
3. Flame loop again, drag from section 2 to section 3
________ growth phase during which bacterial growth rate is greatest
log/exponential
_______ also known as cloudiness of a culture
turbidity
_______ secondary (counterstain) in a gram stain
Safranin
_______ primary stain in a gram stain
Crystal violet
______ growth phase where rate of growth = rate of death
stationary
what is the color of a gram negative organism after gram stain
pink
what is the difference between colony morphology and cellular morphology?
colony morphology is how bacterial colonies plate (shape, elevation, margin, color, size, texture, orders)
Cellular morphology is how bacterial cells look under a microscope (rods, cocci, flagella)
When we make a smear, what is the purpose of heat fixation?
the heat allows it to stay on the wet mount slide
What is the difference between a "simple" stain and a "differential" stain
differential stain is a technique to distinguish 2 or more types of microorganisms based on phys/chem interactions. Simple stain is a general stain used to see cells (one stain used)
You did a gram stain of a culture of E.coli, however you forgot to add safranin, what color would you see?
colorless
why do bacteria produce endospores? at what stage in the bacterial growth curve are the made?
-to help survive in times of environmental stress
-stationary phase
what was peptone iron agar used to detect in our lab?
hydrogen sulfide
if you inoculate a glucose OF tube (green semi solid agar) with an unknown bacterium, what are two ways in which you could tell that the bacteria is anaerobic?
1. Presence of growth at the bottom of the tube where there is little to no O2
2. Yellow color change
Many organisms metabolize sugars through fermentation. The three potential waste products of fermentation are _____ , _____ , _____
acid, alcohol, gases
you are performing a biochemical test on your unknown organism and add a drop of hydrogen peroxide directly on top of your colony. What enzyme are you testing for?
catalase
We used the nitrate reduction test to see if your unknown bacteria can reduce nitrate. If your bacteria could reduce nitrate, what were the 3 forms of nitrogen, nitrate can be reduced to?
1. ammonium
2. nitrate
3. gas
Indole test uses Kovac's reagent and a ______ (red or yellow?) layer on the top is a positive result for the production of indole.
red
please draw a typical bacterial growth curve and label the four distinct phases. you must label your axis for full credit
Vertical : # of cells produced
Horizontal : time

lag, log, stationary, death
based on the volumes we used to make the dilutions, what its the dilution factor of the sixth tube?
1x10^6 = 1,000,000
using the dilution factor you solved in part A, calculate the concentration of the original E.coli culture
(1x10^6)(1.2x10^3) = 1.2 x 10^9
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