Pre-Lab assignment #5 Flashcards
How does a spectrophotometer work?
a. The beam of light hits the diffraction grating like a prism. The light then interacts with the sample and it says how much light is seen through the specimen
List and define the two measurements a spectrophotometer can detect.
a. Absorbance- measurement of light that is absorbed by the sample
b. Transmittance- amount of light that passes completely through to the detector.
Explain how optical density can help determine the number of bacteria present in the medium and what is the purpose of the blank
a. Optical density can help determine the number of bacteria present in the medium by providing a quantitive value. The purpose of the blank is to zero the scale and to show a zero point
What two parameters are plotted to generate a bacterial growth curve? Make sure to indicate which parameter is plotted on the x-axis and which is plotted on the y-axis.
a. Absorbance rate on the y axis
b. Time on the x axis
Assume you are using a spectrophotometer to measure the optimal growth temperature of a bacterial species. Make a hypothesis as to how absorbance will be affected by bacterial growth.
a. The absorbance will be affected based on the growth of bacteria because if there is more growth there will be more absorbance.
Bacteria produce byproducts as part of their metabolism. What does that do to the pH of their environment?
a. It can change the pH resulting in there being less growth because the pH is not the optimal pH
Define acidophile, neutrophile and alkaliphile
a. Acidophile-loves acidic environments
b. Neutrophiles- loves neutral ph’s
c. Alkaliphile- loves basic solutions
What must the growth agar contain in order to protect the bacteria from this change in their environment?
a. Buffers, they keep things from changing in the agars.
Provide two different ways in which anaerobic microbes can be cultured.
a. Anaerobic chamber and anaerobic media with reducing agents
Today in lab, we will use an anaerobic jar and a GasPak. What is a GasPak (BD)? What chemicals are in it? And how does it function?
a. GasPak is a chamber where you suck the air out of it so you can see if microbes are anaerobic. The chemicals are sodium borohydride and sodium bicarbonate. This functions because if there is no air then the anaerobic bacteria will grow.
What two conditions do we need to set up in order to determine oxygen preference for our unknown microbe?
a. Turn on GasPak and remove the air, use the indicator to know when it is gone, and to see the growth on the plate and if it didn’t grow
What is catalase and what function does catalase have? (Include a chemical reaction.)
a. Catalases can break down hydrogen peroxide and break it into water and oxygen.
What ingredients are needed to test for the presence of catalase in a microbe?
a. Bacteria, hydrogen peroxide and look for bubbles
What does it look like if a microbe is catalase positive versus negative?
a. Positive have bubbles, Negative has no bubbles at all
What are cytochrome C and cytochrome C oxidase?
a. Cytochrome C: Cytochrome C oxidase substrate
b. Cytochrome C oxidase: terminal enzyme
