MICR 2420 Lecture Notes - Lipopolysaccharide, Prokaryotic Small Ribosomal Subunit, Lactobacillus
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1.This week, you will be conducting Gram stains of bacteria.Which of the following statements are true? (Mark all thatapply)
Gram-negative bacteria do not stain purple because they do nottake-up crystal violet or iodine | ||
The peptidoglycan in the walls of Gram-positive bacteria bindsto the crystal violet stain more easily than walls of Gram-negativebacteria do | ||
Gram-positive bacteria have cell walls with a thickerpeptidoglycan layer than walls of Gram-negative bacteria | ||
Gram-negative bacteria do not stain purple, because their cellwall structure allows purple-colored iodine-dye complexes to washout of the cells more easily than the cell wall structure ofGram-positive bacteria does | ||
Gram-negative bacteria have an outer membrane (outside thepeptidoglycan layer in their wall) that Gram-positive bacterialack |
2.
What evidence is used to inform our understanding ofrelationships among species? (mark all that apply)
Biochemical similarities between existing species | ||
Fossils | ||
Morphological similarities between existing species (presence ofhair, backbones, etc.) | ||
DNA sequences and molecular clocks |
3.
For each of the groups of organisms below, indicate whether theybelong in (A.) Archaea, (B.) Bacteria, or (C.) Eukarya
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4.
Select all true statements about the relative diversity ofdifferent groups of organisms from among the followingstatements:
There are more species of plants on Earth than species ofmolluscs | ||
There are more plant species on Earth than mammal species | ||
There are more species of plants on Earth than species offungi | ||
There are more species of fungi on Earth than mammal species | ||
There are more species of plants on Earth than species ofarthropods | ||
There are more flatworm species on Earth than mammal species |
Question 1
What is the last step of successfully preparing a bacterial smear for a simple stain?
Spread cells with inoculating loop | ||
Label the slides | ||
Heat fixation | ||
Air dry the smear |
Question 2
When looking at your smear under the microscope, all you see is darkness (despite shining light through your slide)- the best explanation is:
all your bacteria are dead | ||
your smear was too thin | ||
forgot to add the bacteria | ||
your smear was too thick |
Question 3
If a microbe can ferment lactose and its fermentation products include lactic acid and CO2, then the results for this assay should be:
the broth will appear yellow and there will be a gas bubble in the Durham tube | ||
the broth will appear red and there will be no gas bubble in the Durham tube | ||
the broth will appear yellow and there will be no gas bubble in the Durham tube | ||
the broth will appear red and there will be a gas bubble in the Durham tube |
True/Flase
Question 1
If the result for this carbohydrate test is negative, then the organism had NO growth in the tube.
Question 2
The biochemical basis of the Gram stain is the thickness of peptidoglycan layers surrounding cells. Therefore a Gram positive cell with a thin layer of peptidoglycan should stain as Gram negative.
Question 3
If the iodine is not applied during the Gram stain, then gram positive cells will likely stain pink
Question 4
A simple stain allows you to see the cell shape and arrangement.
Question 5
If there were no limit to magnification, a light microscope could enlarge microbes infinitely.
Question 6
When doing a bacteria smear from a broth medium you should first place one to two loopfuls of water on the center of the slide?