1. What are the advantages and disadvantages of the different types of light and electron microscopes discussed in Chapter 3 that are used to study microorganisms? Focus your response in terms of the following parameters:
Range of magnification
Resolving ability
Sample preparation
Possible states of sample (e.g. whole organism, part of, living, non-living, etc.)
Electron microscopes use electrons not protons (light rays) for visualization. They have higher resolution and higher magnification up to 1000-2000 times. The electron microscope has a higher resolving ability compared light microscope. The specimens has to be fixed and completely dehydrated
TEM-transmission electron microscopes-an electron beam passes through the specimen and you will get two-dimensional cross section of the specimen.
SEM-scanning electron microscopes-you will visualize the specimen in a 3D impression.
Scanning tunneling microscope-shows 3D images and very detailed often used for DNA.
The specimens have to be dead because the electron can damage it if it’s living
Preparation includes cryofixation, dehydration, staining, embedding, fixation and sectioning.
Electron microscopes are very expensive, sample preparation can be elaborate compared to light microscopes, the sample does not possess color the image is only black or white.
The light resolving ability can only magnify objects that are less than a micrometer apart, anything further will make the image blurry. Light microscopes are lightweight, and most commonly used due to its inexpensiveness. It has the ability to observe living cells. Staining techniques used are in-vivo staining
Compound microscopes can magnify up to 1000X it has two eyepieces.
Two-Photon microscopes-which can see living organisms in depth
Stereomicroscopes are used to frequently observe larger, opaque specimens.
The sample preparation is commonly a dye used to contrast the specimen and able to see it better.
Samples can be living, non-living, and either whole organism or part as long as it fits the lens
2. What type of microscope would you use to investigate each of the following scenarios and why (your answer to question 1 will help):
Determine the relative sizes of two eukaryotic cells.
The compound light microscope to determine the relative sizes of two eukaryotic cells since I’m just comparing the sizes and not going too much in detail.
Determine how many bacteria are dying after a chemical treatment.
The two-photon microscope can be used to determine how many bacteria are dying after a chemical treatment because you are able to see the living organisms in real time differentiating the living and dying bacteria.
Determine where in a eukaryotic cell a particular protein is localized.
TEM is best to use to determine where in a eukaryotic cell a particular protein is localized because it gives you a cross section of the specimen
Identify a virus from a contaminated sample.
Scanning tunneling microscope is best to use to identify a virus from a contaminated sample because it is able to illuminate the specimen and magnify it showing it more in-depth and detail like that of DNA sample.
Visualize the sensory hairs on the surface of an ant’s antennae.
If the specimen is dead the SEM can be used to visualized the sensory hairs on the surface of an ant’s antennae because it shows more of an in-depth view and a 3D view.
3. What are advantages and disadvantages of the differential staining techniques discussed in Chapter 3 that are used to study microorganisms? Focus your response in terms of the following parameters:
Ease and cost of sample preparation
Why you
