Term
|
Definition
| A technique for making microbes visible by placing them on a glass slide and magnifying them by a light microscrope |
|
|
Term
|
Definition
| A staining procedure that differentiates between 2 common types of bacteria |
|
|
Term
|
Definition
High-resolution microscope observation that uses electrons to illuminate tiny virus particles
|
|
|
Term
|
Definition
| A nutritious extract or mixture of materials that will support the growth of microbes |
|
|
Term
| scanning electron microscopy (SEM) |
|
Definition
| a viewing process in which scattered electrons are detected and the object's surface is reconstructed by computer technology; especially good for visualizing surface structures |
|
|
Term
| transmission electron microscopy (TEM) |
|
Definition
| A process in which electrons pass through a specimen and heavy metals pile up around the virus and scatter electrons. This leaves dark areas that reflect the viral outline on the viewing screen |
|
|
Term
| Describe the procedure of staining |
|
Definition
- Staining is used to improve visibility. Microbes seldom have any color.
- Some algae may be visible because of their light absorbing pigments, but for the most part, contrast needs to be obtained for details to be noted.
- Therefore, a stain (or dye) is often added to the organisms to improve contrast and our ability to recognize the microbes readily.
- Many times, a simple dye, such as methylene blue or crystal violet, is added (with the excess rinsed off), making the organisms appear blue or purple compared to their surroundings.
- When stained bacteria are observed, their shape (cell morphology) becomes readily apparent, as does their microscopic morphology, or arrangements.
|
|
|
Term
|
Definition
- For bacterial-sized objects, a 100x oil immersion objective (lens) of the light microscope is used in concert with a 10x eyepiece for a total magnification of 1000x.
- Because of the properties of light, resolution by a light microscope is limited to 2000x, meaning that objects of 0.2 microns are the smallest to be seen with resolution (clarity).
- Typically, a clinical specimen from a patient may be 1st located and focused using the low power setting of a light microscope (100x total magnification), and then it can be moved to the higher oil immersion lens (1000x total magnification).
- A typical compound light microscope has 3 lenses, but only 2—the objective lens and the ocular (eyepiece) lens—actually magnify the image.
- The condenser lens, located under the stage, simply aims the light rays up through the specimen for optimal contrast and resolution.
|
|
|
Term
| Discuss electron microscopy |
|
Definition
- No light microscope is sufficiently powerful to see viruses, 0.030.3 microns. We stain viruses with a heavy metal and use electron beams to resolve images of them.
- Because electrons are much more powerful than photons (light particles), they can resolve down to about 0.002 microns to show even the tiniest of virus particles.
- There are 2 types of electron microscopy.
- In transmission electron microscopy (TEM)
- electrons pass through the specimen.
- Heavy metals pile up around the virus and scatter electrons leaving dark areas that reflect the viral outline on the viewing screen.
- TEM is used to visualize internal structures of any specimen (not just viruses) at a much higher magnification than light microscopy—sometimes well over 100,000x magnification.
- Scanning Electron Microscopy (SEM)
- the scattered electrons are detected and the object’s surface is reconstructed by computer technology.
- SEM is especially good for visualizing surface structures, and can magnify to much higher levels than a light microscope.
- Resolution
- TEM - down to about 0.002 microns
- SEM - down to about 0.02 microns
|
|
|
Term
|
Definition
- The gram stain uses 2 stains.
- The first is crystal violet which staines Gram+ bacteria
- 2nd is safranin that results in red/pink Gram- bacteria
- This process differentiates the 2 stains and then called a differential stain.
|
|
|
Term
| Name three clinically relevant differential stains |
|
Definition
- Gram stain - differentiates Gram+ from Gram - bacterium
- endospore stain - visualizes spore-forming bacteria (antrhax)
- acid-fast stain - visualizes clinically relevant bacteria (TB)
|
|
|
Term
| most common general-purpose medium in medical microbiology |
|
Definition
tryptic soy agar (TSA)
or
tryptic soy broth (TSB) |
|
|
Term
|
Definition
| a polysaccharaide (polymer of sugars) sometimes used to solidify jams and jellies, added and dissolved to nutrient broths, then the solution is poured into petri dishes and allowed to cool to room temperature, at which time the liquid solidifies |
|
|
Term
|
Definition
| a small sample of culture is placed onto the medium surface using an inoculating lop, streaking the loop accross the surface of the medium in a specific pattern. |
|
|
Term
| Resolution of a light microscope can only go to 2000x, so objects of ____________ are the smallest to be visible with a light microscope |
|
Definition
|
|
Term
| Staining of bacteria serves what purpose? |
|
Definition
| provides contrast of the specimen against the light background |
|
|
Term
| Electron microscopy involves staining viruses with |
|
Definition
|
|
Term
| Electron microscopy allows visualization of viruses which are |
|
Definition
|
|
Term
| In 1 type of electron microscopy, electrons pass through the specimen, but heavy metals pile up around the virus and scatter electrons. This type is known as |
|
Definition
TEM
transmission electron microscopy |
|
|
Term
| Which type of electron microscopy resolves down to the smallest possible micron size? |
|
Definition
TEM
transmission electron microscopy |
|
|
