Explain how immersion oil allows a microscopist to get better resolution
Every time light moves through slide and hits specimen, it bends and refracts. As it goes from glass back into air, some of that light will bend so that it no longer is captured by our magnification lens. We have lost that information. If we eliminate that transition between the glass and the air, by adding immersion oil, we are going to gather as much light as possible up into the mag lens and we have that much better a picture. Increases the numerical aperture.
Explain the connection between resolving power, numerical aperture, and wavelength of light
Resolving power - how far apart can two dots be and you be able to distinguish them as two separate dots and not fuzzy
Wavelength of light - One of the easiest ways to improve microscope resolution is to improve quality and type of light you are using. Light moves as a wave and how tight that wave is depends on the energy level of the light. If we want improved resolution, use short wavelength because light moving in tight pattern and will hit spots tight together and you can distinguish between those spots.
Numerical aperture - the ability of the lens to capture light. Oil immersion increases this ability and thus increases resolution
why is a blue filter used on the microscope?
Blue light has the shortest wavelength of the visible spectrum. The shorter the wavelength, the higher the resolution one can achieve with a light microscope.
The resolution using only blue light is about 4 times better than with using all the wavelengths of visible light.
Increases contrast between a specimen and its background. Better higher resolution.
Describe the change in working distance as magnification increases. What does this mean in regards to observing samples at higher magnification?
Evaluate the advantage to the microscopist of parfocality. (What does parfocal mean?)
Recognize how the optics of the microscope change the orientation of the image seen when compared to the orientation on the slide.
What happens to the size of the field of view as magnification increases? How does this apply to looking at a specimen on a slide?
It decreases. The field of view is how much of your subject you can see through a lens. As you magnify the subject or 'zoom in' you aren't able to see as much of the subject, but zoomed in.
As you increase the magnification, the lens gets closer to the specimen. Increasing the magnification on a light microscope will decrease the diameter of the field of view. You are essentially looking closer and closer at the objects.
Compare the size of human blood cells with yeast cells and typical bacilli and cocci
What is depth of field?
Distinguish between prokaryotic and eukaryotic cells.
Observe, identify, and draw the common shapes (morphologies) and arrangements of procaryotic
Understand the relationship between the arrangement of cells and the number of planes of division which occur.
(Remember: When determining morphology and arrangement look for the most common morphology and the most complex arrangement.)
SHAPES: Cocci (spheres) [coccus—singular], bacilli
(rods) [bacillus—singular], spirilla (spirals) [spirillum—singular] ARRANGEMENTS: diplo or strepto
form in a line, tetrad forms in two lines(an x and y axis), sarcina forms in an x, y, and z axis, staph forms in a grape cluster effect.
Differentiate spirilla and spirochetes by description and observation.
Understand what "pleomorphic" means. Observe and draw pleomorphic cells.
Characteristics of cyanobacteria:
any bacterium of a genus that includes the diphtheria bacillus
Diphtheria is a serious and highly contagious disease caused by bacteria called Corynebacterium diptheriae. This disease affects the upper respiratory tract (nose, throat, voice box and upper windpipe) and occasionally, the skin. It can affect anyone, at any age and can be fatal.
Differentiate between akinetes and heterocyst. What is the function of each?
Akinete - These resting cells, which do not grow or expend much energy on biological functions, have evolved to survive poor growth conditions. An akinete is one type of resting cell, with a characteristically thick wall and a store of nutrients inside. When favorable conditions develop in the environment around the akinete, then this resting cell bursts and releases multiple new cells, which begin growing as normal.
Heterocyst - Some plants use special cyanobacteria, called heterocysts, in order to convert nitrogen in the air to a biologically available form
Identify times when a microbiologist must use a pure culture.
Describe characteristics of a properly adjusted Bunsen burner flame.
Describe instruments microbiologists most often use to transfer microorganisms.
Describe aseptic technique procedures that are performed before, during and after working with
· Disinfect work area and wash hands properly
· Put lab coat and goggles on
· Position work items in an organized way on work table
· Loosen caps off slants and broths
· Label test tubes
· Turn on flame
· Sterilze inoculating loop by burning in flame. Start to flame loop away from tip.
· Flame the lip of slant culture
· Place sterilized loop in slant culture and collect sample of Sm
· Touch loop to inside of slant to get rid of excess Sm
· Flame lip of slant and replace cap
· Flame lip of new slant
· Insert loop with Sm into new slant
· Swerve loop on top of agar
· Flame lip of new Sm slant
· Flame loop
· Tighten cap of original cultures and place in biohazard
· Put all materials away and disinfect work area.
Explain how to protect yourself from a laboratory-acquired infection.
Understand the purpose of stock cultures and why a stock culture is made before using a new culture for other purposes.
List four characteristics of microbial morphology as identified in the lab book.
Differentiate between basic and acidic dyes and how they work.
Understand why, when using solid media, the inoculum is serially diluted on the slide.
Know the purpose of air-drying (or gently warming) smears
Know the purpose and effects of heat fixing a slide.
Explain how a negative stain interacts with bacteria and the result obtained.
Understand why slides prepared with negative stains are not heat fixed.
Identify two reasons for using a negative stain.