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Microbio Lab Final

Terms in this set (47)

What types of microscopes are there?
electron, compound, light
What are the functions of the 3 types of microscopes?
electron - uses electron beam to interact with specimen (used to examine cells, microorganisms, metals, crystals, biopsy samples)
compound - used to view samples at high magnification (40x-1000x) by using ocular and objective lenses
light - uses focused light and lenses to magnify cells
What are the parts of a compound microscope?
ocular lense, objective lense, rotating nosepiece, stage, stage clips, arm, base, light source, condenser, fine adj, coarse adj, iris diaphragm
What are the structural parts of a compound microscope?
base, arm, stage, stage clips
What are the illuminating parts of a compound microscope?
light switch, iris diaphragm
What are the focusing parts of a compound microscope?
fine / coarse adjustment knobs, condensor
What are the magnifying parts of a compound microscope?
ocular lens, nosepiece, 4 objective lenses
What are the synonyms and magnifying power of the 4 objective lenses?
4x - Scanning lens
10x - Low power lens
40x - High power lens
100x - Oil immersion lens
Which adjustment knob do you use with 4x? with 100x?
- use the coarse adjustment while on 4x
- use the fine adjustment knob while on 100x
How do you calculate total magnification?
ocular lens x objective lens
- example: (10x) x (10x) = 100x TM
What is the focal length? Is it small or large with 4x? with 100x?
The focal length is the distance between the lens and the image.
- the focal length is large with 4x
- the focal length is small with 100x
What are parfocal lenses?
a lens that stays in focus when the magnification is changed
Which lens is mostly used in Microbiology? How do you use it?
The 100x lens is mostly used in microbio
- you must do oil immersion while using 100x
-What to do if you cannot focus your slide on 40x? What do you do if you already put the oil drop on 100X but cannot focus it?
- if you can't focus on 40x, go back to 10x and refocus
- if you already put your oil on, you must start over and wipe the oil off your slide and lens.
What is the function of lens paper? Kimwipes?
Lens paper: cleans the lenses
Kim wipes: cleans oil off the slide
Why do we stain bacteria?
to be able to see the specimen - they are small, transparent, and motile
What does "simple" stain mean?
Simple stain means it is a direct stain
- only one stain is used so it is only one color
ex: methylene blue
acidic vs basic dyes
Acidic dyes: Negative stains - acidophilic bacteria stain
Basic dyes: Positive stains - basophilic bacteria
What is the effect of negative stains on bacteria and the background? Which dyes are used?
The specimen is clear but the background stains
- nigrosin, eosin, malachite green
What is the effect of positive stains on bacteria and the background? Which dyes are used?
The specimen is stained but the background stays clear
- methylene blue, safranin, crystal violet
Which stain (positive of negative) is most common in microbiology?
Positive stains
Which stain requires heat fixation? What are the 2 reasons?
Postive stains
1. so bacteria does not wash off when stained
2. to kill the bacteria
What are the 3 most common bacterial shape/morphology?
Coccus: round / spherical
Bacillus: rod / cylindrical
Spiralla: spiral with 2 or 3 curves
What are the 5 bacterial arrangements?
Diplo: pair
Strepto: chain
Stephylo: cluster
Tetrad: packet of 4
Sarcina: packet of 8
What stain / color is used for a simple stain?
Direct stain - methylene blue
What is the Simple Stain procedure? (6 Steps)
1. Flame
2. Prepare smear
3. Air dry
4. Heat fix
5. Stain, flood, blot
6. Observe
What objective lens is used to observe a bacterial image made by simple staining? What is its total magnification?
40x - TM = 400x
What is the difference between preparing a bacterial smear from a liquid vs. a solid medium?
Liquid - water does not need to be spread on slide prior to swabbing
Solid - water must be placed on slide in order to spread bacteria
What is the procedure for preparing a bacterial smear?
1. Obtain slide and draw a circle where bacteria will be placed
2. If using a solid medium of bacteria, place a drop or 2 of distilled water in the circle - if you're using a liquid medium disregard this step
3. Sterilize loop over Bunsen burner and allow to cool
4. Gather sample and smear
5. Air dry 1 minute
6. Heat fix by sliding slide gently over flame
Who discovered the Gram stain? What year?
Hans Christian Gram 1882
Why is the gram stain considered a differential stain?
It is a method of staining bacteria with 2 different dyes (differential) showing 2 different groups of bacteria
Differences between Simple stain and a Differential stain
Simple: method only uses one stain - only one color is seen - reveals size/shape/arrangement of cells
Example: methylene blue
Differential: method uses 2 stains - 2 or more colors appear on cells - reveals size/shape/arrangement - differentiates 2 groups of bacteria
Example: Gram stain, acid fast stain
What is the significance of the Gram stain?
- Smear made from a wound culture directly
- Determines morphology of bacteria
- Useful in planning patient's treatment
- Broad spectrum antibiotics or Narrow spectrum antibiotics
Gram Positive bacteria (color of stain, presence of LPS, cell wall composition)
Stains: purple
Cell Wall: THICK - full of peptidoglycan
Liposaccharides: none present
Gram Negative bacteria (color of stain, presence of LPS, cell wall composition)
Stains: red or pink
Cell Wall: THIN - low level of peptidoglycan
Liposaccharides: present
Gram Positive Bacteria (5) - What do they cause?
- Staphylococcus aureus: wound infection, sepsis
- Streptococcus pneumoniae: pneumonia
- Streptococcus pyogenes: pharyngitis (strep throat)
- Clostridium tetani: tetanus
- Proprionobacterium acnes: acne
Gram Negative Bacteria (4) - What do they cause?
- Neisseria meningitides: meningitis
- Haemophilus influenzae: otitis media (ear infection)
- Escherichia coli: gastrointestinal disease and diarrhea
- Chlamydia trachomatis: chlamydia (STD)
What is Gram Variable bacteria? What stain is used to test Mycobacterium? Why is Gram stain ineffective?
- Not all bacteria can be stained by Gram stain
- One exception is Mycobacterium species due to its waxy cell wall
- Mycobacterium can be identified using and Acid-Fast Stain
Bacterial smear steps (1-4) prior to staining
1. Flame
2. Prepare Smear
3. Air Dry
4. Heat Fix
Order of Gram stain (4 steps)
1. Crystal Violet (primary stain)
2. Iodine (mordant - allows dye to stick)
3. 95% Alcohol (decolorized)
4. Safranin (counterstain)
Colors of Gram +/- Cells on each step of the procedure:
1. All purple
2. All purple
3. G+ purple / G- colorless
4. G+ purple / G- red
After using alcohol (decolorizer) what color is G+/- Bacteria?
Gram+ (purple)
Gram- (colorless)
Which step of the Gram Stain procedure is the most critical and why?
the decolorizer step is the most critical because too much alcohol can remove the dye from the cells - which makes the gram-positive cells appear to be falsely gram-negative.
Gram positive bacteria
Gram negative bacteria
Why are Gram negative bacteria resistant to Penicillin?
Gram negative bacteria outermsmbrane does allow Penicillin to penetrate
5 BSL1 Bacteria species - Are they G+/-? - Cocci or Bacilli?
1. Bacilus subtilus (+) bacilli
2. Micrococcus luteus (+) cocci
3. Escherichia coli (-) bacilli
4. Seratia marcescens (-) bacilli
5. Staphylococcus epidermidis (+) cocci
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