BI323 Lab Final Exam Flashcards
magnify specimens using a 2-lens system
brightfield microscope
light from the specimen passing into a lens. 4X, 10X, 40X, and 100X
objective lens
What lens do you only use oil immersion for?
100X
rotation of objective lens so that they “line-up” adding a magnification of 10X
ocular lens
How do you determine the total magnification?
multiply the objective lens by the ocular lens
used to focus the specimen. the larger knob on the sides of the microscope
coarse focus knob
What does parfocal mean?
if you face your specimen using 1 objective lens, it should be focused when you rotate to the next objective
slight adjustment to focus the specimen when rotating between objective lens. use the small focusing knob
“fine-tuning” focusing
focuses the light in a small area above the stage
substage condenser
controls the amount of light entering the substage condenser
iris diaphragm
What are the 3 basic shaped of bacteria?
bacillus (rod-shaped), coccus (sphere-shaped), and spirillum (rigid helical shaped)
Why do you stain bacteria?
visualize their overall shape and cellular organelles against a contrasted background
How do you disinfect your work area?
disinfectant solution such as 70% ethanol, 4% bleach solution, or lysol
How do you infect your equipment?
alcohol/ethanol and gas burner
What is the autoclave?
large, self-contained pressure cooker that goes through heating, sterilizing, and cooling cycles automatically
How long and at what temperature should MEDIA be sterilized?
15 minutes at 121C and a pressure of 15 psi
How long and at what temperature should glassware and contaminated articles be sterilized?
30 minutes at 121C and a pressure of 15 psi
How do you disinfect an inoculating loop?
hold the loop in the flame until it glows red
How do you maintain aseptic conditions when collecting bacteria?
flame the loop, remove the cap from the tube, pass it through the flame a few times, collect sample, pass the tube through the flame again, flame the loop
produces individual colonies for observing morphology or separating mixed suspensions of bacteria
isolation streaking technique
How do you perform the isolation streaking technique?
streak only the top 1/4 of the plate while raising the cover of the petri dish at just enough of an angle. turn the dish 90 degrees. make 1 streak from area 1 into area 2 then streak area 2 in a zigzag pattern until 1/4 of the plate is covered. repeat for the remaining 2 areas. MAINTAIN ASEPTIC CONDITIONS THROUGHOUT EACH STREAKING
What temperatures do most fungi grow at?
25C
What temperatures do most NONPATHOGENIC bacteria grow at?
room temperature - 30C
What temperatures do most PATHOGENIC bacteria grow at?
37C
How long do you store cultures?
short - term it can be in an incubator at 30C. long - term it is not practical as some do not survive refrigeration and/or may undergo genetic mutations.
What is simple staining?
provides contrast with the background or to make cellular organelles visible. consists of an aqueous or alcoholic solution of a single dye
What are the most common simple staining dyes?
methylene blue, basic fuchsin, and crystal violet
How do you prepare a heat-fixed smear?
1.) place a drop of water onto a clean slide
2.) flame inoculating loop and mouth of culture tube
3.) remove a small quantity of bacteria
4.) flame the mouth of the tube and replace cap
5.) mix bacteria in water on slide and spread thinly
6.) allow smear to air dry
7.) pass the slide through the flame 3 times and allow the slide to cool
8.) flood the slide with dye for 60 sec.
9.) rinse the slide and blot dry
Why do you heat-fix a smear?
fixing the slide kills the bacteria and causes them to stick to the slide
What is gram-staining?
separates almost all bacteria into 2 groups for bacteriological idenfitication
What color is Gm+ bacteria?
purple/blue
What color is Gm- bacteria?
pink
What are the general steps for gram staining?
1.) prepare smear
2.) flood with crystal violet for 60 sec.
3.) flood with gram’s iodine for 60 sec.
4.) decolorize with 5-6 drops of 95% ethanol
5.) flood with safranin for 60 sec.
Why do bacteria take up Gm stain differently?
differ in cell wall composition. Gm+ bacteria have a thick cell wall layer the alcohol does not readily penetrate to decolorize. Gm- bacteria have thinner cell walls that allow alcohol to readily penetrate
What is differential staining?
more complex than simple ones and use more than 1 stains to differentiate cellular components
based on the resistance of cells stained with hot carbol fuchsin to decolorization by acids
acid-fast staining
What do the results of acid-fast staining mean?
non-acid fast cells are counterstained with methylene blue. acid-fast cells stain red
Why was acid-fast staining developed?
to identify the leprosy microbe and tuberculosis microbe
negative staining that contrasts the capsule between the red cells and a blue background. cannot be heat fixed as the capsule will be destroyed
capsule staining
What is endospore staining?
identify endospores that are difficult to stain. resist decolorization and counterstaining
What do the results of endospore staining mean?
endospores are penetrated with malachite green and everything else is counterstained pink
Who developed acid-fast staining?
Paul Erlich in 1882 while working with tuberculosis
molecular complex made from 2 sugar monomers laid together to form a chain that are then cross-linked to form threads that form mats
peptidoglycan
What is the cell wall of Mycobacterium comprised of?
glycolipids and peptidoglycan
no fresh media is added during bacterial doubling as a result of nutrients available for growth steadily decline and toxic metabolic waste products begin to increase
batch culture
What is the lag phase of a growth curve?
bacteria are introduced into fresh nutrient medium. characterized by no new cell growth as bacteria is adjusting to its new environment
What is the log phase of a growth curve?
culture is growing at its maximum rate and can grow in a logarithmic manner at regular intervals
What is the stationary phase of a growth curve?
rate of new bacteria production equals the bacterial death
What is the death phase of a growth curve?
decline in the total number of viable bacteria