Lab 1

Question 1

What is the highest total magnification possible for the microscope you will be using in lab?

Answer 1

1000X

To calculate the highest total magnification possible, multiply the magnification of the ocular lens (10X) times the magnification of the highest objective lens (100X).

Question 2

One objective lens on the compound light microscope MUST always be used with immersion oil. It is also the ONLY one that can be used with immersion oil. The magnification of this objective lens is

Answer 2

100X

The other lenses are not sealed against the immersion oil and can be damaged if oil is used with them. If you accidentally get oil on one of these lenses, clean it off immediately with gauze and lens cleaner.

Question 3

Which of the following slides will you view as part of this lab exercise?

1) dry mount of magazine photo
2) prepared slide of bacteria
3) Wet mount of living unstained microbes
4) all of the above

Answer 3

4) all of the above

Start with the magazine photo since you will likely find it easiest to focus on this specimen.

Question 4

Which one of the following slides will you view using the 100X oil immersion lens?

1) dry mount of magazine photo
2) prepared slide of bacteria
3) wet mount of hay infusion
4) all of the above

Answer 4

2) prepared slide of bacteria

Because bacteria are so small, the oil immersion lens is necessary to view them well. Many of the organisms you will see in the hay infusion are eukaryotic and are easily viewed with just the 40X objective lens.

Question 5

Where should you dispose of gauze used to clean immersion oil off of your microscope?

1) regular trash can
2) red biohazard bucket on lab bench
3) white biohazard bucket in front of lab
4) take it home with you

Answer 5

1) regular trash can

Uncontaminated waste like the gauze and also the paper-towels used to clean your lab bench should go into the regular trash.

Question 6

When you finish using the microscope, what should you have your lab instructor do?

1) clean the scope
2) collect any slides you prepared during the lab
3) inspect your drawings of bacteria
4) inspect the microscope

Answer 6

4) inspect the microscope

Always have your lab instructor check the scope to make sure it has been cleaned properly.

Question 7

You will label the bottom of the plate you streak with an environmental sample before you incubate the plate. Which one of the following information below should not be included on the plate?

1) your name (or initials)
2) your TA’s name
3) date
4) name of the medium used
5) source of the sample

Answer 7

2) your TA’s name

Be sure to label the bottom of the plate around the edge as described in Exercise 3 of your lab manual.

Question 8

You will find a wax pencil in your supply cabinet, but you will need to bring your own “Sharpie-type” marker. Which one should you use to label your plate?

1) wax pencil
2) Sharpie marker

Answer 8

2) Sharpie marker

The Sharpie marker will be used to label plates and tubes of media. You will use the wax pencil to label slides.

Question 9

You will use a sterile swab to inoculate your plate during this exercise. Where should you dispose of the swab and the wrapper?

1) both in the regular trash
2) both in the red biohazard bucket
3) swab in the red biohazard bucket and wrapper in the regular trash
4) swab in the red biohazard bucket and wrapper in the white biohazard bucket

Answer 9

3) swab in the red biohazard bucket and wrapper in the regular trash

Question 10

Your lab section will have a plastic box marked with your TA’s name and the incubation temperature in which to place any plates for incubation.

In order to prevent excess condensation from dropping onto the surface of your plate, how should your plate be oriented when you place it in the box?

1) top up (labeled bottom side down)
2) inverted (labeled bottom side up)
3) placed into holder so they are vertically oriented
4) wrapped in a paper towel right side up

Answer 10

2) inverted (labeled bottom side up)

If condensation drops onto the surface of the plate, it can cause the colonies growing on the plate to run together and you will not be able to identify them properly.

Question 11

Where should you dispose of paper towels used to clean your bench at the end of the lab

1) Regular trash cans
2) Red biohazard bucket on bench
3) White biohazard bins on disposal cart

Answer 11

1) Regular trash cans

Question 12

When you go to inoculate your TSA plate what should you do with the lid of the plate?

1) Take the lid completely off the plate and sit it on the bench top next to the plate while you streak
2) Have your lab partner hold the lid of the plate for you while you streak
3) Partially open the lid of the plate and continue to hold it in your hand while you streak
4) All of the above are acceptable

Answer 12

3) Partially open the lid of the plate and continue to hold it in your hand while you streak

Question 13

microbiology

Answer 13

the study of microscopic organisms, or microbes, that are below the limit of vision of the human eye (which is about 200 µm)

Question 14

objective lens

Answer 14

the lens closest to the objector specimen

Question 15

ocular/eyepiece lens

Answer 15

the lens closest to your eye

Question 16

total magnification

Answer 16

determined by multiplying the magnifications produced by the objective lens and the ocular lens

Question 17

resolving power

Answer 17

the ability to distinguish two closely spaced points or objects as separate

Question 18

numerical aperture

Answer 18

a physical quality of the lens; a measure of its ability to gather light

Question 19

parfocal microscope

Answer 19

remains in focus as it switches from objective to objective

Question 20

motility

Answer 20

the ability of an organism to propel itself through its environment

Question 21

if a bacterial organism appears to simply be vibrating in place, this is not motility, but rather a phenomenon known as ________

Answer 21

Brownian motion

Question 22

Brownian motion is caused by

Answer 22

the random collisions of particles and/or the cells in the suspension

Question 23

current flow

Answer 23

everything on the slide moves in the same direction at once; commonly occurs as a slide begins to dry out

Question 24

dark-field microscope

Answer 24

produces bright images of specimens against a dark background or field

Question 25

dark-field microscope typically used to view _____, and in order to determine their ____

Answer 25

1. viable (living), unstained organisms

2. morphology and motility

Question 26

phase contrast microscope useful for

Answer 26

determining microbial motility and morphology; to visualize certain cellular structures and inclusions that generally cannot be seen clearly under standard bright-field or dark-field microscopes

Question 27

fluorochromes

Answer 27

chemicals that produce fluorescence after they absorb a specific wavelength of light

Question 28

used alone, fluorochromes can be described as a

Answer 28

differential dye

Question 29

immunofluorescence microscopy

Answer 29

fluorochrome is attached to an antibody that binds to specific cellular components

Question 30

transmission electron microscope

Answer 30

electrons are passed through a very thin section of a specimen that has been stained with an electron-dense metal

Question 31

immunoelectron microscopy (variation on TEM)

Answer 31

uses TEM but allows for visualization of specific cellular components through the use of antibody pairs

Question 32

scanning electron microscope

Answer 32

used to visualize the surfaces of objects, and the final image produced is 3-D

Question 33

autotrophic

Answer 33

capable of producing their own “food”/nutrients from inorganic carbon and energy sources

Question 34

heterotrophic

Answer 34

dependent on sources from their environment to provide the nutrients

Question 35

photoheterotrophic

Answer 35

fall between autotrophs and heterotrophs

Question 36

aerobes

Answer 36

require oxygen to survive

Question 37

aerotolerant

Answer 37

aerobes that only tolerate low oxygen concentrations

Question 38

anaerobe

Answer 38

may be killed if exposed to oxygen

Question 39

facultative anaerobe

Answer 39

function either with or without oxygen

Question 40

serial dilution

Answer 40

when the suspension must be diluted several times in succession

Question 41

formula for cfu/mL calculation

Answer 41

(# cfu) / (volume plated [mL] x total dilution used [no unit])

Question 42

if two plates made from different dilutions in a series have produced colony counts in the 30-300 range, then

Answer 42

the calculated original concentrations obtained from each of these counts can be averaged

Question 43

working with grams instead of mL

Answer 43

1 gram of any substance is arbitrarily assigned a volume of 1 milliliter