Laboratory Experiments in Microbiology-Exercise 1

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Lab portion of microbiology
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1

Who was the first person known to observe living microbes in suspension?

Antoni van Leeuwenhoek

2

When looking through a microscope and making observations what should you be playing close attention to?

1. Size relationship: how big are bacteria relative to protozoa?
2. Spatial Relationships: where is the bacterium in relation to the others? Are they all together in chains?
3. Behavior: are individual cells moving? or are they flowing in the liquid medium?
4. Sequence of events: Were cells active when you first observed them?

3

Who invented the microscope?

Zacharias Janssen

4

Early microscopes were called?

Simple microscopes
Biconvex lenses essentially a magnify glass

5

What is used most often to view dark objects in a bright field?

brightfield compound microscope
2 lenses between eye and object and an illumination system

6

Name the basic frame of a microscope

base, a stage to hold the slide, an arm for carrying the microscope and a body tube for transmitting the magnified image.

7

The light source is the ___________?

base

8

Above the light source is the ______________?

condenser- which consists of several lenses that concentrate light on the slide by focusing it into a cone

9

The condenser has an iris diaphragm which controls the ________ and ____________.

angle
size of the cone light

10

What does the ability to be able to control the light ensure?

that optimal light will reach the slide

11

Above the stage, on one end of the body tube is a revolving nosepiece that holds three or four____________________?

objective lenses

12

At the end of the tube is an ___________ or eyepiece lens (10x12.5)

ocular

13

What is an monocular microscope?

one ocular lens

14

A binocular microscope has?

2 ocular lenses

15

Coarse adjustment knob is used for _____________________?

focusing with the low-power objective (4x and 10x)

16

The smaller knob is used for focusing with the ___________ and ____________.

high power and oil immersion lenses

17

Coarse adjustment knob moves the lenses or stage_________________.

longer distances

18

The area seen through a microscope is called _______________.

Field of vision

19

The ________ of a microscope depends on the type of objective lenses used with the ocular.

magnification

20

Compound microscopes have 3 or 4 objective lenses mounted on a nosepiece scanning ______, _________, ___________ and _____________________.

scanning 4x,
low-power 10x
high-dry 40x to 45x
oil immersion 97x to 100x

21

The total magnification of the object is calculated by _________________

multiplying the the magnification of the ocular (usually 10x) by the magnification of the objective lens.

22

Which lens is the most important lens in microbiology?

the oil immersion lens

23

The intensity of light of a compound microscope can be adjusted with a wheel that regulates the amount __________ to the bulb.

current

24

True or false. Higher magnification requires more light?

true

25

Resolution or resolving power refers to the ability of lenses to reveal __________or _________________.

fine detail or two points distinctly separated

26

Numerical Aperture in microscopy is defined by?

NA=n sin O
N= refractive index of medium
O= Angle between the most divergent light ray gathered by the lens and the center of the lens

27

Resolving power=

Wavelength of light used
_________________________
2x numerical aperture

28

Small wavelengths of light improve/or lessen resolving power?

improve

29

What does using immersion oil do?

It minimizes light loss and the lens focuses very close to the slide.

30

What is the focal point?

where an image is formed

31

What is spherical aberration? How can you correct this?

Multiple focal points
By using the iris diaphragm which eliminates light and results in a flat optical system.

32

What is chromatic aberration?

multitude of colors seen in the field
to fix this you can use different colored lenses or use a monochromatic light

33

When using low powered lens keep the ____________ barely open to achieve good contrast.

Iris diaphragm

34

Parfocal means?

That when in focus with 1 lens should be in focus with the rest (exception 4x)

35

More light is needed how can you do this?

with the condenser

36

What are the magnifications on the microscope?

(Ocular Lens: 10x) + The Objective Lens is 4x (scanning) = 40X 10x (low power) = 100X, 40x to 45x (high dry) = 400X, 97x to 100x (immersion oil lens) = 1000X

37

What parts make up the microscope?

Ocular Eyepiece, Body tube, Arm, Objective Lenses Stage, Condenser, Coarse adjustment Knob, Fine Adjustment Knob, Base, Iris Diaphrag, Mechanical Stage knobs, Light

38

What are the four important behaviors in your drawings?

1. Size Relationship
2. Spatial Relationship
3. Behavior
4. Sequence of events

39

Is the numerical aperture dependent on the maximum angle of the light entering the object lens and on the refractive index?

Yes, the amount of light bending of the refractive index and of the material between the objective lens and the slide.

40

What is Immersion oil?

makes the light rays pass straight through the slide and you are able to see the specimen clearly, used to keep light from bending.

41
card image

What shape does the Bacillus Bacteria carry?

rod shaped

42
card image

What shape does the Coccus bacteria carry?

Any spherical or nearly spherical bacteria or berry-shaped bacterium

43
card image

What shape does the Spirillum bacteria carry?

any flagellated aerobic bacteria having a spirally twisted rodlike form

44

Which objectives focuses closest to the slide?

The 97x to 100x with immersion oil.

45

Assume the diameter of the field of vision in your microscope is 2mm under low power. If one Bacillus cell is 2u.m. how many Bacillus cells could fit end to end across the field? How many 10u.m yeast cells could fit across the field?

2u.m./ 1,000u.m. * 1mm = 0.002---> 1000 Bacillus Cells.-
10u.m./1,000u.m. * 1mm = 0.01 ---> 200 Yeast Cells

46

Name two ways in which you can enhance the resolving power?

1.) Decrease the distance by moving the stage by the course adjustment. 2.) Dim the light source to enhance

47

Largest organism observed? And the smallest?

algae- spyro-gyro
bacteria

48

What were the three bacterial shapes observed?

sphere (coccus)
bacillus (rod)
Spiral (spirillum)

49

How does increased magnification affect the field of vision?

decreases

50

Which controls on the microscope affect the amount of light reaching the ocular lens?

Iris diaphragm: less light (higher the contrast)and softer

51

Name 2 ways in which you can enhance the resolving power:

1. Light shortwave
2.Numerical aperture

52

What are the advantages of the low-power objective over the oil immersion objective for viewing fungi or algae?

Fungi is large and its easier to see the whole thing this way rather than a portion of it.

53

What would occur if water were accidentally used in place of immersion oil?

H20 would disperse, less resolution with would make it less dense. "Refractory Index"

54

Clinical Application: Assume you are looking for microorganisms in a tissue sample from a lung biopsy. The microbes become apparent when you switch to 100x. What microbes is most likely?

bacteria

55

What are the 4 objectives of lenses?

Scanning- red band 4x
Low Power- yellow band- 10x
High Dry- blue band- 40x
Oil immersion-white band- 100x

56

Higher magnification- field of vision ____________?

decreases

57

What is agar?

it is extracted from algae for petri dishes- solidifying agent

58

Why agar and not gelatin?

most bacteria can't metabolize it and use it for food
Remains solid @incubation
Gelatin liquefies at 35-37 degrees Celsius

59

In which states is agar used?

liquid-broth 0% agar
semi-solid 0.4-0.7% agar
solid-1.5% agar

60

True or false. Growth patterns are only in broth.

true

61

Bacterial growth patterns in liquid are?

1. turbidity-cloudy
2. pellicle- ring of bacterial growth at top of surface
3.flocculent- fluffy or wooly appearance
4. Sediment- bottom pieces