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97 terms

Micro Lab Quiz 2

a medium that contains living microbes
pure culture
a culture that contains a single species
transfer of microbes from their pure culture to a sterile medium without contamination of yourself, the environment, the source culture, or the medium being inoculated
safety practices for aseptic transfers
1) minimize the potential of contamination
2) be organized
3) place all media tubes in a test tube rack when not in use whether they are sterile or not
4) take your time
5) never hold a tube culture by it's cap
6) hold the inoculating loop or needle in your hand like a pencil in your dominate hand
7) adjust your bunsen burner so your flame has an inner and outer cone
used to grow microbes when fresh cultures or large numbers of cells are required
agar slants
generally used to grow stock cultures that can be refrigerated after incubation and maintained for several weeks
plated media
typically used for obtaining isolation of species, differential testing, and quantifying bacterial densities
instruments used for transfers
inoculating loops or needles
mixed culture
a microbial culture consisting of two or more species
commonly used isolation technique
streak plate
colony-forming unit
term used to define a cell or a group of cells that grows into a colony
the basic categories of colony morphology
shape, margin (edge), elevation, texture, and color
colony shape can be described as :
circular, irregular, or punctiform (tiny)
colony margin may be described as:
entire (smooth with no irregularities), undulated (wavy), lobate (lobed), filamentous, or rhizoid (branched like roots)
colony elevations can be described as:
flat, raised, convex, pulvinate (very convex), and umbonate (raised in the center)
colony texture can be described as:
moist, mucoid, or dry
colony pigment production can be described as:
color, opaque, translucent, shiny, or dull
filiform growth
dense and opaque with a smooth edge
Most species in the genus Mycobacterium produce ___ growth.
2 important factors influencing bacterial growth
incubation time and temperature
What organisms were used in the colony morphology experiment?
Micrococcus luteus
Mycobacterium smegmatis
Corynebacterium xerosis
Proteus mirabilis
Bacillus subtilis
Lactobacillus plantarum
Why are growth characteristics more useful on agar plates than on agar slants?
the plates have a larger surface area for streaking to isolate
Why are agar slants better suited than agar plates to maintain stock cultures?
Slants are better suited because they can be capped, preventing the agar and culture from drying out. The cap also prevents airborne contaminates from entering the slant. Slants take up less storage space.
produces colored growth
spreading edge
solid growth seeming to radiate outward
surface membrane caused by organisms floating on top of the medium
organisms that sink to the bottom of the medium
introduction of a small sample of inoculum into a container of media to produce a culture of observable growth
The 5 I's of culturing microbes
termed a colony forming unit
2 common isolation techniques
streak plates
pour plates
temp-controlled chamber
microbe multiplies and produces macroscopically observable growth
seperating an individual bacterial cell from other cells
consists of one species in a mound of cells formed from a colony formig unit
colony indicator is dependent on :
media, temp, time incubated
observation both macroscopic and microscopic appearance, biochemical tests, genetic characteristics, immunological testing
mixed culture
hold two or more identified species or organisms
contaminated culture
a once pure or mixed culture that has unwanted microbes growing
vortex mixer
small machine that mixes test tubes with broth and microbes in it
a nanometer is ____ of a meter
one billionth
(0.000000001 m)
a micrometer is ____ of a meter
one millionth
(0.000001 m)
distance between 2 corresponding parts of a wave
wave of 400 nm
wave of 650 nm
white light is composed of ____
many colors and an average of 550 nm
magnification results when ___
a beam of radiation refracts (bends) as it passes through a lens
curved glass refrects ___
magnetic fields refract ___
electron beams
Why does a lens refract light?
the lens is optically dense compared to the surrounding medium (light travels more slowly through the lens than through air)
all the wave's crests and troughs are aligned - can enhance contrast
wavelength of radiation
distance between two corresponding parts of a wave
results when a beam of radiation refracts as it passes through a lens
aka resolving power - the ability to distinguish objects that are closer together
differences in intensity between two objects or between an object and its background - important in determining resolution
visible light is made up of __-
a narrow band of wavelengths of radiation
What kind of lights ae used in microscopy?
visible and ultraviolet
A lens refracts light waves that pass through its ___ more than light rays that pass through its ___.
periphery, center
What happens to light rays as they travel past the focal point?
they spread apart and produce an enlarged, inverted image
empty magnification
image is blurry and faint
Todays microscopes can distinguish objects as close together as ___.
0.2 micrometers
magnification occurs in two phases
real image, virtual image
What forms the real image?
the objective lens
What forms the virtual image?
the real image is projected to the ocular where it is magnified again
total magnification
magnification of the final image is a product of the seperate magnifying powers of the objective lens and the ocular
(power of objective times power of the ocular
visible light wavelength is
400 nm- 750 nm
numerical aperture of lens is ____
from 0.1 to 1.25
oil immersion lens
requires the use of oil to prevent the refraction of light
shorter wavelength and larger numerical aperture will provide _____.
better resolution
What is the resolution of the oil immersion lens?
0.2 micrometer
what is numerical aperture?
the ability of a lens to gather light from a specimen and use it to make the image
What is the most common light microscope?
bright field microscope
With a bright field microscope, what is illuminated?
the background (field)
differences in intensity between two objects, or between an object and the background
What is contrast important in determining?
What can increase contrast?
staining and the use of light that is in phase
What does the condensor lens do?
directs light through the specimen as well as one or more mirrors or prisms that deflect the path of the light rays from an objective lens to the ocular lens
What are the 2 types of bright field microscopes?
simple and compound
Simple Bright-field microscope
has a single magnifying lens, is similiar to a magnifying glass, capable of 300x magnification
Compound Bright-light microscope
has a series of lenses for magnification
light passes through specimen into objective lens
oil immersion lens increases resolution
have one or two ocular lenses
most have a condenser lens
What is the limit of useful magnification for light microscopes? Why?
2000x because their resolution is restricted by the wavelength of visible light
magnification of scanning lens
magnification of low-power objective lens
magnification of high power lens
magnification of oil immersion lens
magnification of ocular lens
ocular lens
remagnifies the image formed by the objective lens
transmits the image from the objective lens to the ocular lens using prisms
objective lens
primary lenses that magnify the object
holds the microscope slide in place
focuses light through the specimen
controls the amount of light entering the condenser
light source
coarse focusing knob
moves the stage up and down to focus the image
How do you carry a microscope?
with one hand on the arm and the other beneath the base
How do you store a microscope?
with the short objective lens in place, lower the stage, turn light intensity to minimum and turn it off, clean the lenses, wrap the cord correctly and cover
How do you clean the lenses?
-clean the condenser and objective lenses with lens paper or cotton swabs and a 95% ethanol cleaning solution
-clean the ocular lens with a cotton swab moistened with 95% ethanol cleaning solution