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microbiology > ch. 2 - concepts + tools to study microbiology > Flashcards

ch. 2 - concepts + tools to study microbiology Flashcards

1
Q

where can we collect microorganisms from the environment?

A
  • soil
  • water
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2
Q

where can we collect specimens in a clinical setting?

A
  • blood
  • cerebrospinal fluid
  • sputum
  • urine
  • feces
  • diseased tissue
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3
Q

what are the five I’s of microbiology?

A

1) inoculation

2) incubation

3) isolation

4) inspection

5) identification

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4
Q

what does it mean to inoculate?

A

to put –> onto media (food)

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5
Q

what are the media forms (cultures)?

A

1) solid (2 types - can and cannot be liquefied) - colonies

2) semi-solid - motility

3) liquids - always add more liquid, more bacteria

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6
Q

what are the media food nutrients (cultures)?

A

1) chemically defined - recipe for exact amounts of all chemicals

2) complex - contain “complex ingredients”

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7
Q

what are the special media ingredients (cultures)?

A

1) selective - actively kill microbes
- get a single type of bacteria

2) differential - does not kill
- changes color based on microbe

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8
Q

what is a culture?

A

the propagation of microorganisms with various media

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9
Q

what is a medium?

A

a nutrient used to grow microorganisms outside their natural habitat

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10
Q

what does inoculation mean?

A

the implantation of microorganisms into or onto culture media

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10
Q

what does chemically defined media mean?

A
  • media with compositions that are precisely chemically defined
  • contain pure organic and inorganic compounds that vary little from one source to another
  • molecular content - specified by exact formula
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10
Q

what is agar?

A
  • complex polysaccharide from the alga Gellidium
  • liquifies at 100 degrees celsius (when poured - will not harm microbe or handler)
  • solidifies at 42 degrees celsius
  • flexible + moldable, can hold moisture + nutrients
  • not a digestible nutrient for microorganisms
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10
Q

what is selective media?

A
  • contains one or more agents that inhibit the growth of a certain microbes but not others
  • important in primary isolation of a specific type of microorganism from samples containing dozens of species

ex.) Thayer-Martin Medium - contains four antibiotics ( vancomycin, colistin, Nystatin, and STX) and only grows Neissera

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10
Q

what is differential media?

A
  • allow multiple types of microorganisms to grow —> designed to show differences
  • differentiation shows as variations in colony or media color

ex.) E. coli glows green

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10
Q

what does complex media mean?

A
  • contain at least one ingredient that is not chemically definable
  • extracts of animals, plants or yeasts; blood, serum, meat extracts, or infusions
  • present a rich mixture of nutrients for microbes that have complex nutritional needs
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11
Q

what does incubation mean?

A
  • means “to cook” –> media containing inoculants is placed on temperature-controlled chambers
  • usual lab temps: 20 to 40 degrees celsius, body temp: 37 degrees celsius = 98.6 degrees Fahrenheit
  • atmospheric gases: O2 + CO2 may be needed for certain microbes
  • during this, microbes grow + multiply = visible growth in the media
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12
Q

what does isolation mean?

A
  • concept –> if an individual cell is separated from other cells on a nutrient surface, it will form a colony
  • the faster it grows (shape + color) = more contagious

requires the following items: medium w/ firm surface, a petri dish, + inoculating tools

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13
Q

what is a colony?

A
  • a macroscopic cluster of cells appearing on a solid medium —> arising from the multiplication of a single cell
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14
Q

what is a pure culture?

A

one type of microorganism

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15
Q

what is a mixed culture?

A

two or more microorganisms

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16
Q

steps in a streak plate:

A

1) start w/ a primary streak (using a sterilized loop ) in a triangle shape

2) sterilize the loop + create a secondary streak

3) sterilize the loop + create a third streak

4) sterilize the loop + create a final streak in a triangular shape in the available space

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17
Q

what is inspection and identification?

A

microbes can be identified through:
- microscopic appearance

  • characterization of cellular metabolism,
  • genetic and immunologic characteristics
  • determination of products produced during growth, presence of enzymes, + mechanisms for deriving energy
18
Q

total magnification:

A

4x scanning objective x 10x = 40x

10x low power objective x 10x = 100x

40x high dry objective x 10x = 400x

100x oil immersion objective x 10x = 1000x

18
Q

what are the magnifications lenses in light microscopy?

A

objective lens - closest to the specimen, forms initial image –> called real image

ocular lens (fixed at 10x) - forms the second image called the virtual image –> will be received by the eye and converted to the retinal and visual image

19
what is an oil immersion lens?
- uses oil to capture light that would otherwise be lost to scatter - reducing scatter increases resolution
20
what are the several different types of microscopy?
- bright-field microscope - dark-field microscope - phase contrast microscopy - differential-interference contrast (3-D) - confocal microscope - electron microscope
21
what are the two types of electron microscopy?
- scanning electron microscopy - transmission electron microscopy
22
what is a bright-field microscope (special feature)?
visible light illuminates object
23
what is a dark-field microscope (special feature)?
special condenser scatters light
24
what is a phase-contrast microscope (special feature)?
special condenser throws light rays "out of phase"
25
what is a fluorescent microscope (special feature)?
UV light illuminates fluorescent-coated objects
26
what is a electron transmission microscope (special feature)?
short-wavelength electron beam penetrates sections
27
what is a electron scanning microscope (special feature)?
short-wavelength electron beam knocks loose electron showers
28
what is the natural color of bacteria?
clear - we dye them
29
how do we do preparations for fresh living microorganisms?
- place on wet mounts or in hanging drop mounts to observe ---> closest to nature state - the cells are suspended in water, broth, or saline to maintain viability + provide space for locomotion - these are short-term mounts --> provide true assessment of size, shape, color, arrangement, + motility
30
what is a wet mount?
- consists of a drop or two of culture placed on a slide + overlaid with a cover slip
31
what is a hanging drop mount?
- a drop of culture is placed in a concave (depression) slide - vaseline adhesive or sealant + then a cover slip is placed on top then suspend the sample
32
what is a fixed, stained smear?
- more permanent mounts used for long-term study
33
process for smear technique:
- developed by Robert Koch 1) spread a thin film made from a liquid suspension of cells on a slide 2) air dry 3) heat fix: heat gently to kill the specimen and attach to the slide
34
what is staining?
- unstained cells in a fixed smear are difficult to see - staining is any procedure that applies colored chemicals (dyes) to specimens - acidic dyes are repelled by cells
35
what charge do basic dyes have?
basic = positive charge (+)
36
what charge do acidic dyes have?
acidic = negative charge (-)
37
what is a positive stain?
dye sticks to the specimen + gives it color
38
what is a negative stain?
- dye does not stick to the specimen but settles some distance from its outer boundary = forming a silhouette - negatively charges cells repel the negatively charged dye + remains unstained - smear is not heat fixed = reduced distortion + shrinkage of cells - also used to accentuate a capsule dyes used--> nigrosin + india ink
39
what is a gram stain?
- most important stain in all of microbiology - why it matters: bc most antibodies in use today target either lipids or proteins on cell wall steps: 1) heat fix 2) add crystal violet - wash off after 1 min 3) add iodine (seals dye) - wash off after 1 min 4) add alcohol (slant + add in drops) - wash BEFORE 10 sec 5) add safranin - wash after 20-30 sec
40
what is a gram positive (+) stain?
- retained crystal violet color after alcohol (purple color) - low in lipids - high in proteins -> purple
41
what is a gram negative (-) stain?
- lost color after alcohol (pink color) - high in lipids - purple - low in proteins
42
what are simple stains?
- only require a single dye + uncomplicated procedure - cause all the cells in the smear to appear more or less the same color, regardless of type - reveals shape, size, + arrangement
43
what is a differential stain?
- use two differently colored dyes: the primary dye and the counterstain - distinguish cell types or parts - more complex + require additional chemical reagents to produce the desired reaction
44
history of gram stain:
- developed in 1884 - Hans Christian Gram - crystal violet (primary stain, iodine (the mordant), alcohol rinse (decolorizer), + safranin (the counterstain) - different results --> due to differences in the cell wall structure + how it reacts to the series of reagents applied - remains the universal basis for bacterial classification + identification - practical aid diagnosing + guiding drug treatment
45
what is a acid-fast stain (type of differential stain)?
- differentiates acid-fast bacteria (pink) from non-acid-fast bacteria (blue) - originated as a method to detect Mycobacterium tuberculosis (wax cell wall) - the cell walls have a particularly impervious cell wall that holds fast (tightly) to the dye (carbol fuschin) when washed with an acid decolorizer - also used for other medically important bacteria, fungi, protozoa
46
what is an endospore stain (type of differential stain)?
- similar to acid fast stain --> dye is forced by heat into resistant bodies called spores or endospores - stain distinguishes between spores + vegetative cells - significant in identifying gram-positive, spore-forming members of the genus Bacillus and Clostridium
47
what is a capsule stain (special stain)?
- used to observe the microbial capsule capsule = unstructured protective layer surrounding the cells of some bacteria + fungi - negatively stained w/ India ink
48
what is a flagellar stain (special stain)?
- used to reveal tiny, slender filaments used by bacteria for locomotion - flagella are enlarged by deposited a coating on the outside of the filament and then staining it

microbiology (7 decks)

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