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Microbiology > microbial growth and control > Flashcards

microbial growth and control Flashcards

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Biology 101 flashcards
1
Q

define growth media

A

liquid or solid formulated to support microbial growth

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2
Q

What does growth media contain

A

essential nutrients: provide microbes with source of energy to expand

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3
Q

What do the nutrients include in growth media

A

sugars, amino acids and vitamins

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4
Q

What is the name of large source of nutrients

A

nutrient broth

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5
Q

What is the most common form of growth media

A

LB media

lysogony

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6
Q

What is selective media

A

allows for growth of on microbe and restrict the other

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7
Q

How does one restrict growth of one microbe vs another

A

limit nutrients, vary degree of pH, vary chemical additive, limit unwanted microbial growth( antibiotics)

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8
Q

When is selective media used

A

in medical laboratories for cultivation of human pathogen
ex: neisseria meningitides
because neisseria meningitides is slow growing, other fungi, mold and bacteria outgrow sample and media is needed to inhibit foreign growth

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9
Q

What is differential media

A

a type of selective media
distinguish between 2( often related) microbes
looks to see can ferment lactose or not

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10
Q

How does differential media work with Escherichia coli and salmonella

A

both gram - microbes
distinguished by presence or absence of lactose fermentation
if grown on same differential media: E. coli ferments lactose and turns red
Salmonella does not ferment lactose and remains white

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11
Q

What is enriched media

A

used to grow fastidious microorganism: organism with complex growth requirements so that if absent will not grow
contain essential nutrients required for growth of specific organism
can be a combination of selective, differential and enriched

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12
Q

What are agar plates

A

hold growth media

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13
Q

Describe solid media

A

contained in sterile petri dish: most simple form to use as its liquid media that has a solidifying agent added

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14
Q

What creates agar

A

addition of polysaccharide derived from seaweed( algae)

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15
Q

Why is agar used in plating growth media

A

used to create solid smooth surface for microbes to grow

as they grow form colonies take on appearance of individual isolated dots

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16
Q

what is the term for when microbes cover entire plate

A

lawn

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17
Q

What is the cousin of agar

A

gelatin

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18
Q

Describe LB agar

A

lysogen broth
multi-purpose media capable of growing wide variety of microorganism
pale yellow
classified as non-selective and non-differential
common used used to grow E.coli

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19
Q

Describe TSAYE agar

A

Trypticase soy agar
multi-purpose media: capable growth variety of microorganism
identical in color to LB
media is non- selective and non-differential
is base for specialized enriched media

20
Q

Describe blood agar

A

derivative of TSA where mammal blood( usually sheep) added to plate composition and concentration range of 5-10%
red in color
enriched, non-selective yet differential media
RBC promote growth of fastidious microorganism: streptococcus
differential media used to detect hemolytic activity

21
Q

What is hemoylsis

A

breakdown of RBC classified as alpha, beta or gamma

22
Q

How does alpha hemolysis present

A

alpha hemolysis: present as green-brown due to incomplete lysis of RBC

23
Q

How does Beta hemolysis present

A

Beta hemolysis: present as distinct zone of clear around growing colony- complete lysis

24
Q

How does gamma hemolysis present

A

Gamma hemolysis: designate absence of hemolytic activity- colony white/tan grown on red background of unaffected blood agar plate

25
Q

Describe columbia CNA ager

A

red in color
enriched, selective and differential
media contains antimicrobial agents colistin and nalidixic acid: suppress growth of gram -
used to isolate gram(+) microbe
similar to BAP, enriched allow for differential based on hemolytic activity

26
Q

Describe chocolate agar

A

enriched, non-selective, non-differential derivative of blood agar plate
contain RBC lysed by heat
cooking of RBC gives media chocolate color
Lysed RBC give nutrient to cultivate fastidious pathogenic bacteria
example: gram (-) Haemophilus influenzae and Neisseria meningitidis.

27
Q

Describe MacConkey ager

A 
pale red in color
selective and differential media
presence of crystal violet and bile salt restrict gram (+) growth
only gram (-) grown
28
Q

Why is lactose and pH indicator added to MacConkey ager

A

to differentiate between lactose fermentors and non ferment
if ferments lactose turn red
if does not ferment lactose is white

29
Q

why does base color change of MacConkey ager

A

changes due to microbe consumption of nutrients

30
Q

What are colors ager turn based on pH

A

yellow: pH bigger than 8.0- non ferment microbe

pink/dark red: pH less than 6.8 ferments lactose

31
Q

Which 2 bacteria often grown on MacConkey plates

A

Gram negative Escherichia coli: ferment lactose: pink colonies
Enterobacteriacea: salmonella, shigella- used to isolate intestinal pathogenic microbes such as above

32
Q

Describe Sorbitol-MacConkey ager

A

varient of MacConkey formulated to detect presence of pathogenic strain of escherichia coli
under standard gut condition Escherichia coli able to ferment lactose and sorbitol
E-coli 0157 ferment sorbitol
use sorbitol to differentiate strain escherichia coli- red, acidic from pathogenic 0157: white colony

33
Q

Describe Eosin Methylene Blue Agar

A

red in color
selective and differential
contain Eosin and methylene blue restrict growth of gram (+) bacteria
microbe different based on ability to ferment lactose in media
non ferment lactose grow white
lactose ferment grow dark( purpler/black)
if escherichia coli grown on EMB agar plate colonies have distinctive metallic green

34
Q

Describe Mannitol salt ager

A

red in color
selective and differential
selective for gram (+) bacteria
differentiate members of staphylococci
contain high concentration of sodium chloride- prevent growth of orther microorganism( selectivity)
presence of alternate sugar( mannitol) hype phenol red
differential for pathogenic and non-pathogenic strain of staph

35
Q

How will a pathogenic strain of staphylocooou aurea present

A

ability to ferment mannitol so in mannitol salt ager, lowers pH of medium and change dye from red to yellow

36
Q

What is the process of plating

A

process of spread bacteria culture onto petri dish filled with agar
done using sterile loop
motion: back and forth sweeping

37
Q

what is the advantage of plating

A

bacterial sample onto agar cells held in place
bacteria that’s plated are fixed to support fermentation and visualization
colonies are visible to naked eye only after cells multiplied often over 1 million

38
Q

What is a pure culture

A

culture free of outside contaminate

39
Q

How to obtain a pure culture

A

isolate microbe on agar plate: either quadrant streak or 4-phase dilution
once isolated and expanded, pure culture further examined for size, shape, motility, gram status and biochemical properties

40
Q

Describe 4 phase dilution

A

sample spread across plate to establish dilution gradiant
sample spread onto 4 regions
spread sample then with clean loop dip into end of previous phase and create new streaks
when all finished should be diluted
results should be individual colonies in 4 phase

41
Q

What do you do when done plating

A

invert plate and incubate 12-14 hours at 37 degrees celsius

42
Q

Why is 37 degrees best for incubation

A

best to encourage growth of bacteria

43
Q

What is done following incubation period

A

each region is examined in the 4 phase or 4 quadrant

for changes in color, colonies or signs that selective or differentiation between bacteria

44
Q

Why is 30 degree celsius used at times

A

for yeast growth

45
Q

When would research use 25 degree celsius for incubation

A

restrict growth of pathogenic bacteria

Microbiology (7 decks)

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