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MICROBIOLOGY 2420 > Lab 2 > Flashcards

Lab 2 Flashcards

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Biology 101 flashcards
1
Q

Cellular Morphology

A

Size (short); shape (singular), arrangement (rods)

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2
Q

Successful cultures depend on

A

Medium ingredients and chosen conditions

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3
Q

Media provide both ___________ for growth of organisms

A

Macro and micronutrients

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4
Q

Macronutrients

A

carbon and nitrogen, phosphorous, sulfur, potassium, magnesium, sodium and iron

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5
Q

Macronutrients are used and measured in

A

decreasing quantity and added to media in milligrams and grams

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6
Q

Micronutrients are

A

cobalt, zinc, copper, manganese

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7
Q

Micronutrients are used in (measurement)

A

in micrograms and in very small quantities

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8
Q

Media can be classified into (5)

A
  1. Chemically Defined/synthetic medium
  2. Complex/Undefined medium
  3. Enrichment medium
  4. Differential medium
  5. Selective medium
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9
Q

Chemically defined/synthetic medium

A
  • ingredients are chemically defined and quantifiable
  • they cannot contain any undefined complex soluble extracts from animal (beef extract) or plants (malt extract-sugar) or fungi (yeast) or special supplements like serum or blood
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10
Q

Complex/Undefined medium

A
  • NOT all ingredients are chemically defined and quantifiable
  • Can contain animal and plant extracts and other sources like serum, blood, sea water or soil.
  • These media are rich in nutrients and are ideal for culturing most heterotrophic microorganisms.
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11
Q

Enrichment medium

A
  • Contains an ingredient to encourage growth of a particular fastidious (want a specific thing to grow) organism
  • for example, 5% sheep blood is added to Tryptic Salt agar to prepare Blood Agar
  • This medium is also differential
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12
Q

Differential medium

A
  • It allows for identification of a particular organism by its appearance or by the way in which it changes the medium during growth
  • for example how bacteria interact with added blood
  • Streptococcus pyogenes produces a clear zone (beta haemolysis)-rupture of red blood cells
  • S. pneumonia produces a greenish zone (alpha haemolysis)
  • S. epidermidis produces NO heamolysis (gamma heamolysis)
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13
Q

Mannitol Salt agar and MacConkey agar

A

differential medium AND selective medium in function

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14
Q

Mannitol Salt agar

A
  • fermentation of carbohydrate mannitol leads to acid production, which lowers the pH of the medium and it causes the ph indication to change from red to yellow
  • it forms a yellow zone around its colonies
  • contains 7.5% NACL that inhibits the growth of gram negative and positive bacteria except staphylococci
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15
Q

MacConkey agar

A
  • fermentation of lactose yields brick red colonies

- inhibits the growth of gram positive bacteria

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16
Q

Selective medium

A
  • contains an ingredient(s) inhibitory to all but one particular microorganism.
  • it may even lack an ingredient necessary for most microorganisms to grow like N. (Nitrogen free Mannitol agar)
17
Q

Growth medium

A

Tryptic soy agar

18
Q

Tryptic soy agar

A

-purpose is to grow a wide variety of aerobic and facultative anaerobic heterotrophic bacteria
-Complex medium containing a.a and peptones carbon and nitrogen sources and 0.5% NaCl to maintain the osmotic pressure.
-a.a and petones are derived from the enzymatic digestion of casein and soy meal.
-also it contains, 1.5% of agar as a solidifying agent.
without the agar it is tryptic soy broth NOT an agar

19
Q

Agar

A
  • complex polysaccharide extract from red-purple algae
  • used a solidifying, gelling agent in media at a 1.5% concentration.
  • semi solid media for bacterial motility
  • after preparing it must be sterilized-this is done by autoclaving
20
Q

Skin

A
  • primary function is to not lose moisture
  • physical barrier to the entry of pathogens and toxic substances
  • contains immune defenses-lysozomes
  • 200 genera of bacteria
  • Gram positive are predominant on the skin (thick peptidoglycan)
21
Q

Skin-experiement

A
  • use of Mannitol Salt Agar (MSA)
  • a selective differential medium
  • and the streak technique used to isolate staphylcocci and other gram positive bacteria from skin
  • 7.5% of NACL in MSA selects specifically for gram positive and staphylococcus bc of their greater tolerance to the increased osmotic pressure by the salt
  • Target the isolation of STAPHYLOCOCCUS AUREUS.
  • it is important bc it can ferment the sugar alcohol mannitol and produce colonies with yellow zones on the MSA.
22
Q

SALIVA experiment

A
  • streptococcus mutans-initiation of dental caries
  • use Mitis Salivarius Agar
  • selective differential medium
  • PURPOSE- to isolate S. mitis and S. salivarius
  • Selective ingredient are Potassium Tellurite to inhibit the growth of most bacteria except oral streptococci and crystal violet to inhibit the growth of gram positive bacteria except oral cocci.
  • The differential ingredient is sucrose
  • S. salivarius produces a rough frosted glass or gum drop colony
  • S. mitis doesn’t ferment sucrose and it produces small colonies
23
Q

Fresh water experiement

A
  • purpose to isolate gram negative bacteria and E. coli
  • using the MacConkey (cons and keys) agar (MAC) as a selective and differential medium
  • differential medium-presence of bile salts and crystal violet in mac makes it selective for gram negative bacteria
  • E.coli is inherently more resistant to salts that other gram negative bacteria
  • E. coli can be differentiated from other colonies by their ability to ferment the sugar lactose.
  • Fermentation of lactose yields acids, acids lower the PH of the medium, therefore the ph indicator changes colour from light pink to brick red.
  • As ph lowers further a pink halo of precipitated bile salts will form in the medium around e. coli
  • Indication of brick red colonies with pink halos, indicated successful isolation of E. coli
24
Q

Terms to describe typical colony morphology (6)

A
  1. form-circular
  2. colony size-small, medium
  3. colour-pigment as pink, opacity of a colony as transparent
  4. texture-smooth, dry, glistening
  5. elevation-raised, flat, convex, concave
  6. Margin-entire, irregular
25
Q

Halophiles

A

-organisms that require high salt concentrations for growth (3-15% nacl)

26
Q

extreme halophiles

A

need 20-30% of nacl

  • found in solar salterns, salt mines and ancient salt lakes
  • pinkish red colours bc of presence of carotenoids
27
Q

Halobacterium can grow…..

A
  1. chemoheterotrophically in the dark
  2. phototrophically in the light
    - harvest light energy with the membrane protein bacteriorhodpsin
28
Q

Bacteriorhodpsin

A

-protein functions like a proton pump to generate a proton gradient and then it is used to form ATP

29
Q

Halobacterium diet??

A

-need a source of carbon since they are heterotrophs

30
Q

Halobacterium salinarum (description)

A

-motile rod
-grows aerobically at an optimal temp
it can form intracellular gas vesicles

31
Q

Intracellular gas vescles

A
  • hollow structures surrounding a gas filled space within a cell
  • provides a buoyancy so the cells can remain afloat in the water to optimally absorb light or obtain oxygen for growth
32
Q

Halobacterium is attacked by

A

-brine shrimp

33
Q

Halobacterium description of the experiement

A
  • 25% nacl
  • use the microscope to examine the enrichments for the presence of motile rods and intracellular gas vesicles
  • then we will isolate the colonies on the halobacterium agar medium for isolated colonies and look for the formation of pink to red colonies
34
Q

washing hands 2 techniq

A
  1. soap and water (soap contains antimicrobial 0.3 % chloroxylenol.)
  2. Hand gel has 60% ethyl alcohol
35
Q

efficacy testing of hand washing and alcohol based gel

A

MICROBIOLOGY 2420 (6 decks)

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