Mcb 3020C Lab Midterm

Front 1

PEA:
Type?
Objective?
Significant Components?
Positive Test?

Back 1

Phenylethanol Agar:
-Selective
-Selects for Gram +
Phenylethanol inhibits Gram neg growth
- Growth is a positive test

Front 2

EMB:
Type?
Objective?
Results?

Back 2

Eosin Methylene Blue Agar:
-Sel for Gram - and Diff for Lactose ferm
-Dark Colony: Lactose ferm (MB dye absorbs by high acid production) Pink Colony: Lactose ferm(absorbs Eosin by low acid production) No Dye Absorb: Lactose neg. (orangish)

Front 3

DES:
Objective?
Results?

Back 3

Desoxycholate Agar:
-Selects for Gram - and Diff for Lactose ferm
-Red Colony: Lactose (+)
Non-Red Colony: Lactose (-)

Front 4

Lipase Agar:
Indicator?
Results?

Back 4

-Neutral Blue Dye
-Fatty Acid release lowers pH and Blue dye intensifies = (+)
-No Blue intensification= (-)

Front 5

Milk Agar:
Results?

Back 5

Clearing of opaque Milk = (+)
No Clearing of Opaque Milk = (-)

Front 6

Gelatin:
Objective?
Results?

Back 6

-Detect Gelatinase(hydrolyzes gelatin protein into amino acids)
-Resolidification=(-)
No Resolidification=(+)

Front 7

Nitrate Broth:
-Objective?
-Results?

Back 7

-Detect Nitrate Reductase (Nitrase) (converts nitrate to nitrite)
-Red w/o Zinc = (+)
Red with Zinc = (-)
Never turns red = (+)

Front 8

Litmus Milk Broth:
moderate acid from lactose

Back 8

pink liquid in tube

Front 9

Litmus Milk Broth:
Heavy acid production from lactose

Back 9

pink, hard or soft curds (Coagulation of casein by acid)

Front 10

Litmus Milk Broth:
Alkaline products from metabolism

Back 10

blue, liquid;

Front 11

Litmus Milk Broth:
Reduction of litmus dye to colorless in lower half of broth = ?

Back 11

viewed as whitish from natural milk color when the litmus dye is no longer in the oxidized colored state. This is the action of bacterial reductase in milk

Front 12

Litmus Milk Broth:
Loss of opaque casein protein by caseinase?

Back 12

proteolysis (patronization),
usually seen starting at the top and increases downward;

Front 13

Litmus Milk Broth:
Objective?

Back 13

Detect Moderate/Heavy Acid from Lactose ferm. Detect Caseinase. Detect Reductase

Front 14

Litmus Milk Broth
Slimy strands suspended in liquid state of medium ?

Back 14

= ropiness trait produced by capsule-producing bacteria.

Front 15

Urea Broth:
Indicator?
Results?

Back 15

-Phenol Red: yellow = acid; cerise = alkaline; Red = neutral
-Red to Cerise = (+)
Yellow to light orange = (-)

Front 16

Tryptone Broth:
Objective?
Indicator?
Results?

Back 16

-Detect Tryptophanase (hydrolyses tryptone to indole--Indole is what is tested for)
-Kovac's Reagent (added after growth)
-Red/cerise top = (+)
Yellow top = (-)

Front 17

MR:
Objective?
Indicator?
Results?

Back 17

Methyl Red:
-Tests for Mixed Acid Fermentor
-Methyl Red (added after growth) (3-5 drops) pH below 5.0=Red
-Dye stays red = (+)
Dy turns yellow = (-)

Front 18

VP:
Objectives?
Results?

Back 18

Voges-Proskauer
-Detect 2,3 Butanediol ferm by testing for acetoin (acetyl methyl carbinol)
-Red on top = (+)
No red = (-)

Front 19

Simmon's Citrate Slant:
Results?

Back 19

Growth on slant and Blue Color = (+)
No growth =(-)

Front 20

Phenol Red Sugar Ferm:
Results?

Back 20

Yellow = ferm (+)
Lt Orange to Red = Ferm (-)
Gas in tube = Gas production

Front 21

Phenylalanine:
-Objective?
-Indicator?
-Results?

Back 21

-Detect Phenylalanase (phenylalanine deaminase) which converts phenylalanine to phenylpyruvic acid (PPA)
-10% Ferric Chloride (added after growth) (5-10 drops)
-Green = (+)
No color change to Ferric Chloride = (-)

Front 22

Oxidase:
-Objective?
-Indicator?

Back 22

-Detect Oxidase which removes hydrogen from different substrates
-dimethyl-p-phenylenediamine hydrochloride (Oxidase Reagent-Added after growth)
-BacteriaTurn Dark Blue to Black = (+)
Remain Colorless = (-)

Front 23

Two Genera of Acid Fast organisms?

Two important species in one of the generas?

Back 23

-Mycobacterium; Two important species = tuberculosis and leprae
-Nocardia

Front 24

Mycobacterium staining properties?

Back 24

Do not gram stain well if mature because of high wax content within walls, if young appear as gram + tapered rods that sometimes fragment

Front 25

Nocardia Staining properties?

Back 25

Actually requires use of a less stringent decolorizer than acid alcohol to achieve the same results

Front 26

Three genera of Spore forming organisms?

Back 26

o Bacillus – Aerobic, gram + rod
o Clostridium – Anaerobic gram + rod
o Sporsarcinae – Cocci

Front 27

_______ produces a metallic green sheen on EMB

Back 27

E. Coli

Front 28

(2,3)Butanediol Fermentors produce less acid so that the colonies have pale pink to lavender centers on EMB. Example?

Back 28

Enterobacter

Front 29

Why can the partial clearing on Blood Agar sometimes appear green?

Back 29

Partial clearing sometimes appears green due to partial reduction of hemoglobin in blood

Front 30

An alkaline reaction can occur in sugar fermentation tubes due to?

Back 30

utilization of the peptone in the broth and not the testing sugar.

Front 31

What is tested for when determening if something is a 2,3-butanediol fermentor?

Back 31

acetyl methyl carbinol (acetoin) is easier to detect than 2,3 butanediol, acetoin is tested for when determining if a microorganism is a 2,3 butanediol producer.

Front 32

Barrit's reagents?

Back 32

VP1 = alpha-napthol
VP2 = KOH

Front 33

Oxidase is also known as? What is its function?

Back 33

cytochrome oxidase
functions to oxidize aromatic amines

Front 34

Nitrate 1?
Nitrate 2?

Back 34

Nitrate I = Sulfanilic Acid
Nitrate II = dimethyl-alpha-naphthylamine

Front 35

Kovacks Reagent is used for what test?
What is it?

Back 35

-Tryptophan/Indole
-p-dimethylaminobenzaldehyde, amyl or butyl alcohol, and HCl, which will appear red (cerise) in the presence of the product indole

Front 36

cystine desulfurase?

Back 36

removes the sulfur side chain from cysteine to produce H2S --> in presense of iron forms BLACK precipitate

Front 37

Organism that is H2S positive?

Back 37

Proteus

Front 38

SIM?

Back 38

Tests for Sulfur (H2S production), Indole, and Motility

Front 39

Primary indicator of citrate utilization is?

Back 39

Growth on the media

Front 40

Oil immersion lens uses oil with ___________________ refractive index as glass to prevent light loss due to diffraction (bending of light rays) which would occur if light traveled from _________ to _________

Back 40

-approximately the same
-one refractive index to another

Front 41

As magnification of the objective lens increases, the working distance (distance between the object on slide and the objective lens, when in focus) ______________

Back 41

decreases

Front 42

Condenser

Back 42

directs light towards the objective lens in bright field microscopy

Front 43

Iris Diaphragm (lever located in the condenser)

Back 43

adjusts the diameter of the cone of light so that it just fills the objective lens

Front 44

As you close down the diaphragm:
1. The light intensity _______?
2. Contrast __________?
3. Depth of field __________?

Back 44

As you close down the diaphragm:
1. The light intensity decreases
2. Contrast improves
3. Depth of field increases
4. Limit Resolution (with oil immersion lens)

Front 45

Cationic Dyes?

Back 45

Methylene Blue, Crystal Violet

Front 46

Anionic Dyes?

Back 46

Acid fuschin, Congo Red, Nigrosin

Front 47

Fat Soluble Dyes?

Back 47

Sudan Black stains granules of Poly-B-OH-butyric acid

Front 48

Insoluble Dyes?

Back 48

India Ink (colloid suspension of carbon particles)

Front 49

Two dyes used in negative staining?

Back 49

o Nigrosin – a black anionic (negatively) charged dye. The negatively charged dye is repelled by the negatively charged surface of the bacterial cell
o India Ink – an insoluble dye (a colloidal suspension of carbon particles) which does not penetrate the cell surface

Front 50

What type of staining is best for determining morphology (shape and size)?

Back 50

negative

Front 51

Gram-positive microorganisms have a ________ peptidoglycan and ______ lipid content than gram-negative microorganisms

Back 51

-higher
-lower

Front 52

Gram neg. cells are easily decolorized because?

Back 52

the ethanol dissolves the high lipid cell wall allowing the crystal violet-iodine complex to readily exit the cell

Front 53

Acid Fast microorganisms have____________________, which requires the use of steam to allow dye to penetrate the cell

Back 53

a high wax content in their walls

Front 54

BSA:
Tests for?
Normal color and Positive indicator?

Back 54

Bismuth Sulfide Agar:
-Tests for Salmonella typhi
-Normally dull green, S. typhi produces black or brown color

Front 55

BGA:
Objective?
Positive tests?

Back 55

Brilliant Green Agar:
-Differential for lactose/sucrose fermentation
-Lactose ferm procude yellow/green colony/media
-Sucrose Ferm produce red/pink/white colony + red media

Front 56

SS Agar

Back 56

Salmonella produces a black colony
Shigella a colorless colony
Lactose (+) colonies appear red

Front 57

Desoxycholate CITRATE
Objective?

Back 57

Selects for gram (-), lactose (-)

Front 58

Do lactose (+) grow on desoxycholate citrate

Back 58

Some Lactose + colonies do grow but they will appear Red

Front 59

Coagulates is only valid on?
Why?

Back 59

Test is only valid on gram + staphylococcus like bacteria since gram negative bacteria are able to provide false positive reactions from a non coagulase like mechanism.

Front 60

MSA:
Objective?
Indicator?
Positive test?

Back 60

Manitol Salt Agar:
-Selects for staph d/t high salt concentration 7.5%
-Phenol Red
-plate/colonies turn yellow due to sugar fermentation

Front 61

S110:
Objective?
Indicator?
Positive test?

Back 61

Staph 110:
-selects for staph and allows to observe natural colony color
-no indicator
-growth

Front 62

M-staphylococcus broth

Back 62

Enriched media containing 10% NaCl, which selects for Staphylococcus since Staphylococcus prefer the higher salt concentration, which inhibits most other organisms

Front 63

Endo Agar:
Objective?
Results?

Back 63

-Selects for gram (-)
-Differentiates lactose
-Lactose (+) = red colonies
-Coliforms produce golden metalic sheen

Front 64

Only staph species that can coagulate plasma?

Back 64

S. aureus

Front 65

Staph and Strep results for catalase/NO2 reductase?

Back 65

Strep = (-)(-)

Staph = (+)(+)

Front 66

facultative anaerobe that ferments lactose to produce gas, and is a gram negative, non-spore-forming rod

Back 66

coliform

Front 67

two coliforms?

Back 67

Eschericia coli and Enterobacter aerogenes

Front 68

mENDO Agar

Back 68

pink medium that shows coliforms as a golden sheen

Front 69

mFc Agar

Back 69

light blue medium that shows fecal coliforms as darker blue colonies

Front 70

The MIC is the ?

Back 70

the most dilute (the minimal concentration) tube which prevents growth of the test organism