Microbiology Lab Midterm

Front 1

Gram +
Rod shaped
Bacillus Cereus

Back 1

The following has what gram reaction and what morphology? give a possible species.

Front 2

Gram -ve
Rod shaped
E. Coli

Back 2

what are the gram reaction and morphology of the bacteria? Name a potential species.

Front 3

+ ve
Coccus
StaphyloCOCCUS aureus

Back 3

what gram reaction and cell morphology. Name a potential species

Front 4

why is nutrient broth undefined media?

Back 4

Because we do not know its exact chemical formula

Front 5

How to use spectrophotometer?

Back 5

First set to 0 with left knob

Then put in blank set to 0 with right knob

Put in the actual substance to test and read absorbance from right to left.

Front 6

TFTC vs. TNTC

Back 6

Plate count must be between 30 and 300.

Less than 30 TFTC
More than 30 TNTC

Front 7

Plate dilution-

say 36 counted on a 10-5 plate dilution. How many bacteria?

Back 7

36 X 10^5= 3,600,000

no need to add an extra fold. Plate dilution is the multiplication factor.

Front 8

Why is plate more accurate than spectrophotmetry?

Back 8

In spec some of the dead colonies are counted as well as any debris.

Front 9

What was the point of the Sabouraud plate?

Back 9

it was used to demonstrate person-to-person contact spread of microorganisms.

Front 10

Baker's yeast

Back 10

Sacchaomyces cerevisiae

Front 11

Crystal violet, nigrosin and methelene blue are examples of...

Back 11

Simple stains

Front 12

What is the purpose of a wet mount?

Back 12

To check for motility in microorganisms.

Front 13

What cellular structure is differentially stained using the Gram technique?

Back 13

The cell wall

(peptidoglycan (+ve) vs. none (-ve))

Front 14

What is the bacterial cellular structures that confers motilitiry

Back 14

Flagellum

Front 15

How can we disinguish between Micrococcus luteus and bacillus cereus?

Back 15

Both are gram positive and have a cocci morphology BUT

Micrococcus luteus are often found in tetrads or pairs.

Front 16

Why doesnt nigrosin stain the cell?

Back 16

Because nigrosin is a negative dye it does not stain the cell it stains the background and organisms appear White.

Front 17

When studying wet mounts, which organism moved very quickly?

Back 17

Pseudomonas aeruginosa

Front 18

When studying wet mounts,What organism moved slowly?

Back 18

Bacillus Cereus

Front 19

What is brownian motion?

Back 19

vibrating motion caused by bacteria being struck by H20 molecules.

Front 20

When studying wet mounts, what organism did we observe and identify as engaging in brownian motion?

Back 20

Staphylococcus Auerus

Front 21

In the gram stain what was the:
Primary stain
mordant
decolorizer
differential stain

Back 21

Crystal violet
Gram's iodine
alcohol
safranin

Front 22

The acid fast stain served what purpose?

Back 22

used to differentiate the genus Mycobacterium which can cause TB and leprosy. CLUMPED RED RODS!

Front 23

Why is the gram stain the most important staining procedure in microbiology?

Back 23

Because it differentiates MANY bacteria. Basically cuts in half.

Front 24

What is expected in a capsule stain?

Back 24

The background is dark (crystal violet) and the capsule appears in white with the black bacteria enclosed in the white capsule

Front 25

What is expected in an endospore stain?

Back 25

round endospores are green because they opened due to heat and the bacterial rods (pink- safranin)should surround the endospores.

Front 26

Selective/differential
for what? how?

CRYSTAL VIOLET AGAR

Back 26

selective media for gram -ve

Does not allow gram +ve cell growth b/c hinders cell walls

Front 27

Selective/differential
for what? how?

BLOOD AGAR

Back 27

differential media.

shows to what degree bacteria can hemolyse blood.

Front 28

Selective/differential
for what? how?

Manitol Salt agar plate

Back 28

Differential and selective.

High salinity only allows Staphylococcus genus to grow. while the manitol sugar is broken at different rates to differentiate between species.

Front 29

Selective/differential
for what? how?

MacConkey agar

Back 29

Maconkey is differential and selective.

It has crystal violet (selective) no gram positive)) and lactose w/ indicators (differential)

Front 30

Selective/differential
for what? how?

EMB

Back 30

EMB- Eosin/Methylene blue is both differential and selctive

Selective- not perfect does not allow gram +ve again

differential- obvious (E.coli metallic green)

Front 31

Which organism should not grow on a Crystal violet agar plate, why?

Staph Aureus or E. coli

Back 31

Staph aureus should not grow because crystal violet is a selective media for gram -ve bacteria. (e-coli should grow)

Front 32

What are the classes of hemolysis in the blood agar plate and what does that mean? Identify potential organisms.

Back 32

Beta- complete breakdown
Alpha- partial breakdown
Gamma- no breakdown

Beta- S. pyogenes
Alpha-S. mitis
Gamma- E. faecalis

Front 33

If given a MSA plate broken in 5 pieces and 2 show no growth. and of the three with growth 1 has made the plate yellow. what can you conclude?

Back 33

The two that did not grow are not Stapylococcus.

The two that grew but no yellow are staphylococcus but not maniotol fermenters.

and the one that grew and changed to yellow is both and probably Staph Aureus.

Front 34

If given an EMB plate broken in 5 and 2 did not grow, 1 grew but no change in color, 1 grew and changed ot pink, and a last grew and became green. what can you conclude?

Back 34

The 2 that did not grow are probably gram +ve. the one that grew but no change in color is either gram positive or negative but CANNOT FERMENT LACTOSE. the one that converted to pink is a mediocre fermenter and the metallic green is an excellent fermenter of lactose (E. coli)

Front 35

If given a MacConkey plate where 2 did not grow and 2 others are pinkish red instead of colorless.

Back 35

MAC is selective:
Gram negative organisms will grow, Gram positive organisms will not. This is due to the addition of bile salts and crystal violet.

MAC is differential:
Lactose fermenters will appear pink, non-lactose fermenters will appear colorless. This is due to the addition of the indicator, neutral red.

Front 36

In MSA plate change from red to yellow indicates

Back 36

the organism can ferment mannitol and the acid produced as byproduct lowers pH to YELLOW. (Phenol red)

Front 37

MacConkey plate: organisms changing from colorless to pink.

Back 37

Lactose fermenters will appear pink, non-lactose fermenters will appear colorless. This is due to the addition of the indicator, neutral red.

Front 38

Which plate would you use if you were checking whether your patient's upset stomach was salmonellosis or traveler's diarrhea?

Back 38

Use manitol salt agar plate. if the organism does not grow it is most likely Salmonelosis. if it does and turns yellow (Staph aureus= travelers diarrhea).

To be sure also innoculate Crystal violet and gram -ve salmonella typhimurium should grow and Staph not.

Front 39

Bacteria that thrive in cold climates

Back 39

Psychrophiles
(P. Fragi)

Front 40

Bacteria that thrive in very hot climates

Back 40

Thermophiles
(B. stearothermophilus)

Front 41

Bacteria that thrive in room temperature

Back 41

Mesophiles
(E. coli, S. Marcescens)

Front 42

pH conditions: E coli

Back 42

Grows in alkaline pH
(your intestines)

Front 43

pH conditions: A. faecalis

Back 43

grows in alkaline pH

Front 44

pH conditions: L.Lactis

Back 44

grew in acidic conditions (pH 3-4)

Front 45

Why use buffers in the testing of pH conditions?

Back 45

Because the organisms themselves will begin to change the pH by fermentation and/or wastes.

Front 46

Why are buffers NOT necessary in nutrient broths?

Back 46

because they contain natural buffers in the form of zwitterions from amino acids which can donate or accept protons
(brownsted-lowry definition of acid/base).

Front 47

Obligate aerobes

Back 47

Require Oxygen

Front 48

Obligate anaerobes

Back 48

Cannot have oxygen

Front 49

Facultative Anaerobes

Back 49

Dont need Oxygen but make use of it and grow more abundantly b/c oxygen is their final electron acceptor. (E.coli)

Front 50

Aerotollerant Anaerobes

Back 50

those that can live in the presence of Oxygen or not with no difference.

Front 51

Microaerophiles

Back 51

Species that grow if provided only with a little bit of oxygen.

Front 52

When using the GasPak system, to determine oxygen requirement, the strip contains methylene blue is obviously blue until...

Back 52

no oxygen is present in which case the strip will turn colorless.

Front 53

Growth curve:

Back 53

Lag phase- cells adapt to new surroundings no major growth

Log phase- where growth outnumbers death

Stationary phase- where they are equal (carrying capacity)

Death phase- where more organisms are dying than reproducing.

Front 54

extracellular enzymes

Back 54

Produced within the cell but work outside the cell often to breakdown large substrates into smaller transportable units (amylase, lipase, caseinase, gelatinase)

Front 55

Intracellular enzymes

Back 55

are produced inside the cell and function there. (Catelase)

Front 56

Catabolic reactions

Back 56

breaking down substrates= generates energy or subunits to be used by the cell.

Front 57

Anabolic reactions

Back 57

Synthesizing reactions usually to build cellular constituents at the expense of ATP energy.

Front 58

Amylase

Back 58

Along with maltase breaks down starch.

Front 59

Lipase

Back 59

general term for enzymes which hydrolize lipids to glycerol and fatty acids; extracellular

Front 60

Caseinase

Back 60

The enzyme that breaks the protein CASEIN in milk into its constituent amino acids.

Front 61

Gelatinase

Back 61

reduced gelatin to its amino acids. (Psuedomonas Aeroginosa)

Front 62

Phenol red carbohydrate broths (red to yellow)

Back 62

Organism fermented the carbohydrate.

Front 63

Phenol red carbohydrate broths (red outside yellow inside)

Back 63

organism OXIDATIVELY break down the peptones in the broth~ PROTEOLYSIS (pH goes up)

Front 64

IMVIC test is useful for

Back 64

the genus Enterobacteriaceae

specifically to distinguish between e. coli and e. aerogenes.

Front 65

Indole test

Back 65

If indole is produced from tryptophan (by the enzyme tryptophonase) a floating red ring will form.

Front 66

Methyl red test

Back 66

When glucose is oxidized it may produce a final acid product (RED) or another final product will not be acidic (Yellow).

Hint 66

in other words the methyl red test rules out...

Front 67

Voges-Proskeaur Test

Back 67

If the final of further glucose oxidation is ACETYLMETHYLCARBINOL (AMC) it will produce an orangey-red broth after 30 minutes of vortexing.

Front 68

Citrate test

Back 68

The ability to use citrate as the sole carbon source is detected by a change from green to deep blue. (bromethyl blue)

Front 69

SIM agar deep test

Back 69

In this test if the gas released is hydrogen sulfide it reacts with the iron in the medium to turn black.

Front 70

Carbohydrate phenol red test (gas in durham tube)

Back 70

This means that the carbohydrate was fermented and CO2 was most likely produced and released as a by-product.

Front 71

SIM test stands for...

Back 71

the three tests it can do:
Sulfide- turn black
Indole- unreliable
motility- unreliable

Front 72

Urease test

Back 72

Many organisms convert urea to ammonia and water using urease.

In this case the medium will become hot pink from an orangey-yellow color. (phenol red indicator will show when alkaline ammonia is produced).

Front 73

2 major causes of UTI's. how to test for it.

Back 73

Proteus Vulgaris and Proteus Mirabilis

Urease test

Front 74

Major cause of Stomach ulcer and how to test for it

Back 74

Helicobacter pylori; urease test.

Front 75

Nitrate reduction test

Back 75

Possible products are: (red is always terminal)

Nitrogen- Air in Durham tube if nitrate is reduced to N2.

Nitrite- if after addition of 2 reagents turns red.

Nitrate- if Zinc is added and broth turns red, nitrate was never reduced

Ammonia- no color change nitrate was never reduced.

Front 76

Production of Catelase test

Back 76

Catelase- breaks H202 into water and oxygen. The reason most anaerobes cant live in oxygen.

Add H202 to the slant if it fizzes the organism has catelase to break it down.

Front 77

TSI agar test used to identify members of

Back 77

Enterobacteriaceae

Front 78

TSI- triple sugar iron medium contains:

Back 78

three sugars:
glucose, lactose, and sucrose.
ph indicator: phenol red
iron- to detect production of H2S

Front 79

TSI possible results:

red slant, red butt=
red slant yellow butt=
yellow slant yellow butt=
Black=

Back 79

red/red= nothing fermented no H2S produced.

red/yellow= only glucose fermented

yellow/yellow= glucose and either both or one of the two sucrose/lactose was fermented

black= H2S was produced and fermentation of sugars is obscured.

Front 80

Litmus milk test serves two purposes:

Back 80

1.) redox indicator- showing whether the medium was reduced or oxidized by changing color.

2.) pH indicator- showing if the medium is acidic or basic following the activities.

Front 81

Litmus milk as a pH indicator

Back 81

lactose fermentation yields acid:

Pink- lactose fermented
Pink on top only and curd- excessive fermentation
Deep blue- breakdown of milk proteins (casein)
Brown and purple/blue at top-proteolysis of milk protein

Front 82

Both are gram positive and coccus shape, BUT M. luteus clump in duplets or quads.

Back 82

The following organism has what gram reaction and what morphology and yet it is known not to be Staphylococcus Aureus, why?

Front 83

Capsule, capsules enter the body without detection (NO PHAGOCYTOSIS)

Back 83

What kind of stain is this? what medical importance does this serve?

Front 84

Endospore

Back 84

What kind of stain is this?