Micro-Lab Final

Question 1

Know the steps of the gram stain process

Answer 1

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Question 2

what does a gram negative smear look like (color)?

Answer 2

a pink/red color

Question 3

what is an example of a gram negative?

Answer 3

escherichia coli

Question 4

what does a gram positive smear look like?

Answer 4

purple

Question 5

what is an example of a gram positive bacteria?

Answer 5

staphylococcus epidermis

Question 6

what are the differences between gram positive and negative?

Answer 6

gram positive has a thick layer of peptidoglycan, while gram negative has a thin outer membrane with over a thin layer of peptidoglycan

Question 7

why do gram positive and negative stain differently?

Answer 7

because gram positive doesnt have an outer membrane so the crystal violet is able to penetrate it and stain it but it cant in the gram negative, however safranin does

Question 8

what reagents are used in acid-fast stains

Answer 8

kenians reagent

Question 9

why do most stains not work on acid-fast bacteria?

Answer 9

because they have a layer of mycolic acid (fatty acid) in the cell wall which makes them waxy and harder for dyes to adhere to

Question 10

know how to explain streaking out a plate

Answer 10

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Question 11

why do we streak out plates?

Answer 11

to get isolated colonies

Question 12

what is the purpose of isolating colonies

Answer 12

so that the bacteria replicates a new cluster, so we know it is a pure culture

Question 13

what are advantages that capsules give bacteria?

Answer 13

better adherence and preventing dying out of the cell

Question 14

why is the acid-fast stain needed?

Answer 14

because the fatty acids in the acid-fast bacteria make it very hard for other dyes to adhere to the cell

Question 15

what is an endospore?

Answer 15

a structure that bacteria produce to survive harsh conditions, they are tough, dormit and unable to replicate, but they can survive in very harsh climates

Question 16

what does an endospore look like when using the endospore stain?

Answer 16

it will appear a greenish blue color due to the malachite green dye used, vegetative cells will appear a red color from the safranin

Question 17

know how to calculate CFUs

Answer 17

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Question 18

facultative anerobe

Answer 18

a microbe that can survive both using oxygen and without, however they prefer aerobic conditions

Question 19

aerotolerant

Answer 19

microbe that can survive in aerobic conditions but doesnt use the oxygen

Question 20

microaerophile

Answer 20

a microbe that uses oxygen but it has to be at lower atmospheric concentrations

Question 21

anerobe

Answer 21

a microbe that survives in conditions without oxygen, oxygen is toxic to them

Question 22

halophile

Answer 22

microbes that grow in environments that have a high saline concentration

Question 23

halotolerant

Answer 23

microbes that tolerate saline conditions but dont prefer them

Question 24

mesophile

Answer 24

microbes that prefer moderate temperatures and environments

Question 25

why do a lot of bacteria have a hard time growing in high salt concentrations?

Answer 25

because the high salt levels cause osmosis to occur and for water to move out of the cell causing them to die

Question 26

Know how to describe the process and results of a thiglycolate tube and how they are different, and positive and negative results

Answer 26

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Question 27

how did we test for fermentation of lactose? what was used and what were the results?

Answer 27

a tube high in lactose and purple in color is inoculated, if the color stayed the same then it was negative but if it turned yellow it was positive due to a pH indicator

Question 28

why was the lactose fermentation tube positive? what did it produce?

Answer 28

the products of lactose fermentation were lactic acid and CO2 which would cause the pH to decrease and for the pH indicator to turn yellow

Question 29

what is the mode of action for penicillin?

Answer 29

disrupts the peptidoglycan within the cell wall

Question 30

what is the mechanism of action for SXT?

Answer 30

kills the bacteria by inhibiting folic acid, which disrupts the DNA synthesis in the cell, halting DNA replication

Question 31

what type of agar plates are used in the Kirby-Bauer test?

Answer 31

Mueller-Hinton Agar

Question 32

what do positive and negative results look like in a Kirby-Bauer test?

Answer 32

trick question, they are not positive and negative but theu are used to determine how effective antibiotics are on bacteria, ranging from sensitive to resistant to being in the middle

Question 33

what reagent is added to the starch plate to detect the presence of an alpha amylase?

Answer 33

iodine

Question 34

what are the two properties of OF tubes that are unique to them? why are they important?

Answer 34

a high level of glucose is used to feed the metabolism of bacteria, allowing them to undergo fermentation, the other one is having a very low amount of peptones which makes the environment more alkaline

Question 35

know how the nitrate reductase test is set up, what positive and negative results look like and why zinc is used

Answer 35

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Question 36

why do bacteria secrete exoenzymes?

Answer 36

it is energy saving, they break down big macromolecules outside the cell and then bring the subunits inside the cell

Question 37

what is an example of an exoenzyme secreted by bacteria?

Answer 37

DNase

Question 38

what does a positive nitrate reductase result look like?

Answer 38

pink or red BEFORE the addition of zinc

Question 39

what does a negative result for nitrate reductase look like?

Answer 39

tan before the addition of zinc, red/pink after

Question 40

why is Bacillus subtilis able to survive in long exposures to UV light?

Answer 40

because they are able to produce endospores

Question 41

why does UV light cause species to die?

Answer 41

the UV light causes mutations within the DNA, causes covalent bonds to form between pyrimidines instead of between pyrimidines and purines

Question 42

what is the definition of antiseptic?

Answer 42

a chemical compound that controls the bacteria on living tissues

Question 43

what is the definition of disinfectant?

Answer 43

a chemical compound that controls bacteria on inanimate surfaces

Question 44

what are aseptic techniques?

Answer 44

methods used to prevent contamination of microorganisms

Question 45

know how to determine the thermal death point and thermal death time

Answer 45

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Question 46

what is thermal death time?

Answer 46

how long it takes for a bacterium to die at a constant temperature

Question 47

what is thermal death point?

Answer 47

the temperature it takes for a bacterium to die at a constant time

Question 48

how does an OF tube work?

Answer 48

they are used to determine whether a bacterium undergoes oxidation, fermentation or neither

Question 49

know what positive and negative OF tubes look like

Answer 49

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Question 50

what is a catalase test?

Answer 50

a test to determine of the bacteria contains the enzyme catalase to break down hydrogen peroxide

Question 51

what does a positive catalase test look like?

Answer 51

there will be bubbles forming when hydrogen peroxide is added to the bacteria

Question 52

what is the enzymatic reaction for the catalase test?

Answer 52

H2O2 ---> H2O + O2

Question 53

why do bacteria secrete hemolysins?

Answer 53

in order to lyse open RBC and break down the hemoglobin within them, they do this to obtain the iron within the heme

Question 54

know why MacConkey agar is both selective and differential and the difference between the two

Answer 54

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Question 55

what does a positive MacConkey Agar look like

Answer 55

it turns a bright red/pink

Question 56

what does MacConkey agar test for?

Answer 56

lactose fermentation

Question 57

what are the things that KIA tubes can test for?

Answer 57

lactose fermentation, glucose fermentation, hydrogen sulfide production, and gas production

Question 58

what does MR assay test for?

Answer 58

mixed acid fermentation

Question 59

what reagent is added to MR assay?

Answer 59

methyl red

Question 60

what causes the production of indole?

Answer 60

the breakdown of Trp

Question 61

know how and why the different results of the KIA test can be seen

Answer 61

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Question 62

what does a positive bile esculin test look like?

Answer 62

a dark brown/black color

Question 63

what occurs to make a bile esculin test positive?

Answer 63

the breakdown of esculin into glucose, esculetin, and iron is detected

Question 64

what is in CNA blood agar that inhibits Gram negative growth?

Answer 64

2 antibiotics, collistin and naladixic acid, these break down gram negative membranes by blocking gyrases and breaking the double strands in the DNA

Question 65

what does a positive urea test look like?

Answer 65

bright pink

Question 66

why does the urea test turn color when positive?

Answer 66

due to urease producing CO2 and ammonia, which combine with water to make ammonium carbonate which causes the pH to increase and the pH indicator to change to pink

Question 67

what does a positive citrate test look like?

Answer 67

it is prussian blue in color, negative remains green/teal

Question 68

how does the citrate assay work?

Answer 68

it detects an increase in pH due to the ammonia byproducts forming from a nitrogen source, this is an indirect indicator of the use of carbon sources

Question 69

what is the mechanism of action of novobiocin?

Answer 69

the works by inhibiting gyrases

Question 70

what is detected in the VP test?

Answer 70

acitoin

Question 71

what does a positive VP test look like?

Answer 71

dark red in color

Question 72

what three things does a SIM tube test for?

Answer 72

hydrogen sulfide production, indole, and motility