lab practical 1

Question 1

what does emb select for and if its e. coli what color will it turn

Answer 1

colliforms

metallic green for e coli

Question 2

acid-fast will be what two colors

Answer 2

blue and pink

Question 3

in acid fast staining:
light blue is what
pink is what

Answer 3

non acid fast
acid fast (mycobacterium)

Question 4

gram positive is what color

Answer 4

purple/blueish

Question 5

gram negative is what color

Answer 5

pink/reddish

Question 6

what is the purpose of a streak plate

Answer 6

dilute bacteria to get a single CFU (colony forming unit)

Question 7

parts of gram staining

Answer 7

primary stain- crystal violet
mordant- iodine
decolorization-ethanol
counterstain- safranin

Question 8

shapes of bacteria

Answer 8

bacilli (rod)
cocci (ball)
spirilla (spiral)

Question 9

arrangements of bacteria

Answer 9

cluster

chain

Question 10

what is a gram reaction

Answer 10

whether it is gram + or gram -

Question 11

selective media definition

Answer 11

selective media selects for a desired trait

ex: antibiotic resistance

Question 12

differential media definition

Answer 12

used to differentiate two different types of bacteria

Question 13

iodine binds to crystal violet creating what

Answer 13

CV-I

Question 14

what does blood agar select for?

Answer 14

selects for hemolytic activity

only differential media

Question 15

types of blood agar

Answer 15

hemolysis types:
alpha
gamma
beta

Question 16

alpha hemolysis

Answer 16

• INCOMPLETE LYSIS of red blood cells

- results in GREENISH HALO around the bacteria

Question 17

beta hemolysis

Answer 17

• COMPLETE LYSIS of RBCs resulting in complete destruction of them
• will turn YELLOW around it

Question 18

gamma hemolysis

Answer 18

• NO LYSIS of RBCs

- results in NO SIGNIFICANT CHANGE in the media

Question 19

what is an endospore

Answer 19

a dormant bacteria (not metabollicly active)
blue color
will germinate under appropriate conditions (survival mechanism)

Question 20

what is the layer that forms the plasma membrane in bacteria

Answer 20

peptidoglycan

Question 21

does gram + have a thick or thin layer of peptidoglycan

Answer 21

thick

Question 22

does gram -have a thick or thin layer of peptidoglycan?

Answer 22

thin

Question 23

what is a capsule

Answer 23

a gelatinous layer that is secreted by the cell and that surrounds and adheres to the cell wall

Question 24

components of gram staining

Answer 24

mixed culture
E.coli (G-)
S.epi (G+)

Question 25

components of simple staining

Answer 25

MB (methylene blue) CV (crystal violet) carbol fusion

Question 26

components of endospore staining

Answer 26

B. cereus | b. subtilis (bacillus)

Question 27

components of acid fast stain

Answer 27

m. smeg mycobacterium s. megmatis

Question 28

components of capsule stain

Answer 28

CV (crystal violet) - primary stain | copper sulfate- decolorizing agent

Question 29

parts of the endospore staining procedure

Answer 29

primary stain- malachite green decolorizing agent- water counterstain- safranin

Question 30

what would an autoclave be set to

Answer 30

121 degrees celcius ( 15 mins, 15 psi). | -(increasing temp, increases pressure to completely sterilize)

Question 31

what is the optimum temp for growth of an organism

Answer 31

- room temp= 72 degrees Fahrenheit. 24 degrees Celsius | - human body temp= 98.6 degrees Fahrenheit. 37.5 degrees Celcius

Question 32

identify the bacterial genus in which all species are acid fast

Answer 32

mycobacterium

Question 33

why shouldn't bacterial cells be placed in pure distilled water and what physiological changes will occur

Answer 33

too hypotonic. excess water rushes in, expanding the cell

Question 34

describe the role of buffers in a bacteriological medium

Answer 34

resists radical changes/swings in the pH

Question 35

identify the approximate pH at which most bacteriological media are generally adjusted

Answer 35

approximately 7.0

Question 36

obligate aerobe

Answer 36

will only grow at the top of theoglycolate broth | needs oxygen to survive

Question 37

obligarte anaerobe

Answer 37

will only grow at bottom of theoglycolate broth to get away from the oxygen

Question 38

facultative anaerobe

Answer 38

will grow all throughout but cluster a little on the type. | can grow in oxygen or non oxygen environment but prefers oxygen

Question 39

microaerophilic

Answer 39

prefers lower oxygen levels and higher CO2 levels and grows on top because still needs oxygen to survive

Question 40

aerotolerant

Answer 40

grows all throughout, distributed evenly

Question 41

microbicidal agents definition

Answer 41

kill microbes immediately

Question 42

what are the different microbicidal and microbistatic agents

Answer 42

antiseptics disinfectants chemotherapeutic agents

Question 43

microbistatic definition

Answer 43

stops the cell from reproducing

Question 44

microbicidal definition

Answer 44

will kill the cell immediately

Question 45

types of MacConkey agar

Answer 45

coliform bacteria | dysentery, typhoid, and paratyphoid bacilli

Question 46

dysentery, typhoid, and paratyphoid bacilli

Answer 46

not fermenters dont produce acid tan or transparent

Question 47

coliform bacteria

Answer 47

ferment lactose red coloration medium may be pink

Question 48

why is heat used in acid fast staining

Answer 48

penetration is further enhanced: drives the carbol fuchsin through the lipoidal wall and into the cytoplasm USED IN ZIEHL- NEELSON METHOD for acid-fast staining

Question 49

Kinyoun method

Answer 49

circumvents the use of heat by addition of a wetting agent to the stain reducing surface tension between the cell wall of the mycobacterium and the stain.

Question 50

steps in an acid-fast stain

Answer 50

primary stain- carbol fuschin decolorizing agent- acid-alcohol (3% HCL + 95% Ethanol) counterstain- methylene blue