Lab Practical 1

Question 1

microbial antagonism

Answer 1

normal flora compete with harmful bacteriaand prevent them from colonizing in the organism

Question 2

opportunistic pathogens

Answer 2

cause disease in host if there is some weakness in host’s anatomical barriers or immunity
EX: E. Coli

Question 3

nosocomial infections

Answer 3

infections acquired in hospital

Question 4

types of bacteria

Answer 4

coccus-sphere
bacillus-rod shaped
spiral

Question 5

condenser knob function

Answer 5

concentrates light from the illumination source

Question 6

iris diaphragm knob function

Answer 6

adjust the intensity of light

Question 7

ocular eyepiece lens functions

Answer 7

magnify and measure

Question 8

negative staining

Answer 8

quick and does not involve heat fixing
used to identify cell shape; heating causes slight distortion of cell shape
use acidic stains w/ negative charge to stain background
1. drop india ink on end of slide
2. place small amount of m. luteus and mix
3. spread mixture

Question 9

simple stain

Answer 9

use heat fixing(pass over pilot light)
used to view bacterial size shape or arrangement
highlights the entire organism
use basic stain w/ positive charge
1. heat fix m. luteus
2. flood w/ simple stain and incubate

Question 10

gram stain

Answer 10

groups bacteria due to difference in cell wall
primary stain: crystal violet-turns purple
mordant: iodine-increase binding of primary stain
decolorizer: acetone: removes stain of gram neg
counterstain: safrinin-red color to gram neg
1. E. Coli and S. aureus
2. heat fix
3. flood w/ crystal violet and incubate for 30 sec
4. cover w/ iodine for 1 min
5. acetone 5-10 seconds and immediately rinse
6. cover w/ safrinin for 2 minutes

Question 11

why don’t acidic background dyes stain bacteria

Answer 11

both are negative so repel, staining background

Question 12

why do basic dyes stain the bacteria

Answer 12

dye is positive, bacteria is negative so attract staining bacteria

Question 13

acid fast staining

Answer 13

mycobacterium (mycolic acid in cell wall)
use heat during staining
heat drives carbolfuchsin stain into bacteria through thick waxy lipid in cell wall (mycolic acid)
mycolic acid traps carbolfuchsin and the cells don’t decolorize as easily
mycolic acid is virulence factor
tuberculosis and leprosy
1. e. coli and m. smegmatis- heat fix
2. cut paper towel to fit over slide
3. flood w/ carbolfuchsin and heat over pilot light for 5 minutes
4. remove paper towel and allow to cool then rinse with water
5. decolorize with ACID ALCOHOL for 10 seconds then rinse immediately
6. cover with methylene blue for 2 minutes

Question 14

virulence factor

Answer 14

ability of bacteria to overcome host defenses

Question 15

endospore staining

Answer 15

use heat to drive malachite green stain through the tough spore coat.
bacillus anthacis
clostridium tetani
clostridium boulinium
1. heat fix b. cereus
2. cut paper towel to fit slide
3. flood paper with malachite green and heat over pilot light
4. allow to cool and rinse w/ water
5. cover w/ safranin for 1.5 min

Question 16

capsule staining

Answer 16

sticky sugary layer around bacteria called capsule
helps bacteria attach to a host and hide from phagocytic cells
capsule is virulence factor
combo of negative stain and simple stain
1. E. coli
2. drop india ink, smear bacteria and smear mixture across slide
3. stain smear w/ crystal violet 1 min
4. gently rinse w water
5. stain w/ safranin for 1.5 minutes

Question 17

why does a capsule stain require both negative and basic staining?

Answer 17

because the negative will stain the background and basic will stain bacterium so the clear part is the capsule

Question 18

capsule bacteria cause what type of infections?

Answer 18

upper respiratory infections

Question 19

pipette

Answer 19

top thing: air to create vacuum
middle thing: suck to suck up liquid
bottom thing: expel liquid

Question 20

aseptic technique procedure

Answer 20

1. mix broth by rolling back and fourth
2. hold culture in 1 hand and flame loop in other hand and allow to cool
3. remove cap and hold cap in little finger
4. pass top of culture tube through blue flame quickly
5. remove some culture with inoculating loop
6. reflame top of culture tube through blue flame
7. cap tube and streak petri plate

Question 21

streak plate testing

Answer 21

method to achieve isolated pure colonies

concentrated areas of bacteria are spread out throughout the plate

Question 22

spread plate technique

Answer 22

determine amount of bacteria

dilute bacteria, pipette onto agar plate, spread using glass rod

Question 23

why do we consider all the cells of a colony clonal?

Answer 23

bc its a population growing from one cell through binary fission

Question 24

CFU

Answer 24

colony forming units

Question 25

psychrophiles

Answer 25

optimum growth them between 0-20 degrees celcius

Question 26

mesophiles

Answer 26

optimum growth them between 20-45 degrees celcius

Question 27

thermophiles

Answer 27

optimum growth higher than 55 C

Question 28

why do bacteria have a minimum growth temperature

Answer 28

cell membrane fluidity

Question 29

why do bacteria have a max growth temp

Answer 29

denature protein and membrane becomes too fluid

Question 30

thermoduric

Answer 30

cannot grow at high temps but can survive

endospores

Question 31

acidophiles

Answer 31

grow between ph of 0 and 5.5

Question 32

neutrophiles

Answer 32

ph range is 5.5-8

Question 33

alkalophiles

Answer 33

ph between 8 and 11.5

Question 34

why do bacteria have a minimum/maximum growth ph

Answer 34

bc denatures proteins and affects hydrogen bonding

Question 35

hypotonic environment

Answer 35

low solute, high water content=water moves into cell

Question 36

hypertonic environment

Answer 36

high solute, low water content= water moves out of cell

Question 37

isotonic environment

Answer 37

concentration is the same=no net gain or loss of water

Question 38

which solution will have the greatest effect on a bacterial cell? why?

Answer 38

hypertonic bc plasmolisis occurs, pulling the cell wall

Question 39

plasmolysis

Answer 39

removes necessary water from a cell by pulling the plasma membrane away from the cell wall, and inhibiting the growth of the cell.

Question 40

obligate aerobes

Answer 40

grow only in the presence of oxygen (bacteria growth on top)

Question 41

facultative anaerobes

Answer 41

can grow with or without oxygen, but prefer oxygen (growth on top but coming down)

Question 42

obligate anaerobes

Answer 42

killed by oxgen (growth on bottom)

Question 43

aerotolerant anaerobes

Answer 43

do not use oxygen for growth but are not harmed by it (growth throughout tube)

Question 44

microaerophiles

Answer 44

require less than atmospheric concentrations of oxygen (growth in middle)

Question 45

bacteriostatic

Answer 45

antibiotic inhibits growth (fuzzy ring)

Question 46

bacteriocidal

Answer 46

kills bacteria (very defined zone of inhibition)