CPA #7 Questions

Question 1

What is catalase?

Answer 1

an enzyme that coverts hydrogen peroxide to water and molecular oxygen

Question 2

how do you test for catalase?

Answer 2

add a sample of bacteria to hydrogen peroxide; if it bubbles, catalase is present

Question 3

what organisms DO NOT have catalase?

Answer 3

obligate anaerobes

Question 4

why is nitrogen considered a growth-limiting nutrient?

Answer 4

they do not have enough nitrogen to build proteins and nucleotides; anabolisms stops

Question 5

why are nitrogen fixers critical?

Answer 5

they provide nitrogen in a form that is useable by other organisms; change unusable N2 into usable NH3

Question 6

define: nitrogen fixation

Answer 6

reduction of nitrogen gas to ammonia

Question 7

explain the effect of temperature on proteins

Answer 7

if temp. is too high, a protein will denature and lose their shape and function because the hydrogen bonds break

Question 8

explain the effect of temperature on lipids/phospholipids

Answer 8

if temp. is too low, the membranes of cells will become rigid/fragile; if temp. is too high, lipids can become too fluid and membrane cannot contain the cell/organelle

Question 9

why are organisms sensitive to pH?

Answer 9

sensitive to changes in acidity; hydrogen ions interfere with hydrogen bonding within proteins and nucleic acids

Question 10

how does the pH of the vagina and stomach reduce microbial infection?

Answer 10

the acidity of these areas inhibit microbial growth

Question 11

why is cholera a concern in flooded areas?

Answer 11

Vibrio cholerae (causative agent) grows best outside of the body in water with pH of 9.0

Question 12

why is water important to microbes? (3 reasons)

Answer 12

1. require moist enviro. to be metabolically active
2. water is needed to dissolve enzymes and nutrients
3. water is a reactant in many metabolic reactions

Question 13

why is osmotic pressure important?

Answer 13

restricts certain microbes to certain environments

Question 14

define: obligate halophiles

Answer 14

grow under high osmotic pressure; high salty enviroments; will burst if in freshwater enviro.

Question 15

define: facultative halophiles

Answer 15

do not require high salt enviro; able to tolerate the salty enviro; Staphylococcus aureus can tolerate up to 20% salt (allows it to colonize on human skin)

Question 16

what type of relationship do biofilms represent?

Answer 16

complex synergistic (both sides receive greater benefits than if they were by themselves)

Question 17

where would you find biofilms?

Answer 17

teeth, shower curtains, catheters, mucous membranes of digestive system

Question 18

what percentage of bacterial diseases do biofilms contribute to?

Answer 18

70%

Question 19

define: quorum sensing

Answer 19

when microbes respond to the density of nearby microbes; secrete quorum sensing molecules that communicate number and types of cells among the biofilm; how many other like bacteria are around to create a biofilm

minimum number needed to form a biofilm

Question 20

what is a consequence of quorum sensing?

Answer 20

microbes become more harmful when they are a part of a biofilm; groups of bacteria are more dangerous

Question 21

define: streak-plate method

Answer 21

an innoculating loop is used to streak a set pattern across a petri dish that gradually dilutes a sample to a point that CFUs are isolated from one another

Question 22

define: CFU

Answer 22

colony-forming unit

Question 23

list the 6 types of culture media

Answer 23

defined media, complex media, selective media, differential media, anaerobic media, & transport media

Question 24

define: defined media

Answer 24

aka synthetic medium; the exact chemical composition is known

Question 25

define: complex media

Answer 25

contains nutrients released by the partial chemical breakdown of yeast, beef, soy, or proteins

Question 26

define: selective media

Answer 26

typically contain substances that either favor the growth of particular microbes or inhibit the growth of unwanted ones

Question 27

define: differential media

Answer 27

formulated so that either the presence of visible changes in the medium or differences in the appearance of colonies help differentiate among bacteria

Question 28

define: anaerobic media

Answer 28

stab culture; innoculating wire to the anoxic part of a medium; reducing media uses special anaerobic culturing conditions

Question 29

define: transport media

Answer 29

carry clinical specimens of human bodily fluids/products in such a way to ensure that people are not infected and the sample is not contaminated

Question 30

why do scientists refrigerate bacteria cultures?

Answer 30

to slow down the metabolism to prevent the accumulation of waste and the exhaustion of all nutrients in a medium

Question 31

why do scientists sometimes freeze bacteria?

Answer 31

allows cultures to be restored years later

Question 32

benefit of direct count

Answer 32

know exactly how many are present

Question 33

con of direct count

Answer 33

time consuming

Question 34

pro of indirect count

Answer 34

quick

Question 35

con of indirect count

Answer 35

only an estimate; not exact

Question 36

what are the 4 direct count methods

Answer 36

microscope counts
serial dilution and viable plate count
membrane filtration
flow cytometry

Question 37

What are 4 indirect counts?

Answer 37

1. dry weight
2. turbidity & spectrophmeter
3. PCR
4. metabolic activity

Question 38

counting 1 by 1

Answer 38

microscopic counts (direct)

Question 39

pour liquid onto membrane to count

Answer 39

membrane filtration (direct)

Question 40

count cells that glow

Answer 40

flow cytometry (direct)

Question 41

weigh a pellet

Answer 41

Dry Weight (indirect)

Question 42

cloudiness & amount of light that flows through

Answer 42

turbidity & spectrophotometer (indirect)

Question 43

look for a specific band

Answer 43

PCR (indirect)

Question 44

change in color

Answer 44

metabolic activity (indirect)

Question 45

serial dilution & viable plate count (SD & VPC)

Answer 45

diluting sample until able to count individual (direct)