Bac metabolism Lec 4. 2

Question 1

The citric acid (TCA) cycle plays a major role in respiration of ?

Answer 1

organic compounds

Question 2

Citric acid cycle the generation of?

*supplies intermediates for?

Answer 2

ATP, NADH, FADH

*AA, lipid, purine and pyrimidine synthesis

Question 3

Citric acid cycle is amphibolic meaning?

Answer 3

both catabolic and anabolic

Question 4

Bacterial growth is? (4 things)

Answer 4

1. Increase in mass
2. Increase in number
3. in bacteria growth occurs by binary fission
4. bacterial growth is rapid

Question 5

Microbial populations show a characteristic type of growth pattern called?

Answer 5

exponential (logarithmic) growth

Question 6

how is exponential (logarithmic) growth best understood?

Answer 6

by plotting the number of cells over time on a semilogarithmic graph
*to show microbial population growth

Question 7

Bacterial Growth is divided into 4 phases. What are they IN ORDER?

Answer 7

Lag
Log
Stationary
Death

Question 8

Lag phase

Answer 8

preparation for binary fission

*takes awhile to get enough water/nutrients to divide

Question 9

Log phase

Answer 9

(exponential) phase increase in mass, then number dependent upon generation time and growth rate
* MOST growth here

Question 10

Stationary phase

Answer 10

net growth= 0, still alive

Question 11

death phase

Answer 11

cells die and can canabolize themselves

Question 12

what phase does penicillin work best?

Answer 12

Log phase

Question 13

what are the 3 reliable methods for determining bacterial concentration in a sample?

Answer 13

1) direct microscopic count
2) plate count method
3) spectrophotometric method

Question 14

spectrophotometric method and direct microscopic count have what common problem?

Answer 14

don’t know if the cells you are counting are alive or dead

Question 15

What is Petroff Hauser counter?

Answer 15

direct count microscopically using counting chamber of defined volume

Question 16

explain direct microscopic count?

Equation?

Answer 16

1) microscopic observation of all cells in a large square; typically several
2) numbers are averaged to calculate number per milliliter of sample
* * 12 cells(example) * 25 squares * 50 * 10^3 =1.5x10^7

Question 17

explain the 2 plate count method

Answer 17

Option 1) spread-plate= pipetted- spread over agar surface- incubated- results
option 2) pour plate method= pipetted- sterile medium added- solidification/incubation- results

Question 18

plate count method # of olonies on agar is directly proportional to?

Answer 18

# of viable bacteria in liquid culture
***sometimes dilutions have to be made to obtain accurate count

Question 19

explain spectrophotometric method

Answer 19

1. use a wavelength of light through a spectrophotometer with vile of bacteria
2. the amount of light absorbed tells amount of bacteria present
   (more bacteria will absorb more light)

Question 20

what is the most accorate method to count populations? why?

Answer 20

plate count method

*ONLY can count live cells, dead cells won’t create a colony

Question 21

Klett Unit =

Answer 21

OD x 500

• Klett units are a unified measure to represent the optical density of the culture
• *(At high concentrations of cells relationship between optical density and cell number breaks down)

Question 22

commonly used wavelengths for spectrophotometric method?

Answer 22

480, 540, 600, 660 nm

Question 23

turbidity is a measure of? What leads to different levels of turbidity?

Answer 23

spectrophotometrically

* Bacterial growth in test tubes leads to different levels of turbidity

Question 24

What area the 3 main affects of antimicrobial agents on growth?

Answer 24

1) bacteriostatic
2) bacteriocidal
3) bacteriolytic

Question 25

bacteriostatic

Answer 25

viable organisms and total cell count platue before increasing again (once agent removed)

Question 26

bacteriocidal

Answer 26

organisms cannot grow/die; total cell count paltues

Question 27

bacteriolytic

Answer 27

viable organisms and total cell count decline/die

Question 28

a LOT of antibiotics have _____ affects on microbial growth

Answer 28

bacteriostatic

*Allows the immune system to catch up! stops cell growth for a while but does NOT kill them

Question 29

Usually chemical agents that control microbial growth are measured at what concentration? Ex?

Answer 29

minimal inhibitory concentration

*sometimes done by the spectrophotometric method

Question 30

what is “zone of growth inhibition”?

Answer 30

it is a method to test a microbe and see what antimicrobial agent provide the best inhibitory affect

Question 31

explain the process of “zone of growth inhibition”?

Answer 31

1) inoculate a plate with a liquid culture of a test organism
2) disc containing antimicrobial agents are placed on surface
3) test organism shows susceptibility to some agents; indicated by inhibition of bacterial growth around discs

Question 32

the best inhibition is show by smaller or larger rings around antimicrobial soaked discs?

Answer 32

larger; larger the ring or zone then the better the inhibition worked