Bac metabolism Lec 4. 2 Flashcards
The citric acid (TCA) cycle plays a major role in respiration of ?
organic compounds
Citric acid cycle the generation of?
*supplies intermediates for?
ATP, NADH, FADH
*AA, lipid, purine and pyrimidine synthesis
Citric acid cycle is amphibolic meaning?
both catabolic and anabolic
Bacterial growth is? (4 things)
- Increase in mass
- Increase in number
- in bacteria growth occurs by binary fission
- bacterial growth is rapid
Microbial populations show a characteristic type of growth pattern called?
exponential (logarithmic) growth
how is exponential (logarithmic) growth best understood?
by plotting the number of cells over time on a semilogarithmic graph
*to show microbial population growth
Bacterial Growth is divided into 4 phases. What are they IN ORDER?
Lag
Log
Stationary
Death
Lag phase
preparation for binary fission
*takes awhile to get enough water/nutrients to divide
Log phase
(exponential) phase increase in mass, then number dependent upon generation time and growth rate
* MOST growth here
Stationary phase
net growth= 0, still alive
death phase
cells die and can canabolize themselves
what phase does penicillin work best?
Log phase
what are the 3 reliable methods for determining bacterial concentration in a sample?
1) direct microscopic count
2) plate count method
3) spectrophotometric method
spectrophotometric method and direct microscopic count have what common problem?
don’t know if the cells you are counting are alive or dead
What is Petroff Hauser counter?
direct count microscopically using counting chamber of defined volume
explain direct microscopic count?
Equation?
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
explain the 2 plate count method
Option 1) spread-plate= pipetted- spread over agar surface- incubated- results
option 2) pour plate method= pipetted- sterile medium added- solidification/incubation- results
plate count method # of olonies on agar is directly proportional to?
# of viable bacteria in liquid culture ***sometimes dilutions have to be made to obtain accurate count
explain spectrophotometric method
- use a wavelength of light through a spectrophotometer with vile of bacteria
- the amount of light absorbed tells amount of bacteria present
(more bacteria will absorb more light)
what is the most accorate method to count populations? why?
plate count method
*ONLY can count live cells, dead cells won’t create a colony
Klett Unit =
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)
commonly used wavelengths for spectrophotometric method?
480, 540, 600, 660 nm
turbidity is a measure of? What leads to different levels of turbidity?
spectrophotometrically
* Bacterial growth in test tubes leads to different levels of turbidity
What area the 3 main affects of antimicrobial agents on growth?
1) bacteriostatic
2) bacteriocidal
3) bacteriolytic
bacteriostatic
viable organisms and total cell count platue before increasing again (once agent removed)
bacteriocidal
organisms cannot grow/die; total cell count paltues
bacteriolytic
viable organisms and total cell count decline/die
a LOT of antibiotics have _____ affects on microbial growth
bacteriostatic
*Allows the immune system to catch up! stops cell growth for a while but does NOT kill them
Usually chemical agents that control microbial growth are measured at what concentration? Ex?
minimal inhibitory concentration
*sometimes done by the spectrophotometric method
what is “zone of growth inhibition”?
it is a method to test a microbe and see what antimicrobial agent provide the best inhibitory affect
explain the process of “zone of growth inhibition”?
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
the best inhibition is show by smaller or larger rings around antimicrobial soaked discs?
larger; larger the ring or zone then the better the inhibition worked
