Term
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Definition
The Z-Ring forms a scaffold for the recruitment of other cell division proteins |
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Term
| How do we measure bacterial growth? |
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Definition
You can measure the changes in the number of cellsin a population or can measure changes in mass of population
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Term
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Definition
The time required for a population to double in number.
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Term
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Definition
The assemblage of these proteins at the site of Z-Ring has been called the divisome |
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Term
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Definition
Growth rate describes how fast a bacterium grows in a particular environment |
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Term
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Definition
No increase in cell numbers, but cells may increase in mass. Unbalanced growth - cell components and proteins for nutrient uptake are synthesized |
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Term
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Definition
Cells are in balanced growth - all aspects of metabolism and growth are operating in unison. Every cell has identical generation time. Important factor in food spoilage and onset of infectious diseases. |
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Term
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Definition
Exponential growth cannot be maintained. Resources become limiting or inhibitory factors build up. Some populations sense density and stop growing. Cells continue metabolism, but most biosynthesis stops. |
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Term
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Definition
After time in stationary phase, cells begin to die. Death rate varies with species and environmental conditions |
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Term
| What is the principle behind viable count method? |
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Definition
A viability count determines the number of living cells in a sample |
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Term
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Definition
- Cell elongates and DNA is replicated
- Cell wall and plasma membrane begin to divide
- Cross-wall forms completely around divided DNA
- Cells separate
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Term
| Serial Dilutions (Plate Counts) |
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Definition
- Perform serial dilutions of a sample with sterile saline
- Inoculate Petri plates from serial dilutions
- After incubation, count colonies on plates that have 25-250 colonies (CFUs)
- Multiply number of CFUs by dilution factor
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Term
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Definition
| It is a rapid method to determine cell mass |
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Term
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Definition
A machine where a beam of light is passed through a suspension of cells; light is scattered in proportion to the number of cells present |
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Term
| How can one estimate the number of bacteria in a population? Do the various techniques provide the same information? |
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Definition
- Direct cell counts iwth a microscope counting chamber
- To determine total number of cells
- Viable cell counts with plate counts
- To determine the number of living cells
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Term
| The mathematics of growth |
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Definition
n = (logN - logN0)/0.301 N = final cell number N0 = initial cell number n = number of generations g = t/n t = hours/minutes of growth g = generation (doubling) time |
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Term
| Rate of Growth (Equation) |
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Definition
k = 2.303 (logN - logN0)/t k = mean growth rate constant |
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Term
Bacterial population increases from 103 to 109 cells in 10 hours. |
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Definition
N0 = 103 N = 109 t = 6 Hours n =(log109 - log103)/0.301 = 6/0.301 = 19.9 = 20 Generations g = t/n = 10/20 = 1/2
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Term
| Bacterial population increases from 103 to 108 in 6 hours. What is k? |
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Definition
N0 = 103 N = 108 t = 6 Hours k = 2.303*(log108 - log 103)/6 k = 2.303*(8-3)/6 k = 1.92 |
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Term
| How can one measure the rate f growth of a bacterial culture? |
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Definition
By measuring over time any growth relevant parameter - Cell mass
- Viable cell number
- Total cell number
- Dry weight
- Any chemical cell constituent (DNA, RNA, Protein)
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Term
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Definition
A small population of bacteria added to a growth medium
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Term
Why might a culture have a long lag phase after inoculation? |
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Definition
It might have a long lag phase because it needs to change to accomidate to the new medium (i.e. synthesize cell materials) |
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Term
| Possible reasons for entry into stationary phase |
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Definition
- Nutrient limitation
- Limited oxygen availability
- toxic waste accumulation
- critical population density reached
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Term
| List two physiological changes that are observed in stationary phase cells. How do these changes impact the organism's ability to survive? |
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Definition
- Morphological changes (e.g. endospore formation)
- Decrease in size
- Nucleoid condensation
- Production of starvation proteins
- Protect DNA
- Prevent protein denaturation
- Prevent oxidative damage
- Long-term suvival
- Increased Virulence
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Term
| Why can't one always tell when a culture enters the death phase by the use of total cell count? |
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Definition
This is because you cannot tell the difference between live and dead cells |
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Term
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Definition
Nutrients are added in excess of amount needed to attain maximum growth rate. Results in a balanced state of growth for a few generations
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Term
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Definition
Minimum needed to stay alive and perform basic functions
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Term
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Definition
Used to keep bacterial cultures in exponential phase
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Term
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Definition
Nutrients are continuously added and waste products removed |
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Term
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Definition
Nutrients are consumed and end products accumulate
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