-
Lag Phase
- - No increase in cells
- - May grow in size
- - Period of unbalanced growth
- - Proteins necessary for the uptake of available nutrients may be synthesized
- - A period of adjustment; no cell division occurs.
-
Exponential Growth Phase
- - Cells are in balanced growth
- - Each cell in the population doubles within an essentially identical unit
- - Important factor in rapid food spoilage on the onset of an infectious disease
- - General time in time for doubling if the # of cells is constant.
-
Stationary
- - Cells continue to metabolize slowly.
- - Some cells die and lyse when energy is exhausted.
- - Period of survival and may mimic the condition in nature.
- - Reproduction of cell death are exactly the same.
-
Death Phase
- - When culture is maintained in stationary phase beyond a certain length of time.
- - When death phase exceeds the rate of reproduction.
-
Calculations of microbial growth
- No - Initial amount of bacteria.
- t - Amount of time it was growing.
- Nt - Amount of bacteria present at t.
- n - Amount of generations.
- generation time = time/generation
- n = (logNt - logNo)/log2
- Nt = No * 2n
-
Growth Measurement:Total Dry Weight
Kept alive? Limitations, Basic method.
-
Growth Measurement: Total Wet Weight
Kept alive? Limitations, Basic method.
-
Growth Measurement: Chem. Analysis of Component
Kept alive? Limitations, Basic method.
-
Growth Measurement: Direct Cell Count: Serial dilution
Kept alive? Limitations, Basic method.
-
Growth Measurement: Direct Cell Count: Concentration
Kept alive? Limitations, Basic method.
-
Growth Measurement: Viability Count
Kept alive? Limitations, Basic method.
-
Growth Measurement: Turbidity
Kept alive? Limitations, Basic method.
-
Turbidity: scattered light and density
- A= log(Io/I)
- High absorbance readings are no longer proportional to mass because no enough light is being transmitted enough to get an accurate measurement.
-
Synchronous Culture
- A culture of organism where every cell in the same stage of division.
- It is used to research bacterial cell division. It is difficult to study the cell division from one specific cell so can a synchronous culture will work. The events at the molecular level pertaining to protein synthesis, polymerization reactions, and subsequent cell assembly reactions. The sequence of events during a cell cycle can be quantitated with reasonable accuracy only when we examine a population in which all of the cells are at the same stage of division.
-
Efficiency
Higher ymax (g of cell/ mol glucose) and yatp (g of cell/ mol ATP) is more efficient.
-
Under what conditions is cell yield proportional to nutrient concentration.
If nutrient level is adequate.
-
What is a microorganism growing on a liquid nutrient in a closed system under favorable conditions for a set period of time called?
Batch culture -a nutrient liquid medium is prepared in an Erlenmeyer flask, sterilized, inoculated. The inoculated flask is then placed on a shaker (if aerobic) at appropriate growth temperature for a suitable growth period.
-
Continuous culture
- Dilution rate (D)
- Volume (v)
- Flow rate (f) - v/t
- D= f/v
-
Washout
When the substrate level does not exceed the requirements for maintenance energy.
-
Psychrophiles
- Bacteria that favors bellow 20 oC.
-
Mesophiles
Bacteria that favors between 20 oC - 44 oC
-
Thermophiles
Bacteria that favors 45 oC - 70 oC.
-
Hyperthermophiles
Bacteria that favors 70 oC to higher than 110 oC
-
Nonhalophile
Microbes found in freshwater that can not tolerate moderates amount of salt.
-
Halotolerant
Bacteria that can adapt to fresh wash and moderate amounts of salt (less than .75M NaCl )
-
Acidophiles
Bacteria that is lives at pH 5 or below.
-
Neutralphiles
Bacterial that lives at pH 5.1 - 8.9.
-
Alkaliphiles
Bacterial that lives at pH 9-11.
-
Obligate aerobe
Only grows in the presence if molecular oxygen. It has no mechanism for energy generation other than a respiratory pathway that is geared to O2 as terminal electron acceptor.
-
Facultative aerobe
Follows a respiratory pathway when oxygen is available, but it can employ alternate anaerobic energy-generating systems when oxygen is not available.
-
Microaerophiles
Organisms that occupy niches where the atmosphere has limited levels of oxygen.
-
Obligate anaeroble
Cannot grow in the presence of oxygen.
-
Barophile
Thrives at high pressure.
-
What is the osmolarity of 4 M NaCl.
- Osmolarity of .9% saline.
- MW of Na = 23 g/mol
- MW of Cl = 35.5 g/mol
- .9gNaCl x 1 mol NaCl x 100ml
- 100ml 58.5 g L = .16 M NaCl
- .16 M NaCl x 2 = .32 Osm
- .32(4) = 1.28 Osm
-
Heat Sterilization - Wet
- Conditions - Under pressure 15 Psi, 121.6 oC
- - In an auotoclave, pV = nRT so P keeps H2O from boiling off.
-
Heat Sterilization - Dry
- Conditions- 160 - 180C in oven for 2-4 hours.
- - Glassware, pippettes in cannisters wrapped in foil, protect from contamination. (Endospre contamination)
-
Pasteurization
- Conditions: 63 - 66 C 30 min, or 71.6 C 15s
- - For mil/beer, doesn't sterilize.
-
Ionizing Radiation
- Condition: High in Gamma rays.
- - Destructive to genetic material, free radicals (OH*) Resistance varies between species.
-
Ultraviolet Radiation
- Condition: Blast of ray between 220 and 320 nm.
- - Thymine dimers, but microbes have repair mech. Must: UV damage > repair.
-
Filter Sterilization
- Usually room temp and pressure conditions.
- - Glass fiber depth filters, membrane filters isospore membrane filter. The size of the spores can vary depending on the size of the bacteria.
-
Antimicrobials
Array of chemical agents that are used in the control of undesirable organisms. The agent will eliminate a pest without doing significant harm to other species.
-
Antibiotics
They are more selective in that they target a specific process of the bacteria. They can gain resistances to them.
-
Germ-
Involves all microbes.
-
-
-
Disinfectant
Can destroy microorganisms on contact but causes harm to host tissue.
-
Antiseptics
Kills or prevents growth without causing harm to host tissue.
-
Chemotherapeutic
A chemical compound that can be applied topically, taken orally, or injected that will inhibit or kill microbes that cause infection.
-
MIC
Minimum inhibitory concentration - The lowest concentration that will inhibit growth.
|
|