Exam 2: Microbial Nutrition & Growth Part 1 Flashcards
What is meant by the term bacterial growth? How does this compare to the growth you personally displayed as a child?
Increase in the number of cells. Not in the size of the cell like humans.
In a sentence or two, briefly describe the process of binary fission.
Chromosomes are replicated, cell elongates separating chromosomes. Cell is pinched in half and divides.
Describe the concept of exponential growth. How would an exponential growth curve appear on a graph?
Every number of individuals doubles with each generation. The graph gets steeper and steeper going to the right.
How quickly can the bacterium Escherichia coli grow? Does it always grow at this rate? Explain.
Every 20 minutes. No, it varies depending on environmental conditions.
Are bacteria able to grow exponentially? Can they do so indefinitely? Explain.
Yes , no they are limited by environmental factors such as nutrient availability.
binary fission vs. mitosis
Both result in identical daughter cells however binary fission occurs in prokaryotes while mitosis only occurs in eukaryotes.
What are the four distinct phases in a bacterial growth curve? Describe each phase.
Lag phase- only phase when no cell division, reasonably short, cells getting ready to divide.
Log (exponential) phase- positive steep slope, cells are dividing very quickly, antibiotics are most effective. During this time food is abundant and very little waste products are present.
Stationary phase- horizontal line, number of living cells does not change, rate at which new cells are being produced is roughly equivalent to the rate at which cells are dying. More nutrients being consumed and water producers being produced.
Death phase- number of living cells decreases. Cell division is slow and death rate is greater than growth.
Is the y-axis of a bacterial growth curve a measure of viable cells or total cells? Explain.
Number of living (viable) cells. Total number of cells would include both the living and dead/dying cells.
Are both axes of a bacterial growth curve linear? Explain.
No, logarithmic scale on y-axis and linear on x-axis.
Compare the rate of cell division with the rate of cell death in each of the four phases of the bacterial growth curve.
lag phase- death rate is negligible and birth rate is zero since cells are not ready for division.
log phase- death rate greater than zero but not by much, birth rate significantly higher.
stationary phase- Birth and death equal
death phase - death rates exceed birth rates
During which phase of a bacterial growth curve are the cells displaying the fastest rate of division?
Log (exponential) phase
During which phase of a bacterial growth curve are cells most sensitive to antibiotics? Why do you think this might be the case?
log phase, because antibiotics mechanisms normally target dividing cells so they would have a greater effect when cells are dividing rapidly.
Why do bacterial populations transition from the log phase to the stationary phase? (What causes the rate of cell division to decrease?)
Nutrients start to decrease and waste products are starting to grow. Rate of division starts to decrease and death starts to increase making them equal.
Are any cells dying during the log phase of a bacterial growth curve? Explain.
Some but it’s negligible compared to the growth rate.
Explain, in terms of rates of cell division and cell death, why the slope of the log phase is steeper than the slope of the death phase.
Cell division slows but does not come to a complete stop. So while the death rate is greater than the growth rate there is still growth present.
Where in a bacterial colony would you expect to find log phase cells? How about a subpopulation in the death phase?
The edges of the colony where the newest cells are and where the most nutrients and space are present. Center would be at the death phase.
In nature, species live in mixed communities. Give at least two examples of how the presence of one species can alter the local environment in a manner that is beneficial to a second species.
1) Aerobes consume O2 and anaerobes benefit from the reduced oxygen.
2) One species produces a particular waste product that provides nutrients for another species.
Define the term microbial nutrition.
Process by which chemicals are obtained from the environment and used in cellular activities. These chemicals are called nutrients.
Do you have the same essential nutrients as Escherichia coli? Explain.
No, they can produce all 20 amino acids.
Nutrition serves as a source of what two key things?
Energy and necessary elements.
List the two categories of organisms based on energy source.
Phototrophs: “ light feeders” uses light as their energy source.
Chemotrophs: “chemical feeders” obtain energy from redox reactions. May involve either organic or inorganic chemicals.
List the two categories of organisms based on carbon source.
Autotrophs: “self feeders”, convert CO2 into organic compounds. No need to acquire organic carbon from other organisms.
Heterotrophs: “other feeders’ ‘, obtain organic carbon from other organisms. Catabolize these reduced organic molecules.
autotroph vs. heterotroph
Autotrophs and heterotrophs are both living organisms that require some form of food to get energy. But autotrophs make their own food via photosynthesis or some other similar method. Heterotrophs get their food by eating autotrophs or other heterotrophs
chemotrph vs. phtotroph
Phototrophs use sunlight to make their own food and then they produce things for others like fruit, oxygen, etc., Chemotrophs use chemical energy (like heat energy) to make food and they can live off of some of the bacterias that live in their bodies.
Macronutirent vs. micronutrient
Macronutrients are needed in large quantities and micronutrients are needed in small amounts. Macronutrients play principal roles in cell structure and metabolism. Micronutrients function as enzyme cofactors, examples included metal ions and vitamins.
Inorganic vs. Organic nutrients
organic contains both carbon and hydrogen while inorganic lacks either carbon, hydrogen, or both. Organic nutrients are not required by all organisms while inorganic nutrients are required by all organisms.
