Bacterial Growth Curve

Question 1

Steps in Binary Fission

Answer 1

1. Cell elongates and dna is replicated
2. Cell wall and plasma being to come apart
3. Cross wall forms completely separating the two dna copies
4. Cells seperate

Question 2

Generation Time

Answer 2

• the time required for a cell to divide and its population to double is the generation time
  
  • so what ever number u have that double…think about binary fission is always splitting to two. So if you have 4 cells you get 8. 16 cells split and doubles to 32
    ex. 5 is the generation time. So 2^5 equals 32 cells. Always go by the power of 2
• varies w environmental conditions such as temperature
• its hard to graph population changes of this magnitude so logarithmic scales are used

Question 3

Logarithmic Representation of Bacterial Populations

Answer 3

-the arthimic to show the generation of the bacteria would be too much to show graphically

Question 4

Phases of Growth

Answer 4

• when a few bacteria are inoculated into a liquid growth medium and the population is counted at intervals it is possible to plot a growth curve
• the four basic phases of growth are the lag, log, stationary, and death phases

Question 5

The Lag Phase

Answer 5

• the culture is newly inoculated. Cells are adjusting to environment. Some die and some reproduce. No net binary fission than dying
• the number of cells change very little because the cells do not immediately reproduce in a new medium and this is called the lag phase
• Time varies
• the cells are not dormant, the population is going through an intense metabolic activity involving the synthesis of enzymes and various molescules
• the calm before the storm

Question 6

The Log Phase

Answer 6

• best time to make new culture. These cells made it through the lag phase. Culture conditions are ideal, nutrients abundant, waste minimal, and organisms are spread out. Everything above makes the population growth exponential. Best time for gram stain, capsule.
• eventually the cells begin to divide and enter a period of growth or logarithmic increase hence the log phase
• cellular reproduction is most active during this period and generation time reaches a constant minimum
• because the gen time is constant, a logarithmic plot of growth during the log phase is a straight line
• the cells are most active metabolically

Question 7

The Stationary Phase

Answer 7

• Conditions are becoming challenging. Ph buffering may not be working or fluxuates. Mad cells large and crowded
• cells form endospores here
• Growth rate slows, the number of microbial deaths balances the number of new cells, and the population stabilizes
• the exhaustion of nutrients, accumulation of waste products, and harmful change in PH causes exponential growth to stop

Question 8

The Death Phase

Answer 8

• nutrients become scarce, dead cells and the break down of their molecules add to the waste, buffering capacity is loss and results in extreme ph changes. extreme stress
• the number of deaths eventually exceeds the number of new cells formed
• this phase continues until the population is diminished to a tiny fraction of the number of the cells in the previous phase or cells die completely
• cells survive depending on what species