Reading the Map: A standard bacterial growth curve (Figure 6.3) Stationary phase
ID: 276718 • Letter: R
Question
Reading the Map: A standard bacterial growth curve (Figure 6.3) Stationary phase Log phase Decline, or death, phase E Lag phase Time This is the growth of a population of bacteria when introduced into a fresh, nutrient-rich medium. The population will undergo four major phases of growth. 1) What is occurring in the population during lag phase? What factors determine how long the lag phase lasts? 2) You have two cultures of E. coli, one in relatively fresh, nutrient-rich media and one in spent, nutrient-poor media. If you inoculate a small sample of each into two identical tubes of fresh nutrient-rich media, which one would you anticipate to have the longer lag phase? Why? (3) What is occurring during the log phase of growth? What factors determine how long the log phase lasts? 4) What is occurring during stationary phase of growth? Why does a population enter stationary phase? (5) We previously have discussed chemicals such as penicillin that disrupt cell wall synthesis. Penicillin is most effective against replicating cells. In which phase of growth would you expect penicillin to be most effective?Explanation / Answer
1. Cells are adjusting to new environment, Cells are preparing to divide, creating new structure/elongatingCells are recovering/repairing damage from transfer. Lag phase is extra long-dramatic change in culture media, dramatic change in culture temp, older cells have longer lags.
2. Spent poor nutrient media have longer lag phase.
3. Second portion of growth curve with MAXIMUM increase in cell number
4. nutrients and space become limited, waste begins to accumulate, makes environment less favorable for cell division, equal number of cell deaths and cell division cells are alive
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