growth curve pt 3

describe Lag Phase

$\text{Growth rate} = 0$. Bacteria adapt and prepare for division by

• synthesizing enzymes,

• starting DNA synthesis,

• and metabolizing energy sources to produce ATP.

Cause of zero growth rate during the Lag Phase

Bacteria are preparing for cellular division rather than actively increasing population size.

Acceleration Phase

The phase during which the bacterial growth rate begins to increase.

Exponential/Log Phase

The phase during which bacteria grow and divide at their maximum growth rate.

Deceleration Phase

The phase during which the bacterial growth rate begins to slow down.

Causes of the Deceleration Phase

Depletion of food sources and the accumulation of toxic waste products.

Stationary Phase

$\text{Growth rate} = 0$ because the rate of new cell production equals the rate of cell death.

Population dynamics during the Stationary Phase

New cells are produced at the same rate that organisms die, maintaining a relatively constant population size.

Metabolic substances during the Stationary Phase

Dead bacterial cells rupture, releasing metabolic substances into the environment.

Dying/Death Phase

The phase during which cell death exceeds division and the majority of bacteria die.

Causes of the Dying/Death Phase

Severe nutrient exhaustion and heavy accumulation of toxic waste products.

Bacterial survival at the end of the Death Phase

No, not all bacteria are dead. Most die, but a small subset of cells may remain alive.

Sequential order of the six bacterial growth phases

1. lag

2. acceleration

3. exponential log

4. decceleration

5. stationary

6. death

Progression of growth rate across the six phases

$$0 \rightarrow \text{increasing} \rightarrow \text{maximum} \rightarrow \text{slowing} \rightarrow 0 \rightarrow \text{mass death}$$

Summary of events across phases A through F

• Phase A: preparation;

• Phase B: growth rate increases;

• Phase C: maximum growth;

• Phase D: food depletion/waste buildup;

• Phase E: cell division equals cell death;

• Phase F: majority of population dies.