Final answer:
The four phases of bacterial growth on a growth chart are lag, log, stationary, and decline. The lag phase is for adaptation, the log phase is characterized by rapid cell division, the stationary phase reaches a balance between cell birth and death, and the decline phase marks a reduction in viable cells.
Step-by-step explanation:
The four phases of growth in a bacterial growth chart are: A) Lag, log, stationary, decline. Each phase represents a different metabolic state of the bacterial culture.
- Lag phase: This is the initial preparation phase after inoculation where bacteria adapt to the growth conditions. There is no increase in cell number, but cells are metabolically active, preparing for division.
- Log phase: Also known as the exponential phase, the number of bacteria increases rapidly, and this growth is best seen when plotted on a semilogarithmic scale which gives a linear appearance.
- Stationary phase: Growth rate slows due to depleted nutrients and accumulation of waste products. The number of living bacterial cells plateaus as the rate of cell division equals the rate of cell death.
- Decline phase: Also referred to as the death phase, where the number of viable bacteria decreases because the environment becomes less suitable for growth due to factors such as nutrient exhaustion and toxic waste accumulation.
Cells in the log phase are preferentially used for industrial and research applications due to their uniform metabolic activity and vulnerability to antibiotics. In contrast, the stationary phase is ideal for producing certain secondary metabolites like antibiotics.