The bacterial growth cycle
Start with the big picture
In batch culture, bacteria typically pass through lag, log (exponential), stationary, and death phases. Lag is a period of metabolic adaptation without division; in log phase, cells divide at a constant rate. As nutrients become depleted and waste accumulates, net growth stops in stationary phase, where stress responses and other adaptations may occur. In the death phase, viability declines, although some cells may remain viable but non-culturable. Growth can be assessed using optical density, viable plate counts, dry weight, or metabolic assays. The lesson also introduces continuous culture, which can maintain cells in a steady log phase, and considers how species and environmental conditions affect the curve.
What you'll learn
- Describe the defining features of the four phases of the bacterial growth cycle.
- Explain how inoculum size, nutrient shifts, and temperature can affect lag phase.
- Identify methods used to monitor bacterial growth.
- Contrast batch culture with continuous culture.
- Relate growth phase to selected microbial adaptations and clinical relevance.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
