Trillions of bacteria live in your gut, helping digest food and fend off invaders — a whole ecosystem you carry around. Microbes multiply astonishingly fast, and the community living with us, the microbiome, keeps us healthy in ways we're only starting to grasp.
From one cell to billions
In good conditions, bacteria divide exponentially — one becomes two, two becomes four. A growth curve shows four phases: a slow lag phase, an explosive log phase, a stationary plateau as nutrients run low, and finally death. Some microbes need oxygen (aerobes); others are poisoned by it (anaerobes).
Trillions of microbes live in and on you — the microbiome. Most are harmless or helpful, aiding digestion and crowding out invaders. Health depends on this community, not just its absence.
- Sketch cell count over time for bacteria in fresh broth.
- Label the lag, log, stationary, and death phases.
- Explain what causes the log phase to level off into stationary.
- Predict how adding fresh nutrients mid-curve would change the shape.
What you should see: You read a bacterial growth curve and linked each phase to nutrient and waste conditions.