Organisms and Populations

Choose the correct sequence of stages of growth curve for bacteria.

1. Lag, log, stationary, decline phase
2. Lag, log, decline, stationary phase
3. Stationary, lag, log, decline phase
4. Decline, lag, log phase, stationary

Answer

(1) Lag, log, stationary, decline phase

Solution

When bacteria are inoculated into a fresh medium, the growth curve shows four phases.

In the lag phase the cells adjust to the medium, with little or no increase in number; then in the log (exponential) phase they divide at the maximum rate.

Later nutrients decrease and wastes accumulate, so in the stationary phase the rate of division = rate of death, and finally in the decline (death) phase the death rate exceeds the division rate.

∴ Correct sequence: lag, log, stationary, decline phase.

Answer: (1)