Question

Choose the correct sequences of stages of growth curve for Bacteria.
(A) Lag, Log, Stationary, Decline phase
(B) Lag, Log, Stationary phase
(C) Stationary, Lag, Log, Decline phase
(D) Decline, Lag, Log phase

Answer 1

Mainly there are four phases involved in the growth cycle of bacteria. These are lag phase, log phase, stationary phase and decline phase. Each phase has its own significant role in the bacterial growth phases.

Complete answer:
Initially, in the lag phase bacteria instantly after injection of the bacterial cells into the fresh growth medium, the development of the proteins, enzymes and other molecules occurs. After this the bacteria acclimatise themselves according to growth conditions. In the lag phase, the individual bacteria mature and are unable to replicate. After the lag phase, log phase or exponential phase takes place. In this phase all the bacterial cells divide frequently through the process of binary fission and the growth takes place through geometric progression. All the cells divide at a constant rate based upon the content of the growth media and the incubation situations. The exponential growth pattern shows a constant and balanced growth in which all the cells use to divide in a constant pattern. As soon as the cell passes through the exponential phase it enters into the stationary phase. In this phase the growth of the bacterial population gets restricted by either of the three factors including reduction in the available nutrients or gathering of the residual products or enervation of space. At the last, death phase or decline phase occurs in which the population of the viable or living cells deteriorates.

Hence, the correct answer is option (A)

Note: Dissimilar to the initial stationary phase, where a little of cell division takes place, long-standing stationary phase is an extremely dynamic phase where 'birth' and 'death' rates are stable.