Question

The maximum growth phase is:
(a) Lag phase
(b) Steady phase
(c) Log phase
(d) Senescent phase

Answer 1

Hint: Bacteria grow by the process of binary fission. If we take a certain number of bacterial cells in a vessel with fresh nutritive materials. So, the bacteria will start dividing rapidly and will also finish up nutrients while doing so. After a certain point, the nutrient supply will get exhausted and growth will also slow down accordingly.

Complete answer:
When microorganisms are first introduced in a fresh medium, they do not start dividing immediately. This period is called the Lag phase. The microorganisms need this lag time to get acquainted with nutrients in the surrounding medium, synthesize essential cofactors and enzymes needed to utilize these nutrients. Once all of this is done, a period of rapid growth begins. In this period, the microorganisms divide at the maximum possible rate. The genetic potential of the bacteria, the nature of the medium are also the factors that influence the growth of bacteria. This phase is called the Log phase or exponential phase. The growth of bacteria is measured and put in the graph. This graph is called a growth curve –
So, the correct answer is ‘Log phase’.

Note: Eventually, population growth ceases and the growth curve becomes horizontal, this is called a stationary phase. This may result from a balance between cell division and cell death, or the population may simply cease to divide. This is because the supply of nutrients gets exhausted. Once all the nutrients get used up, the death phase begins and the cells begin to die.