Bacterial growth curves typically can be divided into four distinct phases: lag phase, log phase, stationary phase, and death phase. Drag the following descriptions to the appropriate location on the bacterial growth curve.

(Look at picture)

Explanation:

Bacterial growth is the division of a bacterium into two daughter cells in a process called binary fission. Assuming no mutation occurs, the resulting daughter cells will be genetically identical to the original cell. In this way "local duplication" of the bacterial population takes place. The two daughter cells created after the division do not necessarily survive. However, if the number of survivors exceeds one, on average, the bacterial population experiences an exponential growth.

Bacterial growth in a batch culture that can be modelled assuming four different phases: A) Adaptation phase (lag), B) Exponential phase (log), C) Stationary phase and D) Decline phase.

A. During the adaptation or lag phase, bacteria adapt to growing conditions. This is the period when individual bacteria are maturing and do not yet have the ability to divide. During the adaptation phase of the bacteria's growth cycle, the synthesis of RNA, enzymes and other molecules takes place. So in this phase the microorganisms are not dormant.

B. The logarithmic or exponential release phase is a period characterized by cell duplication. The number of new bacteria that appear per unit of time is proportional to the current population. If growth is not limited, duplication will continue at a constant rate, therefore the number of cells in the population doubles with each consecutive time period. For this type of exponential growth, the graphical representation of the logarithm of the number of cells versus time generates a straight line. Exponential growth cannot continue indefinitely, because the medium soon becomes depleted of nutrients as waste accumulates.

C. During the stationary phase, the growth rate decreases as a result of nutrient depletion and the accumulation of toxic products. This phase is reached when the bacteria begin to deplete the resources available to them. This phase is characterized by a constant value of the number of bacteria as the growth rate of the bacteria equals the bacterial death rate.

D. In the decline phase, bacteria run out of nutrients and die.

This model of basic batch culture growth is maintained and emphasizes aspects of bacterial growth that may differ from those of macrofauna growth. Emphasis is placed on clonality, asexual binary division, the short development time in relation to replication itself, the apparently low mortality rate, the need to move from a dormant state to a reproductive state and finally the tendency for adapted laboratory strains to deplete their nutrients. In reality, even in batch cultures, the four phases are not well defined. Cells do not reproduce in synchrony without explicit and continuous instigation and their exponential growth phase often does not always follow a constant rhythm, but instead has a slow decay rate, a constant stochastic response to simultaneous pressures to reproduce and to remain dormant in the face of decreasing nutrient concentrations and increasing residue concentrations.