The right answer is exponential.
The bacterium multiplies by binary fission: the bacteria grow and then divide into two daughter cells separated by a septum of division formed by the cell wall. During division, the DNA is duplicated as well as the other constituents. Various enzymatic systems of synthesis and degradation participate in cell division.
Bacterial growth is the orderly growth of all components of the bacteria. It results in an increase in the number of bacteria.
During the growth, there is, on one hand, depletion of nutrients in the culture medium and, secondly, an enrichment of by-products of metabolism, potentially toxic. Growth can be studied in a liquid or solid medium.
1 - Growth curve: The growth of a bacterium is studied in a liquid medium. There are 6 phases which together constitute the growth curve.
. Latency phase: the zero growth rate (μ = 0). The duration of this phase depends on the age of the bacteria and the composition of the medium. This is the time required for the bacteria to synthesize the enzymes adapted to the new substrate (no lag phase if transplanting on the same medium as the previous one).
. Acceleration phase: There is an increase in the growth rate.
. Exponential growth: the growth rate reaches a maximum (μ = max). This phase lasts as long as the growth rate is constant. The doubling time of bacteria is the shortest. The cell mass is represented by viable cells (zero mortality).
. Slowing phase: the speed of growth decreases. There is a depletion of the culture medium and an accumulation of waste. There is a beginning of autolysis of bacteria.
. Stationary maximum phase: the growth rate becomes naked (μ = 0). Bacteria that multiply compensate for those that die.
. Decline phase: the growth rate is negative (μ <0). All the nutritional resources are exhausted. There is accumulation of toxic metabolites. There is a decrease in viable organisms and cell lysis under the action of endogenous proteolytic enzymes. However, growth persists by release of substances released during lysis (cryptic growth).
