Question

Question 2 (1 point) Saved The generation time of bacterial cells is shortest during the phase • stationary Olag O log longitudinal

Answer 1

Ans.

The correct answer is 'Log Phase'

Explanation:

Microorganisms that are grown in a closed culture where no nutrients are added and removal of waste is not done,follows a reproducible growth pattern called as the growth curve.A growth curve consists of four phases:

1. The Lag Phase - This is the initial phase of the growth curve where there is no increase in the number of living bacterial cells and it represents small number of cells,also called as an inoculum,which is usually added to a fresh culture medium which serves as a nutritional broth that supports growth.In this phase the number of cells does not change but they grow larger and become metabolically active and synthesize proteins that are needed to grow within the medium.
2. The Log Phase -This is the logarithmic growth phase,also called as exponential growth phase,where the cells starts to actively divide by binary fission and the number of cells begins to increase exponentially.The generation time for any given bacterial species,under specific growth conditions such as nutrients,temperature,pH etc is determined genetically and it is called as the intrinsic growth rate.The cells show constant growth rate and the metabolic activity remains uniform in this phase.This phase has the shortest generation time,which rises exponentially and reaches the stationary phase.
3. The Stationary Phase -The log phase where the number of cells increases,due to several factors such as accumulation of waste products,depletion of nutrients etc will start contributing to the slowing of the growth rate.Over time the depletion of oxygen will result in limiting of aerobic cell growth.At this point the growth curve stalls and number of live cells reaches a plateau called as the stationary phase.At this phase the number new cells created by division becomes equivalent to number of cells dying,the net population of living cells is considered to be stagnant.The cells thus starts switching to survival mode of metabolism because the slow growth rate results in slower synthesis of proteins and nucleic acids.
4. The Death Phase -As the culture medium slowly accumulates toxic wastes and all the nutrients are exhausted,the cells die in greater numbers,which exceeds the number of cells dividing,resulting in an exponential decrease in the number of cells.This phase is called as the death phase or the decline phase.The cells starts to lyse and release nutrients into the medium,thus allowing the surviving cells to maintain viability and produce endospores.