promoter: mglB inducer: casamino acids Optical Density is a measurement of cell
ID: 261907 • Letter: P
Question
promoter: mglB
inducer: casamino acids
Optical Density is a measurement of cell density.
Was there a lag phase, a log phase and a stationary phase growth in each culture?
Was there a difference in the length of each phase (especially the lag and log phases) amongst the 5 cultures?
What do you think is the cause? If there is a culture without any significant growth, what do you think is the cause?
ODv.sTime 0.6 0.55 Lactose 0.5 L-arabinose Casamino acids +glucose 0.45 Casamino acid 0.4 O 0.35 no carbon source 0.3 0.25 0.2 0.15 0.1 200 400 600 800 1000 1200 TimeExplanation / Answer
A) Yes there is lag phase, log phase clearly present in all the cultures but stationary phase is present only in the lactose and L-arabinose cultures.
B) Lag phase in each culture is almost of the same duration but the log phase duration varied. The culture containing lactose and L-arabinose had the same log phase duration which is the lowest in all the five cultures. The cultures other than these two have same duration of log cultures.
The difference in the length is due to the fact that casamino acids is the inducer which promotes the cell division and groeth of the cells in the culture. In case where carbon sources like lactose and L-arabinose are present the growth of the culture is very fast (Higher cell density) which leads to exhaustion of the nutrients and hence the stationary phase is achieved. Slow growth of the culture gives conditions that mimic the uncontrolled division without depletion of media for a long period of time pertaining to the longer duration of lag phase.
C) If a culture without any significant growth would have been present then it can be concluded that there was lack of carbon sources and the inducer (caamino acids). It could also be a result of absence of promoter (mglB). If the promoter is absent then the division and growth of culture is inhibited.
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