This question has different parts. Please type your answer which covers all part

Question

This question has different parts. Please type your answer which covers all parts:

A) Explain how certain bacteria "sense" the density of cells

B) Why would it be beneficial for cells to wait until a critical population density is present before expressing certain genes E. coli cells use a two-component system to sense nitrate in the environment.

C) What would happen if they lost the ability to sense that compound

D) Why would the biosynthetic enzymes of a cell be repressible rather than constitutive or inducible

E) How is a corepressor different from an inducer? How is it similar? How do activators facilitate transcription?

Explanation / Answer

A). Bacteria sense the density by using quorum sensing. The regulation of gene expression in accordance with the cell population size fluctuations is known as quorum sensing. Autoinducers are the signaling molecules released by the quorum sensing bacteria, the concentration of these molecules increases as a function of the density of the cell.

B). The critical population is needed to allow the molecules released by the cells in the group to bind the other cells in the group in an effective manner.

C). The bacteria fail to communicate with the other organisms and cannot regulate the gene expression in response to change in cell density

D). The biosynthetic pathways are always repressible because they synthesize the molecules necessary for the survival. Means, the operon (for example, the trp operon) remain expressed as long as the cell needs tryptophan, and once the product starts accumulating, the operon expression is repressed, so the continuous expression can be avoided.

In contrast, in case of inducible systems, the operon is expressed when the molecule needed to be broken down. So, these enzymes are produced only when the substrate is available. For example, lac operon.

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