Final answer:
In B. subtilis, the regulation of gene transcription is controlled by repressive mechanisms such as the trp operon and attenuation, which respond to the cellular levels of tryptophan to either inhibit or promote gene expression.
Step-by-step explanation:
Regulation of Transcription in B. subtilis by TPP
The regulation of gene expression in prokaryotic cells, such as Bacillus subtilis, occurs primarily at the transcriptional level through mechanisms involving an operon structure. One key element in this regulation is the tryptophan (trp) operon which utilizes repressive control to modulate transcription depending on the cellular need for tryptophan. When tryptophan levels are high, the trp repressor protein binds to the operator sequence, blocking the RNA polymerase and thus preventing transcription of genes responsible for tryptophan synthesis. Conversely, if tryptophan is scarce, the repressor does not bind, allowing RNA polymerase to transcribe the operon's genes and synthesize tryptophan. Additionally, the attenuation mechanism, which involves the formation of stem-loop structures within the mRNA transcript's 5' end, helps fine-tune this regulation process by either terminating transcription or allowing it to continue based on tryptophan availability.