Field of Science

More puzzles/questions about purine regulation of competence

Why does adding purine nucleotides to MIV repress competence more strongly than adding the corresponding nucleosides? And why does adding purine bases have little effect?
  • Did Amy do experiments to address this? Look in her notebooks.

Does adding these nucleotides, nucleosides and bases affect transcription of the purine biosynthetic genes in the same way that it affects transcription of Sxy-dependent competence genes?
  • Answer by measuring transcriptional effects on one or more PurR-repressed gene as well as on a Sxy-regulated gene.

Does adding purine nucleotides to MIV repress only transcription of CRP-S competence genes (and the purine biosynthetic genes), or is it a more general effect on transcription?
  • Answer by measuring transcriptional effects on CRP-regulated genes that are Sxy-independent.

How big a contribution does endogenous synthesis of purines make to the purine pools , relative to the level maintained in log phase by salvage from sBHI?
  • Answer by comparing transcription of a PurR-regulated gene in sBHI (log and late-log) and MIV, in wildtype cells and a purH mutant (no endogenous purine synthesis). First I think we'd need to make the purH mutant, but I should check our strain records in case we already did this.

Why did we conclude that adding purine nucleotides etc. to sBHI makes cells grow poorly?
  • First repeat this to get solid data.

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