Microbial regulation I

29 important questions on Microbial regulation I

For what environmental changes is regulation important?

Nutrient availability, O2, temperature, pH, osmolarity and UV radiation

How can transcription be regulated?

By influencing the binding of the RNA polymerase to the promoter

What are regulatory proteins?

DNA-binding proteins that interact with DNA without opening the double helix
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What is the function of regulatory proteins?

Control the rate of gene transcription

What two types of effectors are there?

Inducer and inhibitor

What two types of positive control are there in transcriptional regulation?

Induction and inhibition

How does inhibition stop transcription?

The transcription is stopped due to binding of the inhibitor to the activator. Due to this the polymerase can’t bind and transcription can’t occur

What two types of negative control are there in transcriptional regulation?

Repression and induction

What does induction of enzyme synthesis ensure?

That the enzymes are synthesized only when needed

What does the Lac operon encode?

Genes involved in the breakdown of lactose into galactose and glucose

By which enzyme is the breakdown of lactose done?

β-galactosidase

What happens when there is no lactose present in the cell?

The repressor is active and binds to the operator, there is no transcription

What happens when lactose is present in the cell?

Allolactose binds to the repressor and inactivates it, thereby activating transcription

What is catabolite repression?

A process that controls the use of carbon sources if more than one is available

How does catabolite repression prioritize carbon sources?

Based on the energy-yield and easiness of the breakdown.

Why is glucose always a better carbon source?

It does not need to be modified before entering the central carbon pathways

What is the activator protein in catabolite repression?

Cyclic AMP receptor protein (CRP)

What is the effector in catabolite repression?

Cyclic adenosine monophosphate (cAMP)

When does CRP bind to DNA?

Only when cAMP is bound

What happens to catabolite repression when glucose is present?

There is a low cAMP level, CRP is inactive and cannot bind to alternative sugar operons for RNA polymerase recruitment

What happens to catabolite repression when glucose is not present?

EnzIIa remains phosphorylated and activates adenylate cyclase,  cAMP is produced

What is the repressor in catabolite repression?

Lacl

Why does high glucose overule high lactose?

Because it is the favourable sugar to use

What is diauxic growth?

A distinct two-phase growth pattern observed when microbes are presented with two different carbon sources

What does diauxic growth illustrate?

How organisms efficiently prioritize and switch their metabolic machinery to maximize growth.

What is RNA-based regulation based on?

Trans-acting or cis-acting RNA

What different types of RNA-based regulation are there?

Attenuation, riboswitches and regulatory small RNAs

What happens if there is a high tryptophan availability?

A termination loop forms between the regions 3 and 4, this results in the RNA polymerase being ejected from mRNA

What happens if there is a low tryptophan availability?

An anti-termination loop occurs between the regions 2 and 3, since the RNA polymerase is faster than ribosome

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