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BMS662: MICROBIAL PATHOGEN > C5 > Flashcards

C5 Flashcards

1
Q

What system use by bacteria to control the production of virulence factor

A

Two complement regulatory system

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2
Q

2 complement system allow to regulate metabolism in response to environmental factors such as

A
  • Temperature changes
  • Changes in pH & oxygen availability
  • Changes in nutrient availability
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3
Q

2 complement system involved mechanism of

A
  • Cell receive signal from environment
  • Transmit it to specific target to be regulated
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4
Q

Define signal transduction

A

External signal not transmit directly to regulatory protein but detect by sensor that transmit it to regulatory machinery

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5
Q

Parts of signal transduction

A
  • Sensor kinase: cell membrane
  • Response regulator protein: cytoplasm
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6
Q

Explain sensor kinase

A
  • Detect signal from environment & phosphorylate themselves (auto phosphorylation) at specific histidine residue
  • Sensory kinase also called histidine kinase
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7
Q

Explain regulatory system

A
  • Phosphoryl group transfer to response regulator
  • DNA binding protein that regulates transcription which function as activator or repressor
  • Must have a feedback loop to complete the control mechanism
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8
Q

Explain feedback loop in 2 complement system

A
  • Involves phosphatase that remove phosphoryl group from response regulator protein
  • In many systems, this reaction carried out by response regulator
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9
Q

Define global regulators

A

Regulatory mechanisms that respond to environmental signal by regulating the expression of many different genes

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10
Q

Explain global regulators

A
  • Called global control system
  • Include set of operon & regulon in chromosome but all coordinately controlled
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11
Q

Example of global regulators response

A
  • Catabolite repression
  • Stringent repression
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12
Q

What is catabolite repression

A
  • Occur when cell grown in medium containing more than one substrate
  • Substrate which is a better carbon & energy source would repress the use of other substrate
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13
Q

Why catabolite repression also called the glucose effects

A
  • Glusoce was the first substance shown to initiate response
  • Protein of lac operon, include beta galactosidase required for using lactose & induce its presence
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14
Q

Explain the mechanism of glucose in catabolite repression

A
  • When glucose present, lac operon is not expressed
  • When glucose absent, lac operon expressed & cell growth on lactose
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15
Q

Two exponential growth phases in catabolite repression are called

A

Diauxic, diauxie or diphasic growth

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16
Q

Catabolite repression transcription controlled by

A
  • cyclic AMP receptor protein (CRP)
  • CAP (catabolite activator protein)
17
Q

Explain mechanism of CAP

A
  • Gene encode for catabolite repressible enzyme expressed only if CAP bind to DNA in promoter region
  • Allow RNA polymerase to bind to promoter
  • CAP only bind if there’s cAMP
18
Q

Relationship between cAMP & glucose

A
  • Glucose inhibit synthesis of cAMP & stimulate transportation of cAMP out the cell
  • Glucose present: level cAMP low, CAP & RNA polymerase cannot bind, catabolite repression
19
Q

Direct cause of catabolite repression is

A

Decrease in cAMP level

20
Q

Why catabolite repression considered a mechanism of global control

A
  • When glucose is the preferred energy source, catabolite repression prevent other expression
  • Many other open effected such as lactose, maltose
21
Q

Explain flagella synthesis controlled by catabolite repression

A
  • Controlled gene for synthesis of flagella
  • If bacteria have good carbon source, there is no need to swim around
22
Q

Define stringent response

A

Mechanism where gene are regulated to depleted nutrient level in the environment

23
Q

Explain stringent response

A
  • Found in bacteria & chloroplast when nutrient excess or when cell starved
  • When a culture transfer from rich to poor medium with a single carbon source
  • synthesis of rRNA & tRNA stopped
24
Q

Explain the course of stringent response event

A
  • When biosynthesis new amino acid activated, new protein must be made to synthesised amino acid no longer in the environment
  • rRNA synthesis began but remain downgraded
25
Q

Types of nucleotide that triggers stringent response

A
  • ppGpp
  • pppGpp
  • ReIA
  • SpoT
26
Q

Explain mechanism of stringent response

A
  • When AA limited, pool of uncharged tRNA increase
  • Uncharged tRNA insert to ribosome during protein synthesis
  • Ribosome shut down & lead to synthesis of ReIA using ATP
  • Adding 2 phosphate group from ATP to GTP/GDP to produce pppGpp or ppGpp
  • Protein Gpp convert pppGpp to ppGpp
27
Q

How pppGpp & ppGpp inhibit rRNA & tRNA synthesis

A
  • Binding to RNA polymerase
  • Prevent initiation of transcription
28
Q

Explain mechanism by addition of ReIA & SpoT in stringent response

A
  • Addition of ReIA & SpoT help trigger stringent response
  • SpoT protein make or degrade pppGpp or ppGpp
  • SpoT also synthesis pppGpp/pppGpp in response to stress or shortage of energy
  • Result when absent of precursor of protein synthesis & lack of energy
29
Q

Define quorum sensing

A

Process of cell-cell that allow bacteria to share information about cell density & adjust gene expression

30
Q

Function of quorum sensing

A
  • Virulence
  • Conjugation
  • Biofilm formation
  • Sporulation
31
Q

What molecule that induce activity of quorum sensing

A
  • Autoinducers
  • Diffuse freely across cell envelope
  • When many cell make the autoinducer, it accumulates & reach high conc inside cell
  • Once they reach threshold level, it bind to regulatory protein & activate transcription
32
Q

Example of autoinducer

A
  • Acyl homoserine lactones (AHL)
  • AI-2: Gram -
  • Short peptide: Gram +
33
Q

Explain heat shock protein

A
  • Bacteria response to high temperature
  • Mostly stable but if higher temperature, some are less stable & unfold
  • Recognised by protease enzyme
34
Q

What influence heat shock protein

A
  • When cell are heat stressed induce the synthesis of heat protein to assist in damage & recovery
  • Most induce by heat, chemical (ethanol) & high dose of ultraviolet radiation
35
Q

Major class of heat shock protein

A
  • Hsp70
  • Hsp 60
  • Hsp 10
36
Q

Function of heat shock protein

A
  • Assisting the folding newly synthesised proteins
  • Prevent aggregation of protein
  • Recovering protein that partially or completely unfolded
37
Q

In E.coli heat shock response controlled by

A
  • RpoH: control gene regulation
  • RpoE: regulate quality control & envelope integrity
38
Q

Explain the relationship between RpoH & DnaK in normal temperature

A
  • RpoH degrade by proteases
  • Stimulated by binding of DnaK protein to RpoH
  • Rate of RpoH degradation depend on level of free DnaK which bind to inactivate RpoH
  • In unstressed cell, level of free DnaK high & level of intact RpoH low
39
Q

Explain the relationship between RpoH & DnaK in high temperature

A
  • Some protein denature & DnaK recognise & bind to the unfolded protein
  • DnaK remove from RpoH which slow the degradation rate of RpoH
  • More denature protein, low level of free DnaK & high level of RpoH
  • When temp normal, RpoH inactivated by DnaK

BMS662: MICROBIAL PATHOGEN (7 decks)

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