Microbiology 3-6

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Author:
atomsk13
ID:
246743
Filename:
Microbiology 3-6
Updated:
2013-11-13 15:43:06
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Thurston
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Study guide 3-6
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  1. What is quorum sensing?
    • Communication between cells through the exchange of small molecules.
    • It can be used to regulate genes.
    • Can use signal transduction system.
  2. Describe the mechanism involved in the regulation of bioluminescence in Vibrio 
fischeri bacteria:
    • Uses AHL (N-acylhomoserine) as signal.
    • Made by AHL synthase, the product of luxI gene.
    • luxI is subjective to autoregulation-transcription of luxI increases as AHL accumulates.
    • Transcriptional factor luxR is only active when bound to AHL.
    • No activated luXR by AHL means luxI is at a basal level.
    • AHL diffuses easily out into the environment.
    • AHL eventually is higher outside than inside and flows back into the cell.
    • AHL binds to luxR and activates high transcription of luxI and other bioluminescent genes.
  3. Describe the mechanism involved in the regulation of bioluminescence in Vibrio 
harveyi bacteria:
    • Two component signal transduction system.
    • Responds to two autoinducer molecules: AI-1 and AI-2, their synthesis depends on the luxM gene.
    • AI-2 has a boron. It relies on the synthesis of the luxS gene.
    • AI-1 & 2 are secreted by the cell, which then uses separate proteins called luxN and luxPQ to detect their presence.
    • At low cell density in absence of AI-1 or 2 luxN and luxPQ autophosphorylate and converge on a phosphotransferase protein (luxU) who accepts their phosphates and then phosphorylates luxO.
    • luxO then activates transcription of RNA that destabilize luxR mRNA.
    • luxR is the transcriptional activator of the luxCDABE operon-which encodes proteins needed for bioluminescence.

    • WHEN AUTOINDUCER DENSITY INCREASES:
    • LuxN binds to AI-1 and LuxPQ binds to AI-2.
    • LuxO is inactivated, and LuxR mRNA is translated. Which activates transcription of lux CDABE and light is produced.
  4. Describe regulation of genes involved in sporulation of Bacillus subtilis:
    • WHEN GROWING:
    • RNA poly uses sigma factors A and H to recognize genes for normal survival.
    • WHEN STARVING:
    • KinA senses nutrient starvation and autophosphorylates a histidine residue that then transfers its phosphoryl group to apartic acid on Spo0F.
    • Spo0F then donates a P group to a His residue on Spo0B.
    • Spo0B relays to Spo0A.
    • Spo0A positively controls genes needed for sporulation (sif F-which makes sigmaF, and spoIIB which codes inactive form of sigmaE.)
    • This forms the spore septum.
    • SigmaF is found in forespore, and inactive sigmaE is localized to mother cell, then cleaved to form active sigmaE.
    • Two sigmas F and E then bind to promoters of genes needed in the cell.
    • These genes make sigmaG and sigmaK in inactive forms which are then activated.
  5. General mechanisms of control of gene expression in eukarya:
    • Regulatory transcription factors to regulate transcription initiation.
    • Antisense RNAs to regulate translation
  6. Identify the general mechanisms of control of gene expression of Archaea:
    • Most regulatory proteins function like bacterial activators and repressors.
    • Som function like eukaryotic regulatory transcription factors.

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