Bacterial Evolution and Gene Transfer
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Questions and Answers

What is the primary consequence of advantageous mutations in bacterial populations?

  • They cause the organism to die off rapidly.
  • They allow the organism to outgrow competitors. (correct)
  • They have no effect on the organism's fitness.
  • They lead to decreased replication rates.

    • What is the significance of SNPs in bacteria?

  • They lead to immediate large-scale evolution.
  • They are the only method of genetic variation in bacteria.
  • They cause slow but progressive evolution. (correct)
  • They result in rapid death of bacterial clones.

    • Which mechanism does NOT describe horizontal gene transfer in bacteria?

  • Conjugation
  • Transduction
  • Replication (correct)
  • Transformation

    • What happens during conjugation in bacteria?

    <p>Bacteria exchange DNA through a conjugative pilus.</p> Signup and view all the answers

    Which bacterial species mechanism involves DNA uptake from the environment?

    <p>Transformation</p> Signup and view all the answers

    How do rapid replication rates affect bacterial evolution?

    <p>They allow advantageous mutations to spread quickly.</p> Signup and view all the answers

    Which of the following describes natural transformation in bacteria?

    <p>It occurs after bacterial lysis releases DNA.</p> Signup and view all the answers

    How do mutations impacts the efficacy of antibiotics in bacteria?

    <p>They can modify antibiotic target sites.</p> Signup and view all the answers

    What role does quorum sensing play in bacteria?

    <p>It regulates gene expression associated with biofilm formation and virulence.</p> Signup and view all the answers

    How does the EnvZ/OmpR system assist bacteria in different osmotic environments?

    <p>It regulates pore size in the bacterial membrane.</p> Signup and view all the answers

    What initiates the autophosphorylation of the kinase domain in a two-component transduction system?

    <p>A conformational change in the sensor protein.</p> Signup and view all the answers

    Which bacterial organism is associated with two quorum sensing systems for regulating enzyme production?

    <p>Pseudomonas aeruginosa</p> Signup and view all the answers

    What happens to the expression of OmpF under low salt concentrations according to the EnvZ/OmpR system?

    <p>OmpF is preferentially transcribed resulting in a larger pore.</p> Signup and view all the answers

    Which of the following is NOT an example of a two-component regulatory transduction system?

    <p>Operon system</p> Signup and view all the answers

    What is the primary function of the response regulator protein in a two-component system?

    <p>To act as a transcriptional regulator for specific genes.</p> Signup and view all the answers

    What technology is used to study the capacity of bacteria to modify gene expression in response to environmental conditions?

    <p>Transcriptomics</p> Signup and view all the answers

    What signal triggers the EnvZ protein to phosphorylate OmpR?

    <p>Increase in salt concentration</p> Signup and view all the answers

    What advantage does the larger pore created by OmpF provide to bacteria in low salt concentrations?

    <p>It enhances the uptake of nutrients.</p> Signup and view all the answers

    What is a key characteristic of enterotoxigenic E.coli?

    <p>It modifies water absorption in the colon.</p> Signup and view all the answers

    Which E.coli strain is known to integrate plasmids into its chromosome?

    <p>Enterohemorrhagic E.coli</p> Signup and view all the answers

    What is a pathogenicity island?

    <p>A large DNA sequence encoding multiple virulence genes.</p> Signup and view all the answers

    How can horizontal gene transfer be detected in bacteria?

    <p>Identification of scars following homologous recombination.</p> Signup and view all the answers

    What role does the CRISPR/Cas system play in bacteria?

    <p>It destroys incoming foreign DNA.</p> Signup and view all the answers

    What initiates the expression of the Lux operon in Aliivibrio fischeri?

    <p>Accumulation of autoinducer at high concentrations.</p> Signup and view all the answers

    What is an autoinducer in the context of quorum sensing?

    <p>A substance that accumulates and regulates gene expression.</p> Signup and view all the answers

    Which of the following bacteria uses a type 3 secretion system for attachment?

    <p>Salmonella</p> Signup and view all the answers

    What is the primary advantage for bacteria to regulate gene expression tightly?

    <p>To efficiently use limited resources.</p> Signup and view all the answers

    Which gene in the Lux operon is responsible for producing the autoinducer?

    <p>luxI</p> Signup and view all the answers

    How does quorum sensing affect bacterial behavior?

    <p>It leads to synchronized gene expression based on population density.</p> Signup and view all the answers

    What happens when the concentration of an autoinducer is low?

    <p>The bacterium will not glow.</p> Signup and view all the answers

    What is the initial step in quorum sensing for Aliivibrio fischeri?

    <p>Production of low amounts of autoinducer.</p> Signup and view all the answers

    What is the primary purpose of the mechanisms involved in horizontal gene transfer among bacteria?

    <p>To allow natural repair and exchange of DNA between closely related bacteria.</p> Signup and view all the answers

    Which signal triggers the expression of competency factors in bacteria?

    <p>Quorum sensing signals.</p> Signup and view all the answers

    What role do conjugative plasmids play in bacterial DNA transfer?

    <p>They facilitate the direct transfer of DNA between bacteria.</p> Signup and view all the answers

    What is the process through which a single strand of plasmid DNA is transferred from one bacterium to another?

    <p>Rolling circle transfer.</p> Signup and view all the answers

    What is High frequency transfer (Hfr transfer) in the context of plasmid transfer?

    <p>Plasmid integration resulting in stable chromosomal presence.</p> Signup and view all the answers

    What characterizes generalised transduction in bacteriophages?

    <p>Random packaging of bacterial DNA into phage heads.</p> Signup and view all the answers

    Which life cycle of bacteriophages results in the immediate production of new viral particles?

    <p>Lytic cycle.</p> Signup and view all the answers

    What typically characterizes specialized transduction?

    <p>Transfer of viral and adjacent bacterial DNA upon imprecise excision.</p> Signup and view all the answers

    What is a relaxasome in the context of conjugation?

    <p>A complex that facilitates the transfer of DNA.</p> Signup and view all the answers

    What is one consequence of plasmid excision from the bacterial chromosome?

    <p>Plasmids may acquire adjacent chromosomal material.</p> Signup and view all the answers

    Why is DNA polymerase important in the rolling circle transfer process?

    <p>It re-synthesizes the complementary strand of transferred DNA.</p> Signup and view all the answers

    What effect can horizontal gene transfer have on bacterial virulence?

    <p>It can enhance virulence traits between strains.</p> Signup and view all the answers

    Which structural feature is critical for the attachment and transfer during conjugation?

    <p>Pilus.</p> Signup and view all the answers

    What is the primary function of tra or transfer genes found in conjugative plasmids?

    <p>To encode proteins for DNA transfer mechanisms.</p> Signup and view all the answers

    Study Notes

    Bacterial Evolution and Adaptation

    • SNPs (single nucleotide polymorphisms) are frequent DNA replication errors. Most have no effect, but some are detrimental (killing the clone) or advantageous (allowing for greater competition).

    Mechanisms of Horizontal Gene Transfer

    • Bacteria exchange DNA via:
    • Vertical transfer: From parent to offspring (during cell division).
    • Horizontal gene transfer: Between two bacteria, via three methods:
    • Transformation: Uptake of free DNA from the environment. Naturally competent bacteria readily take up and incorporate foreign DNA. This is often triggered by quorum sensing.
    • Conjugation: Direct DNA transfer through a conjugative pilus. Conjugative plasmids carry genes for pilus formation and DNA transfer. The F pilus in E. coli is a well-described example. Rolling circle transfer facilitates the transfer. Plasmids can integrate into the bacterial chromosome. Hfr transfer occurs when integrated plasmids transfer flanking chromosome segments more readily.
    • Transduction: Transfer via bacteriophages (bacteria-infecting viruses).
    • Lytic cycle: Virus replicates and lyses the cell.
    • Lysogenic cycle: Virus DNA integrates into bacterial chromosome.
    • Generalized transduction: Defective phage packages bacterial DNA by mistake, transferring it to a new cell.
    • Specialized transduction: Phage DNA excision mistakes package chromosomal DNA adjacent to the integration site, transferring it to a new cell.

    Bacterial Virulence Traits

    • Horizontal gene transfer allows for acquisition of virulence traits.
    • Pathogenicity islands are large gene clusters acquired by horizontal transfer responsible for causing disease.
    • Examples include toxins in E. coli strains, Salmonella, and Shigella.

    Bacterial Quorum Sensing

    • Quorum sensing: Bacteria communicate at high cell density to regulate gene expression.
    • Autoinducer molecules (AI) regulate gene expression based on their concentrations. High concentrations lead to AI re-entry into bacteria and activation of specific genes.
    • Lux operon, involved in light production in Aliivibrio fischeri, is a classic example.
    • Quorum sensing also controls biofilm formation, virulence, and antibiotic production in various pathogen species (e.g., Staphylococcus aureus and Pseudomonas aeruginosa.)

    Two-Component Regulatory Systems

    • Two-component regulatory systems allow bacteria to respond to external signals (pH, osmolarity, ionic levels).
    • A membrane-bound sensor detects the signal, activating an internal kinase that phosphorylates a response regulator protein.
    • This activated response regulator protein regulates gene expression.
    • EnvZ/OmpR system regulates pore size in bacterial membranes in response to osmotic pressure.
    • CheAW/Y system regulates flagella movement based on chemical signals
    • phoPQ system in Salmonella senses the phagocytic environment.

    Transcriptomics for Understanding Adaptations

    • Transcriptomics (mRNA sequencing) reveals genes expressed under different environmental conditions, helping determine the molecular basis of adaptation.

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    Description

    This quiz explores the intricacies of bacterial evolution, focusing on single nucleotide polymorphisms and their effects. It also delves into the mechanisms of horizontal gene transfer, including transformation, conjugation, and vertical transfer. Test your understanding of how these processes impact bacterial adaptation and competition.

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