Microbiology: Bacterial Transduction
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Questions and Answers

What is the process called when transformed DNA is incorporated at a random site on the chromosome?

  • Horizontal gene transfer
  • Electroporation
  • Homologous recombination
  • Nonhomologous recombination (correct)

    • What is the purpose of the competence-stimulating peptide in Streptococcus pneumoniae?

  • To provide antibiotic resistance
  • To regulate gene expression
  • To stimulate competence for DNA uptake (correct)
  • To inhibit DNA uptake

    • What is the method used to make cells permeable to small DNA molecules in artificial transformation?

  • Heat shock
  • Electroporation
  • Calcium chloride and high temperature shock (correct)
  • DNA uptake signal sequences

    • What is the process in which an organism receives genes from another organism without being a direct offspring?

    <p>Horizontal gene transfer</p> Signup and view all the answers

    What is the main consequence of horizontal gene transfer in bacteria?

    <p>Increased antibiotic resistance</p> Signup and view all the answers

    What is the reason for the widespread antibiotic resistance in bacteria?

    <p>Horizontal gene transfer</p> Signup and view all the answers

    What is the term for the process by which bacteria take up DNA from the same species?

    <p>Natural competence</p> Signup and view all the answers

    What is the function of DNA uptake signal sequences in bacteria?

    <p>To facilitate DNA uptake</p> Signup and view all the answers

    What is the term for the laboratory method used to get plasmids into cells?

    <p>Artificial transformation</p> Signup and view all the answers

    What is the consequence of the spread of methicillin-resistant Staphylococcus aureus (MRSA) strains?

    <p>Serious skin infections</p> Signup and view all the answers

    What is the process by which a bacterium takes up extracellular DNA released by a dead bacterium?

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

    Who discovered the process of transformation in bacteria?

    <p>Frederick Griffith</p> Signup and view all the answers

    What is the term for bacterial cells that can take up DNA?

    <p>Competent cells</p> Signup and view all the answers

    What is the function of competence factors in transformation?

    <p>To facilitate DNA uptake and incorporation</p> Signup and view all the answers

    What occurs during homologous recombination in transformation?

    <p>The introduced DNA is incorporated into the host chromosome</p> Signup and view all the answers

    What is the result of the transformation process in a bacterial cell?

    <p>The cell becomes lys +</p> Signup and view all the answers

    What type of transformation occurs naturally in certain bacteria?

    <p>Natural transformation</p> Signup and view all the answers

    What is the function of extracellular endonuclease in transformation?

    <p>To degrade one strand of DNA</p> Signup and view all the answers

    What is the result of a mismatch between the introduced DNA and the host chromosome?

    <p>A heteroduplex is formed</p> Signup and view all the answers

    What repairs the mismatch between the introduced DNA and the host chromosome?

    <p>DNA repair enzymes</p> Signup and view all the answers

    What is the primary mechanism by which bacterial DNA is transferred from one bacterium to another?

    <p>Via a bacteriophage's ability to transfer DNA</p> Signup and view all the answers

    What is the primary component of a bacteriophage?

    <p>Genetic material</p> Signup and view all the answers

    Which of the following bacteriophages is known to infect Escherichia coli?

    <p>P1</p> Signup and view all the answers

    What is the result of a bacteriophage infecting a recipient cell with a his + gene?

    <p>The recipient cell becomes a recombinant bacterium that is his +</p> Signup and view all the answers

    What is the purpose of the protein coat in a bacteriophage?

    <p>To protect the genetic material</p> Signup and view all the answers

    What is the name of the process by which bacterial DNA is transferred from one bacterium to another via a bacteriophage?

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

    What is the role of the donor cell in transduction?

    <p>To package the his + gene into a phage particle</p> Signup and view all the answers

    Which of the following is a characteristic of a lysogenic cycle?

    <p>The bacteriophage incorporates its genetic material into the host genome</p> Signup and view all the answers

    What is the term for the bacteriophage's ability to infect bacterial cells?

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

    Which of the following best describes the process of transduction?

    <p>A bacteriophage transfers genetic material from one bacterium to another</p> Signup and view all the answers

    What is the process by which a bacterium takes up extracellular DNA released by a dead bacterium?

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

    What type of transformation occurs naturally in certain bacteria?

    <p>Natural transformation</p> Signup and view all the answers

    What are bacterial cells called that can take up DNA?

    <p>Competent cells</p> Signup and view all the answers

    What is the role of extracellular endonuclease in transformation?

    <p>To cleave DNA into smaller fragments</p> Signup and view all the answers

    What is the result of a mismatch between the introduced DNA and the host chromosome?

    <p>Heteroduplex formation</p> Signup and view all the answers

    What repairs the mismatch between the introduced DNA and the host chromosome?

    <p>DNA repair enzymes</p> Signup and view all the answers

    What is the final step of the transformation process in a bacterial cell?

    <p>Expression of the new trait</p> Signup and view all the answers

    What is the purpose of competence factors in transformation?

    <p>To facilitate the binding, uptake and incorporation of DNA</p> Signup and view all the answers

    What is the function of the protein coat in a bacteriophage?

    <p>To surround the genetic material</p> Signup and view all the answers

    What type of bacteriophage is known to infect Escherichia coli?

    <p>P1</p> Signup and view all the answers

    What is the result of a bacteriophage infecting a recipient cell with a his + gene?

    <p>The recipient cell becomes a recombinant bacterium that is his +</p> Signup and view all the answers

    What is the role of the donor cell in transduction?

    <p>To package the his + gene into a phage particle</p> Signup and view all the answers

    What is the primary mechanism by which bacterial DNA is transferred from one bacterium to another?

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

    What is the name of the process by which bacterial DNA is transferred from one bacterium to another via a bacteriophage?

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

    What is the result of homologous recombination in a bacterial cell?

    <p>The DNA is incorporated into the chromosome at a specific site.</p> Signup and view all the answers

    Why do some bacteria preferentially take up DNA from the same species?

    <p>To ensure the survival of the species.</p> Signup and view all the answers

    What is the role of calcium chloride in artificial transformation?

    <p>It makes the cells permeable to small DNA molecules.</p> Signup and view all the answers

    What is the consequence of horizontal gene transfer in terms of antibiotic resistance?

    <p>It leads to the acquisition of antibiotic resistance genes.</p> Signup and view all the answers

    What is the term for the process by which bacteria take up DNA from the environment?

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

    What is the function of DNA uptake signal sequences in bacteria?

    <p>They facilitate the uptake of DNA from the same species.</p> Signup and view all the answers

    What is the result of the spread of methicillin-resistant Staphylococcus aureus (MRSA) strains?

    <p>It leads to serious skin infections.</p> Signup and view all the answers

    What is the characteristic of acquired antibiotic resistance in bacteria?

    <p>It is acquired through horizontal gene transfer.</p> Signup and view all the answers

    What is the role of electroporation in artificial transformation?

    <p>It makes the cells permeable to small DNA molecules.</p> Signup and view all the answers

    What is the consequence of nonhomologous recombination in a bacterial cell?

    <p>The DNA is incorporated at a random site on the chromosome.</p> Signup and view all the answers

    What is the primary mechanism by which bacterial DNA is transferred from one bacterium to another?

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

    What is the term for the process by which bacteria take up DNA from the environment?

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

    What is the purpose of competence factors in transformation?

    <p>To stimulate the uptake of DNA</p> Signup and view all the answers

    What is the result of a mismatch between the introduced DNA and the host chromosome?

    <p>The introduced DNA is repaired</p> Signup and view all the answers

    What is the ECTS credit value for the course?

    <p>6</p> Signup and view all the answers

    What is the function of extracellular endonuclease in transformation?

    <p>To degrade introduced DNA</p> Signup and view all the answers

    What is the focus of the course?

    <p>Regulation of transcription and translation in eukaryotic and prokaryotics</p> Signup and view all the answers

    What is the workload distribution for the course?

    <p>2 LCT + 0 TUT + 2 LAB + 0 OTH</p> Signup and view all the answers

    What is the total number of hours for the course?

    <p>150</p> Signup and view all the answers

    What is the prerequisite for the course?

    <p>Introduction to molecular genetics</p> Signup and view all the answers

    What is the primary purpose of conjugation in mapping the order of genes along the E. coli chromosome?

    <p>To map the order of genes in a bacterial chromosome</p> Signup and view all the answers

    What is the role of competence-stimulating peptide in Streptococcus pneumoniae?

    <p>To regulate the expression of competence genes</p> Signup and view all the answers

    What is the function of DNA uptake signal sequences in bacterial transformation?

    <p>To recognize and bind to specific DNA sequences</p> Signup and view all the answers

    What is the primary mechanism by which bacterial DNA is transferred from one bacterium to another?

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

    What is the result of a mismatch between the introduced DNA and the host chromosome during transformation?

    <p>Homologous recombination occurs</p> Signup and view all the answers

    What was constructed by Wollman and Jacob from the data?

    <p>A genetic map</p> Signup and view all the answers

    What was identified in the Hfr strains?

    <p>The origin of transfer</p> Signup and view all the answers

    What was compared among the Hfr strains?

    <p>The order of genes</p> Signup and view all the answers

    What was demonstrated by comparing the order of genes among the Hfr strains?

    <p>The E</p> Signup and view all the answers

    What is the significance of the Hfr strains?

    <p>They have integrated the origin of transfer at different places</p> Signup and view all the answers

    What is the purpose of constructing a genetic map?

    <p>To analyze the order of genes</p> Signup and view all the answers

    What is the primary assumption behind the interrupted conjugation technique?

    <p>The time it takes for genes to enter the recipient cell is directly related to their order along the bacterial chromosome.</p> Signup and view all the answers

    What is the purpose of using streptomycin in the interrupted conjugation experiment?

    <p>To kill the donor Hfr cells following conjugation.</p> Signup and view all the answers

    What is the reason for Wollman and Jacob's goal to determine the order of gene transfer?

    <p>To map the bacterial chromosome.</p> Signup and view all the answers

    What is the significance of the thr + and leu + genes in the interrupted conjugation experiment?

    <p>They are the first genes to be transferred during conjugation, in that order.</p> Signup and view all the answers

    What is the relationship between the time of conjugation and the length of the chromosome transferred?

    <p>The longer the conjugation time, the longer the length of the chromosome transferred.</p> Signup and view all the answers

    Study Notes

    Transduction

    • Transduction is the transfer of DNA from one bacterium to another via a bacteriophage, a virus that specifically infects bacterial cells.
    • Bacteriophages that can transfer bacterial DNA include P22, which infects Salmonella typhimurium, and P1, which infects Escherichia coli.
    • The process of transduction involves a donor cell with a his+ gene on a chromosome fragment being packaged into a phage particle, which then infects a recipient cell, making it recombinant and his+.

    Transformation

    • Transformation is the process by which a bacterium takes up extracellular DNA released by a dead bacterium.
    • It was discovered by Frederick Griffith in 1928 while working with strains of Streptococcus pneumoniae.
    • There are two types of transformation: natural and artificial.
    • Natural transformation occurs naturally in a wide variety of bacteria, while artificial transformation occurs with the help of experimental techniques.
    • Competent cells are able to take up DNA and have genes that encode proteins called competence factors, which facilitate the binding, uptake, and incorporation of DNA into the bacterial chromosome.

    Steps of Transformation

    • Extracellular DNA is broken down into smaller fragments, and one strand is degraded and transported into the competent bacterial cell.
    • Homologous recombination can occur, leading to the repair of any mismatched regions.
    • Transformed cells can now take up the new DNA.

    Recombination

    • If the transformed DNA is homologous to a region in the bacterial chromosome, it can be incorporated by homologous recombination.
    • If the DNA is not homologous, it may be incorporated at a random site on the chromosome through nonhomologous recombination.

    Taking up DNA from the same species

    • Some bacteria preferentially take up DNA released from dead bacteria of the same or a related species.
    • Streptococcus pneumoniae secretes a competence-stimulating peptide, leading to competence only when many cells of the same species are nearby.
    • Other species use DNA uptake signal sequences that are repeated throughout the genome and are preferentially taken up.

    Artificial Transformation

    • Laboratory methods are commonly used to get plasmids into cells, such as treating with calcium chloride and a high temperature shock or electroporation.
    • These methods make the cells permeable to small DNA molecules.

    Medical Relevance of Bacterial Genetic Transfer

    • Horizontal gene transfer is the process in which an organism receives genes from another organism without being a direct offspring.
    • Conjugation, transformation, and transduction are examples of horizontal gene transfer, which can occur within and between species.
    • Horizontal gene transfer has contributed to the phenomenon of acquired antibiotic resistance, where bacteria acquire genes that break down antibiotics, pump them out of the cell, or block their inhibiting effects.

    Transduction

    • Transduction is the transfer of DNA from one bacterium to another via a bacteriophage, a virus that specifically infects bacterial cells.
    • Bacteriophages that can transfer bacterial DNA include P22, which infects Salmonella typhimurium, and P1, which infects Escherichia coli.
    • The process of transduction involves a donor cell with a his+ gene on a chromosome fragment being packaged into a phage particle, which then infects a recipient cell, making it recombinant and his+.

    Transformation

    • Transformation is the process by which a bacterium takes up extracellular DNA released by a dead bacterium.
    • It was discovered by Frederick Griffith in 1928 while working with strains of Streptococcus pneumoniae.
    • There are two types of transformation: natural and artificial.
    • Natural transformation occurs naturally in a wide variety of bacteria, while artificial transformation occurs with the help of experimental techniques.
    • Competent cells are able to take up DNA and have genes that encode proteins called competence factors, which facilitate the binding, uptake, and incorporation of DNA into the bacterial chromosome.

    Steps of Transformation

    • Extracellular DNA is broken down into smaller fragments, and one strand is degraded and transported into the competent bacterial cell.
    • Homologous recombination can occur, leading to the repair of any mismatched regions.
    • Transformed cells can now take up the new DNA.

    Recombination

    • If the transformed DNA is homologous to a region in the bacterial chromosome, it can be incorporated by homologous recombination.
    • If the DNA is not homologous, it may be incorporated at a random site on the chromosome through nonhomologous recombination.

    Taking up DNA from the same species

    • Some bacteria preferentially take up DNA released from dead bacteria of the same or a related species.
    • Streptococcus pneumoniae secretes a competence-stimulating peptide, leading to competence only when many cells of the same species are nearby.
    • Other species use DNA uptake signal sequences that are repeated throughout the genome and are preferentially taken up.

    Artificial Transformation

    • Laboratory methods are commonly used to get plasmids into cells, such as treating with calcium chloride and a high temperature shock or electroporation.
    • These methods make the cells permeable to small DNA molecules.

    Medical Relevance of Bacterial Genetic Transfer

    • Horizontal gene transfer is the process in which an organism receives genes from another organism without being a direct offspring.
    • Conjugation, transformation, and transduction are examples of horizontal gene transfer, which can occur within and between species.
    • Horizontal gene transfer has contributed to the phenomenon of acquired antibiotic resistance, where bacteria acquire genes that break down antibiotics, pump them out of the cell, or block their inhibiting effects.

    Interrupted Conjugation Technique

    • Developed by Elie Wollman and François Jacob in the 1950s
    • Purpose: to map the order of genes along the E. coli chromosome
    • Method: interrupting conjugations at different times to determine the order of genes
    • The time it takes genes to enter the recipient cell is directly related to their order along the chromosome

    Strains Used in Interrupted Mating

    • Donor (Hfr) strain:
      • thr + : able to synthesize threonine
      • leu + : able to synthesize leucine
      • azi s : sensitive to azide
      • ton s : sensitive to T1 bacteriophage
      • lac + : able to metabolize lactose
      • gal + : able to metabolize galactose
      • str s : sensitive to streptomycin
    • Recipient (F-) strain:
      • thr - : unable to synthesize threonine
      • leu - : unable to synthesize leucine
      • azi r : resistant to azide
      • ton r : resistant to T1 bacteriophage
      • lac - : unable to metabolize lactose
      • gal - : unable to metabolize galactose
      • str r : resistant to streptomycin

    Goal of the Experiment

    • Determine the times at which genes azi s, ton s, lac +, and gal were transferred
    • Use streptomycin to kill the donor cell following conjugation

    Results and Conclusion

    • A genetic map was constructed based on the data
    • The order of genes along the E. coli chromosome was determined
    • Various Hfr strains with different origins of transfer were identified and compared to demonstrate the order of genes

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    Description

    Learn about bacterial transduction, a process where DNA is transferred from one bacterium to another via a bacteriophage. Understand the life cycles of bacteriophages, including lytic and lysogenic cycles.

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