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Questions and Answers
What was the primary cause of the E.coli outbreak in Walkerton in May 2000?
What was the primary cause of the E.coli outbreak in Walkerton in May 2000?
Which strain of E.coli is associated with the Walkerton outbreak?
Which strain of E.coli is associated with the Walkerton outbreak?
Which virulence factor is associated with Vibrio cholerae?
Which virulence factor is associated with Vibrio cholerae?
In the context of transduction, what is a characteristic of specialized transduction?
In the context of transduction, what is a characteristic of specialized transduction?
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How many genes does E.coli K-12 possess that are not found in O157:H7?
How many genes does E.coli K-12 possess that are not found in O157:H7?
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What is the outcome of generalized transduction?
What is the outcome of generalized transduction?
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Which of the following is NOT a key recommendation for preventing future outbreaks based on the Walkerton incident?
Which of the following is NOT a key recommendation for preventing future outbreaks based on the Walkerton incident?
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Which bacterium produces botulinum toxin?
Which bacterium produces botulinum toxin?
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What determines whether a phage enters the lytic or lysogenic cycle?
What determines whether a phage enters the lytic or lysogenic cycle?
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What happens to the phage DNA once it enters the E. coli cell?
What happens to the phage DNA once it enters the E. coli cell?
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In which scenario is the lytic cycle typically favored?
In which scenario is the lytic cycle typically favored?
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How can lysogenic phages impact the characteristics of bacterial cells?
How can lysogenic phages impact the characteristics of bacterial cells?
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What is the function of the cI gene in the context of phage infection?
What is the function of the cI gene in the context of phage infection?
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Which strain of E. coli has clear genomic differences compared to the harmless K-12 strain?
Which strain of E. coli has clear genomic differences compared to the harmless K-12 strain?
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What is a significant clinical implication of lysogenic phages?
What is a significant clinical implication of lysogenic phages?
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Which gene acts as an 'anti-repressor' that prevents the establishment of lysogeny?
Which gene acts as an 'anti-repressor' that prevents the establishment of lysogeny?
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What type of vaccine uses live pathogens that have been weakened?
What type of vaccine uses live pathogens that have been weakened?
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Which of the following vaccines is based on purified surface antigens of a virus?
Which of the following vaccines is based on purified surface antigens of a virus?
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What is the primary function of mRNA vaccines?
What is the primary function of mRNA vaccines?
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Which concern regarding vaccines is addressed in relation to the MMR vaccine?
Which concern regarding vaccines is addressed in relation to the MMR vaccine?
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What type of vaccine uses a harmless virus to deliver genetic information?
What type of vaccine uses a harmless virus to deliver genetic information?
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Which type of vaccine is derived from inactivated or killed pathogens?
Which type of vaccine is derived from inactivated or killed pathogens?
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Which of the following statements is true regarding thimerosal in vaccines?
Which of the following statements is true regarding thimerosal in vaccines?
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Which vaccine type targets the toxic activity of a bacteria rather than the bacteria itself?
Which vaccine type targets the toxic activity of a bacteria rather than the bacteria itself?
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What is a major challenge in the development of vaccines for complex pathogens like HIV?
What is a major challenge in the development of vaccines for complex pathogens like HIV?
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What is antigenic drift in viruses, such as influenza?
What is antigenic drift in viruses, such as influenza?
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What was significant about the Ebola vaccine developed by Canada's National Microbiology Laboratory?
What was significant about the Ebola vaccine developed by Canada's National Microbiology Laboratory?
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What is a potential disadvantage of edible vaccines derived from transgenic plants?
What is a potential disadvantage of edible vaccines derived from transgenic plants?
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Which of the following statements is true about bacteriophages?
Which of the following statements is true about bacteriophages?
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What does the structure of a bacteriophage include?
What does the structure of a bacteriophage include?
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What is the implication of 'consistency from fruit-fruit, plant-plant' in edible vaccine development?
What is the implication of 'consistency from fruit-fruit, plant-plant' in edible vaccine development?
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What is a major drawback of using edible vaccines in practice?
What is a major drawback of using edible vaccines in practice?
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Which statement about emerging pathogens and pandemics is true?
Which statement about emerging pathogens and pandemics is true?
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How do bacteriophages become active?
How do bacteriophages become active?
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What is the primary function of the tail in bacteriophages?
What is the primary function of the tail in bacteriophages?
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What was the significant outcome of the Hershey-Chase experiments?
What was the significant outcome of the Hershey-Chase experiments?
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Which of the following is a current application of bacteriophages?
Which of the following is a current application of bacteriophages?
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What is a potential risk associated with the use of bacteriophages?
What is a potential risk associated with the use of bacteriophages?
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Which part of a bacteriophage contains the genetic material?
Which part of a bacteriophage contains the genetic material?
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How do bacteriophages affect the microbiome?
How do bacteriophages affect the microbiome?
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What is a common characteristic of all phages?
What is a common characteristic of all phages?
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In which size range do most bacteriophage chromosomes fall?
In which size range do most bacteriophage chromosomes fall?
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What type of phage structure has an icosahedral head and no tail?
What type of phage structure has an icosahedral head and no tail?
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Which of the following bacterial infections is particularly targeted by phage therapy?
Which of the following bacterial infections is particularly targeted by phage therapy?
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Study Notes
Bacteriophage Genetics
- Bacteriophages (phages) are viruses infecting bacteria, first described by Twort (1915) and d'Herelle (1917).
- They are obligate intracellular parasites, dormant as virions until contacting a host.
Bacteriophage Structure
- Typically consist of a protein coat (capsid) enclosing DNA or RNA.
- Head contains genetic material.
- Tail acts like a syringe injecting genetic material.
- Tail fibers aid attachment to bacterial receptors.
Phage Role in Scientific Discoveries
- Hershey-Chase experiment using T2 phage confirmed DNA as the genetic material (Hershey's 1969 Nobel Prize).
Current Bacteriophage Applications
- Phage therapy treats antibiotic-resistant bacterial infections (e.g., MRSA, Pseudomonas aeruginosa).
- Used in wound care and burns to reduce infections.
- Act as biocontrol agents in agriculture and aquaculture.
- Enhance food safety by reducing pathogen contamination (e.g., Listeria monocytogenes).
- Used in biosensors for rapid bacterial detection.
Dangers and Concerns of Phage Use
- Emergence of phage-resistant bacteria.
- Narrow host range can cause treatment failure.
- Bacterial mutations affecting phage-host interactions.
- Horizontal gene transfer (transduction) may increase bacterial pathogenicity.
- Impact on the microbiome.
- Ineffectiveness against bacteria in biofilms.
Bacteriophage Life Cycles
- Bacteriophages are significantly smaller than the bacteria they infect.
- Composed of an icosahedral head, hollow protein sheath, and sometimes tail fibers.
- The head contains a single chromosome (5,000–100,000 base pairs).
- Replication and gene expression require host cell enzymes and factors.
Lytic vs. Lysogenic Cycle
- Lytic cycle: phage replicates and lyses the host cell.
- Lysogenic cycle: phage DNA integrates into the host genome (prophage), replicating with the host.
- The choice between lytic and lysogenic cycles depends on a contest between cI (repressor of lytic cycle) and cro (anti-repressor) genes.
- Nutrient availability influences cycle choice: sufficient nutrients favor the lytic cycle, while limited nutrients favor the lysogenic cycle.
Significance of Lysogeny
- Lysogeny (phage conversion) alters bacterial properties by expressing phage genes.
- This has clinical significance, for example, modifying bacterial surface antigens.
E. coli K12 vs. O157:H7
- E. coli K12 (harmless lab strain): 4.64 x 106 bp, 4288 proteins.
- E. coli O157:H7 (pathogenic): 5.44 x 106 bp, 5416 genes (1387 genes not in K12).
Walkerton E. coli Outbreak (May 2000)
- Water contamination with E. coli O157:H7 caused seven deaths and 2500 illnesses.
- The contamination originated from farm runoff.
Virulence Factors Carried on Phages
- Phages can carry genes encoding virulence factors (toxins), contributing to bacterial pathogenicity (examples provided for various bacteria and resulting diseases).
Transduction
- Phages transfer bacterial DNA between cells.
- Generalized transduction: random DNA fragments transferred.
- Specialized transduction: specific genes transferred (e.g., phage λ).
Vaccines
- Vaccines improve immunity to particular diseases.
- Viral vaccines target viral surface antigens.
- Bacterial vaccines use bacterial lysates or whole cells.
- Vaccine types include live-attenuated, inactivated, subunit, toxoid, viral vector, and mRNA vaccines. Examples of each are provided.
Vaccine Development Problems
- Understanding complex pathogens (e.g., HIV, malaria).
- Rapid pathogen mutation (e.g., influenza).
- Antigenic drift (gradual gene changes) and shift (combination of different strains).
Canada’s Ebola Vaccine Discovery
- World's first approved Ebola vaccine (100% efficacy) developed in Canada's National Microbiology Laboratory (NML).
- Developed in 2004, used in outbreaks starting in 2014.
Edible Vaccines
- Transgenic plants triggering an immune response (e.g., potato, banana, tomato).
- Advantages: needle-free, no skilled professionals needed, no adjuvants, stimulates mucosal and systemic immunity, low cost.
- Disadvantages: need to eat raw, cooking destroys antigens, maturation time, spoilage, dosage evaluation, public perception of genetically modified food.
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Description
Explore the fascinating world of bacteriophages, the viruses that infect bacteria. This quiz covers their genetics, structure, and significant role in scientific discoveries, including phage therapy and their applications in modern medicine and agriculture. Test your knowledge on how phages are revolutionizing healthcare and food safety!
