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Questions and Answers
What role do plasmids play in providing bacteria with a selective advantage?
What role do plasmids play in providing bacteria with a selective advantage?
Plasmids confer selective advantages by enabling bacteria to become resistant to certain toxins or gain new metabolic capabilities.
What are the two types of plasmids based on their copy number within a bacterial cell?
What are the two types of plasmids based on their copy number within a bacterial cell?
The two types of plasmids are single copy plasmids and multi-copy plasmids.
Define Pathogenicity Islands (PAI) and their significance in bacterial pathogens.
Define Pathogenicity Islands (PAI) and their significance in bacterial pathogens.
PAIs are unique genetic elements encoding virulence factors that contribute to the pathogenicity of certain bacteria.
List three methods of horizontal gene transfer in bacteria.
List three methods of horizontal gene transfer in bacteria.
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What is transformation in the context of bacterial genetics?
What is transformation in the context of bacterial genetics?
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Provide an example of a natural transformable organism.
Provide an example of a natural transformable organism.
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How do plasmids like episomes differ from others?
How do plasmids like episomes differ from others?
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Discuss the process of Curing in relation to plasmids.
Discuss the process of Curing in relation to plasmids.
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Why are virulence factors important for pathogenicity?
Why are virulence factors important for pathogenicity?
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Explain the importance of horizontal gene transfer in bacterial evolution.
Explain the importance of horizontal gene transfer in bacterial evolution.
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Study Notes
Types of Symbiotic Relationships
- Commensalism: One organism benefits while the other remains neutral, with no harm or benefits involved.
- Parasitism: One organism (the parasite) benefits at the expense of the other (the host).
Pathogens and Disease
- Pathogen: Microorganism capable of causing disease.
- Virulence: Measure of pathogenicity, quantified by the organism count needed to induce disease.
Key Efficiency Measurements
- LD50 (Lethal Dose 50%): Organism amount needed to kill half of the exposed hosts.
- ID50 (Infectious Dose 50%): Organism quantity required to infect half of the exposed hosts.
Factors Influencing Virulence
- Number of infecting bacteria.
- Route of entry into the body.
- Host defense mechanisms (both specific and nonspecific).
- Virulence factors produced by bacteria.
Virulence Factors
- Essential for bacteria to invade hosts, cause disease, and survive defenses.
- Adherence Factors: Enable bacteria to attach to host cells, e.g., glycocalyx and pili.
- Capsules: Protect against opsonization and phagocytosis (e.g., Streptococcus pneumoniae).
- Secretion Systems: Type III and IV systems secrete proteins directly into host cells (e.g., Pseudomonas aeruginosa).
Invasion and Toxins
- Invasion Factors: Allow bacteria to invade and propagate within hosts (e.g., hyaluronidase and collagenase).
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Exotoxins: Proteins released by bacteria that can spread disease.
- Cytolytic Toxins: Disrupt cell membranes (e.g., haemolysins).
- A-B Toxins: Composed of active (A) and binding (B) portions (e.g., diphtheria and tetanus toxins).
- Super-antigens: Trigger large immune responses, resulting in fever and serious health issues (e.g., TSST).
Endotoxins
- Found only in Gram-negative bacteria as lipopolysaccharides.
- Released upon bacterial cell death, potentially causing severe reactions such as fever and septic shock.
Plasmids and Genetic Material
- Plasmids: Small DNA fragments that can carry resistance genes or metabolic pathways.
- Plasmid types include single-copy or multi-copy, known as episomes when attached to bacterial chromosomes.
- Curing: Process that removes plasmids from bacterial cells.
Pathogenicity Islands (PAIs)
- Unique genetic elements in bacterial chromosomes that encode virulence factors.
- Characteristics include acquisition through horizontal gene transfer and presence in pathogenic strains (e.g., Helicobacter pylori).
Horizontal Gene Transfer
- Mechanisms include:
- Transformation: Uptake of free DNA from the environment by competent bacteria.
- Conjugation: Transfer of genetic material between bacteria through direct contact.
- Transduction: Transfer of genetic material via bacteriophages.
- Natural transformable species include Streptococcus pneumoniae and Neisseria gonorrhoeae.
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Description
Test your knowledge on the different types of interactions among bacteria, including commensalism, parasitism, and the role of pathogens. Understand how these relationships affect organisms and ecosystems. Perfect for biology students exploring microbial life.
