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Questions and Answers
What is the typical rate of logarithmic growth for bacteria?
What is the typical rate of logarithmic growth for bacteria?
Which of the following is NOT a mechanism of horizontal gene transfer in bacteria?
Which of the following is NOT a mechanism of horizontal gene transfer in bacteria?
What happens during natural transformation in bacteria?
What happens during natural transformation in bacteria?
In conjugation, what is exchanged between bacteria?
In conjugation, what is exchanged between bacteria?
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How do bacteriophages facilitate gene transfer among bacteria?
How do bacteriophages facilitate gene transfer among bacteria?
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What is a potential outcome of a mutation in bacterial DNA?
What is a potential outcome of a mutation in bacterial DNA?
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What ensures the rapid spread of acquired genetic traits within a bacterial population?
What ensures the rapid spread of acquired genetic traits within a bacterial population?
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Which type of DNA uptake occurs only in naturally competent bacteria?
Which type of DNA uptake occurs only in naturally competent bacteria?
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What occurs during autophosphorylation in a two-component signal transduction system?
What occurs during autophosphorylation in a two-component signal transduction system?
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How does OmpF differ from OmpC in terms of osmotic shock susceptibility?
How does OmpF differ from OmpC in terms of osmotic shock susceptibility?
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What environmental condition leads to the preferential expression of OmpC?
What environmental condition leads to the preferential expression of OmpC?
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Which genetic feature is enhanced in Salmonella when sensing low Mg+ ions?
Which genetic feature is enhanced in Salmonella when sensing low Mg+ ions?
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What does comparative transcriptomics reveal about bacteria in different niches?
What does comparative transcriptomics reveal about bacteria in different niches?
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What component influences flagella rotation in response to environmental stimuli?
What component influences flagella rotation in response to environmental stimuli?
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What is the main consequence of Goldilocks syndrome in bacterial environments?
What is the main consequence of Goldilocks syndrome in bacterial environments?
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What factor influences the expression of porins like OmpF and OmpC?
What factor influences the expression of porins like OmpF and OmpC?
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What type of genes does transcriptomics typically illuminate in bacteria?
What type of genes does transcriptomics typically illuminate in bacteria?
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Which of the following mechanisms is associated with horizontal gene transfer in bacteria?
Which of the following mechanisms is associated with horizontal gene transfer in bacteria?
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What is the primary role of conjugative plasmids in bacteria?
What is the primary role of conjugative plasmids in bacteria?
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What characterizes HFr strains of bacteria?
What characterizes HFr strains of bacteria?
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Which lifecycle of bacteriophages leads to the destruction of bacterial cells?
Which lifecycle of bacteriophages leads to the destruction of bacterial cells?
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What is the process called when DNA is transferred between bacteria via bacteriophages?
What is the process called when DNA is transferred between bacteria via bacteriophages?
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What occurs during a bacterium's response to quorum sensing?
What occurs during a bacterium's response to quorum sensing?
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How does the integration of foreign DNA into bacterial chromosomes usually get recognized?
How does the integration of foreign DNA into bacterial chromosomes usually get recognized?
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What mechanism do bacteria use to control gene regulation due to their size and resource constraints?
What mechanism do bacteria use to control gene regulation due to their size and resource constraints?
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What is one consequence of the horizontal gene transfer process in bacteria involving antibiotic resistance?
What is one consequence of the horizontal gene transfer process in bacteria involving antibiotic resistance?
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What is unique about the two-component regulation in bacteria?
What is unique about the two-component regulation in bacteria?
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What effect does the integration of pathogenicity islands have on bacteria?
What effect does the integration of pathogenicity islands have on bacteria?
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Study Notes
Bacterial Adaptation and Survival
- Bacteria adapt rapidly to changing circumstances and pressures.
- Most DNA changes are lethal.
- Advantageous mutations, in the right conditions, lead to rapid proliferation of the organism.
- Single nucleotide polymorphisms (SNPs) are one type of genetic change in bacterial DNA.
Lecture Aims
- Explore genetic mechanisms by which bacteria acquire new genes that influence their survival.
- Explain how genetic changes enhance a bacteria's ability to cause disease.
- Discuss how bacteria use different mechanisms to sense and communicate within their environment.
Genetic Change Drivers
- Bacteria's genetic change is driven by "tiny boxes of secrets" (a reference to genetic mechanisms).
Bacterial Multiplication Rates
- Humans have longer generation times (10-12 years for puberty, 9 months gestation).
- Bacteria have much shorter generation times (20-25 minutes for a doubling time).
- Bacteria can rapidly reproduce.
- A single bacterial clone can quickly generate a vast colony in 8 hours (108 colonies).
- The rapid multiplication of bacteria has significant evolutionary implications.
Bacterial Mutations
- Adaptations of bacteria may result from mutations that alter antibiotic efficacy.
- Adaptations may also alter receptor recognition of host tissue and the response of the host's immune system.
- Bacteria can gain genes associated with virulence factors like toxins and adhesins.
Acquiring New Genetic Traits
- Horizontal gene transfer is the acquisition of new genetic traits in bacteria.
- This process enables rapid growth and spread within bacterial populations.
Horizontal Gene Transfer Mechanisms
- Natural Transformation: Uptake and incorporation of "naked" DNA.
- Conjugation: Genetic exchange between bacteria.
- Transduction: Genetic exchange during or as a consequence of phage predation (infection).
Transformation
- Transformation occurs when bacteria take up and incorporate "naked" DNA.
- Transformation is a mechanism for natural repair that can involve the uptake of foreign DNA.
- Some bacteria naturally become competent (capable of accepting DNA) in response to specific compounds released by other organisms.
- Sometimes transformation can result in antibiotic resistance.
Conjugation (Bacterial Sex)
- Conjugative plasmids carry genes for pilus (protein tube) formation and transfer of genetic material.
- Transfer of DNA is initiated by a special pilus extending from a donor cell.
- Transfer occurs in close proximity of cells (by contact).
Transduction (Phage Predation)
- Bacteriophages infect bacteria and often have two reproduction lifecycles:
- Lytic cycle: Genome replication and destruction of the bacteria.
- Lysogenic cycle: Integration of the phage genome into the bacteria's chromosome.
Integration of New DNA - Pathogenicity Islands
- Insertion of foreign DNA into bacterial chromosomes is often detected by differences in GC content.
- Large DNA inserts (pathogenicity islands) often encode virulence traits.
Chromosomal Integration/Excision
- Introduced DNA sometimes doesn't persist due to restriction systems that recognize foreign DNA sequences.
- Endonuclease activity can degrade the introduced DNA.
- Persisting DNA can integrate and multiply within a bacteria's chromosome.
Capacity to Sense and Respond
- Bacteria use multiple mechanisms to regulate gene expression due to their resource constraints.
- Quorum sensing is a method for communication between bacteria based on density.
- Environmental sensing, using two-component systems, allows individuals to respond to changes in their external environment.
Symbiotic Relationship (Aliivibrio fischeri)
- Aliivibrio fischeri produces fluorescent light that helps to camouflage squid.
Quorum Sensing (Bacterial Tweeting)
- Quorum sensing is defined as a minimum number of bacteria needed for coordinated response.
- The behavior of bacteria changes based on their population density, which triggers the accumulation of autoinducer proteins.
Quorum Sensing in Aliivibrio fischeri
- Lux operon controls light production in A. fischeri.
- LuxR produces a transcription activator.
- Luxl produces AHL.
- High AHL binds to LuxR, increasing activation of luxl and resulting in expression of lux genes and light production.
Quorum Sensing in General
- Many bacteria exploit quorum sensing to control expression of traits.
Environmental Sensing and Two Component Signal Transduction
- Transmembrane sensor kinase is a sensor that detects external environmental conditions.
- Phosphorylation cascade with a response regulator leads to gene expression changes.
Goldilocks Syndrome
- EnvZ/OmpR two component system (in pathogens like Salmonella) ensures optimal nutrient intake.
- Lifestyle exposure to different nutrients is reflected in the membrane pore size.
- OmpF pores are larger and susceptible to osmotic shock, while OmpC pores are smaller and less susceptible to osmotic shock.
Pore Size and Bacterial Sensing
- OmpC and OmpF pore variations in response to osmotic stress.
Other Two Component Regulation Examples
- PhoPQ sensing low Mg+ ions found within phagolysosomes during infection.
- PhoPQ system influences virulence traits and intracellular survival in bacteria.
Transcriptomics
- Understanding bacterial adaptation to various environments using mRNA sequencing.
- Increased gene transcripts and adaptation are correlated in a given bacterial niche.
Comparative Transcriptomics
- Using mRNA sequencing to identify genes that are up-or down-regulated in bacteria experiencing particular environmental conditions.
Lecture Summary
- The lecture highlighted bacterial adaptation to different environments, which include their ability to mutate and acquire new genetic characteristics.
- The lecture explained how bacteria communicate and sense their environment through different mechanisms, including quorum sensing and two-component systems.
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Description
Test your knowledge on how bacteria adapt to their environment and the genetic mechanisms that drive their survival. This quiz covers topics including DNA changes, mutation rates, and bacterial communication. Understand the implications of these adaptations on disease causation as well.
