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Questions and Answers
What wavelength is most effectively absorbed by DNA, causing significant mutations?
What wavelength is most effectively absorbed by DNA, causing significant mutations?
What is the main consequence of excessive exposure of microorganisms to UV light?
What is the main consequence of excessive exposure of microorganisms to UV light?
Which of the following accurately describes biofilms?
Which of the following accurately describes biofilms?
What type of radiation falls within the near-UV range?
What type of radiation falls within the near-UV range?
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How do most microbes typically grow in their natural environments?
How do most microbes typically grow in their natural environments?
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What critical event occurs during the replication of the nucleoid in bacteria?
What critical event occurs during the replication of the nucleoid in bacteria?
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Which statement correctly describes the septum's role during cell division?
Which statement correctly describes the septum's role during cell division?
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What is the primary function of multinucleoid filaments in Streptomyces?
What is the primary function of multinucleoid filaments in Streptomyces?
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What happens to the cell wall and plasma membrane as a parent cell prepares for division?
What happens to the cell wall and plasma membrane as a parent cell prepares for division?
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Which characteristic is true for the nucleoid in bacterial cells?
Which characteristic is true for the nucleoid in bacterial cells?
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What is the significance of the growth pattern of hypha filament during cell division?
What is the significance of the growth pattern of hypha filament during cell division?
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Which of the following does NOT characterize septum formation during bacterial cell division?
Which of the following does NOT characterize septum formation during bacterial cell division?
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What structural role does MreB play in bacterial cell shape?
What structural role does MreB play in bacterial cell shape?
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What is the primary function of the divisome during bacterial cytokinesis?
What is the primary function of the divisome during bacterial cytokinesis?
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Which of the following statements is true regarding the elongasome?
Which of the following statements is true regarding the elongasome?
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What characterizes extremophiles among microorganisms?
What characterizes extremophiles among microorganisms?
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How does crescentin contribute to bacterial cell shape?
How does crescentin contribute to bacterial cell shape?
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What happens during bacterial cell division involving a Z ring?
What happens during bacterial cell division involving a Z ring?
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Which component is primarily responsible for determining the placement and timing of bacterial cell wall synthesis?
Which component is primarily responsible for determining the placement and timing of bacterial cell wall synthesis?
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How do molecular machineries in bacterial cell division differ?
How do molecular machineries in bacterial cell division differ?
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What effect does peptidoglycan synthesis have during bacterial growth?
What effect does peptidoglycan synthesis have during bacterial growth?
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What effect does low levels of ionizing radiation have on microorganisms?
What effect does low levels of ionizing radiation have on microorganisms?
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What are the two forms of ionizing radiation mentioned?
What are the two forms of ionizing radiation mentioned?
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What occurs when visible light is present in sufficient intensity?
What occurs when visible light is present in sufficient intensity?
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What role do photosynthesizers play when exposed to light?
What role do photosynthesizers play when exposed to light?
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Which of the following effects is NOT caused by ionizing radiation?
Which of the following effects is NOT caused by ionizing radiation?
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What is a consequence of high levels of ionizing radiation?
What is a consequence of high levels of ionizing radiation?
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What does near-UV radiation induce when interacting with tryptophan?
What does near-UV radiation induce when interacting with tryptophan?
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Which of the following is NOT a property of visible light regarding microbial cells?
Which of the following is NOT a property of visible light regarding microbial cells?
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What is generated at high intensities of light exposure to photosynthesizers?
What is generated at high intensities of light exposure to photosynthesizers?
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Which of the following best describes the primary effect of ionizing radiation on cell structures?
Which of the following best describes the primary effect of ionizing radiation on cell structures?
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What primarily drives the movement of water during osmosis?
What primarily drives the movement of water during osmosis?
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Which type of halophile requires NaCl concentrations between 0.8 M and 3.4 M?
Which type of halophile requires NaCl concentrations between 0.8 M and 3.4 M?
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In a hypertonic solution, what effect does water have on microbial cells?
In a hypertonic solution, what effect does water have on microbial cells?
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What is the impact of osmotic concentration on cells in a hypotonic solution?
What is the impact of osmotic concentration on cells in a hypotonic solution?
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What mechanism allows certain microorganisms to withstand high salt concentrations?
What mechanism allows certain microorganisms to withstand high salt concentrations?
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What role does the cell wall play in microbial cells when exposed to hypotonic solutions?
What role does the cell wall play in microbial cells when exposed to hypotonic solutions?
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Which factor is least likely to affect osmotic concentration?
Which factor is least likely to affect osmotic concentration?
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Extreme halophiles are characterized by their requirement for salt concentrations in the range of:
Extreme halophiles are characterized by their requirement for salt concentrations in the range of:
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What is the definition of osmolarity?
What is the definition of osmolarity?
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Which characteristic describes a semipermeable membrane in relation to osmosis?
Which characteristic describes a semipermeable membrane in relation to osmosis?
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Study Notes
Eukaryotic Reproduction
- Alternate between diploid and haploid stages in a life cycle
- Types
- Sexual
- Asexual
Microbial Reproduction
- Haploid only:
- Binary fission
- Budding
- Filamentous
Multiple Fission
- Progeny cells (baeocytes) form within the parent cell wall
- Small spherical cell, 1-2 um in diameter, grows to 13 um in diameter
- DNA replication occurs repeatedly within a cellular matrix
Bacterial Cell Cycle (Binary Fission)
- Complete events of a new cell formation
- Simple cycle
- Increasing volume, splitting into two
- Peptidoglycan synthesis during the cycle is a target for antibiotics
- Major phases
- Growth period
- Chromosome replication and partitioning
- Cytokinesis (cytoplasmic division)
- Involves:
- Origin of replication
- Replisome
- Replication and separation of chromosomes into two daughter cells
- Septum formation (cell wall)
- Cytokinesis
- Chromosome segregation
Bacterial Cell Cycle (Binary Fission; Continued)
- Chromosome replication and partitioning occur concurrently
- Cytokinesis
- Events of cytokinesis occur prior to chromosome replication and partitioning
- Cytokinesis is completed when the cell pinches into two cells
Chromosome Replication and Partitioning
- Replication starts at the origin, completes at terminus (located opposite the origin)
- Orienting to opposite halves of the cell
- DNA machinery (group of proteins) required for synthesis
- Replication proceeds in both directions from the origin
- Septum formation begins with Z ring formation
- Z ring links to the plasma membrane
- Cell wall synthesizing machinery assembles (Z ring constricts cell wall synthesis)
Cellular Growth and Determination of Cell Shape
- Determined by peptidoglycan synthesis in bacteria
- Existing peptidoglycan must be maintained
- Peptidoglycan subunits are added
Cell Shape and its Process
- Cocci: New peptidoglycan forms only at the central septum
Water Activity (aw)
- Degree of water availability
- Microorganisms take up water due to water activity gradient
- Higher water activity outside cells - lower water activity inside
pH
- Measure of relative acidity of a solution (pH = -log[H+])
- Use: Determines each pH levels for hydrogen ion concentration
Environmental Factors Affecting Microbial Growth
- Extremes of temperature/pressure can be harmful. Extremophiles grow under these conditions
Cardinal Temperatures
- Three portions: minimum, optimal, and maximum
- Psychrophiles, psychrotolerants, mesophiles, thermophiles, hyperthermophiles
- Survivability mechanisms vary
Oxygen
- Correlates with microbial energy conserving metabolic processes
- Electron transport chain (ETC)
- Obligate aerobes
- Microaerophiles
- Facultative anaerobes
- Aerotolerant anaerobes
- Obligate anaerobes
Mechanisms of Microbial Control
- Methods to control microbial growth
- Types:
- Physical agents: heat (dry, moist), radiation
- Chemical agents: liquids, gases
Chemical Control Agents
- Used in food and medical fields
- Sterilization
- Disinfection
- Antisepsis
Antimicrobials
- Target specific cellular processes
- Broad spectrum
- Narrow spectrum
- Static
- Cidal
- Methods of Action
- Cell wall
- Protein synthesis
- Metabolic antagonists
- Nucleic acid synthesis
- Cell membrane disruption
- Antimetabolites
- Antibiotic effectiveness is measured by the Minimal Inhibitory Concentration (MIC)
Determining Levels of Antimicrobial Activity
- Dilution Susceptibility Test
- Kirby Bauer (Disk) Diffusion Tests, and E test
- Measures MIC and MLC values
Anti-infective Agents
- Used to prevent microbial infections
- Examples of antibiotics, antivirals, antifungals, antiparasitics
- Treatment of drug-resistant infections
Microbial Growth
- One of the attributes of life
- Growth may increase cell number and cell size
- Exponential phase = population growth at constant rate of division
- Additional phases: lag phase, stationary phase, death phase
Biofilms
- Microorganisms that reside in a self-produced matrix on a surface.
- Involved in many infections and other infections, such as:
- Microbial interaction
- Communication (quorum sensing)
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Description
Test your knowledge on microbial genetics and the processes of cell division. This quiz covers topics such as UV light effects on microorganisms, DNA absorption, biofilms, and bacterial nucleoid replication. Prepare to explore the fascinating world of microbes and their cellular structures.
