Podcast
Questions and Answers
What is the lag phase in microbial growth?
What is the lag phase in microbial growth?
- The period before growth begins for synthesis of enzymes. (correct)
- The time when cells double in number.
- The phase where cells die due to lack of nutrients.
- The time when nutrients are used up.
During which phase do bacterial cells double in number at a constant rate?
During which phase do bacterial cells double in number at a constant rate?
- Lag phase
- Death phase
- Exponential phase (correct)
- Stationary phase
What triggers the transition from exponential phase to stationary phase?
What triggers the transition from exponential phase to stationary phase?
- Synthesis of new enzymes
- Cellular reproduction rate doubling
- Accumulation of metabolic waste (correct)
- Rapid nutrient influx
What happens during the death phase of bacterial growth?
What happens during the death phase of bacterial growth?
What limitation does the total cell count method face?
What limitation does the total cell count method face?
What does turbidity measurements rely on for assessing cell mass?
What does turbidity measurements rely on for assessing cell mass?
How is net cell mass determined in the viable count method?
How is net cell mass determined in the viable count method?
Why is a standard curve important in turbidity measurement?
Why is a standard curve important in turbidity measurement?
What primarily influences the growth rate of bacteria?
What primarily influences the growth rate of bacteria?
Which bacterial reproduction method involves a parent cell forming a smaller new cell that eventually separates?
Which bacterial reproduction method involves a parent cell forming a smaller new cell that eventually separates?
What type of mutation results in a change to a stop codon?
What type of mutation results in a change to a stop codon?
Which of the following accurately describes auxotrophic bacteria?
Which of the following accurately describes auxotrophic bacteria?
Which term describes the addition, deletion, or substitution of a few bases in DNA?
Which term describes the addition, deletion, or substitution of a few bases in DNA?
In which genetic transfer method do bacteria take up naked DNA from the environment?
In which genetic transfer method do bacteria take up naked DNA from the environment?
What does it mean if a bacterium is labeled as 'AmpR'?
What does it mean if a bacterium is labeled as 'AmpR'?
What type of bacteria can synthesize their own nutritional requirements from minimal media?
What type of bacteria can synthesize their own nutritional requirements from minimal media?
What is the primary purpose of making a smear of bacterial cells on a slide?
What is the primary purpose of making a smear of bacterial cells on a slide?
What happens to Gram-negative cells during the Gram staining process after the decolorization step?
What happens to Gram-negative cells during the Gram staining process after the decolorization step?
Which of the following describes the term 'generation' in microbial growth?
Which of the following describes the term 'generation' in microbial growth?
In differential staining, what is the role of the counterstain?
In differential staining, what is the role of the counterstain?
What characteristic of endospores makes them difficult to stain with normal dyes?
What characteristic of endospores makes them difficult to stain with normal dyes?
Which staining method involves treating cells with hydrochloric acid?
Which staining method involves treating cells with hydrochloric acid?
Which of the following best describes bacterial growth?
Which of the following best describes bacterial growth?
What is the first step in spore staining?
What is the first step in spore staining?
What type of medium is defined by having an exact and consistent composition, avoiding any organic materials from yeast, animals, or plants?
What type of medium is defined by having an exact and consistent composition, avoiding any organic materials from yeast, animals, or plants?
Which of the following media is designed to suppress unwanted organisms while allowing certain bacteria to grow?
Which of the following media is designed to suppress unwanted organisms while allowing certain bacteria to grow?
What characteristic of enriched media distinguishes it from other types of media?
What characteristic of enriched media distinguishes it from other types of media?
Which media is specifically used for isolating Vibrio cholerae?
Which media is specifically used for isolating Vibrio cholerae?
Which media would result in a purple/pink color change to indicate a positive urease test?
Which media would result in a purple/pink color change to indicate a positive urease test?
What defines complex media in comparison to basal media?
What defines complex media in comparison to basal media?
What is the purpose of using an indicator in certain types of media?
What is the purpose of using an indicator in certain types of media?
Which type of media can be classified as semi-solid due to the 0.5% agar content?
Which type of media can be classified as semi-solid due to the 0.5% agar content?
What color do lactose fermenters produce on Mac Conkey's medium?
What color do lactose fermenters produce on Mac Conkey's medium?
Which method is NOT used to generate anaerobiosis in a culture?
Which method is NOT used to generate anaerobiosis in a culture?
What is typically used to confirm and identify microorganisms in a pure culture?
What is typically used to confirm and identify microorganisms in a pure culture?
What role does reduced methylene blue indicator play in anaerobic media?
What role does reduced methylene blue indicator play in anaerobic media?
Why is it often up to the scientist to find the best conditions for culturing an organism?
Why is it often up to the scientist to find the best conditions for culturing an organism?
What is the function of the Durham's tube in culture media?
What is the function of the Durham's tube in culture media?
What is a common initial step in identifying microorganisms?
What is a common initial step in identifying microorganisms?
In microbiology, what is a pure culture?
In microbiology, what is a pure culture?
What is the primary mechanism by which moist heat kills microorganisms?
What is the primary mechanism by which moist heat kills microorganisms?
Which type of pasteurization method exposes milk to 72ºC for 15 seconds?
Which type of pasteurization method exposes milk to 72ºC for 15 seconds?
What is required for reliable sterilization when using moist heat?
What is required for reliable sterilization when using moist heat?
Which pathogen is a notable exception that survives boiling for up to 30 minutes?
Which pathogen is a notable exception that survives boiling for up to 30 minutes?
What temperature is reached in an autoclave to effectively kill all organisms and endospores?
What temperature is reached in an autoclave to effectively kill all organisms and endospores?
What is the main advantage of Ultra High Temperature Pasteurization (UHT) for milk?
What is the main advantage of Ultra High Temperature Pasteurization (UHT) for milk?
Which of the following is a consequence of longer heat exposure in microbial control?
Which of the following is a consequence of longer heat exposure in microbial control?
What occurs during the lag phase of microbial growth?
What occurs during the lag phase of microbial growth?
What is the role of filtration as a physical method of microbial control?
What is the role of filtration as a physical method of microbial control?
Which measurement method allows for distinguishing viable cells from non-viable cells?
Which measurement method allows for distinguishing viable cells from non-viable cells?
In which phase of microbial growth does exponential growth cease?
In which phase of microbial growth does exponential growth cease?
What is a limitation of the total cell count method?
What is a limitation of the total cell count method?
What process is used to determine the net cell mass of a culture?
What process is used to determine the net cell mass of a culture?
What is essential for a spectrophotometer to function accurately in turbidity measurements?
What is essential for a spectrophotometer to function accurately in turbidity measurements?
What is the consequence of prolonged incubation after reaching the stationary phase?
What is the consequence of prolonged incubation after reaching the stationary phase?
Which method is used for direct microscopic counting of cells?
Which method is used for direct microscopic counting of cells?
What is the primary function of High Efficiency Particulate Air Filters (HEPA)?
What is the primary function of High Efficiency Particulate Air Filters (HEPA)?
Which statement about membrane filters with 0.22 and 0.45um pores is correct?
Which statement about membrane filters with 0.22 and 0.45um pores is correct?
What process occurs when cells undergo plasmolysis due to osmotic pressure?
What process occurs when cells undergo plasmolysis due to osmotic pressure?
What is a major disadvantage of ionizing radiation for sterilization?
What is a major disadvantage of ionizing radiation for sterilization?
Which form of radiation is primarily used to disinfect surfaces but does not penetrate well?
Which form of radiation is primarily used to disinfect surfaces but does not penetrate well?
What does sterilization aim to achieve?
What does sterilization aim to achieve?
How do alcohols primarily kill microorganisms?
How do alcohols primarily kill microorganisms?
What is the optimum concentration of ethanol used for disinfection?
What is the optimum concentration of ethanol used for disinfection?
Which process effectively kills endospores of Clostridium botulinum in food products?
Which process effectively kills endospores of Clostridium botulinum in food products?
What can be an issue when cooking food in microwaves?
What can be an issue when cooking food in microwaves?
What is the main purpose of antiseptics in medical settings?
What is the main purpose of antiseptics in medical settings?
What is the difference between disinfectants and antiseptics?
What is the difference between disinfectants and antiseptics?
What does degerming specifically refer to in microbial control methods?
What does degerming specifically refer to in microbial control methods?
Which factor does NOT influence the effectiveness of antimicrobial treatment?
Which factor does NOT influence the effectiveness of antimicrobial treatment?
What is the primary goal of sanitization in food handling?
What is the primary goal of sanitization in food handling?
Which statement best describes the concept of sepsis?
Which statement best describes the concept of sepsis?
Flashcards
Bacterial Generation Time
Bacterial Generation Time
The time it takes for a bacterial population to double in size.
Lag Phase (Bacterial Growth)
Lag Phase (Bacterial Growth)
The initial period where bacterial growth is slow or non-existent. Cells adapt to new conditions.
Exponential Phase (Bacterial Growth)
Exponential Phase (Bacterial Growth)
The phase where bacterial cells divide at a constant rate.
Stationary Phase (Bacterial Growth)
Stationary Phase (Bacterial Growth)
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Total Cell Count
Total Cell Count
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Viable Cell Count
Viable Cell Count
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Turbidity Measurement of bacterial growth
Turbidity Measurement of bacterial growth
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Bacterial Growth Measurement Methods
Bacterial Growth Measurement Methods
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Bacterial Growth Rate
Bacterial Growth Rate
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Binary Fission
Binary Fission
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Unusual Bacterial Division
Unusual Bacterial Division
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Bacterial Mutations
Bacterial Mutations
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Horizontal Gene Transfer
Horizontal Gene Transfer
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Antimicrobial Resistance Mutation
Antimicrobial Resistance Mutation
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Point Mutation
Point Mutation
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Nutritional Mutants
Nutritional Mutants
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Bacterial Smear
Bacterial Smear
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Simple Staining
Simple Staining
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Differential Staining
Differential Staining
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Gram Staining
Gram Staining
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Acid-Fast Staining
Acid-Fast Staining
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Spore Staining
Spore Staining
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Growth Rate
Growth Rate
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Generation Time
Generation Time
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Simple Media
Simple Media
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Complex Media
Complex Media
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Synthetic Media
Synthetic Media
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Enriched Media
Enriched Media
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Indicator Media
Indicator Media
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Inhibitory Substances
Inhibitory Substances
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Motility Media
Motility Media
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Nutrient Broth
Nutrient Broth
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MacConkey's medium
MacConkey's medium
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Anaerobic media
Anaerobic media
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Gaspak
Gaspak
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Differential Media
Differential Media
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Pure culture
Pure culture
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Microscopic identification
Microscopic identification
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Microbial Growth Conditions
Microbial Growth Conditions
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Bacterial Smear
Bacterial Smear
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Generation Time
Generation Time
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Lag Phase
Lag Phase
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Exponential Phase
Exponential Phase
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Stationary Phase
Stationary Phase
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Total Cell Count
Total Cell Count
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Viable Count
Viable Count
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Turbidity
Turbidity
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Total Cell Count Limitations
Total Cell Count Limitations
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Sterilization
Sterilization
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Commercial Sterilization
Commercial Sterilization
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Disinfection
Disinfection
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Aseptic Techniques
Aseptic Techniques
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Degerming
Degerming
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Sanitization
Sanitization
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Sepsis
Sepsis
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Factors influencing antimicrobial effectiveness
Factors influencing antimicrobial effectiveness
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Moist Heat
Moist Heat
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Boiling
Boiling
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Autoclave
Autoclave
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Pasteurization
Pasteurization
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Heat Resistance
Heat Resistance
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Environmental Factors (Microbial Control)
Environmental Factors (Microbial Control)
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Time of Exposure (Microbial Control)
Time of Exposure (Microbial Control)
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Dry Heat
Dry Heat
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Dry Heat
Dry Heat
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Low Temperatures
Low Temperatures
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Filtration
Filtration
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Desiccation
Desiccation
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Osmotic Pressure
Osmotic Pressure
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Radiation (Ionizing)
Radiation (Ionizing)
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Radiation (Nonionizing)
Radiation (Nonionizing)
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Alcohols (Sterilization)
Alcohols (Sterilization)
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Study Notes
Bacterial Growth and Control
- Bacteria growth rate depends on species (e.g., E. coli 20 minutes, Mycobacterium tuberculosis 2 weeks) and environmental conditions.
- Bacteria can adjust their growth speed depending on available nutrients.
- Bacteria reproduce asexually via binary fission.
- Some bacteria have unusual division patterns, like budding or multiple divisions after exceeding their starting size.
Unusual Division Patterns
- Some bacteria grow larger than their starting size before dividing.
- Some bacteria create a new cell that grows out of the parent cell, a process called budding.
- Other bacteria develop offspring internally within the cytoplasm of a larger "mother" cell.
Genetic Changes in Bacterial Populations
- Mutations are changes in DNA.
- Point mutations involve addition, deletion, or substitution of bases.
- Missense mutations alter a single amino acid.
- Nonsense mutations change a codon into a stop codon.
- Silent mutations change a base without altering the amino acid.
- Spontaneous mutations or mutations induced by mutagens can occur.
- Horizontal/lateral gene transfer includes transformation, conjugation, transduction, and vesicles.
Bacterial Mutants
- Antimicrobial-resistant mutants can grow even in the presence of antimicrobial agents (e.g., AmpR for ampicillin resistance).
- Antibiotic-sensitive mutants cannot grow in the presence of antimicrobial agents.
Horizontal or Lateral Genetic Transfer
- Bacteria can acquire new genes without sexual reproduction
- Important for adapting to new toxins or environments.
- Can lead to antibiotic resistance in bacteria, which is a risk for humans.
- Four main mechanisms are transformation, conjugation, transduction, and vesicles.
Bacterial Transformation
- A donor DNA molecule is taken up and incorporated into the recipient cell's genome.
Bacterial Conjugation
- Direct transfer of genetic material between bacterial cells via a conjugation bridge.
Bacterial Transduction
- Viruses (bacteriophages) transfer genetic material from one bacterium to another.
- Two types: Generalized (any portion of the host's genome is transferred) and Specialized (only specific portions are transferred).
Bacterial Vesicles
- Internal organelles containing genetic material that are transferred between cells.
Culture Methods in Microbiology
- Isolating and culturing microorganisms to understand them.
- Identification steps: Inoculation, Incubation, Isolation, Inspection.
- Isolating pure cultures: Identifying and separating microbial species from a mixed population
- First bacterial growth media often used urine or meat broth.
Types of Media
- Based on consistency: solid, liquid, semi-solid.
- Based on chemical composition: simple, complex, synthetic.
- Also specific to different requirements, like ones for aerobic or anaerobic microbes.
- Different media can support the growth of specific organisms while inhibiting the growth of others.
Special Media
- Enriched: Contain additional nutrients for fastidious organisms (e.g., blood agar, chocolate agar).
- Enrichment: Used for isolating specific microorganisms from a mixed culture (e.g., selenite F broth).
- Selective: Contain inhibitory substances to prevent/suppress the growth of unwanted organisms (e.g., MacConkey's, Mannitol salt agar).
- Indicator: Contain indicators which change color upon microbial growth (e.g., MacConkey's).
- Sugar media: Contains any fermentable substances used to determine fermentation types.
Staining Procedures
- Simple stains: Use one dye to visualize cell morphology and structure.
- Differential stains: Use multiple dyes to distinguish between cells based on cell wall structures (e.g., Gram stain). Acid-fast stain, and spore stain.
Bacterial Growth Cycle
- Lag phase: Initial period of adjustment before growth begins.
- Exponential phase: Rapid increase in cell number.
- Stationary phase: Growth rate slows as resources are depleted.
- Death phase: Cell death exceeds cell growth.
Measurement of Bacterial Growth
- Total cell count: Direct microscopic count (counting cells in a known volume).
- Viable cell count: Spread plate method (plating dilutions to count colonies).
- Cell mass: Measuring the dry weight of cells (for large populations).
Factors Influencing Bacterial Growth
- Temperature: Microbes have optimal growth temperatures (Psychrophiles, Mesophiles, Thermophiles, Hyperthermophiles)
- pH: Microbes have optimal pH ranges (Acidophiles, Alkaliphiles, Neutrals)
- Water availability: Microbes need water for metabolic reactions (Osmosis)
- Oxygen: Microbes require oxygen (aerobes, anaerobes) or don't (facultative anaerobes) for growth.
Methods of Microbial Control
- Heat: Boiling, autoclaving, pasteurization, dry heat sterilization
- Low temperature: Refrigeration, freezing
- Filtration: Removing microbes via membranes
- Desiccation: Removing water to inhibit growth
- Osmotic pressure: High salt/sugar concentrations
- Radiation: Ionizing (gamma, X-rays), non-ionizing (UV)
- Chemical agents: Alcohols, aldehydes, heavy metals, phenols, peroxygens, halogens)
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