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Questions and Answers
Which of the following organisms would be most likely to cause food spoilage in a refrigerator?
Which of the following organisms would be most likely to cause food spoilage in a refrigerator?
Which of the following statements accurately describes the growth of an obligate anaerobe in the presence of oxygen?
Which of the following statements accurately describes the growth of an obligate anaerobe in the presence of oxygen?
Which of the following organisms would be most likely to be found in a hot spring?
Which of the following organisms would be most likely to be found in a hot spring?
What is the primary reason why refrigeration can slow down food spoilage?
What is the primary reason why refrigeration can slow down food spoilage?
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Which of the following enzymes are involved in the detoxification of reactive oxygen species (ROS)?
Which of the following enzymes are involved in the detoxification of reactive oxygen species (ROS)?
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Which of the following describes the optimal pH range for most bacteria?
Which of the following describes the optimal pH range for most bacteria?
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Which of the following conditions would be MOST unfavorable for the growth of Mycobacterium leprae, the bacteria responsible for Leprosy?
Which of the following conditions would be MOST unfavorable for the growth of Mycobacterium leprae, the bacteria responsible for Leprosy?
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Which of the following statements about extremophiles is TRUE?
Which of the following statements about extremophiles is TRUE?
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Which metabolic pathway is responsible for generating most of the reducing power in cells?
Which metabolic pathway is responsible for generating most of the reducing power in cells?
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What type of reaction involves the breaking down of molecules, releasing energy, and is considered exergonic?
What type of reaction involves the breaking down of molecules, releasing energy, and is considered exergonic?
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What is the role of enzymes in metabolic reactions?
What is the role of enzymes in metabolic reactions?
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Which of the following is NOT a type of enzyme regulation?
Which of the following is NOT a type of enzyme regulation?
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Which of the following is an example of a coenzyme?
Which of the following is an example of a coenzyme?
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What is the main function of ATP in cellular processes?
What is the main function of ATP in cellular processes?
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Which of the following describes the process of oxidation?
Which of the following describes the process of oxidation?
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What is the primary reason agar is an ideal solidifying agent for microbial growth media?
What is the primary reason agar is an ideal solidifying agent for microbial growth media?
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During which stage of bacterial growth are the cells metabolically active but not yet dividing?
During which stage of bacterial growth are the cells metabolically active but not yet dividing?
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Which of the following is NOT a characteristic of the exponential phase of bacterial growth?
Which of the following is NOT a characteristic of the exponential phase of bacterial growth?
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What is the primary reason bacteria become more resistant to drugs during the stationary phase of growth?
What is the primary reason bacteria become more resistant to drugs during the stationary phase of growth?
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What is the most common method used to isolate bacteria in a laboratory setting?
What is the most common method used to isolate bacteria in a laboratory setting?
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Which of the following is a characteristic of a pure culture?
Which of the following is a characteristic of a pure culture?
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What is the term used to describe a visible cluster of microorganisms that originate from a single parent cell on a growth medium?
What is the term used to describe a visible cluster of microorganisms that originate from a single parent cell on a growth medium?
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Which of the following is a common method for preserving bacterial cultures?
Which of the following is a common method for preserving bacterial cultures?
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Flashcards
Agar
Agar
Agel-like substance used to solidify culture media; not a nutrient.
Binary Fission
Binary Fission
A method of bacterial reproduction where one cell divides into two.
Biofilms
Biofilms
Communities of microbes encased in polysaccharides, enhancing survival.
Pure Culture
Pure Culture
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Colony
Colony
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Streak-Plate Method
Streak-Plate Method
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Exponential Growth Phase
Exponential Growth Phase
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Lag Phase
Lag Phase
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Aerobes
Aerobes
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Anaerobes
Anaerobes
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Anabolism
Anabolism
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Catabolism
Catabolism
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Oxidation
Oxidation
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Reduction
Reduction
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Feedback Inhibition
Feedback Inhibition
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Cofactors
Cofactors
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Psychrophiles
Psychrophiles
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Mesophiles
Mesophiles
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Thermophiles
Thermophiles
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Obligate Anaerobes
Obligate Anaerobes
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Superoxide Dismutase
Superoxide Dismutase
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Optimal pH for Most Bacteria
Optimal pH for Most Bacteria
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Hansen's Disease
Hansen's Disease
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Facultative Anaerobes
Facultative Anaerobes
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Study Notes
Agar
- Agar is not a nutrient
- Robert Koch developed methods for pure culture
- Agar is ideal for solidifying media due to chemical and physical properties that make it neutral and remain solid at room temperature.
Bacterial Reproduction
- Bacterial reproduction is known as binary fission.
Biofilms
- Most microbes live in poly saccharide-encased communities termed biofilms.
- Biofilms may enhance bioremediation efforts and protect organisms against harmful chemicals.
Pure Culture and Colony
- Pure culture: All bacterial cells that result from the replication of a single original bacteria species/organism.
- Colony: A visible cluster of microorganisms that originate from a single parent cell on growth medium.
- Streak-plate method : A method for isolating bacteria.
Bacterial Culture Storage
- Agar slant in refrigerator.
- Frozen in glycerol solution.
- Freeze-dried.
Bacterial Growth Curve
- Lag Phase: Introduction to sterile medium, cells are maturing but not dividing, and begin synthesizing enzymes required for growth.
- Exponential/Log Phase: Bacteria are rapidly increasing in number, and most susceptible to antibiotics.
- Stationary Phase: Nutrient level is low to sustain growth, and the total number of cells remains constant.
- Death Phase: Total number of viable cells declines. Some cells survive and adapt to tolerate worsened conditions.
- Bacteria can become more resistant to drugs during the death phase.
Bacterial Growth Considerations
- During which phase of growth are bacteria most susceptible to antibiotics? Exponential phase
- In which phase does the bacterial population rapidly multiply and cell numbers increase? Exponential phase
Bacterial Groups Based on Temperature, pH and Oxygen Preference
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Temperature:
- Psychrophiles: -5 to 15 degrees Celsius, found in arctic regions.
- Psychrotrophs: 20 to 30 degrees Celsius, associated with food spoilage.
- Mesophiles: 25 to 45 degrees Celsius, includes pathogens (35 to 40 degrees Celsius).
- Thermophiles: 45 degrees to 70 degrees Celsius (hot springs).
- Hyperthermophiles: 70 to 110 degrees Celsius, members are Archaea, found in hydrothermal vents.
- Limiting growth of fast-growing mesophiles; Psychrophiles and trophs still grow but slowly; Freezing preserves but does not kill microbes; Temperature and disease: Hansen's disease/leprosy (coolest regions - ears, hands, feet and fingers) due to preference of MYCOBACTERIU M LEPRAE.
-
Oxygen:
- Obligate aerobe: Grows only when oxygen is available; requires oxygen for respiration; produces superoxide dismutase and catalase.
- Facultative anaerobe: Grows best when oxygen is available but can grow without it; uses O2 for respiration if available, produces superoxide dismutase.
- Obligate anaerobe: Cannot grow when oxygen is present; does not use O2; does not produce superoxide dismutase and catalase.
- Microaerophile: Grows only if small amounts of oxygen are available; requires O2 for respiration; produces some superoxide dismutase and catalase.
- Aerotolerant anaerobe: Grows equally well with or without oxygen; does not use oxygen; produces superoxide dismutase but not catalase.
- Shake tube growth demonstrates organisms' oxygen requirements.
pH
- Most microbes are neutrophils (range of pH 5 to 8, optimum near pH 7).
- Acidophiles are optimally at pH below 5.5.
- Alkaliphiles are optimally at pH above 8.5.
Proteins in Thermophiles
- Resist denaturing; PCR = polymerase chain reaction
Human Pathogens
- Human pathogens prefer which temperature range? 35 to 40 degrees Celsius (human body = 37).
- Optimum pH for most bacteria is near pH 7.
- Enzymes deal with toxic oxygen-containing molecules (superoxide dismutase and catalase deal with ROS (o2 in cells)).
### Food Preservation
- Dissolved salts and sugars make water unavailable to cells, which helps preserve food.
Metabolism
- Anabolism: Building up molecules, forming bonds between molecules, dehydration synthesis, monomer + monomer = polymer
- Catabolism: Breaking down molecules, exergonic reactions, energy released.
Energy
- Potential energy: at rest
- Kinetic energy: movement
- Exergonic vs. endergonic reaction.
- Oxidation vs. reduction.
- Oxidation = Atom loses an electron, exergonic, supply of oxygen and removal of electron
- Reduction = Atom gains an electron, reduced due to negative charge, endergonic
ATP Production
- REDOX = couple to make ATP, Electron acceptor = oxygen. Presence of Hydrogen = reduced, no hydrogen = oxidized
Enzymes
- Enzymes speed up conversions of substrates into products by lowering activation energy; structure and function.
- Factors influencing enzyme activity include activation energy and regulation (allosteric, competitive, non-competitive).
Inhibition
- Competitive inhibition: Inhibitor binds to active site (mimics structure of substrate)
- Non-competitive inhibition: Inhibitor binds to a different site than active site.
- Example: Sulfa drugs blocking folic acid synthesis (mimics PABA, needed for folate -> amino acid required for growth) and reversible.
- What is Feedback Inhibition? Show it schematically; Regulating the amount of product produced and often involves the use of allosteric enzymes; end-product inhibits enzyme 1.
Cofactors
- Cofactors assist enzymes.
Electron Carriers
- What are electron carriers? Give two examples; NAD, FAD, and NADP.
- Coenzymes are organic factors: FAD, NAD, and NADP.
Metabolic Pathway
- Which central metabolic pathway generates most of the reducing power? Krebs cycle (or TCA cycle).
Fermentation
- In anaerobic fermentation, carbon atoms stay in lactate or ethanol + CO2; End = no more carbon.
Electron Transport Chain
- Requires a membrane and generates a concentration gradient of protons; oxygen serves as the terminal electron acceptor.
- ATP synthase.
- Hydrogen flow down concentration gradient
Energy Production
- Ready to use energy:
- Substrate level phosphorylation
- Oxidative phosphorylation
- Photophosphorylation (light energy donation)
- Proton Motive force: Flow of protons, drives ATP synthase
- Chemiosmosis
Respiration
- Catabolism of proteins, lipids, and polysaccharides if oxygen is not available. Aerobic vs. anaerobic respiration; Fermentation as an alternative to cellular respiration.
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Description
Test your knowledge on microorganisms and their roles in food spoilage, growth conditions, and survival in extreme environments. This quiz covers key concepts related to anaerobes, extremophiles, and the factors affecting bacterial growth in various conditions.
