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Questions and Answers
What characterizes psychrotrophic bacteria?
What characterizes psychrotrophic bacteria?
Which of the following is NOT a physical requirement for microbial growth?
Which of the following is NOT a physical requirement for microbial growth?
What is the minimum temperature effect on microbial cells?
What is the minimum temperature effect on microbial cells?
How do cardinal temperatures vary among organisms?
How do cardinal temperatures vary among organisms?
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Which of the following describes the growth temperature range for microbes?
Which of the following describes the growth temperature range for microbes?
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What is the main structural component that surrounds the nucleic acid core in viruses?
What is the main structural component that surrounds the nucleic acid core in viruses?
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Which of the following descriptions correctly identifies features of eukaryotic cells?
Which of the following descriptions correctly identifies features of eukaryotic cells?
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What is a common requirement for the growth of psychrophilic bacteria?
What is a common requirement for the growth of psychrophilic bacteria?
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Which of the following accurately describes the life cycles of helminths?
Which of the following accurately describes the life cycles of helminths?
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Which organism is classified as a multicellular eukaryote that absorbs organic material from its environment?
Which organism is classified as a multicellular eukaryote that absorbs organic material from its environment?
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Study Notes
Helminth Life Cycle
- Microscopic helminth life cycle stages are identified using traditional microbiology methods.
Prokaryotic Cell Size and Shape
- Average size: 0.2 – 1.0 µm × 2 – 8 µm
- Most bacteria are monomorphic (single shape)
- Some bacteria are pleomorphic (multiple shapes)
Microbial Growth Requirements
- Physical Requirements: Temperature, pH, osmotic pressure
- Chemical Requirements: Carbon, nitrogen, sulfur, phosphorus, trace elements, oxygen, organic growth factors
Temperature Requirements for Growth
- Minimum growth temperature: Lowest temperature for growth
- Optimum growth temperature: Temperature for fastest growth
- Maximum growth temperature: Highest temperature for growth
Cardinal Temperatures & Microbial Groups
- Cardinal temperatures depend on pH and nutrient availability.
- Minimum temperature: reduced membrane fluidity affects nutrient transport.
- Optimum temperature: highest growth and reproduction rate.
- Maximum temperature: growth stops due to protein inactivation or membrane damage.
- Temperature range for a microbe is usually 30-40°C.
- Five microbial groups based on temperature optima: psychrophiles, psychrotrophs, mesophiles, thermophiles, hyperthermophiles.
Psychrophiles
- Optimum growth temperature ≤ 15°C; maximum around 20°C.
- Heat-sensitive; cannot survive temperate climates.
- Adaptations: low-temperature-optimum enzymes; high unsaturated fatty acid content in membranes.
Psychrotrophs (Psychrotolerant)
- Grow at 0°C, but optimum temperature is 20-30°C.
Mesophiles
- Optimum temperature: 25-40°C.
- Minimum temperature: 15-20°C.
- Maximum temperature: ≤ 45°C.
- Most common type of microbe (e.g., E. coli).
Thermophiles
- Optimum temperature: 50-60°C.
- Minimum temperature: around 45°C.
- Maximum temperature: ≤ 45°C.
- Only prokaryotes grow above 60°C.
- Archaea are the most thermophilic.
Hyperthermophiles
- Optimum temperature > 80°C.
- Mostly Archaea.
- Maximum growth temperature: 113°C (Pyrolobus fumarii).
- Adaptations: heat-stable enzymes and proteins; heat-stable membranes with branched, saturated fatty acids or lipid monolayers; DNA stabilized by histone-like proteins.
Applications of Thermophily
- High-temperature enzymes for industrial processes (e.g., feed pelleting).
- PCR: Taq DNA polymerase from Thermus aquaticus.
pH Requirements for Growth
- Most bacteria: pH 6.5-7.5.
- Molds and yeasts: pH 5-6.
- Acidophiles: grow in acidic environments.
pH Definition
- pH = -log[H+]; a measure of hydrogen ion activity.
- The pH scale ranges from 0.0 (1.0 M H+) to 14.0 (1.0 × 10⁻¹⁴ M H+), each unit representing a tenfold change in H+ concentration.
Microbial Classification
- Bacteria: Unicellular prokaryotes; peptidoglycan cell walls; binary fission; various shapes (bacillus, coccus, spiral); diverse nutritional needs.
- Archaea: Unicellular prokaryotes; lack peptidoglycan; include methanogens, extreme halophiles, and extreme thermophiles.
- Fungi: Eukaryotes; mostly multicellular (mushrooms, molds, yeasts); absorb organic matter.
- Protozoa: Unicellular eukaryotes; absorb or ingest nutrients.
- Algae: Unicellular or multicellular eukaryotes; photosynthetic; produce oxygen and carbohydrates.
- Viruses: Noncellular parasites; nucleic acid core (DNA or RNA) surrounded by a protein coat, sometimes with an envelope.
- Helminths: Multicellular animal parasites (flatworms and roundworms). Cause food spoilage.
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Description
Test your knowledge on the life cycles of helminths and the growth requirements for microbes. This quiz covers various topics including microbial sizes, temperature requirements, and essential nutrients. Perfect for microbiology students and enthusiasts.
