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Questions and Answers
What is the primary reproduction mechanism for bacteria?
What is the primary reproduction mechanism for bacteria?
Viruses can grow in foods.
Viruses can grow in foods.
False
Name one characteristic used to categorize bacteria.
Name one characteristic used to categorize bacteria.
Cell type or growth capability.
Bacteria can reproduce asexually through __________.
Bacteria can reproduce asexually through __________.
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Match the following microorganisms with their growth ability in foods:
Match the following microorganisms with their growth ability in foods:
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Which group of microorganisms cannot grow in foods?
Which group of microorganisms cannot grow in foods?
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Mould is categorized as a multicellular microorganism.
Mould is categorized as a multicellular microorganism.
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What are the growth phases of bacteria?
What are the growth phases of bacteria?
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In which condition do facultative anaerobes grow faster?
In which condition do facultative anaerobes grow faster?
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Viruses contain traditional chromosomes.
Viruses contain traditional chromosomes.
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What is binary fission?
What is binary fission?
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A __________ is the viral DNA that integrates into a bacterial genome during the lysogenic cycle.
A __________ is the viral DNA that integrates into a bacterial genome during the lysogenic cycle.
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Match the following taxonomic levels with their order:
Match the following taxonomic levels with their order:
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What is the maximum density of bacteria that can be achieved in foods?
What is the maximum density of bacteria that can be achieved in foods?
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Gram-negative bacteria appear purple after Gram staining.
Gram-negative bacteria appear purple after Gram staining.
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What are the optimal growth temperatures for psychrotrophs?
What are the optimal growth temperatures for psychrotrophs?
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Bacteria form endospores in response to ______ conditions.
Bacteria form endospores in response to ______ conditions.
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Match the following bacteria with their oxygen requirements:
Match the following bacteria with their oxygen requirements:
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Which category of bacteria thrive in extremely cold temperatures?
Which category of bacteria thrive in extremely cold temperatures?
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Bacterial spores can replicate while in their dormant state.
Bacterial spores can replicate while in their dormant state.
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What is the optimal growth temperature for mesophiles?
What is the optimal growth temperature for mesophiles?
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Study Notes
Learning Objectives
- List different types of microorganisms found in foods
- Compare and contrast cellular characteristics and replication methods of microorganisms
- Apply microbial naming conventions correctly
- Differentiate between microbial taxonomy levels
- Describe characteristics used to categorize bacteria
- Categorize microorganisms based on growth, survival, and death in foods
- Differentiate between harmful and non-harmful microorganisms in foods
Microorganism Characteristics
| Category | Cell Type | Single/Multicellular | Can grow in food? |
|---|---|---|---|
| Bacteria | Prokaryote | Single | Yes |
| Yeast | Eukaryote | Single | Yes |
| Mould | Eukaryote | Multicellular | Yes |
| Viruses (human/bacteriophages) | Acellular | None | No |
| Parasites | Eukaryote | Single/Multicellular (protozoa/helminths) | No |
Study Questions
- Plasmids: Bacteria can have one or more plasmids. These are small extrachromosomal DNA molecules that carry useful genes, such as resistance to antimicrobial agents.
- Chromosomes vs. Plasmids: Chromosomes contain essential genes for survival and reproduction, while plasmids carry additional genes providing benefits.
Bacterial Growth Phases
- Lag phase: Little to no increase in cell number as bacteria adapt to the environment.
- Log phase: Exponential growth with rapid cell division.
- Stationary phase: Growth rate equals death rate due to resource depletion.
- Death phase: Death rate exceeds growth rate.
Bacterial Maximum Density
- The maximum bacterial density in nutritionally rich environments is approximately 9 log CFU/mL (109 CFU/mL).
Gram-Positive vs. Gram-Negative Bacteria
- Gram-positive: Thick peptidoglycan layer, retain crystal violet stain (purple).
- Gram-negative: Thin peptidoglycan layer surrounded by an outer membrane, do not retain crystal violet (pink).
Temperature Growth for Microorganisms
- Psychrotrophs: Grow between 0°C and 30°C (optimal around 20-30°C).
- Mesophiles: Grow between 20°C and 45°C (optimal around 37°C).
- Psychrophiles: Thrive in extremely cold temperatures (-5°C to 15°C).
Oxygen Requirements
- Aerotolerant anaerobes: Do not use oxygen but can survive and grow in its presence.
- Microaerophiles: Require low levels of oxygen to grow, but are inhibited by higher concentrations.
- Facultative anaerobes: Grow with or without oxygen.
Endospores
- Bacteria form endospores in response to harsh conditions like nutrient depletion, extreme temperatures.
- Endospores are dormant structures and do not replicate until environmental conditions improve.
Bacterial Genetic Material Transfer
- Transformation: Uptake of free DNA from the environment
- Transduction: Transfer of genetic material via bacteriophages
- Conjugation: Transfer of plasmids through direct cell-to-cell contact.
Bacterial Reproduction
- Binary fission: Asexual reproduction (prokaryotes)
- Mitosis: Cell division in eukaryotes
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Description
This quiz covers various types of microorganisms found in foods, their characteristics, and methods of replication. It also delves into microbial taxonomy and highlights the difference between harmful and non-harmful microorganisms. Understanding these concepts is crucial in food safety and microbiology.
