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Questions and Answers
What is the purpose of taxonomy?
How many domains are there in modern phylogeny?
What is a phylogenetic tree?
What is the main difference between prokaryotes and eukaryotes?
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Why are viruses not found on phylogenetic trees?
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What do the terms 'pro' and 'eu' mean in the context of prokaryotes and eukaryotes?
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Which of the following is a characteristic of Eukaryotic cells?
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What is the main difference between Prokaryotic and Eukaryotic cells?
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What is the term for the protein coat that surrounds a virus?
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What is the term for a dormant, highly resistant structure formed by some Bacteria?
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What is the purpose of a capsule in Bacteria?
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What is the term for the region in Prokaryotes where DNA is found?
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What is a key feature of Gram-positive cell walls?
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What is a characteristic of Archaea?
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What is the main component of the cell wall in Gram-negative bacteria?
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What is a characteristic of Protozoa?
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What is the main difference between Archaea and Bacteria?
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What is a characteristic of Algae?
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What is the primary difference between prokaryotes and eukaryotes?
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What is the function of a virus's protein capsid?
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What is the purpose of fixation in microscopy?
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What is the characteristic of fungi that makes them resemble animals?
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What is the difference between a positive stain and a negative stain?
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What is the name of the microscope that uses a beam of electrons to produce an image?
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What is the primary purpose of Gram staining?
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What is the name of the staining technique used to identify encapsulated yeast and bacteria?
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What is the term for the normal populations of microorganisms that inhabit the body?
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How do normal flora prevent colonization of pathogenic bacteria?
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What is a potential harmful effect of normal flora?
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What can lead to overgrowth of normal flora and secondary infection?
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Study Notes
Cell Wall Structure
- Gram-positive cell walls feature a thick peptidoglycan layer with embedded teichoic acid situated outside the plasma membrane.
- Gram-negative cell walls consist of three layers: an inner membrane, a thin peptidoglycan layer, and an outer membrane containing lipopolysaccharides.
Prokaryotes: Archaea
- Archaea are unicellular organisms with significant genetic and metabolic differences from bacteria.
- Their cell walls are composed of pseudopeptidoglycan, not peptidoglycan.
- Extremophiles, Archaea can survive in extreme conditions including high temperatures, varied pH, and high salinity.
Eukaryotes: Protists
- Protists form an informal grouping of eukaryotes not classified as plants, animals, or fungi.
- This group includes algae, which can be unicellular or multicellular, photosynthetic, and have cellulose-based cell walls.
- Protozoa, another subgroup, are diverse and often regarded as "not alive".
Classification of Microbial Organisms
- Modern phylogeny identifies three main domains: Bacteria, Archaea, and Eukarya.
- Prokaryotes are defined as organisms without membrane-bound nuclei; eukaryotes possess such nuclei.
- Viruses are acellular and lack a cellular structure, composed of a protein capsid with either DNA or RNA, and are not classified on phylogenetic trees.
Prokaryotic vs Eukaryotic Cells
- Most microbes are unicellular; bacteria typically measure about 1 μm, while viruses can be smaller.
- Bacteria inhabit numerous environments, can be harmless, beneficial, or pathogenic, and possess peptidoglycan in their cell walls.
- Bacterial shapes vary and they exhibit diverse metabolic capabilities, including photosynthesis.
Cell Structures of Bacteria
- Key structures include nucleoid, endospores, ribosomes, capsules, fimbriae, and pili.
- Bacterial staining techniques help distinguish between gram-negative and gram-positive cells, utilizing methods like Gram staining and acid-fast staining.
Normal Flora
- Each area of the body harbors unique flora, comprising mixed populations of bacteria and fungi, contributing to natural immunity.
- Colonization begins at birth influenced by maternal transfer, the environment, and social interactions.
Benefits of Normal Flora
- Prevent colonization of pathogenic bacteria by competing for binding sites and nutrients.
- Can produce antimicrobial substances and vitamins, aiding in digestion.
- Stimulate lymphoid tissue development.
Harmful Effects of Normal Flora
- Some normal flora can become opportunistic pathogens if overgrown, like E. coli.
- Dysbiosis may lead to secondary infections.
- Certain organisms like Giardia can be pathogenic.
Eukaryotic Microbes: Fungi
- Fungi resemble plants in form but are heterotrophic, requiring external nutrients.
- Their cell walls are made of chitin, encompassing macroscopic forms like mushrooms as well as molds and yeasts, some of which can cause diseases.
Acellular Microbes: Viruses
- Viruses cannot survive independently; they require a host organism to replicate.
- They can infect various organisms, including bacteria (bacteriophages), protozoa, and animals.
Microscopy Techniques
- Wet mount: specimen observation in a droplet of liquid under a cover slip.
- Fixation methods: heat or chemical fixing to attach specimens to slides while killing them.
- Staining: procedures include positive staining (where cells absorb dye) and negative staining (where the background absorbs the stain) to enhance visualization.
- Simple staining highlights specific structures within the microbes.
Taxonomy in Microbiology
- Taxonomy involves classification, description, and identification of organisms based on shared characteristics.
- Phylogenetic trees illustrate relationships through genetic, biochemical, and embryological comparisons, moving beyond just visible similarities.
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Description
Test your knowledge of microbial classification, taxonomy, and phylogenetic trees. Learn how microorganisms are grouped based on shared characteristics and how genetic, biochemical, and embryological comparisons are used to determine relatedness.