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Questions and Answers
What is taxonomy?
The science of classifying organisms
What is systematics or phylogeny?
The study of the evolutionary history of organisms
Which of these is NOT one of the three domains?
Which characteristics define Archaea?
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Archaea comprise ___% of the microbiome.
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All bacteria are classified strictly as either Gram-positive or Gram-negative.
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What is Bergey's Manual of Determinative Bacteriology used for?
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What do morphological characteristics help identify?
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What do Gram-positive bacteria have?
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What are methanogens?
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Study Notes
Taxonomy & Phylogeny
- Taxonomy is the classification of organisms based on similarities.
- Systematics, or phylogeny, studies the evolutionary history of organisms.
- There are three domains: Eukarya, Bacteria, and Archaea.
- Eukarya includes animals, plants, and fungi.
- Archaea includes methanogens, extreme halophiles, and hyperthermophiles.
Phylogenetic Tree
- A phylogenetic tree represents the evolutionary relationships between organisms.
Taxonomic Hierarchy
- Nomenclature identifies groups and subgroups with shared characteristics.
Classifying & Identifying Microorganisms
- Classification places organisms into groups of related species.
- Identification matches characteristics of an unknown organism with known organisms.
- Bergey's Manual of Determinative Bacteriology provides identification schemes for bacteria and archaea.
Methods for Identifying Microorganisms
- Morphological characteristics are useful for identifying eukaryotes, but tell little about phylogenetic relationships.
- Differential staining, such as Gram staining and acid-fast staining, is not useful for bacteria without cell walls.
- Biochemical tests determine the presence of bacterial enzymes.
Prokaryotic Classification
- A prokaryotic species is a population of cells with similar characteristics.
- A culture refers to bacteria grown in laboratory media.
- A clone is a population of cells derived from a single parent cell.
- A variant exhibits slight genetic differences with no functional change.
- A strain accumulates genetic differences leading to changes in behavior or properties.
Classification of Viruses
- Viruses are not part of any domain and are not composed of cells.
- They require a host cell to replicate.
- A viral species is a population of viruses with similar characteristics occupying a specific ecological niche.
Archaea Classification Overview
- Archaea are distinct from other domains and lack peptidoglycan.
- They are often extremophiles:
- Halophiles require salt concentrations greater than 25%.
- Thermophiles require growth temperatures above 80°C.
- Methanogens are anaerobic and produce methane.
Important Contributions of Archaea
- Archaea are primarily beneficial rather than harmful.
- They play crucial roles in global ecosystems:
- Nutrient cycling
- Wastewater treatment
- Plant immunity
- Their ability to thrive in extreme environments allows them to access areas and nutrients inaccessible to other organisms.
Archaea and Human Health
- Archaea can be manipulated to produce chemicals and drugs.
- They are the source of Taq polymerase, an enzyme used in PCR.
- They compose 1.2% of the human microbiome:
- They reduce skin pH, enhancing defense against infection.
- They may produce compounds preventing cardiovascular disease.
- Their ability to withstand extreme conditions makes them attractive for pharmacological processes, but also difficult to grow and culture.
Bacteria Classification Overview
- Bacteria are primarily divided into two groups:
- Gram-positive: Thick peptidoglycan cell wall, stain purple.
- Gram-negative: Thin peptidoglycan cell wall, lipopolysaccharide wall with associated endotoxins, stain pink.
- There are exceptions, and some bacteria do not fit neatly into either group.
Bacteria of Medical Importance (Gram-Negative)
- Domain: Bacteria (Gram-Negative)
- Phyla:
- Proteobacteria:
- Alphaproteobacteria: Includes Ehrlichia, Agrobacterium, and Rickettsia.
- Betaproteobacteria: Includes Bordetella and Burkholderia.
- Gammaproteobacteria: Includes Vibrio, Salmonella, Helicobacter, and Escherichia.
- Deltaproteobacteria: Includes Bdellovibrio.
- Epsilonproteobacteria: Includes Campylobacter and Helicobacter.
- Cyanobacteria: Includes oxygenic photosynthetic bacteria.
- Chlorobi: Includes anoxygenic photosynthetic green sulfur bacteria.
- Chloroflexi: Includes Chloroflexi..
- Proteobacteria:
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Description
Test your knowledge on the classification and evolutionary relationships of organisms in this quiz on taxonomy and phylogeny. Explore the domains of life and the methods used to identify microorganisms through various characteristics.
