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Questions and Answers
What characteristic is NOT used for the classification of microorganisms?
Which of the following describes prokaryotes?
Which category contains organisms that can produce their own food?
What is the highest level of taxonomic classification?
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How many kingdoms of life are there in total?
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What are the two main groups of microorganisms based on cell structure?
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Which of the following is an example of heterotrophic organisms?
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What is the lowest level of taxonomic classification?
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What shape do bacilli bacteria typically have?
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Which classification criterion is NOT used for bacteria?
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What type of fungi typically grow as tube-like structures known as hyphae?
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How are viruses primarily classified according to ICTV?
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Which of the following is a characteristic of gram-negative bacteria?
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What is a common feature of dimorphic fungi?
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Which of the following represents a major classification of DNA viruses?
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What is NOT a component of viral classification?
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Study Notes
Classification of Microorganisms
- Microorganisms are categorized into five main groups: Bacteria, Archaea, Fungi, Protists, and Viruses.
- Classification is based on characteristics such as cell structure, metabolism, and genetics.
Cell Structure
- Prokaryotes: Lack a nucleus and membrane-bound organelles; DNA is found in the nucleoid. Includes Bacteria and Archaea.
- Eukaryotes: Have a nucleus and membrane-bound organelles. Includes Fungi, Protists, and Animals.
Metabolism
- Autotrophs: Produce their own food using sunlight or chemicals (e.g., plants, algae).
- Heterotrophs: Rely on consuming other organisms or their by-products for nourishment (e.g., animals, fungi, most bacteria).
Genetics
- Domains: Three primary taxonomic classifications: Archaea, Bacteria, and Eukarya.
- Kingdoms: Six kingdoms include Archaea, Bacteria, Fungi, Plantae, Animalia, and Protista.
- Taxonomic hierarchy: Domain > Kingdom > Phylum > Class > Order > Family > Genus > Species.
Bacterial Classification
- Bacteria are classified by:
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Shape:
- Cocci (spherical)
- Bacilli (rod-shaped)
- Spirilla (spiral)
- Vibrios (comma-shaped)
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Cell Wall Composition:
- Gram-positive: Thick peptidoglycan layer.
- Gram-negative: Thinner cell wall with an outer membrane.
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Respiration Mode:
- Aerobic: Require oxygen.
- Anaerobic: Do not require oxygen.
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Nutrition Mode:
- Autotrophs: Self-sufficient in food production.
- Heterotrophs: Need to consume other organisms.
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Shape:
Fungal Classification
- Three types of fungi:
- Filamentous Fungi: Composed of hyphae; can form molds.
- Yeasts: Unicellular, oval-shaped organisms ranging from 2-60 µm, some capsulated.
- Dimorphic Fungi: Change form based on temperature; appear filamentous at lower temps and yeasts at higher temps (e.g., Histoplasma capsulatum).
Viral Classification
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Viruses are classified by:
- Virion Morphology: Size, shape, and presence of an envelope.
- Genome Properties: Characteristics of viral nucleic acids.
- Protein Properties: Type of proteins present.
- Biological Properties: Such as host range.
- Genome Organization: Structure and replication mechanisms.
- Antigenic Properties: Immune response characteristics.
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Per the International Committee on Taxonomy of Viruses (ICTV), over 30,000 viruses have been isolated, categorized into more than 3,600 species across 164 genera and 71 families.
Viral Taxonomic Structure
-
Taxonomic levels for viruses include:
- Order (-virales)
- Family (-viridae)
- Subfamily (-virinae)
- Genus (-virus)
- Species
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Example:
- Order: Mononegavirales
- Family: Filoviridae
- Genus: Filovirus
- Species: Ebola virus Zaire
Classification by Nucleic Acid
-
DNA Viruses:
- Single-stranded (ssDNA): Parvoviridae.
- Double-stranded (dsDNA): Papovaviridae, Adenoviridae, Herpesviridae, Iridoviridae, Poxviridae.
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Description
Test your knowledge on the classification of microorganisms, including bacteria, fungi, archaea, protists, and viruses. This quiz aims to help you understand the fundamental characteristics that differentiate each type of microorganism.
