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Questions and Answers
What arrangement is formed when cocci divide in two planes?
What type of bacilli arrangement consists of cells appearing in chains?
Which bacterial shape is characterized by a flexible, helical body?
What is the key characteristic of a glycocalyx capsule?
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What component anchors the flagellum to the bacterial cell wall?
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Which type of bacteria has no flagella?
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How do capsules contribute to the virulence of certain bacteria?
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What is the function of extracellular polysaccharides in bacterial cells?
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What is the average size range of bacterial cells?
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Which of the following is not a shape classification of bacteria?
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What does the term 'pleomorphic' refer to in bacteria?
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What component is present in the cell walls of prokaryotes?
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What is the primary mode of reproduction in prokaryotes?
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Study Notes
Prokaryotes vs Eukaryotes
- Prokaryotes are defined as "prenucleus" and include organisms like bacteria.
- Eukaryotes are termed "true nucleus" and are generally more complex.
Bacterial Characteristics
- Bacteria possess peptidoglycan cell walls.
- They reproduce through a process called binary fission.
- Energy sources may include organic or inorganic chemicals, or photosynthesis.
Bacterial Cell Morphology
- Average bacterial size ranges from 0.2 - 1.0 µm in width and 2 - 8 µm in length.
- Morphological types include:
- Cocci: Spherical or oval cells.
- Bacilli: Rod-shaped cells.
- Vibrios: Comma-shaped curved rods.
- Spirilla: Rigid spiral forms.
- Spirochetes: Flexible spiral forms.
- Actinomycetes: Branching filamentous bacteria.
- Mycoplasmas: Cell wall-deficient bacteria with variable morphology.
Unusual Bacterial Shapes
- Unique forms include star-shaped Stella and square Haloarcula.
- Most bacteria are monomorphic, while some can be pleomorphic.
Bacterial Cell Arrangements
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Cocci Arrangements:
- Diplococci: Pairs formed by division in one plane.
- Streptococci: Chains formed by the same process.
- Tetrads: Groups of four formed by division in two planes.
- Sarcinae: Cubical packets from division in three planes.
- Staphylococci: Clusters formed by division in multiple planes.
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Bacilli Arrangements:
- Single Bacilli: Individual cells.
- Diplobacilli: Pairs.
- Streptobacilli: Chains.
- Coccobacilli: Oval or slightly rounded shapes.
Other Bacterial Structures
-
Glycocalyx (Capsule):
- Located outside the cell wall, often sticky.
- Capsules are well-organized; slime layers are loose.
- Vital for attachment and can enhance bacterial virulence by avoiding phagocytosis.
- Important in biofilms as extracellular polymeric substance (EPS).
-
Flagella:
- Appendages outside the cell wall for motility, composed of flagellin proteins.
- Structure includes three components: filament, hook, and basal body.
- The basal body anchors the flagellum to the cell wall and membrane, with gram-negative bacteria having two pairs of rings, while gram-positive bacteria possess one.
Classification of Bacteria by Flagella
- Atrichous: Bacteria, like streptococci, that lack flagella.
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