Questions and Answers
What is the shape of a coccus?
What shape are bacillus bacteria?
Rod shaped
What is a coccobacillus?
Oval bacterium that is intermediate between the coccus and bacillus forms
What is a diplococcus?
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Define streptococcus.
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What is a staphylococcus?
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What is a tetrad?
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What is the glycocalyx formed by?
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Which of the following is NOT a function of the glycocalyx?
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What is the structure of the cell wall in bacteria?
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What does Gram staining indicate for Gram-positive bacteria?
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How thick is the cell wall of Gram-positive bacteria?
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How thick is the cell wall of Gram-negative bacteria?
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What is the periplasmic space?
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What composes the outer membrane of Gram-negative bacteria?
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What is LPS O antigen?
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What is antigenic variation?
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What connects O antigen to lipid A?
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What is lipid A?
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What are exotoxins?
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What is an endotoxin?
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What are teichoic and lipoteichoic acids?
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What is the function of flagella in bacteria?
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What are pili?
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What are endospores?
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What does fosfomycin block during bacterial cell wall synthesis?
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What does D-cycloserine interfere with?
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What does daptomycin interfere with?
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What do oxacillin and penicillins target?
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Monotrichous means __________.
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Lophotrichous means __________.
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Amphitricous means __________.
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Peritrichous means __________.
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What process secretes proteins across the inner and outer membrane in one step?
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What does T3SS do?
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What is a virulence factor for glycocalyx?
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Study Notes
Bacterial Morphology
- Coccus: Spherical shape of bacteria.
- Bacillus: Rod-shaped bacteria.
- Coccobacillus: Oval shape, intermediate between cocci and bacilli.
- Diplococcus: Bacteria occurring in pairs of cocci.
- Streptococcus: Bacteria arranged in chains of cocci.
- Staphylococcus: Clusters of cocci bacteria.
- Tetrad: Clusters of four cocci.
Glycocalyx and Functions
- Glycocalyx: Comprised of polysaccharides and glycoproteins, formed into a capsule or slime layer.
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Functions:
- Poorly antigenic.
- Inhibits phagocytosis.
- Promotes bacterial attachment.
- Acts as a virulence factor in some bacterial species.
Cell Wall Structure
- Cell Wall: Semi-rigid structure made of cross-linked peptidoglycan, crucial for maintaining bacterial shape and preventing lysis.
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Gram Staining:
- Gram-positive: Retains violet stain; thick peptidoglycan layer (~25 layers).
- Gram-negative: Retains pink counter stain; thin peptidoglycan layer (~2 layers).
Gram-Negative Bacteria Structure
- Periplasmic Space: Area between cytoplasmic membrane and outer membrane in Gram-negative bacteria, facilitates transport of proteins and enzymes.
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Outer Membrane:
- Bilayer with inner layer like cytoplasmic membrane and outer layer containing phospholipids and lipopolysaccharides (LPS), which serve as a protective barrier.
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LPS Structure:
- O Antigen: Antigenic component, composed of long carbohydrate units, highly variable among species.
- Core Polysaccharide: Branched structure connecting O antigen to lipid A.
- Lipid A: Embedded in outer membrane, acts as an endotoxin and is a virulence factor.
Toxins
- Exotoxins: Proteins secreted by living bacteria, contributing to virulence.
- Endotoxins: Structural elements of lipopolysaccharide, specifically lipid A.
Bacterial Virulence Factors
- Teichoic and Lipoteichoic Acids: Found in Gram-positive bacteria, these act as virulence factors.
- Flagella: Filamentous protein structures providing motility; source of H antigen.
- Pili: Hair-like structures facilitating adherence and genetic material exchange (conjugation), also a virulence factor.
- Endospores: Dormant, resistant forms produced by mainly Gram-positive bacteria in stress; examples include Bacillus anthracis and Clostridium tetani.
- Virulence Factor for Glycocalyx: Functions in antiphagocytic properties.
Antibiotics and Their Targets
- Fosfomycin: Inhibits MurA, crucial in N-acetylglucosamine (NAG) synthesis.
- D-Cycloserine: Interferes with addition of D-Alanine.
- Daptomycin: Disrupts membrane polarization.
- Oxacillin/Penicillins: Target transpeptidase for crosslinking in peptidoglycan.
Flagella Arrangement
- Monotrichous: Single flagellum at one pole.
- Lophotrichous: Multiple flagella at one pole.
- Amphitricous: Multiple flagella at both poles.
- Peritrichous: Flagella distributed all around the bacterial surface.
Protein Secretion Systems
- Type 1, 3, and 4 Secretion Systems (T1SS, T3SS, T4SS): Mechanisms to secrete proteins across membranes in Gram-negative bacteria.
- Type 3 Secretion System (T3SS): Injects virulence factors directly into host cells using a needle-like structure.
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Description
Explore the various shapes of bacteria, including cocci and bacilli, and their classifications. Understand the structure and functions of the glycocalyx and the importance of cell walls in bacterial survival. This quiz covers vital concepts in microbiology essential for students.
