Podcast
Questions and Answers
Which of the following is NOT considered an essential structure of eubacteria?
Which of the following is NOT considered an essential structure of eubacteria?
- Cell membrane
- Ribosome
- Plasmids
- Flagella (correct)
What is the primary distinction between Gram-positive and Gram-negative cell walls?
What is the primary distinction between Gram-positive and Gram-negative cell walls?
- Presence of a nuclear membrane
- Type of ribosomal RNA present
- Quantity of cytoplasm
- Thickness of the peptidoglycan layer (correct)
Which structure is responsible for bacterial movement?
Which structure is responsible for bacterial movement?
- Fimbriae
- Ribosome
- Capsule
- Flagella (correct)
Which of the following structures is directly involved in the formation of bacterial spores?
Which of the following structures is directly involved in the formation of bacterial spores?
Among the following, which is classified as a surface structure found outside the bacterial cell wall?
Among the following, which is classified as a surface structure found outside the bacterial cell wall?
Which of the following best describes the function of pili in bacteria?
Which of the following best describes the function of pili in bacteria?
What structure in eubacteria is usually considered a non-essential component?
What structure in eubacteria is usually considered a non-essential component?
What is the primary component differentiating the outer membrane of Gram-negative bacteria from Gram-positive bacteria?
What is the primary component differentiating the outer membrane of Gram-negative bacteria from Gram-positive bacteria?
Which internal bacterial structure is primarily involved in protein synthesis?
Which internal bacterial structure is primarily involved in protein synthesis?
Which term best describes the slime layer of bacteria?
Which term best describes the slime layer of bacteria?
What is the primary composition of glycocalyx in bacteria?
What is the primary composition of glycocalyx in bacteria?
Which type of glycocalyx is organized, thick, and firmly attached to the cell wall?
Which type of glycocalyx is organized, thick, and firmly attached to the cell wall?
Which organism is known to possess a slime layer?
Which organism is known to possess a slime layer?
What is the role of glycocalyx in bacterial virulence?
What is the role of glycocalyx in bacterial virulence?
What is a critical function of flagella in bacteria?
What is a critical function of flagella in bacteria?
Which term describes the movement of bacteria in response to light?
Which term describes the movement of bacteria in response to light?
Which of the following correctly defines biofilm?
Which of the following correctly defines biofilm?
What does the K antigen refer to in relation to bacteria?
What does the K antigen refer to in relation to bacteria?
What characteristic of slime layer contributes to biofilm formation?
What characteristic of slime layer contributes to biofilm formation?
Which type of appendage is primarily responsible for motility in bacteria?
Which type of appendage is primarily responsible for motility in bacteria?
Which flagella arrangement describes the presence of a tuft of flagella at one end of a bacterium?
Which flagella arrangement describes the presence of a tuft of flagella at one end of a bacterium?
What component connects the filament of a flagellum to its basal body?
What component connects the filament of a flagellum to its basal body?
What type of flagellar arrangement has flagella all over the cell surface?
What type of flagellar arrangement has flagella all over the cell surface?
In which type of bacteria are axial filaments mainly found?
In which type of bacteria are axial filaments mainly found?
Which type of pili is primarily involved in attachment and colonization?
Which type of pili is primarily involved in attachment and colonization?
What is the typical length range of a flagellum?
What is the typical length range of a flagellum?
Which of the following statements about axial filaments is incorrect?
Which of the following statements about axial filaments is incorrect?
What defines a bacterium with atrichous flagella?
What defines a bacterium with atrichous flagella?
Which component of the flagellum is predominantly located within the cell membrane?
Which component of the flagellum is predominantly located within the cell membrane?
Which characteristic is common to both pili and fimbriae?
Which characteristic is common to both pili and fimbriae?
Flashcards
What is the Glycocalyx?
What is the Glycocalyx?
Outermost layer that surrounds some bacterial cells. Provides protection, helps bacteria attach to surfaces, and can evade immune system.
What is the Bacterial Cell Wall?
What is the Bacterial Cell Wall?
A rigid layer that gives bacteria their shape and protects them from osmotic pressure changes. It is made up of peptidoglycan.
What is the Cell Membrane?
What is the Cell Membrane?
A thin, selectively permeable membrane that controls the movement of substances into and out of the cell.
What is the Cytoplasm?
What is the Cytoplasm?
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What are Ribosomes?
What are Ribosomes?
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What is the Nuclear Material?
What is the Nuclear Material?
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What are Flagella?
What are Flagella?
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What are Pili and Fimbriae?
What are Pili and Fimbriae?
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What is a Spore?
What is a Spore?
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What are Plasmids?
What are Plasmids?
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What is Glycocalyx?
What is Glycocalyx?
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What is a Capsule?
What is a Capsule?
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What is a Slime Layer?
What is a Slime Layer?
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How does Glycocalyx contribute to Virulence?
How does Glycocalyx contribute to Virulence?
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How does Glycocalyx aid in Attachment?
How does Glycocalyx aid in Attachment?
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How does Glycocalyx provide Resistance to Drying?
How does Glycocalyx provide Resistance to Drying?
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What role does Glycocalyx play in Biofilm formation?
What role does Glycocalyx play in Biofilm formation?
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What does the K antigen indicate?
What does the K antigen indicate?
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What is Taxis?
What is Taxis?
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How are flagella arranged?
How are flagella arranged?
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What is the significance of flagellar arrangement?
What is the significance of flagellar arrangement?
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What are the parts of a flagellum?
What are the parts of a flagellum?
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What are axial filaments?
What are axial filaments?
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What is the filament of a flagellum made of?
What is the filament of a flagellum made of?
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What is the function of flagella?
What is the function of flagella?
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What is the function of the basal body of a flagellum?
What is the function of the basal body of a flagellum?
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What is the function of ordinary pili (fimbriae)?
What is the function of ordinary pili (fimbriae)?
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Study Notes
Pathogenic Microorganisms 222 PHARM
- Course name: Pathogenic Microorganisms
- Course code: 222 PHARM
- University: King Saud University
Bacterial Structures and Function
- Objectives:
- Detail microscopic bacterial structure (intra cytoplasmic structure).
- Detail bacterial cell wall structure.
- Detail surface structures (outside cell wall).
- Distinguish between gram-positive and gram-negative cell walls.
- Explain bacterial movement.
- Explain spore formation.
Bacterial Structure (Images and diagrams)
- Diagrams show structures like:
- Capsule
- Peptidoglycan layer
- Inclusion body
- Cytoplasmic membrane
- Ribosome
- Surface proteins
- Flagellum
- Chromosome
- Outer membrane
- Pili
- Porin proteins
- Periplasmic space
- Division septum (Gram positive and negative)
Structure of Eubacteria
- Two categories of structures: essential and additional (non-essential)
- I. Essential structures:
- Cell wall
- Cell membrane
- Cytoplasm
- Ribosome
- Nuclear material
- II. Additional structures (non-essential):
- Capsule
- Slime layer
- Flagella
- Pili/fimbriae
- Inclusions
- Spores
- Plasmids
- I. Essential structures:
Structure of Eubacteria - Another View
-
- External structure (extracytoplasmic):
- Glycocalyx
- Flagella
- Pili
- Fimbriae
-
- Cell envelope
- Outer membrane
- Cell wall
- Cell membrane
-
- Internal structure (intra cytoplasmic)
- Cytoplasm
- Ribosome
- Nuclear material
- Inclusions
- Spores
- Plasmids
Glycocalyx
- Capsule or slime layer.
- Description of glycocalyx.
- Surround whole bacterial cell.
- Gelatinous, sticky, high molecular weight.
- Usually polysaccharide, but sometimes polypeptide (unique).
- Capsule: thick, organized, rigid, firmly attached to cell wall.
- Slime Layer: thin, unorganized, loosely attached to cell wall.
- Examples of bacteria with capsule: S. pneumoniae, H. influenzae and N. meningitidis.
- Examples of bacteria with slime layer: S. epidermidis and Pseudomonas aeruginosa.
- Colonies with glycocalyx are smooth or mucoid.
Glycocalyx Function
- Virulence factor
- Prevents phagocytosis
- Aids attachment
- Resistance to drying
- Immunogenic
- K antigen (used for identification) e.g. E. coli K1
- Important in biofilm formation e.g. Streptococcus mutans on tooth enamel.
Extracellular Polymeric Substances (EPS)
- Component of biofilm (aggregation of microbes).
- Microorganisms within biofilms are resistant to antibiotics.
- Biofilm formation makes infections hard to treat.
Surface Appendages (Filamentous)
- Flagella and pili
- Pili: hair-like
- Flagella: whip-like
- Flagella on gram positive and negative bacteria
- Flagella mainly on bacilli, rarely on cocci
- Protein subunits form cylindrical structure with hollow core.
Flagella (H antigen) Function
- Motility (organ of locomotion)
- Propel cell by beating in a whip-like motion
- Movement towards or away from stimuli (taxis)
- Chemotaxis (chemicals)
- Phototaxis (light)
- Aid in pathogenesis
- Useful in identification, e.g., E. coli O157:H7.
Flagella Arrangement
- Location on the cell varies by species.
- Polar region(s) (one or both ends).
- Lateral regions (sides of bacterium)
- Atrichous (no flagella)
- Monotrichous (single flagellum)
- Lophotrichous (tuft of flagella)
- Amphitrichous (one flagellum at each end)
- Amphilophotrichous (tuft of flagella at each end)
- Peritrichous (flagella all over the cell).
Flagella Structure
- Long filament
- External to cell surface
- Chains of flagellin protein
- ~10 µm length and ~10-20 nm diameter
- Hook
- Wider diameter, curved tubular structure
- Connects basal body to filament
- Basal body
- Only structure within cell membrane
- Connected to the hook
- Rod-shaped structure with microtubule rings
Axial Filaments (Endoflagella)
- In spirochetes
- Unique spinning motion
- 6 thin endoflagella between outer membrane and peptidoglycan layer
- Anchored at one end of cell
- Rotation causes cell to move
Pili and Fimbriae
- Usually interchangeable terms
- Shorter, rigid, straighter, thinner than flagella
- Composed of protein called pilin.
- Not for motility. Found on non-motile and motile species.
- Two types of pili:
- Ordinary pili (fimbriae) - attachment (colonization). Loss of pili = avirulent.
- Sex pili (F pili) - conjugation.
Pili (sex pili) vs. Fimbriae (short pili)
| Item | Pili (sex pili) | Fimbriae (short pili) |
|---|---|---|
| Presence | Gram negative | Gram positive & negative |
| Size | Longer & thicker | Shorter & thinner |
| Number/cell | 1-4/cell | 200-400/cell |
| Rigidity | Very rigid structure | Less rigid structure |
| Encoded on | Plasmid | Chromosome |
| Function | Conjugation | Attachment (colonization) |
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