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Questions and Answers
Which bacterial cell envelope component is responsible for host mimicry, antigenic variation, and phase variation?
In terms of technique, which stain uses heat to help penetrate the mycolic acid layer of acid-fast bacteria?
Which bacterial group has a cell envelope structure characterized by the absence of a true cell wall and sterols?
Which bacterial group is medically relevant and includes genera categorized by the presence of mycolic acids in their cell envelope?
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What is the general role of penicillin-binding proteins (PBPs) in bacterial cells?
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Which bacterial structure is highly conserved among genera and often used for differentiating bacterial strains based on serotyping?
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Which of the following bacteria are Gram-negative and have flagella between the peptidoglycan and outer membrane?
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Which of the following antibiotics prevents recycling of bactoprenol-PP and affects the synthesis of several cell-surface polymers?
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Which of the following bacteria are Gram-negative and have an outer membrane with LPS but no peptidoglycan?
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Which antibiotic inhibits the first step to build peptidoglycan monomer?
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Which genus has a very resistant cell wall permitting specific staining techniques with very strong decolorization?
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Which antibiotic prevents the transfer of NAM-P to Und-P?
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Which bacteria have a soft, pleomorphic structure and lack a cell wall?
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Which antibiotic inhibits alanine racemase and D-ala-D-ala synthetase?
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Which of the following antibiotics binds the stem peptide D-ala-D-ala, preventing transpeptidation and transglycosylation?
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Which bacteria are best visualized using dark field microscopy or fluorescence microscopy due to their very thin structure that is not visible by light microscopy?
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Which antibiotics inhibit transpeptidases, leading to weak new peptidoglycan and eventual cell lysis?
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Which of the following bacteria has an acid-fast cell wall resistance to chemicals found in phagolysosomes and some antibiotics?
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Which component of the bacterial cell envelope is responsible for host mimicry and antigenic variation?
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What is the main function of capsules in bacterial cells?
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In which part of the bacterial cell envelope do you find proteins within a phospholipid bilayer, with no sterols except in mycoplasmas?
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Which structure in Gram-positive bacteria helps resist deformation upon desiccation?
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What is the function of periplasm in bacterial cells?
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Which component of the bacterial outer membrane forms a selective barrier and provides protection against lysis?
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What is the main function of slime in bacterial cells?
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What structure in bacterial cells is referred to as a PAMP (Pathogen Associated Molecular Pattern)?
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What is the general role of teichoic and lipoteichoic acids in Gram-positive bacteria?
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What is the function of pili/fimbriae in bacterial cells?
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Study Notes
- Dr. Sean D. Reid's learning objectives cover the organization and components of a bacterial cell.
- A bacterial cell has an outer membrane, plasma membrane, and peptidoglycan (PG) as part of its cell envelope.
- The plasma membrane is a phospholipid bilayer with proteins, no sterols except in mycoplasmas, and acts as a barrier against aqueous ions.
- Peptidoglycan, or murein, is a 3D multilayered net made of alternating GlcNAc and MurNAc, with a peptide tail on MurNAc, and forms the cell wall.
- Outer membranes, present in Gram-negatives and Chlamydiaceae, have a lipopolysaccharide (LPS) outer leaflet and a phospholipid inner leaflet.
- The periplasm, the space between the plasma membrane and the PG/outer membrane, is a viscous solution of proteins and solutes that protects against osmotic lysis.
- Some bacteria, like mollicutes and Chlamydiaceae, don't have a peptidoglycan layer.
- The biosynthesis of peptidoglycan involves transglycosylases and transpeptidases (PBPs) that create the 3D cell wall structure, and bactoprenol, which plays a role in the transfer of peptidoglycan precursors.
- The outer membrane contains porins (OMPs) and plays a role in selective barrier protection, while lipoteichoic acids and teichoic acids are important in regulation and adhesion.
- Capsules and slime, structures made of long chains of sugars or amino acids, serve antiphagocytic functions and can vary in structure and function between different species.
- Pili/fimbriae are short protein strands on the cell surface that serve functions like adhesion, twitching motility, and conjugation.
- Flagella, helical protein filaments anchored in the membrane, provide motility for many bacteria.
- Gram-positive bacteria have a thick layer of PG and teichoic acids, while Gram-negative bacteria have a thin layer of PG and an outer membrane with LPS.
- Acid-fast bacteria, like Mycobacterins, have a more complex cell wall with mycolic acids and lipoarabinomannan, making them resistant to certain staining techniques.
- Mollicutes, extracellular bacteria without a cell wall, have a membrane containing sterols acquired from the host.
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