Bacterial Physiology: Week 2 Overview

Bacterial Cell Components

• Prokaryotic cells consist of various structures that aid in functionality and protection.
• Cytoplasmic structures include the nucleoid, plasmids, ribosomes, and inclusions.

Cell Envelope Structure

• The cell envelope protects the cell interior and is crucial for maintaining cellular integrity.
• In Gram-negative bacteria, the cell envelope features periplasmic space and an outer membrane.

Plasma Membrane

• Composed of a phospholipid bilayer embedded with proteins, it encloses the cytoplasm and regulates substance entry.

Cell Wall

• Made primarily of peptidoglycan, it maintains cell shape and protects against osmotic pressure.
• Key components of peptidoglycan include:
  • N-acetylglucosamine (NAG)
  • N-acetylmuramic acid (NAM)
  • Side chain amino acids
  • Cross-bridge amino acids

Periplasmic Space

• Located between the inner and outer membranes in Gram-negative bacteria, it contains a gel-like matrix with nutrients and enzymes.

Outer Membrane

• Acts as an initial barrier against antibiotics and protects from phagocytosis.
• Composed of lipopolysaccharides (LPS), lipoproteins, and phospholipids, it is critical for bacterial defense.
• Contains porins that facilitate nutrient and solute passage.

Ribosomes

• Sites for protein synthesis, composed of ribosomal RNA and proteins.

Inclusions

• Storage structures, including:
  • Metachromatic granules: reserves of polyphosphates important for ATP synthesis.
  • Polysaccharide granules: consist of glycogen and starch, serving as energy reserves.

Spores

• Highly durable, dehydrated cells with thick walls that resist extreme environmental conditions including heat and disinfectants.

Flagella Characteristics

• Peritrichous flagella: distributed over the entire cell, exemplified by Escherichia coli.

Comparative Cell Envelope Characteristics

• Gram-positive bacteria:
  • Thick peptidoglycan layer (multilayered)
  • Teichoic acids present
  • No periplasmic space or outer membrane
  • Virtually no LPS content
  • High lipid/lipoprotein content
• Gram-negative bacteria:
  • Thin (single layered) peptidoglycan layer
  • Lacks teichoic acids
  • Present periplasmic space and outer membrane
  • High LPS content
  • Low lipid/lipoprotein content due to the outer membrane

Fimbriae and Pili

• Hairlike appendages that aid in attachment to surfaces and other cells, enhancing bacterial virulence.

This quiz covers key topics from Week 2 of Bacterial Physiology, focusing on aspects like metabolism, genetics, and growth. It includes details on prokaryotic cell structures such as the plasma membrane and cell envelope in gram-negative bacteria.