Bacterial Physiology: Week 2 Overview

Study Notes

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.

Description

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.