Archaeal Cell Biology Overview

Study Notes

Archaeal Cell Structure

Archaeal cell walls do not contain peptidoglycan.
Variability in structure includes two main types: S-layer and pseudo-cell wall.
Pseudo-cell walls are composed of pseudomurein, located between the plasma membrane and S-layer.

Archaeal Plasma Membranes

Composed of branched isoprene chains instead of fatty acids.
Features ether linkages, enhancing resistance to heat and pH fluctuations.
Some archaeal membranes exist as monolayers rather than the typical bilayer structure.

Cell Interior Components

The nucleoid region contains the genetic material.
70S ribosomes are present within the cytoplasm.
Inclusions may be found, along with cytoskeletal proteins that aid in structure and function.

Archaeal Appendages

Pili (singular: pilus) and flagella are key types of appendages found in archaeal cells.

Hami

Hami are specialized, stable protein structures resembling grappling hooks, aiding in surface attachment and biofilm formation.
Hundreds of hami can extend beyond the S-layer for increased adhesion.

Cannulae

Cannulae are hollow, tube-like structures made from glycoprotein subunits arranged in a helix.
They are notably wider than flagella, can reach lengths of up to 40 mm, and are specific to thermophilic archaea.
Cannulae are formed during cell division.

Comparative Aspects of Archaeal and Bacterial Structures

Cell Envelope: Archaeal cell walls predominantly consist of an S-layer made of glycoproteins, while bacteria typically have peptidoglycan.
Some archaeal membranes are monolayers, contrasting with bacterial bilayers.

Flagella

Both archaeal and bacterial flagella are powered by proton motive force, but structural and compositional differences exist.
Archaeal and bacterial flagella are made of flagellin proteins, but their assembly mechanisms vary.

Function of Hami

Hami facilitate cell motility and adhesion to surfaces, crucial for biofilm formation.
These structures are thinner in archaea compared to bacterial counterparts and maintain a grappling hook-like design.

Key Corrections about Archaeal Cell Envelopes

Archaea do not have cell walls made of peptidoglycan, and hopanoids are typically not found in archaeal membranes.
The prevalent archaeal cell wall type is an S-layer, with some cells exhibiting monolayer membranes.

Flagellar Motion

Flagellar movement in both domains is driven by proton motive force.
Flagella in both archaea and bacteria are constructed by adding protein subunits to the filament's growing tip.
Although both types share a basal body structure, significant differences remain in their overall configurations.

Description

Explore the fascinating world of archaeal cell structure, including unique features such as cell walls, plasma membranes, and appendages. This quiz covers the composition and function of key cellular components found in archaea, providing insights into their resilience and evolutionary significance.