Characteristics and Features of Archaea

Questions and Answers

How are Archaea like Eukarya?

Genes encoding protein (replication, transcription, translation)

How are Archaea like Bacteria?

Genes for metabolism

What elements are unique to Archaea?

Unique rRNA gene structure, capable of methanogenesis

Where are Archaea normally found?

Hypersaline, pH extremes, high temperature habitats Signup and view all the answers

What kind of shapes do Archaea show?

Same as bacteria, though no spirochete-like Archaea have been observed. Unique shapes include branched and flat. Signup and view all the answers

What is different about the cell membrane of Archaea?

Lipids are unique and strange, monolipid Signup and view all the answers

Do Archaeal cell walls have peptidoglycan?

False Signup and view all the answers

Do Archaeal cells always have cell walls? What do they use instead?

Usually not, S layer Signup and view all the answers

Do Archaeal cells have slime layers and capsules?

False Signup and view all the answers

How are the lipids in Archaea unique?

Hydrocarbon tails are derived from isoprene units and have ether linkages. Signup and view all the answers

What is pseudomurein?

A peptidoglycan-like molecule present in some 'cell walls' of bacteria Signup and view all the answers

Do Archaea have inclusions?

True Signup and view all the answers

What size are the ribosomes in Archaea?

Same as bacteria Signup and view all the answers

What group are Archaeal ribosomes more similar to, Bacteria or Eukarya?

Eukarya Signup and view all the answers

What shape is Archaeal DNA?

Circular chromosomes Signup and view all the answers

How is Archaeal DNA compacted?

Histones and supercoiling Signup and view all the answers

What is different about the nucleoid compared to Bacteria?

Irregularly shaped and not membrane bound Signup and view all the answers

What two external structures are unique to Archaea?

Cannulae, Hami Signup and view all the answers

What are cannulae?

Hollow, tubelike structures observed on the surface of thermophilic Archaea belonging to the genus Pyrodictium; function is unknown. Signup and view all the answers

What are Hami?

Look like hooks, might aid in attaching to surfaces. Signup and view all the answers

How are bacterial cell envelopes and archaeal cell envelopes different?

Archaeal have isoprenoid hydrocarbons with the bonds, and some are monolayers; Archaea have no peptidoglycan in their cell walls; some cell walls are only S-Layers. Signup and view all the answers

How are the ribosomes in Archaeal cells and Bacterial cells different?

Although the same size, nucleotide sequences are distinguishable. Signup and view all the answers

How is the nucleoid different in Archaea compared to Bacteria?

Archaea have histones sometimes, same circular DNA. Signup and view all the answers

Study Notes

Characteristics of Archaea

Archaea share genetic similarities with eukarya, especially in genes responsible for protein synthesis (replication, transcription, translation).
Similar to bacteria, Archaea possess genes essential for metabolic processes.

Unique Features of Archaea

Possess a distinctive rRNA gene structure not found in other domains.
Capable of methanogenesis, a process of generating methane.

Habitat and Environment

Typically thrive in extreme conditions: hypersaline environments, high acidity or alkalinity, and elevated temperatures.

Morphology

Exhibit various shapes similar to bacteria, with unique forms such as branched and flat structures; not observed as spirochetes.

Cell Structures

Archaea have unique cell membranes composed of monolipid structures, differing significantly from typical bacterial lipid compositions.
Lack peptidoglycan in their cell walls, using an S-layer instead for structural integrity.
Inclusions are present within archael cells.

Cell Wall Composition

Most archaea do not possess cell walls; when present, they are primarily composed of S-layer proteins.
Rarely exhibit slime layers or capsules, distinguishing them from many bacteria.

Lipid Characteristics

The lipids in archaea feature hydrocarbon tails derived from isoprene units with ether linkages, setting them apart from other organisms.

DNA Organization

Archaea possess circular DNA, similar to bacteria, but their nucleoid is irregularly shaped and not membrane-bound.
DNA is compacted with histones and supercoiling, offering a sophisticated level of organization.

Ribosomes and Genetic Relationships

Archaea and bacteria possess ribosomes of similar size, but archaeal ribosomes are more closely related to those of eukarya based on nucleotide sequences.

External Structures

Unique external structures include cannulae, hollow tubelike projections from thermophilic archaea whose function remains unclear.
Hami resemble hooks and may facilitate adherence to surfaces.

Differences from Bacterial Structures

Archaea's cell envelopes contain isoprenol hydrocarbons and may form monolayers, in contrast to the bilayer structure of bacterial cell membranes.
Absence of peptidoglycan in archaea cell walls, with alternative S-layers often providing structural support.

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Description

Explore the fascinating world of Archaea, unique microorganisms that share some similarities with both bacteria and eukarya. This quiz covers their genetic traits, metabolic processes, and distinctive features such as their unique cell structure and extreme environmental habitats. Test your knowledge on their morphology and cell structures as well.