Archaea

Archaebacteria are some of the world’s oldest living organisms. They’re classified as bacteria because many of their characteristics, when viewed under a microscope, resemble those of bacteria. They’re called Archaebacteria because they’re from the Archaea kingdom. They share some characteristics with eukaryotes, but they are not the same as prokaryotes. Extremophiles are organisms that are able to survive in extreme environments and thrive in them. Examples include the seafloor and volcanic vents.

Archaeal cells have characteristics that set them apart from Bacteria and Eukarya. Archaea are further classified into several phyla. Classification is difficult because most have not been isolated in a laboratory and have only been detected in environmental samples by their gene sequences.

Although some archaea have very different shapes, such as the flat, square cells of Haloquadratum walsbyi, in general, archaea and bacteria are similar in size and shape. Despite their morphological similarities to bacteria, archaea have genes and metabolic pathways that are more closely related to those of eukaryotes, particularly transcription and translation enzymes. 

Other features of archaeal biochemistry are distinctive, such as their reliance on ether lipids, including archaeols, in cell membranes. Archaea use a broader range of energy sources than eukaryotes, such as organic compounds such as sugars, ammonia, metal ions, and even hydrogen gas. 

The salt-tolerant Haloarchaea uses sunlight as an energy source, and other archaea species fix carbon, but unlike plants and cyanobacteria, no known archaea species does both. Archaea reproduce asexually through binary fission, fragmentation, or budding; archaea, in contrast to bacteria, do not produce endospores or other reproductive structures.

The first archaea discovered were extremophiles, which live in extreme environments such as hot springs and salt lakes with no other organisms. Thanks to improved molecular detection tools, Archaea has been discovered in almost every habitat, including soil, oceans, and marshlands. Archaea are common in the oceans, and plankton archaea may be one of the most numerous groups of organisms on the planet.

It was believed that prokaryotes were a single group of organisms that were classified based on their biochemistry, morphology and metabolism for much of the twentieth century, but this was not true. Microbiologists attempted to categorise microorganisms using cell wall structures, shapes, and the substances they consume. Instead, Emile Zuckerkandl and Linus Pauling proposed in 1965 that gene sequences from different prokaryotes be used to determine their relationship. The phylogenetic approach is the most widely used method today.

The name archaea is derived from the Ancient Greek word archaea, which means “ancient things,” because the first members of the domain Archaea were methanogens, whose metabolism was thought to reflect Earth’s primitive atmosphere and the organisms’ antiquity, but more organisms were discovered as new habitats were studied. Extreme halophilic and hyperthermophilic microbes were also found in Archaea. Archaea were once thought to be extremophiles found only in extreme environments such as hot springs and salt lakes, but by the end of the twentieth century, archaea had been discovered in non-extreme settings as well.

 They are now recognised as a large and diverse group of organisms that can be found in large numbers throughout nature. The application of polymerase chain reaction (PCR) to detect prokaryotes in environmental samples (such as water or soil) by multiplying their ribosomal genes resulted in a new appreciation for archaea’s importance and ubiquity. This allows for the detection and identification of organisms that have not been cultured in the lab.

Characteristics of Archaebacteria

• The cell membranes of Archaebacteria are made of lipids.
• The rigid cell wall of Archaebacteria gives them shape and support. It also prevents the cell from bursting under hypotonic conditions.
• They are obligate anaerobes, which means they can grow in the absence of oxygen, and are thus the only organisms capable of methanogenesis.
• The cell membrane of an archaebacterium is made of lipids.
• Because archaebacteria are obligate or facultative anaerobes, which means they thrive in the absence of oxygen, they are the only bacteria that can undergo methanogenesis.
• Pseudomurein is a cell wall component that protects archaebacteria from the effects of Lysozyme. Lysozyme is an enzyme produced by the host’s immune system that dissolves the cell walls of pathogenic bacteria.In hypotonic conditions, the rigid cell wall protects the archaebacteria from bursting while also providing shape and support.
• The cell walls of pathogenic bacteria can be dissolved by the enzyme lysozyme, which is released by the host’s immune system, but the cell wall of archaebacteria is made of Pseudomurein, which protects it from the lysozyme’s negative effects.
• Membrane-bound organelles found in Archaebacteria include nuclei, endoplasmic reticulum, mitochondria, lysosomes, and chloroplasts. It has a dense cytoplasm that contains all of the compounds required for nutrition and metabolism.

Types of Archaebacteria

Euryarchaeota

These organisms, unlike any other living thing on the planet, can survive in extremely alkaline conditions and have the ability to produce methane, something that no other living thing on the planet can do. Methanogens and halophiles are examples of such organisms.

Korarchaeota

They share genes with the Crenarchaeota and Euryarchaeota, which means they are related to them. According to popular belief, all three are descended from a single common ancestor. The oldest known living organism on the planet, according to legend, is this one. Hyperthermophiles are among those who suffer from this condition.

Crenarchaeota

The crenarchaeota are a type of archaea that can be found in a wide variety of environments. They are able to withstand extreme heat and high temperatures because they contain a special type of protein that allows them to function at extremely high temperatures, such as 230 degrees Celsius. They can also be found deep within the ocean’s vents and in natural hot springs. There are three types of thermophiles: thermophiles, hyperthermophiles, and thermoacidophiles.

Conclusion:

Archaebacteria are thought to be the world’s oldest living organisms, having evolved over billions of years. They are members of the kingdom Monera and are classified as bacteria because, when viewed under a microscope, they appear to be similar to bacteria. Aside from this, they are completely distinct from prokaryotes in all other respects. They do, however, share a few characteristics with eukaryotes that are worth mentioning.