Archaebacteria, also known as archaea, are one of the oldest and most unique types of life on Earth. They belongs to the kingdom Monera. They form their own group and have developed separately from bacteria and eukaryotes. Archaea have special chemical, genetic, and physical features that set them apart from other living things.
Archaebacteria are special since they inhabit the most extreme environment on earth such as extreme salty areas(halophiles), hot springs(thermoacidophiles), marshy areas(methanogens), and deep ocean vents. The members of Archae shows variation in their shapes like spherical, rod, spiral, lobed, rectangular, square shaped or even irregular in shape. Certain archaea are single-celled, whereas others aggregate into colonies. Archaea bacteria are distinct from other bacteria due to their unique cell wall composition, which enables them to thrive in harsh environments.
Characteristics of Archeabacteria
- Archaebacteria are obligate anaerobes and can only survive in oxygen-free conditions.
- The cell membranes of the Archaebacteria contain lipids.
- The cell wall of archaebacteria is composed of pseudomurein. This distinctive cell wall provides protection and reduces the vulnerability to the effects of lysozyme. Lysozyme is an enzyme produced by the host to break down the cell walls of pathogenic bacteria.
- The rigid cell wall supports the cell and help in maintaining the shape. It also protects the cell from bursting under hypotonic environments.
- The archaea lack nuclei, so their genetic material floats freely in the cytoplasm.
- They are known as extremophiles, as they can thrive in a wide range of extreme environments. Some species can survive at temperatures as high as 100°C, while others can live in acidic, alkaline, or saline conditions. Some archaebacteria can withstand a pressure of more than 200atmospheres.
- Their size can vary from one-tenth of a micrometer to over 15 micrometers.
- Certain archaea are capable of movement and have flagella.
- Like all prokaryotes, archaebacteria lack membrane-bound organelles.
- They do not have nuclei, endoplasmic reticula, Golgi complexes, mitochondria, chloroplasts, or lysosomes.
- Archaebacteria contain plasmids which code for antibiotic resistance or specific enzymes.
- Archaebacteria reproduce by binary fission.
Classification Of Archaebacteria
Archaebacteria can be classified into subdivisions on the basis of phylogenetic relationship.
Euryarchaeota– They are diverse and specialized in surviving extreme alkaline conditions. This include methane-producing methanogens and halophilic bacteria, which can thrive in environments with high salt concentrations.
Crenarchaeota – They are found in a variety of environments and encompass a group of microorganisms that can grow at the highest temperatures among all living organisms. These microorganisms are microscopic and unicellular, and they thrive in temperatures ranging from 80° to 100°C. Also, many species live in acidic environments. These includes thermophiles, hyperthermophiles, and thermoacidophiles.These organisms are typically found in marine environments.
Korarchaeota – They also flourish and survive in hot environments. Korarchaeota have been found only in laboratory cultures that contain a diverse array of microorganisms. They are also known as Xenarchaeota. Furthermore, Korarchaeota have been discovered exclusively in hydrothermal environments. These includes hyperthermophiles.
Thaumarchaeota – they are ammonia-oxidizing organisms isolated from soil environments, marine environments and hot springs. They able to oxidize ammonia to nitrite aerobically.
Nanoarchaeota – They inhabit high-temperature environments, with Nanoarchaeum equitans as the sole representative. This organism is an obligate symbiont of another archaeon from the genus Ignicoccus.
