Life Science

The similarities and differences between organisms in the domains of archaea and bacteria are, archaea generally have the same shape, size and appearance as bacteria, archaea and bacteria multiply by binary fission and move primarily by means of flagella. These similarities make it difficult to visually identify archaea and bacteria and archaea are more phylo-genetically similar to eukarya than bacteria is to either of them. Archaea are also the oldest organisms that have been discovered. They range in from 0.1 micrometers (μm) to over 15 μm in diameter and occur in various shapes including spheres, rods, spirals, plates, lobed cells, needle-like filaments and rectangular rods. The domain archaea consists of three main branches, which microbiologists call kingdoms, which are:

1. Korarchaeota: only known by fragments of their DNA found in boiling hot springs; reside on some of the lowest branches on the tree of life and may be similar to the most recent ancestor of all surviving life forms on earth.

2. Crenarchaeota: includes thermophiles (heat lovers) that use sulfur as an electron acceptor in their energy metabolism rather than oxygen (as most species do).

3. Euryarchaeota: includes methanogens, methane generating organisms and extreme salt-loving organisms or halophiles.

While the archaea are a diverse and ancient domain of life, species in the domain bacteria rival their variety and are much better known. Archaea cell walls lack peptidoglycan, which is present in bacteria. In most archaea the wall is assembled from surface-layer proteins, which form a rigid array of protein molecules to cover the outside of the cell, similar to a chainmail. Archaea acquire energy from various sources such as sugars, ammonia, metal ions, hydrogen gas, sunlight and carbon, while producing nitrogen, methane, sulphuric acid, etc. as a byproduct. Archaea played and continues to play a huge part in the carbon cycle and nitrogen cycle on the earth.

Bacteria are the largest domain of the prokaryotic microorganisms, they are believed to be among the first life forms that appeared on the earth and are present on most habitats, including residing inside the bodies of humans, animals and plants. Biologists have determined that there