Archaea and bacteria are both prokaryotes, but differ in biochemistry, genetic structure, cell membranes, and environments. Archaea can survive extreme conditions and have unique ribosomes and RNA polymerase. They were discovered in the 1970s and are one of three domains of life.
Archaea and bacteria are both single-celled microorganisms known as prokaryotes, but this is one of the few things they have in common. While both look vaguely similar when viewed under a microscope, each represents an entirely different group of creatures. In fact, archaea differ from bacteria as much as humans, in terms of biochemistry and genetic structure. Archaea and bacteria have different cell membranes and cell structures, and archaea are found in extreme environments where most bacteria could not survive.
The cell walls of bacteria contain a substance known as peptidoglycan, while the cell walls of archaea do not. Archaea and bacteria also differ because the cell membranes of archaea have a unique structure and do not contain the same lipids, or fats, found in the cell membranes of other organisms. Archaeal membranes contain a substance known as isoprene, which forms heat-resistant structures and is not present in bacterial cell membranes.
Within archaea, protein synthesis molecules called ribosomes are different from those found in bacteria and are closer to the ribosomes found in eukaryotic cells. Eukaryotic cells are found in humans, animals, plants, fungi and protozoa. The enzyme RNA polymerase, which enables the production of RNA in cells, has a simple form in bacteria. In archaea, it is more complex.
Archaea and bacteria differ in the environments in which they can survive. While bacteria live almost everywhere, only archaea are able to survive in extreme conditions, although they are found elsewhere as well. Some archaea, known as thermophiles, live in very hot environments such as the vents of volcanoes. Others are able to withstand extremely acidic or alkaline conditions or locations without oxygen. Some highly salty places, such as the Dead Sea, are too dry for most organisms, but some archaea known as halophiles can live there.
Unlike bacteria, which were discovered in the 1600s, archaea only came into existence in the 1970s, when some prokaryotes were found to have a different genetic makeup from bacteria. It was noted that these were also prokaryotes living in extreme environments, and a new group of life forms was recognised. This meant that life could be divided into three main groups, or domains, known as eukaryotes, archaea and bacteria. Some experts believe that archaea’s ability to live in inhospitable conditions may be due to the fact that they are an ancient group of microbes, originally adapted to a time when the earth was warmer and had a methane-rich atmosphere and ammonia.
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