ARCHAEA AND OTHER EXTREMISTS TYPES OF ARCHAEA

Microbes World BETA

There are three main types of archaea: the crenarchaeota, which are characterized by their ability to tolerate extremes in temperature and acidity. The euryarchaeota, which include methane-producers and salt-lovers; and the korarchaeota, a catch-all group for archaeans about which very little is known. Among these three main types of archaea are some subtypes, which include:

Methanogens archaeans that produce methane gas as a waste product of their "digestion," or process of making energy.
Halophiles those archaeans that live in salty environments.
Thermophiles the archaeans that live at extremely hot temperatures.
Psychrophiles those that live at unusually cold temperatures.

ARCHAEA OF NOTE

Archaeoglobus fulgidus is a sulfur-reducer that can sour oil wells.

Halobacteria are salt-loving microbes that give a pink tinge to salt water evaporation ponds, the Dead Sea and salted fish.

Pyrolobus fumarii led scientists to extend the upper temperature limit for life to 113 degrees Celsius (235.4 degrees Fahrenheit).

Pyrococcus furiosis is the source of an extra-stable enzyme that can endure many cycles in the process of PCR, the method behind gene sequencing and DNA fingerprinting.

Sulfolobus acidocaldarius is used to leach copper and iron from ore.

Archaea look and act a lot like bacteria. So much so that until the late 1970s, scientists assumed they were a kind of “weird” bacteria.
Then microbiologist Carl Woese devised an ingenious method of comparing genetic information showing that they could not rightly be called bacteria at all. Their genetic recipe is too different.
So different Woese decided they deserved their own special branch on the great family tree of life, a branch he dubbed the Archaea.

HOW THEY ARE DIFFERENT

Although many archaea have tough outer cell walls, these walls contain different kinds of amino acids and sugars than those found in bacteria. Archaeal cell membranes also are chemically distinct from bacterial membranes with differing lipid structures and chemical links. This means that drugs that slow or kill bacteria by interfering with their ability to produce certain key proteins have no effect on archaea.

The archaea very much resemble bacteria, so much so that they were once thought to be a weird group of bacteria. However, by studying archaeal cells on a molecular level, scientists have now come to think that these "weird bacteria" actually are a separate category of life altogether. In fact, in some ways, archaea are more like you than they are like bacteria!

CLASSIFICATION

Archaeans are single-celled creatures that join bacteria to make up a category of life called the Prokaryotes. Prokaryotes' genetic material, or DNA, is not enclosed in a central cellular compartment called the nucleus. Bacteria and archaea are the only prokaryotes. All other life forms are Eukaryotes, creatures whose cells have nuclei. (Note: viruses are not considered true cells, so they don't fit into either of these categories.)

However, while archaeans resemble bacteria and have some genes that are similar to bacterial genes, they also contain other genes that are more like what you'd find in eukaryotes. Furthermore, they have some genes that aren't like any found in anything else.
For more details about the differences between bacteria and archaea.

EARLY ORIGINS

Archaeans are among the earliest forms of life that appeared on Earth billions of years ago. It’s now generally believed that the archaea and bacteria developed separately from a common ancestor nearly 4 billion years ago. Millions of years later, the ancestors of today's eukaryotes split off from the archaea. So historically, archaeans are more closely related to us than they are to bacteria.