Thermoproteota

The Thermoproteota are a group of tiny living things called archaea that belong to a big family known as the domain Archaea. They were first thought to need sulfur to survive, but newer research shows they might be the most common archaea in the ocean.

Scientists separate Thermoproteota from other archaea by looking at special parts of their cells called rRNA sequences. Some other features, like not having certain proteins called histones, also help show they are different.

Until 2005, all Thermoproteota that scientists could grow in labs needed very hot temperatures to live. These tiny creatures don’t have a thick outer layer like some bacteria and can look different, such as rods, round balls, long strings, or strange shapes. Some Thermoproteota can also make a gas called methane.

The name "eocyte" used to describe Thermoproteota now refers to either Thermoproteota or another group called TACK.

Sulfolobus

One well-known member of the Crenarchaeota is Sulfolobus solfataricus. This tiny creature was first found in very hot, sulfuric springs in Italy. It can survive in extremely hot conditions, up to 80 °C, and in very acidic places with a pH of 2–4. After being discovered by Wolfram Zillig, a scientist who studied heat-loving microbes, similar types of this organism have been found around the world. Unlike most heat-loving microbes that do not need oxygen, Sulfolobus can use oxygen and gets its energy from organic sources like sugars. This makes it easier for scientists to grow in labs, so Sulfolobus is often used to study very heat-tolerant microbes and the many viruses that live inside them.

Recombinational repair of DNA damage

When scientists shine ultraviolet light on some tiny organisms, they can form special connections. These connections let them share pieces of their DNA with each other.

Sharing DNA helps them fix any damage from the ultraviolet light and keep their DNA healthy.

Scientists think this sharing of DNA is like a simple way for these tiny organisms to stay strong.

Marine species

Since 1992, scientists have found genes from Thermoproteota in the ocean. These tiny organisms are very common in the sea and help change carbon into other important substances. They can also live in soil and freshwater.

In 2005, the first Thermoproteota that could live in warmer water was discovered. It was named Nitrosopumilus maritimus and was found in a marine aquarium tank. This organism helps change ammonia into other useful materials.

Possible connections with eukaryotes

Main articles: Eocyte hypothesis and Two-domain system

Scientists are studying how tiny living things called crenarchaea and eukaryotes might be related. Research from 2008 and 2017 shows that eukaryotes may have come from organisms similar to the Thermoproteota. Another group called asgards is also thought to be a possible ancestor. This idea links to a theory from 1984 called the eocyte hypothesis, created by James A. Lake. While some parts of this theory are no longer accepted, the main idea is still being explored.

This topic is still being discussed, and scientists are continuing to learn more.