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 be special kinds of life that need sulfur to survive, but newer research shows they might actually be the most common archaea in the ocean. At first, scientists separated 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 helped show they are different, even though a few similar archaea were later found to have histones.

Until 2005, all Thermoproteota that scientists could grow in labs needed very hot temperatures to live, some even growing at temperatures as high as 113 °C. 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. New discoveries also show that some Thermoproteota can make a gas called methane, which is important for understanding life in very hot places.

The name "eocyte" used to describe Thermoproteota has changed over time and now refers to either Thermoproteota or another group called TACK.

Sulfolobus

One well-studied member of the Crenarchaeota is Sulfolobus solfataricus. This tiny creature was first found in naturally heated sulfuric springs in Italy. It can live in very 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 all around the world. Unlike most heat-loving microbes that need no oxygen to live, Sulfolobus can use oxygen and gets its energy from organic sources like sugars. This makes it easier for scientists to grow in labs compared to microbes that need no oxygen, 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 certain tiny organisms, they form special connections that help them share pieces of their DNA with each other. This sharing makes it easier for them to fix any damage caused by the ultraviolet light and keep their DNA healthy.

Scientists think this process of sharing DNA is like a very simple form of interaction that helps these tiny organisms stay strong.

Marine species

Since 1992, scientists have found genes from Thermoproteota in the ocean. These tiny organisms are thought to be very common in the sea and play a big role in turning carbon into other important substances. We also know they can live in soil and freshwater, showing up almost everywhere.

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 exploring how tiny living things called crenarchaea and eukaryotes might be connected. Studies from 2008 and 2017 suggest that eukaryotes may have come from organisms similar to the Thermoproteota. Another group called asgards is also considered a possible ancestor. This idea is related 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 studied.

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