Nitrososphaeria

Tiny life lives in the sea and the soil. These small things are called archaea. They can live in hot springs, too.

Some of them live in sponges. Others live in the deep, blue ocean. They can even live in garden soil.

These tiny things help the world. They turn ammonia into something else. This helps the air and the water.

They also make a special vitamin. Many other living things need this vitamin to grow. They depend on these tiny life forms.

It is amazing how much they do. They help keep our planet healthy.

Nitrososphaeria is a group of tiny life forms called archaea. Scientists first found a member of this group in 1996. It lived inside a sponge near California. Later, scientists found more members in the ocean and in hot springs. These tiny life forms are very important to our planet.

Most members of this group are ammonia oxidizers. This means they use ammonia to get power. They can do this even when food is very scarce. They also work well in places with very little oxygen. This helps them live in deep sea mud or hot springs.

These archaea help move nutrients through the world. They are part of the nitrogen cycle and the carbon cycle. They also make a special vitamin called B12. Many other tiny sea plants need this vitamin to grow. Without it, those plants could not live.

Scientists can even use these tiny life forms to study history. They have special fats in their skin. These fats change based on how warm the water is. By looking at these fats in old mud, we can learn about past temperatures.

Nitrososphaeria is a special group of tiny living things called archaea. These microscopic life forms are very important to our planet. They help move nutrients through the world in the nitrogen cycle and the carbon cycle. Most members of this group are ammonia oxidizers. This means they get energy by breaking down a substance called ammonia. They can do this even when food is very scarce in the water. They also work well in places with very little oxygen, like deep sea mud.

These tiny organisms have a very clever way of working. They use a special path to turn carbon dioxide into food. This way of making food is called the hydroxypropionate/hydroxybutyrate cycle. This cycle is actually more efficient than other known ways of making food. Because they are so efficient, they can thrive in places with very few nutrients. Some members, like Nitrosopumilus maritimus, can even use both organic and inorganic carbon. This ability to use different food sources is called mixotrophy.

Scientists have spent many years studying how to name these organisms. In 1996, biologists at the University of California found the first species. They found it living inside a sponge near Santa Barbara. They named this first species Cenarchaeum symbiosum. In 2005, researchers at the University of Washington found more in Seattle. Later, in 2008, a species was found in a Siberian hot spring. In 2014, Michaela Stieglmeier and her team found a species in garden soil in Vienna, Austria.

There are many important facts about where these archaea live. In the ocean, many live in the subphotic zone between 100 and 350 meters deep. Some even live in tropical mangrove swamps. Scientists have found two very large species there called Candidatus Giganthauma insulaporcus and Candidatus Giganthauma karukerense. These two form long shapes called filaments. Most members of this group are mesophilic, which means they like medium temperatures. However, their ancestors were likely thermophilic, meaning they loved heat.

We can learn a lot about the history of Earth from these tiny creatures. They have special fats in their skins called lipids. One specific fat is called crenarchaeol, and it is found only in Nitrososphaeria. These lipids change their shape based on how warm the water is. Scientists use these changes to study past temperatures through a method called the TEX86 proxy. They can also use these fats to study the history of the carbon cycle. This makes these tiny life forms like little time capsules from the past.

Nitrososphaeria is a distinct class of Archaea belonging to the phylum Thermoproteota. These microscopic organisms play vital roles in the Earth's biogeochemical cycles. They are primary drivers in both the nitrogen and carbon cycles. Most species in this class function as chemolithoautotrophic ammonia-oxidizers. This means they derive energy from chemical reactions involving ammonia. They also create their own food from inorganic carbon. Because of these roles, they are essential to the health of aquatic and terrestrial environments.

The way these organisms process energy is highly specialized. Most members use an ammonia oxidation pathway to gain energy. This process allows them to thrive in oligotrophic conditions, where nutrients are very scarce. They can function at much lower ammonia concentrations than ammonia-oxidizing bacteria. Furthermore, their pathway requires less oxygen to work. This allows them to dominate in low-oxygen environments like sediments or hot springs. Some species can even use urea as a substrate for nitrification. This allows them to compete with phytoplankton for resources.

Nitrososphaeria also possess a unique method for fixing carbon. They use the hydroxypropionate/hydroxybutyrate cycle to turn bicarbonate into organic matter. This specific cycle appears to have evolved independently from other Thermoproteota. Notably, this carbon-fixation pathway is more efficient than any other known aerobic autotrophic pathway. This high efficiency is why they succeed in nutrient-poor areas. Some species, such as Nitrosopumilus maritimus, exhibit mixotrophy. Mixotrophy is the ability to use both organic and inorganic carbon sources. At least two isolated strains are obligate mixotrophs, meaning they must have organic carbon to grow.

The history of discovering Nitrososphaeria is a journey of changing scientific classifications. In 1996, biologists at the University of California found Cenarchaeum symbiosum inside a sponge near Santa Barbara. Initially, researchers thought it was related to the Crenarchaeota group. However, genetic analysis of ribosomal RNA and DNA polymerase suggested otherwise. In 2005, biologists at the University of Washington identified Nitrosopumilus maritimus in Seattle. By 2008, Nitrososphaera gargensis was discovered in a Siberian hot spring. Because these organisms were so genetically different from known phyla, scientists created the phylum Thaumarchaeota in 2008.

Taxonomy continued to evolve as new data emerged. In 2014, Michaela Stieglmeier and her colleagues discovered Nitrososphaera viennensis in Austrian garden soil. They established the class Nitrososphaeria and several other taxonomic ranks. In 2021, the phylum Nitrososphaerota was formalized by Aharon Oren and George M. Garrity. However, a team of Australian scientists led by Christian Rinke and Philip Hugenholtz published a new classification. They merged Nitrososphaerota into the phylum Thermoproteota. This change demoted Nitrososphaeria from a phylum to a class level.

These organisms serve as incredible tools for understanding Earth's history. They produce unique membrane-spanning lipids called glycerol dialkyl glycerol tetraethers, or GDGTs. One specific lipid, crenarchaeol, is found only in Nitrososphaeria. These lipids act as a potential biomarker for the class. Because the structure of these lipids varies with temperature, scientists use them as a proxy. This method is known as the TEX86 paleotemperature proxy. By studying GDGTs in marine sediments, researchers can reconstruct ancient ocean temperatures. Additionally, their ability to fix CO2 allows their lipids to record past carbon cycle changes.

Beyond climate records, Nitrososphaeria support massive biological networks. They are likely the dominant producers of vitamin B12 in many environments. Vitamin B12 is critical for DNA synthesis and the citric acid cycle. Many eukaryotic phytoplankton are auxotrophic, meaning they cannot make B12 themselves. They must acquire it from the environment. Therefore, Nitrososphaeria may influence algal blooms and global atmospheric CO2 levels. In the ocean, many species live in the subphotic zone between 100 and 350 meters deep. They even exist in extreme places like tropical mangrove swamps. Some species there, like Candidatus Giganthauma, form very large filaments.