Bacteroidota

Tiny living things live in many places. They live in soil and sea water. Many live on the skin of animals. Some live inside your belly.

These tiny things help you stay healthy. They turn food into things your body needs. They can break down proteins and sugars.

They are even in babies. Milk helps them grow inside a baby. They live in lakes and rivers too. They can even live in very salty water. These tiny things are everywhere on Earth.

Bacteroidota is a large group of bacteria. These tiny life forms live in many places. You can find them in soil and sea water. They also live in the guts of animals.

Many of these bacteria help us stay healthy. They live in our intestines. They break down complex sugars and proteins. This helps our bodies get what they need from food. In babies, milk helps these bacteria grow.

Some of these bacteria live in the mouth. Others live in the soil. Some can even live in very salty water.

Scientists study these bacteria to learn about health. For example, they look at how these bacteria change in people. Some studies link them to things like obesity. Other studies look at how they relate to diabetes. Scientists also use special proteins to group these bacteria together. They found 27 proteins that most of them share. These proteins act like markers to help us identify them.

Bacteroidota is a huge group of tiny living things called bacteria. These bacteria are found almost everywhere on our planet. You can find them in soil, river water, and even the deep ocean. They also live on the skin of animals. Many of them live inside the guts of animals, including humans. In our intestines, they are very common. They can reach numbers as high as 10^11 cells in just one gram of material. These bacteria are important because they help our bodies work. They break down complex sugars and proteins from the food we eat. Without them, our bodies might not get all the energy we need. Even tiny babies have these bacteria in their guts. Mother's milk contains special sugars that help these bacteria grow.

These bacteria work in many different ways to stay alive. Some species are saccharolytic, which means they eat sugars. Others are asaccharolytic, meaning they do not rely on sugar. Some can even break down tough plant parts like starch and cellulose. They also use proteases, which are tools that help them break down proteins. This process helps turn food into things the body can use. Some of these bacteria even make acids like acetic acid. These acids are left over after the bacteria finish eating. Some members of this group even have bright colors. They can look yellow-orange or pink-red because of special pigments.

Scientists have been studying these bacteria for a long time. In 1898, a scientist isolated a species called Bacteroides fragilis. This was the first time a member of this group was found in a human. It was linked to a medical problem called appendicitis. Since then, we have learned much more about different groups. For example, we know about Porphyromonas, which lives in the human mouth. We also know about Bacteroides, which live in the waste of warm-blooded animals. The way we name these bacteria has changed as we learn more.

There are many different types of Bacteroidota to learn about. Some live in the soil, like the classes Flavobacteriales and Sphingobacteriales. Others live in very salty water, like the genus Salinibacter. These salty-water bacteria live in places called hypersaline lakes. They are so similar to other life forms that they were hard to identify at first. Scientists also use special proteins to study them. They found 27 proteins that most Bacteroidota share. These proteins act like markers to help scientists tell them apart. These markers are very helpful for researchers today.

Bacteroidota are closely linked to other groups of bacteria. They are part of a larger group called the FCB superphylum. This group includes the phyla Chlorobiota and Fibrobacterota. Scientists know they are related because they share certain proteins. They also share something called a conserved signature indel. This is a tiny change in their proteins that stays the same across different species. This evidence shows they all likely came from one common ancestor. Studying these links helps us understand how all life on Earth is connected.

Bacteroidota is a massive phylum of bacteria that plays a vital role in Earth's ecosystems. These organisms are Gram-negative, meaning they have a specific cell wall structure. They are also nonsporeforming, so they do not create tough protective shells to survive harsh conditions. Most species are rod-shaped and can live in environments without oxygen, known as anaerobic, or with oxygen, known as aerobic. They are found in many places, including soil, sediments, and seawater. Many of these bacteria live in the guts of animals, where they are highly abundant. In the intestines, they can reach concentrations of 10^11 cells per gram of material.

Inside the gastrointestinal tract, Bacteroidota perform essential metabolic conversions for their hosts. They are highly adjusted to this environment and are considered a stable part of the gut microflora. These bacteria are often saccharolytic, which means they break down complex sugar polymers like starch, cellulose, xylans, and pectins. Other species are asaccharolytic, meaning they do not rely on sugar for energy. Some also use proteases, which are enzymes, to perform proteolytic activity to degrade proteins. Through these processes, they produce major end-products like succinic acid, acetic acid, and sometimes propionic acid. This metabolic work helps provide nutrients that the host animal needs to survive.

Bacteroidota are categorized into different classes based on where they live and how they behave. The class Bacteroidia is the most well-studied group. It includes the genus Bacteroides, which is common in the feces of warm-blooded animals, and Porphyromonas, which lives in the human oral cavity. Other classes, such as Flavobacteriales and Sphingobacteriales, consist of typical soil bacteria. These soil-dwelling types are only occasionally found in the human gut. However, some specific types like Capnocytophaga and Sphingobacterium can be found in the human mouth. This shows how the phylum is divided into many specialized groups.

Scientific understanding of this group has evolved significantly since the late 19th century. In 1898, the species Bacteroides fragilis was the first member of this group isolated as a human pathogen. It was linked to clinical cases of appendicitis. For a long time, scientists believed most Gram-negative gut bacteria belonged to the genus Bacteroides. However, recent research has led to many species undergoing reclassification. Today, most gastrointestinal Bacteroidota belong to families like Bacteroidaceae, Prevotellaceae, Rikenellaceae, and Porphyromonadaceae.

These bacteria also have unique physical traits and specialized habitats. Many members of the genera Flexibacter and Cytophaga appear yellow-orange or pink-red. This color comes from pigments called flexirubins, or sometimes carotenoids in marine species. In extreme environments, the genus Salinibacter lives in hypersaline lakes. These bacteria live in salt-saturated brines and are so similar to halophilic Archaea that they were difficult to identify for a long time. This shows the incredible diversity of how Bacteroidota can adapt to different chemical conditions.

Modern science uses genomics to study the deep connections between these organisms. Researchers have identified 27 proteins that serve as molecular markers for the phylum. One protein is found in every sequenced Bacteroidota species. Other proteins are missing in certain groups, like the genus Bacteroides, likely due to selective gene loss. Scientists also look for a conserved signature indel, which is a specific three-amino-acid deletion in the ClpB chaperone protein. These genetic signatures help scientists map the history of the bacteria.

Bacteroidota are part of a much larger evolutionary group known as the FCB superphylum. This group includes the phyla Chlorobiota and Fibrobacterota. Phylogenetic trees, which show evolutionary relationships, show that these three phyla branch very closely together. They share unique proteins and specific signature indels in proteins like RpoC. These shared traits provide compelling evidence that they all descended from a single common ancestor. This connection links many different types of bacteria across the tree of life.