Some tiny living things are special. They live in very hot places. Some use light to make food. They are very small. You cannot see them. They help the world work. Can you find them?
There are tiny living things called Chloroflexota. They are very small. You cannot see them with your eyes.
Some of them love the heat. They grow well in hot places. They also use the sun to make food.
Other kinds do not use light. They use special things in the water to live. This helps them stay alive.
These tiny things have one skin. This skin holds them together. They are very different from other tiny things.
Scientists keep finding new kinds. They learn more about them every day. It is a big, tiny world!
Chloroflexota is a large group of bacteria. These tiny living things are very diverse. They live in many different ways.
Some members are aerobic thermophiles. This means they use oxygen to live. They also grow well in very hot places. Other members use light to make food. We call these anoxygenic phototrophs. They are often green non-sulfur bacteria.
Some members do not use light or oxygen. They use halogenated organics to live. These are special chemicals. This group of bacteria is called anaerobic halorespirers.
Most bacteria have two skins. Chloroflexota are monoderms. This means they have only one cell membrane. They do not have an outer membrane. Even so, they often stain gram-negative. This is a way scientists identify them.
Scientists are still learning about them. New species are found all the time. This helps us build new classes. A class is a way to group related bacteria. Some scientists think the group is still changing. They study the tiny parts of their cells to find out.
Chloroflexota is a large group of bacteria with many different ways of living. These tiny organisms can be found in many environments. Some members are aerobic thermophiles. This means they use oxygen and grow well in high temperatures. Other members are anoxygenic phototrophs. These are often called green non-sulfur bacteria because they use light for photosynthesis. Some members are anaerobic halorespirers. These bacteria use halogenated organics to live. This includes things like toxic chlorinated ethenes and polychlorinated biphenyls.
Understanding how these bacteria are built helps scientists group them. Most members of Chloroflexota are monoderms. A monoderm is a bacterium with only one cell membrane. They do not have an outer membrane. Even though they have one membrane, they mostly stain gram-negative. This is a way scientists identify bacteria using special dyes. Many other well-studied bacteria are diderms. Diderms are bacteria that have two membranes. Other known monoderms include Firmicutes and Actinomycetota. These groups usually stain gram-positive instead.
Scientists have spent many years studying these bacteria. In 1987, Carl Woese helped start a revolution in how we group life. He used 16S ribosomal RNA sequences to divide bacteria into 11 divisions. He grouped the genera Chloroflexus, Herpetosiphon, and Thermomicrobium together. This group was called "green non-sulfur bacteria and relatives." It was later named Chloroflexi in Bergey's Manual of Systematic Bacteriology. The official name Chloroflexota was created in 2001. It comes from the Latin plural of Chloroflexus.
Since 2001, the group has grown much larger. New species are found all the time. This has led to many new classes being created. For example, Hugenholtz and Stackebrandt used the name Dehalococcoidetes in 2004. This was a placeholder name for a species described in 1997. In 2009, Moe and others fully described Dehalogenimonas lykanthroporepellens. This species shares only 90% 16S ribosomal RNA identity with others. This means they might belong to different families.
Today, scientists use many tools to study these connections. They look at large datasets of proteins to build phylogenetic trees. These trees show how different classes relate to each other. Recent analysis shows very weak support for grouping all these classes together. Some classes like Chloroflexi and Thermomicrobia do group together well. They share specific traits in their proteins and enzymes. Some scientists think the phylum should only include those two classes. The other four classes might actually be independent phyla.
The Chloroflexota are a diverse phylum of bacteria with many different ways of living. These microscopic organisms occupy many different environments on Earth. Some members are aerobic thermophiles, meaning they require oxygen and thrive in high temperatures. Other members are anoxygenic phototrophs, often called green non-sulfur bacteria, because they use light for photosynthesis. There are also anaerobic halorespirers within this group. These bacteria use halogenated organics, such as toxic chlorinated ethenes or polychlorinated biphenyls, as electron acceptors to survive.
Scientists study the structure of these bacteria to understand how they are classified. Most members of Chloroflexota are monoderms, which means they possess only one cell membrane and no outer membrane. Interestingly, despite having only one membrane, they mostly stain gram-negative during laboratory tests. This is a unique trait among bacteria. Many other well-studied phyla are diderms, which means they have two membranes and also stain gram-negative. Other known monoderms include the phyla Firmicutes and Actinomycetota, but these usually stain gram-positive instead.
The history of this group involves major shifts in how we understand life. In 1987, Carl Woese helped lead a molecular phylogeny revolution. He used 16S ribosomal RNA sequences to divide Eubacteria into 11 different divisions. He grouped the genera Chloroflexus, Herpetosiphon, and Thermomicrobium into a group called "green non-sulfur bacteria and relatives." This group was temporarily named Chloroflexi in the Bergey's Manual of Systematic Bacteriology. The official taxon name Chloroflexota was eventually created in the 2001 edition of that same manual. The name is the Latin plural of Chloroflexus, which is the type genus of the phylum.
Since 2001, the phylum has expanded significantly as new species are discovered. This growth has led to the creation of many new classes. For instance, Hugenholtz and Stackebrandt used "Dehalococcoidetes" as a placeholder name in 2004. This name followed the description of the species Dehalococcoides ethenogenes in 1997. In 2009, Moe and colleagues fully described the species Dehalogenimonas lykanthroporepellens. However, because this species shares only 90% 16S ribosomal RNA identity with others, scientists cannot yet officially place it into specific families or orders.
Modern scientists use complex tools to map the relationships within Chloroflexota. They use phylogenetic analysis to build trees based on large datasets of proteins. Recent studies have found very weak support for grouping all current classes into one single phylum. The six classes do not always form a well-supported clade in these protein-based trees. Furthermore, researchers have not identified any conserved signature indels, which are specific genetic markers, that are uniquely shared by every member of the phylum.
Despite this uncertainty, some connections remain very strong. The classes Chloroflexi and Thermomicrobia group together consistently in many studies. This grouping is supported by both standard phylogenetic methods and the identification of shared conserved signature indels. Specifically, they share traits in the 50S ribosomal protein L19 and the enzyme UDP-glucose 4-epimerase. Because of these strong links, some scientists suggest that the phylum Chloroflexi "sensu stricto" should only include these two classes.
This scientific debate changes how we view the entire group. It is possible that the other four classes—Dehalococcoidetes, Anaerolineae, Caldilineae, and Ktedonobacteria—belong elsewhere. Some researchers suggest these classes might represent one or more independent phyla. These groups branch out in the neighborhood of the Chloroflexi rather than being part of them. As technology improves, our understanding of these bacterial connections continues to evolve through new genetic data and protein analysis.
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