Bacteria are a large, diverse and heavily studied group of microorganisms that can be found almost everywhere on earth. They are distinct from archaea in the way they live and what they consist of.
Actinobacteria were originally soil microbes. They help decomposing organic matter. Some species in this group can produce antibiotics as a mechanism of defence against other bacteria. They are close relatives of Firmicutes. Together they represent the majority of known probiotic bacteria.
Bacteroidota break down non-digestible sugar chains for you such as plant-based dietary fiber. When they can’t get that they can switch to eating simpler sugars found in the layer of mucus that lines the inside of your gut.
Bdellovibrionota could be described as bacterial parasites. These predators break into the cells of other bacteria and feed on them from the inside.
Campylobacterota can move around easily using their flagella. They know many different ways to generate energy for themselves.
Fun fact: Species in this group can be free-living on deep-sea vents or prefer to inhabit gastrointestinal tracts of warm-blooded hosts. This is a group containing a few well-known human pathogens.
Cyanobacteria get their energy from the sun just like plants through photosynthesis and can be found almost anywhere on Earth. Strangely enough bacteria belonging to this phylum could be found in our gut too. Scientists believe that these gut-dwelling Cyanobacteria belong to a related phylum called Vampirovibrionia. This group is able to create B and K vitamins and generate energy by fermenting simple sugars, amino acids and organic acids. They produce hydrogen which other Bacteria can use to grow.
Desulfobacterota are specialists predominantly focused on using different forms of Sulfur. In our gut, this Sulfur becomes available from drinking water and dietary proteins but also from bile acids and degraded mucins (sugar + protein complexes).
Elusimicrobiota is a group that includes extremely small and slow-growing bacteria. Bacteria belonging to this group have been discovered in sewage sludge, contaminated soils, toxic wastes but also in the guts of various insects like termites and scarab beetles.
Eremiobacterota is a very recently discovered group of bacteria that prefer cold and acidic conditions and are tolerant to oxygen. Individual species in this group are associated to mosses and able to carry out a special-type of photosynthesis themselves.
Fibrobacterota thrive on cellulose, a typical but to humans non-digestible component of dietary fiber.
Fun fact: They are essential in the guts of larger plant-eating animals such as cows and sheep but also in plant-eating insects, specifically termites.
Firmicutes eat starches found in legumes and unprocessed grains, falling back on mucins (sugar + protein complexes) produced by our bodies to create mucus that protects the inside of our gut.
Fun fact: Scientists are currently reclassifying this group, hence there will likely be changes in the future. We show re-grouped members by adding a letter to the group name i.e. Firmicutes_A.
Firmicutes_A eat starches found in legumes and unprocessed grains, falling back on mucins (sugar + protein complexes) produced by our bodies to create mucus that protects the inside of our gut
Fun fact: Scientists are currently reclassifying this group, hence there will likely be changes in the future. We show re-grouped members by adding a letter to the group name i.e. Firmicutes_A.
Firmicutes_B eat starches found in legumes and unprocessed grains, falling back on mucins (sugar + protein complexes) produced by our bodies to create mucus that protects the inside of our gut
Fun fact: Scientists are currently reclassifying this group, hence there will likely be changes in the future. We show re-grouped members by adding a letter to the group name i.e. Firmicutes_A.
Firmicutes_C eat starches found in legumes and unprocessed grains, falling back on mucins (sugar + protein complexes) produced by our bodies to create mucus that protects the inside of our gut
Fun fact: Scientists are currently reclassifying this group, hence there will likely be changes in the future. We show re-grouped members by adding a letter to the group name i.e. Firmicutes_A.
Firmicutes_G eat starches found in legumes and unprocessed grains, falling back on mucins (sugar + protein complexes) produced by our bodies to create mucus that protects the inside of our gut
Fun fact: Scientists are currently reclassifying this group, hence there will likely be changes in the future. We show re-grouped members by adding a letter to the group name i.e. Firmicutes_A.
Fusobacteriota cannot tolerate oxygen. They populate the mouths and digestive systems of various animals: humans, mice, horses, crocodiles, fish and whales. Bacteria in this group are neutral but could also contribute to escalating diseases such as periodontal disease and colorectal cancer.
Myxococcota are a collection of predators that could be described as acid-spewing wolf bacteria. A pack of members of this group may swarm their prey, other bacteria, and dissolve them with digestive enzymes.
Patescibacteria are ultra-small and extremely simple bacteria that live in groundwater.
Fun fact: Scientists think that some of these can actually only survive by living in symbiosis with larger single-cell microorganisms.
Proteobacteria is a hugely diverse group of bacteria that typically make up a small portion of your gut’s microbiome. This group contains harmful but also beneficial bacteria.
Spirochaetota can ferment simple sugars, amino-acids, or fibers, and are found both free-living and living in or on animals and humans.
Some members of this group are enriched in the guts of tribal groups in Africa and South America that maintain a traditional diet. This group contains a number of bacteria that can cause diseases such as lyme disease and syphillis.
Fun fact: They have their name from their distinct corkscrew shape visible in the microscope.
Synergistota are a group of bacteria that live in environments with no oxygen. They are found in humans, animals but also the soil and ocean where they chiefly feed on amino acids.
Verrucomicrobiota is the group most well-known for containing Akkermansia muciniphila, which has a proven beneficial effect on high-fat diet induced metabolic disorders in mice. A. muciniphila specialises in eating components of the gut mucus and has been isolated from humans and mice.
Archaea are evolutionary ancient microorganisms distinct from bacteria. They have initially only been found in extremely harsh environments but have now been identified virtually everywhere else. No pathogens are currently known. Archaea are the only organisms that are able to produce methane.
Euryarchaeota are almost exclusively specialised in producing methane from hydrogen and carbon dioxide.
Halobacterota are, despite the confusing name, a group of archaea and not bacteria. These thrive in water that is almost or entirely saturated with salt. Members in this group can produce methane from acetate, from hydrogen, or from methanol.
Thermoplasmatota are a group of archeae. Some members in this group can tolerate very strong acid and high temperatures others are found in the surface layer of the ocean. Some members of this group can produce methane from methanol and similar compounds.
