Microbiome Reference Table
Our microbiology and epidemiology teams have compiled this reference table to accompany our cohort's gut microbiome results. For each bacterial taxon identified in our samples to date, you'll find a description, relative abundance (RA) literature-based reference ranges, our cohort's average RA, and supporting sources.
Meet the Microbes
We're excited to share initial results of our cohort's microbiome and help make a little more sense of your individual gut bacteria residents. Although we've put a lot of work into consolidating this information from the best available research, it's important to highlight that the scientific community as a whole is still learning about the microbiome. This means our study RA averages and literature-based reference ranges come with an important caveat:
Published reference ranges come from a variety of study populations that may differ from our own in age, geography, diet, and other factors known to shape the gut microbiome. As a result, these ranges should be viewed as general context rather than a precise standard for what is “normal” for you specifically. There is currently no universally agreed-upon definition of a healthy gut microbiome, and substantial variation exists even among healthy individuals. Additionally, our cohort's characteristics mean averages sometimes differ from published ranges, meaning wide variation may be expected.
A Quick Reminder
This table reflects relative abundance (RA): the share of your total identified bacteria that each phylum or family makes up, not an absolute count of bacteria in your gut. Think of your gut microbiome as a 100-piece pie: RA tells us how many pieces of that pie belong to each type of bacteria, not how big the whole pie is. So if Firmicutes make up 45% of your results, that means 45 out of every 100 identified bacteria belonged to that group, relative to everything else found in your sample.
Bacterial Taxa by the Numbers: Phylum Level
| Rank | Taxa | Long Description | Short Description | Average Study RA* | RA Reference Range** | References |
|---|---|---|---|---|---|---|
| phylum | Actinobacteria | Actinobacteria play an important role in maintaining a healthy gut environment by making sure the walls of the gut are strong so nothing can leak out into the blood stream | Support gut barrier function | 3.80% | <5% | https://www.sciencedirect.com/science/article/pii/S159086581830210X https://doi.org/10.1038/s41421-020-00239-w https://doi.org/10.3389/fmicb.2021.682721 https://doi.org/10.1371/journal.pone.0206484 https://taylorandfrancis.com/knowledge/Medicine_and_healthcare/Medical_… https://doi.org/10.3389/fmicb.2017.01221 |
| phylum | Bacteria unclassified | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Diverse bacteria that were not classified by our database | 0.07% | Not applicable | |
| phylum | Bacteroidetes | Bacteroidetes make up a large proportion of the gut microbiome and are involved with breaking down carbohydrates and maintaining balance in the gut | Digest carbohydrates for gut cell use | 20% | 14-73% | https://www.sciencedirect.com/science/article/pii/S1075996424000027 https://doi.org/10.3389/fmicb.2021.682721 https://doi.org/10.1038/s41421-020-00239-w https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| phylum | Candidatus Melainabacteria | Candidatus Melainabacteria are a group of bacteria in the gut that we are still learning more about. They are able to produce vitamins B and K in the gut and are also found in soil and water | Produce vitamins B and K | 0.20% | <4% | https://pubmed.ncbi.nlm.nih.gov/35454968/ https://doi.org/10.7554/eLife.01102 |
| phylum | Candidatus Thermoplasmatota | Group of archaea which produce methane in the gut, which helps other bacteria fully break down carbohydrates | Help other bacteria digest carbohydrates by producing methane | 0.01% | No quantitative reference range identified | https://www.researchgate.net/publication/285163735_Methanogens_in_Human… |
| phylum | Elusimicrobia | Group of bacteris typically associated with insect microbiomes, which can ferment carbohydrates efficiently | Associated with insects, ferment carbohydrates | <0.01% | 0.70% | https://pmc.ncbi.nlm.nih.gov/articles/PMC7785019/ https://doi.org/10.1016/j.cell.2019.01.001 |
| phylum | Eukaryota unclassified | These eukaryotic organisms were not classified in our database. They highlight the diversity of the gut microbiome | Diverse eukaryotes that were not classified by our database | <0.01% | Not applicable | |
| phylum | Euryarchaeota | Euryarchaeota is a phylum of archaea, a type of bacteria-like organism. They are responsible for fermentation in the gut and produce methane | Produce methane in the gut | 0.45% | <1.4% | https://pubmed.ncbi.nlm.nih.gov/20079831/ https://doi.org/10.1016/j.mib.2022.102146 https://pmc.ncbi.nlm.nih.gov/articles/PMC10824687/ https://doi.org/10.3389/fmicb.2017.01221 https://doi.org/10.1371/journal.pone.0206484 |
| phylum | Firmicutes | Firmicutes often make up a large proportion of the gut microbiome and are responsible for degrading dietary fiber in the gut to get energy from the food you eat | Maintain metabolic and immune balance in the gut | 59% | 11-71% | https://pmc.ncbi.nlm.nih.gov/articles/PMC7285218/ https://doi.org/10.3389/fmicb.2021.682721 https://doi.org/10.1038/s41421-020-00239-w https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| phylum | Fusobacteria | Normally found at low levels and in the mouth, but can be associated with diseases | Found in the mouth and at low levels in the gut | 0.03% | <0.2% | https://pmc.ncbi.nlm.nih.gov/articles/PMC6313651/ https://doi.org/10.1371/journal.pone.0025042 https://doi.org/10.3389/fmicb.2017.01221 |
| phylum | Lentisphaerae | Bacteria found in low levels in the gut, which have been associated with better sleep health and neurological function | Associated with sleep and neurological health | 0.02% | <0.2% | https://pmc.ncbi.nlm.nih.gov/articles/PMC7093326/ https://doi.org/10.3389/fmicb.2017.01221 |
| phylum | Proteobacteria | Proteobacteria are often one of the top four phyla in the human gut. They are also found on other parts of the body (skin, mouth, etc) and are an essential part of the gut microbiome, but are sometimes associated with inflammation in high levels. | Abundance can correspond to environmental factors like diet and stress | 1.50% | 2-5% | https://www.sciencedirect.com/science/article/pii/S0167779915001390 https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.3389/fmicb.2021.682721 https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| phylum | Spirochaetes | Spiral-shaped organisms that can latch to human intestinal cells. They are normally harmless but high levels can cause diarrhea. | Spiral-shaped microbes that attach to gut cells | <0.01% | <3% | https://pmc.ncbi.nlm.nih.gov/articles/PMC2830567/ https://doi.org/10.1038/ncomms4654 https://doi.org/10.3389/fmicb.2017.01221 |
| phylum | Synergistetes | A phylum of bacteria that can break down proteins in the gut to provide nutrients to human cells | Digest proteins in the gut | 0.01% | <0.2% | https://link.springer.com/rwe/10.1007/978-3-642-38954-2_384 https://doi.org/10.1016/j.resmic.2009.12.008 https://doi.org/10.3389/fmicb.2017.01221 |
| phylum | Tenericutes | Tenericutes are a group of bacteria found in diverse environments, like soil, saltwater lakes, and the human gut. They have diverse genes and we are still learning about their role in the human gut. | Environmental bacteria that can be in the gut | 0.12% | <2% | https://pmc.ncbi.nlm.nih.gov/articles/PMC7301438/ https://doi.org/10.1186/s40101-016-0121-7 https://doi.org/10.3389/fmicb.2017.01221 |
| phylum | Unclassified bacteria in the unknown kingdom | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Diverse bacteria that were not classified by our database | 14% | Not applicable | |
| phylum | Verrucomicrobia | Verrucomicrobiota are responsible for maintaining the mucus layer in the intestines and are highly associated with a healthy gut and body. | Maintain a healthy mucus layer | 0.92% | 1-8.5% | https://www.nature.com/articles/s41598-019-49081-5 https://doi.org/10.1371/journal.pone.0149564 https://pmc.ncbi.nlm.nih.gov/articles/PMC8262928/ https://doi.org/10.3389/fmicb.2017.01221 https://taylorandfrancis.com/knowledge/Medicine_and_healthcare/Medical_… |
RA: relative abundance; *average RA for each bacteria and rank within our study sample so far; **RA reference range for each bacteria and rank based on existing literature, if applicable and available; values <0.01% represent rare bacteria with values as low as 0.000008%
Bacterial Taxa by the Numbers: Family Level
| Rank | Taxa | Long Description | Short Description | Average Study RA* | RA Reference Range** | References |
|---|---|---|---|---|---|---|
| family | Acidaminococcaceae | Bacteria which can break down amino acids in the gut. They have sometimes been associated with diseases like depression and irritable bowel syndrome | Break down proteins in the gut | 0.33% | <10% | https://pmc.ncbi.nlm.nih.gov/articles/PMC7960967/ https://pmc.ncbi.nlm.nih.gov/articles/PMC8890582/ |
| family | Actinomycetaceae | Normally found in the mouth and digestive tract, these bacteria are often found at low levels and help break down food into energy. In high levels they typically cause disease | Often at low levels, help break down food | <0.01% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC6129341/ |
| family | Akkermansiaceae | This family contains a key gut species, Akkermansia muciniphila. It is known to have strong probiotic abilities and is highly associated with health | Probiotics which promote a healthy gut | 0.52% | 1-8% | https://pmc.ncbi.nlm.nih.gov/articles/PMC9259768/ https://pubmed.ncbi.nlm.nih.gov/31599433/ https://doi.org/10.1371/journal.pone.0206484 |
| family | Atopobiaceae | This family is uncommon in the gut. It has been implicated with lipid modulation, oxidative stress, and the immune reaction | Uncommon in the gut, involved in fat metabolism and immunity | <0.01% | No quantitative reference range identified | https://academic.oup.com/jid/article/232/4/767/7863217 |
| family | Bacillaceae | This family is one of the most abundant on earth, most often in soil, where it helps maintain a healthy soil environment. In the gut it can exist as spores and some species can cause disease | Soil bacteria that can sometimes pass through the gut | <0.01% | 0.28% | https://pubmed.ncbi.nlm.nih.gov/26104706/ https://doi.org/10.3390/microorganisms13010185 |
| family | Bacillales unclassified | Unclassified bacteria in the Firmicutes phylum (Bacillales order) | Break down a variety of materials and have industrial applications | <0.01% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC9781867/ https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| family | Bacteroidaceae | Bacteroidaceae is a family which helps you digest carbohydrates, produce hormones, and reduce inflammation in your digestive tract | Digest carbohydrates and reduce inflammation | 7.10% | <12% | https://pmc.ncbi.nlm.nih.gov/articles/PMC10558969/ https://doi.org/10.1371/journal.pone.0206484 |
| family | Bacteroidales unclassified | Unclassified bacteria in the Bacteroidetes phylum (Bacteroidales order) | Most abundant and stable type of gut bacteria | <0.01% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC11466702/ https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| family | Barnesiellaceae | This family helps maintain a balanced microbial environment in the gut and keeps the gut barrier strong. | Maintains gut balance and strengthens gut barrier | 0.14% | 0.42% | https://pmc.ncbi.nlm.nih.gov/articles/PMC12540160/ https://doi.org/10.3390/microorganisms13010185 |
| family | Bifidobacteriaceae | Bifidobacteriaceaeae are one of the first bacteria in your gut microbiome after birth and they are often used as probiotics, or added into the gut through pills or foods (like yogurt) to help improve digestion | Probiotic bacteria that aid digestion | 1.20% | 1-15% | https://pmc.ncbi.nlm.nih.gov/articles/PMC8605840/ https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1371/journal.pone.0206484 |
| family | Brachyspiraceae | Spiral-shaped bacteria which live in the large intestines. They typically are harmless, but overgrowth can lead to chronic diarrhea and abdominal pain | <0.01% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC3697658/ | |
| family | Campylobacteraceae | This family gets energy from fats and proteins, rather than carbohydrates. Some bacteria in the Campylobacteraceae family are responsible for causing food poisoning-related diarrhea | Digest fats and proteins for energy | 0.03% | 0% | https://www.sciencedirect.com/topics/medicine-and-dentistry/campylobact… https://doi.org/10.3390/microorganisms13010185 |
| family | Candidatus Borkfalkiaceae | This family is not well characterized, but is found in the intestinal tract of mammals and birds. It is commensal and found at low levels | Commensal gut bacteria found in mammals and birds | <0.01% | No quantitative reference range identified | https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi |
| family | Candidatus Gastranaerophilales unclassified | Although this family is unclassified, other closely-associated bacteria are involved with starch digestion and it may be associated to protein digestion and aging | Potentially linked to changes in protein digestion with aging | 0.03% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC5990381/ |
| family | Candidatus Methanomethylophilaceae | This family is not well characterized, but we know that it produces methane and is found in human stool | Methane producing organism in the gut | <0.01% | No quantitative reference range identified | https://pubmed.ncbi.nlm.nih.gov/23209209/ |
| family | Carnobacteriaceae | This family is often found in the gastrointestinal tract of fish and helps them break down food to get nutrients | Associated with the fish gut microbiome | <0.01% | 0.01% | https://www.sciencedirect.com/topics/agricultural-and-biological-scienc… https://doi.org/10.3390/microorganisms13010185 |
| family | Christensenellaceae | Widespread family in the gut of humans and other animals. It is inversely related to a higher body mass index (BMI), where individuals with a higher BMI have lower levels of Christensenellaceae. | Low levels linked to obesity | <0.01% | <0.53% | https://pmc.ncbi.nlm.nih.gov/articles/PMC6819567/ https://doi.org/10.3390/microorganisms13010185 https://pmc.ncbi.nlm.nih.gov/articles/PMC4255478/ |
| family | Clostridia unclassified | Unclassified bacteria in the Firmicutes phylum (Clostridia class) | Support digestion and ferment fiber | 0.20% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC5453186/ https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| family | Clostridiaceae | Clostridiaceae break down fiber, produce short-chain fatty acids (which give your digestive cells energy and regulate your immune system), and more in the gut. | Break down fiber for gut cell energy | 1.50% | 0.26% | https://pmc.ncbi.nlm.nih.gov/articles/PMC3751348/ https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1371/journal.pone.0022109 |
| family | Clostridiales unclassified | Unclassified bacteria in the Firmicutes phylum (Clostridiales order) | Support digestion and ferment fiber | 0.04% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC5453186/ https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| family | Coprobacillaceae | This family can produce short chain fatty acids, which support gut cell health, from glucose. | Produce molecules to benefit gut cell health | 0.01% | 0.08% | https://onlinelibrary.wiley.com/doi/10.1002/9781118960608.gbm00762 https://doi.org/10.3389/fmicb.2025.1684303 |
| family | Coriobacteriaceae | Coriobacteriaceae species play an important role in lipid (fat) metabolism, helping maintain a healthy level of fat in the body | Help digest lipids (fat) in the gut | 0.71% | 1-7% | https://www.microbiologyresearch.org/content/journal/acmi/10.1099/acmi… https://doi.org/10.3389/fmicb.2025.1684303 https://pmc.ncbi.nlm.nih.gov/articles/PMC2679024/ https://doi.org/10.1371/journal.pone.0039743 |
| family | Corynebacteriaceae | This family lives in human mucous membranes, like in the nose, throat, and the gut. Some members can cause disease, and stress may reduce the levels of this bacteria in the gut | Lives in mucous membranes in the nose, throat, and gut | <0.01% | 0.00% | https://pmc.ncbi.nlm.nih.gov/articles/PMC6748977/ https://doi.org/10.3389/fmicb.2025.1684303 |
| family | Desulfovibrionaceae | This family is found in a wide variety of environments, such as freshwater, animal and human guts, soil, and ocean water. It uses sulfur compounds for energy | Bacteria that use sulfur compounds for energy | 0.06% | 0.13% | https://link.springer.com/rwe/10.1007/978-3-642-39044-9_272 https://doi.org/10.3389/fmicb.2025.1684303 |
| family | Dysgonomonadaceae | A family often associated with a variety of insects, but has been found in human feces, wounds, and abcesses | Insect-associated bacteria that can be found in the gut | <0.01% | No quantitative reference range identified | https://www.sciencedirect.com/science/article/pii/S107599642030158X |
| family | Eggerthellaceae | Bacteria in this family are able to modify a wide range of molecules in the gut which implicates them in human health. | Can modify many metabolites in the gut | 0.19% | <0.73% | https://www.nature.com/articles/s41467-022-33576-3 https://doi.org/10.3389/fmicb.2025.1684303 https://doi.org/10.1016/j.mib.2022.102146 |
| family | Elusimicrobiaceae | Bacteria in this family have been associated with insects. They are able to remove oxygen from the surrounding environment and produce metabolites like lactate, acetate, ethanol, and hydrogen | Insect-associated bacteria which can remove oxygen from the environment | <0.01% | No quantitative reference range identified | https://www.sciencedirect.com/science/article/pii/S0723202025000281 |
| family | Enterobacteriaceae | A family that is often found at low abundances in the gut. They help maintain the anaerobic gut environment, produce vitamins, and fight against infections, although some members are pathogenic | Create an anaerobic gut environment and produce vitamins | 0.16% | <11% | https://pmc.ncbi.nlm.nih.gov/articles/PMC10967970/ https://doi.org/10.3389/fmicb.2025.1684303 https://doi.org/10.1371/journal.pone.0206484 |
| family | Enterococcaceae | Found at low levels in the gut, they help maintain proper pH levels, digest molecules, and produce vitamins. | Maintain a healthy gut environment and produce vitamins | 0.04% | 0.02% | https://pmc.ncbi.nlm.nih.gov/articles/PMC10888668/ https://doi.org/10.3389/fmicb.2025.1684303 https://doi.org/10.3390/microorganisms13010185 |
| family | Erysipelotrichaceae | A family of bacteria that can break down fats. It is associated with a high-fat diet and is sometimes linked to diseases like colorectal cancer and irritable bowel disease when found in high concentrations in the gut | Breaks down fats, high levels may indicate disease | 0.60% | <2% | https://pmc.ncbi.nlm.nih.gov/articles/PMC4653637/ https://pmc.ncbi.nlm.nih.gov/articles/PMC7339541/ https://www.nature.com/articles/s41598-018-28671-9 https://doi.org/10.1371/journal.pone.0039743 |
| family | Eubacteriaceae | Organisms that ferment fibers into short chain fatty acids. This helps maintain intestinal barrier integrity and reduce inflammation | Ferment fiber, reduce inflammation, and maintain the gut barrier | 0.47% | 0.05% | https://pmc.ncbi.nlm.nih.gov/articles/PMC7524325/ https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1371/journal.pone.0022109 |
| family | Eubacteriales Family XIII Incertae Sedis | Unclassified bacteria in the Firmicutes phylum (Eubacteriales order) | Uncharacterize bacteria that support gut health | 0.03% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC7524325/ https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| family | Eubacteriales unclassified | Unclassified bacteria in the Firmicutes phylum (Eubacteriales order) | Core component of the microbiome, supports a healthy gut | 1.20% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC7524325/ https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| family | Eukaryota unclassified | Unclassified eukaryotic organisms. Eukaryotic organisms are unqiue because they have a cell nucleus. Examples of eukaryotic organisms include fungi, animals and humans, and small single-celled organisms called protozoans | Unclassified organisms with nuclei in their cells | <0.01% | Not applicable | https://www.sciencedirect.com/topics/immunology-and-microbiology/eukary… |
| family | Firmicutes unclassified | Unclassified bacteria in the Firmicutes phylum | Maintain metabolic and immune balance in the gut | 0.23% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC7524325/ https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| family | Fusobacteriaceae | A family of bacteria which live in the gut and the mouth. They live at low oxygen levels and may alter the function of other gut bacteria when they grow to high levels | Mouth- and gut-associated bacteria often found in low levels | 0.02% | <4% | https://www.sciencedirect.com/topics/medicine-and-dentistry/fusobacteri… https://doi.org/10.1371/journal.pone.0039743 |
| family | Hafniaceae | Hafniaceae are often found in the human gut and may be linked to health benefits like weight loss. They can produce vitamins and other compounds to help gut cells thrive. | Health-associated bacteria that produce vitamins | <0.01% | No quantitative reference range identified | https://pubmed.ncbi.nlm.nih.gov/38646847/ |
| family | Helicobacteraceae | These bacteria normally live in the mouth, stomach, and intestines of mammals, but some live in diverse freshwater environments. A few members can cause stomach pain and ulcers. | Acid-tolerant bacteria that can live in the stomach | <0.01% | No quantitative reference range identified | https://link.springer.com/rwe/10.1007/978-3-642-39044-9_275 |
| family | Lachnospiraceae | Lachnospiraceae are found in the gut from birth all the way to adulthood and they are able to break down many different molecules found in food into energy for your body | Break down food to generate energy | 15% | 10-45% | https://pmc.ncbi.nlm.nih.gov/articles/PMC7232163/ https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.3390/microorganisms13092061 https://doi.org/10.1371/journal.pone.0206484 |
| family | Lactobacillaceae | Diverse family that benefits the intestines by helping the immune system fight pathogens. They are often given as a probiotic | Probiotic bacteria that helps the immune system function | 0.07% | <0.6% | https://pmc.ncbi.nlm.nih.gov/articles/PMC9888405/ https://doi.org/10.3389/fmicb.2025.1684303 https://pmc.ncbi.nlm.nih.gov/articles/PMC5897428/ https://doi.org/10.3389/frmbi.2023.1192773 |
| family | Methanobacteriaceae | Family of archaea that produce methane in the gut. They are found in diverse environments such as the gut, hot springs, and sewage. | Methane-producing archaea in the gut | 0.26% | 0.04% | https://link.springer.com/rwe/10.1007/978-3-642-38954-2_411 https://doi.org/10.3390/microorganisms13010185 |
| family | Methanomassiliicoccaceae | Family of archaea that produce methane and are found in a wide variety of environments, particularly in rumen (cows, sheep). In humans they have been linked to cardiovascular disease risk | Methane-producing archaea in the gut of rumens | <0.01% | 0.04% | https://link.springer.com/article/10.1186/s13059-024-03167-0 https://doi.org/10.1016/j.mib.2022.102146 |
| family | Micrococcaceae | This family is not often found in the gut due to low oxygen levels, but it can survive there, particularly in the small intestines. | Lives in the small intestines in low abundances | <0.01% | 0.01% | https://pmc.ncbi.nlm.nih.gov/articles/PMC12001467/ https://doi.org/10.3390/microorganisms13010185 |
| family | Morganellaceae | A family of bacteria that promote a healthy gut environment. Some members can help your immune system prevent bacteria from leaking out of the gut. | Promote a healthy gut environment and help immune system | <0.01% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC4855262/ |
| family | Muribaculaceae | Short-chain fatty acid producers that digest dietary fiber and sugars in gut mucus. They work together with the Lactobacillaceae and Bifidobacteriaceae families to maintain a healthy gut environment | Digest fiber to produce energy for gut cells | 0.05% | <0.5% | https://pmc.ncbi.nlm.nih.gov/articles/PMC11356848/ https://doi.org/10.3389/fmicb.2025.1684303 https://www.nature.com/articles/s42003-025-08895-y |
| family | Odoribacteraceae | A probiotic family which reduces inflammation, helps the immune system, and breaks down a variety of molecules to help the gut stay healthy | Regulates the immune system and provides energy for gut cells | 0.13% | <8% | https://pmc.ncbi.nlm.nih.gov/articles/PMC12029356/ https://doi.org/10.1371/journal.pone.0206484 |
| family | Oscillospiraceae | Oscillospiraceae is a beneficial family of bacteria which is common in the gut. They grow slowly and break down fiber to produce beneficial molecules in the gut and are associated with lower fat levels and human health | Associated with health and help break down fiber | 8.40% | 0.56% | https://pmc.ncbi.nlm.nih.gov/articles/PMC11315831/ https://www.nature.com/articles/s42003-025-08895-y https://doi.org/10.1371/journal.pone.0022109 |
| family | Oxalobacteraceae | Diverse bacterial family found in many environments. Many species are beneficial to the gut. | Break down plant sugars and benefit the gut | <0.01% | <6% | https://www.sciencedirect.com/science/article/pii/S0923250823000517 https://doi.org/10.1016/j.ajcnut.2023.11.001 https://doi.org/10.5281/zenodo.16945401 |
| family | Pasteurellaceae | A family of commensals and some pathogens found in mammals and birds. Most Pasteurella in the gut are harmless, but species in the mouth and respiratory tract can cause disease | Gut commensals but can cause oral and respiratory disease | <0.01% | <0.8% | https://www.sciencedirect.com/science/chapter/bookseries/pii/S058095172… https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.3389/fmicb.2017.01221 https://doi.org/10.1016/j.ajcnut.2023.11.001 |
| family | Peptococcaceae | A family of bacteria found in the gut. Low levels have been associated with higher HDL cholesterol, and high levels have been associated with insulin resistance | Levels may be associated with cholesterol or insulin resistance | <0.01% | <0.03% | https://pmc.ncbi.nlm.nih.gov/articles/PMC9735734/ https://doi.org/10.3390/microorganisms13010185 |
| family | Peptoniphilaceae | Bacterial family that can produce biogas, a renewable energy source made by microbes. It is associated with human infections but found in farm animal manure | Associated with animal guts, can produce biogas | <0.01% | <2% | https://www.sciencedirect.com/science/article/pii/S0168165617302687 https://www.homd.org/taxa/ecology |
| family | Peptostreptococcaceae | A family of bacteria normally found in the gut. When levels are depleted it can be a sign of dysbiosis. This family helps maintain balance and normal function in the gut. | Helps maintain a balanced gut environment | 0.08% | <8% | https://www.nature.com/articles/srep43412 https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1016/j.ajcnut.2023.11.001 https://pmc.ncbi.nlm.nih.gov/articles/PMC12783075/ https://doi.org/10.1371/journal.pone.0039743 |
| family | Porphyromonadaceae | This family is found in the human gastrointestinal tract and mouth. Most species are helpful but a few can cause infections | Found in the gut and mouth, some species cause infections | <0.01% | <6% | https://link.springer.com/rwe/10.1007/978-3-642-38954-2_132 https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1016/j.ajcnut.2023.11.001 https://pmc.ncbi.nlm.nih.gov/articles/PMC12783075/ https://doi.org/10.1371/journal.pone.0039743 https://doi.org/10.1371/journal.pone.0022109 |
| family | Prevotellaceae | Prevotellaceae is a family strongly associated with the gut microbiome. It is highly diverse and can be found throughout the digestive tract, from the mouth to the colon. Prevotellaceae is linked to a vegetable-rich diet and has been found to play a mixed role in the development of some diseases like type 2 diabetes | Diverse bacteria found throughout the digestive tract | 1.70% | 1.5-10% | https://pmc.ncbi.nlm.nih.gov/articles/PMC10713913/ https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1016/j.ajcnut.2023.11.001 https://pmc.ncbi.nlm.nih.gov/articles/PMC12783075/ https://doi.org/10.1371/journal.pone.0039743 https://doi.org/10.1371/journal.pone.0022109 |
| family | Promicromonosporaceae | Bacteria from this family are used in industrial settings to break down a variety of compounds found in plants and fungi. | Break down plant and fungal molecules | <0.01% | <0.1% | https://link.springer.com/rwe/10.1007/978-3-642-30138-4_173 https://pmc.ncbi.nlm.nih.gov/articles/PMC7298784/ |
| family | Propionibacteriaceae | This family is associated with some human infections, particularly skin-related infections. They can survive in slightly acidic environments. | Acid-tolerant bacteria often found on skin | <0.01% | No quantitative reference range identified | https://link.springer.com/rwe/10.1007/978-1-4614-6418-1_453-2 |
| family | Pseudomonadaceae | This family is often found in soil, fresh water, and marine environments, however can be found on plants and animals. Some species are known to be pathogenic in humans | Environmental bacteria that can cause human infections | <0.01% | <0.3% | https://link.springer.com/chapter/10.1007/978-3-662-13187-9_58 https://pmc.ncbi.nlm.nih.gov/articles/PMC10715013/ |
| family | Puniceicoccaceae | Puniceicoccaceae is a family associated with the environment. We do not know much about this family yet | Uncharacterized bacteria from the environment | <0.01% | No quantitative reference range identified | https://link.springer.com/rwe/10.1007/978-3-642-38954-2_148 |
| family | Rikenellaceae | Rikenellaceae is associated with urban populations and with a diet higher in fat and animal products (meat, dairy). It helps digest bile and produces molecules that help regulate fat storage | Digests bile and regulates fat storage | 1.60% | 1-5% | https://journals.asm.org/doi/pdf/10.1128/spectrum.01027-23 https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1016/j.ajcnut.2023.11.001 https://pmc.ncbi.nlm.nih.gov/articles/PMC12783075/ https://doi.org/10.1371/journal.pone.0206484 |
| family | Ruminococcaceae | Ruminococcaceae members are known as primary degraders, breaking down resistant starch (found in foods like potatoes, rice, and beans) in the gut to produce molecules that help which regulate the immune system in the gut and maintain a healthy digestive system | Break down starch to regulate the immune system and gut health | 0.64% | 18-27.5% | https://pmc.ncbi.nlm.nih.gov/articles/PMC11315831/ https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1016/j.ajcnut.2023.11.001 https://pmc.ncbi.nlm.nih.gov/articles/PMC12783075/ https://doi.org/10.1371/journal.pone.0206484 |
| family | Selenomonadaceae | A family found at low levels in the gut. This family is known to be depleted after a heart attack and was found at higher levels in atheletes than non-athletes | This family is associated with improved athletic and cardiac perfomance | 0.07% | <1% | https://pmc.ncbi.nlm.nih.gov/articles/PMC8911090/, https://advanced.onlinelibrary.wiley.com/doi/10.1002/adbi.202400069 https://doi.org/10.3389/fendo.2022.942383 |
| family | Streptococcaceae | This family can be found throughout the mouth, nose, and skin, and normally makes up a small portion of the gut microbiome. This family can act as a pathogen if it overgrows in the gut. | Found in the nose, mouth, and gut at low levels | 0.35% | <2% | https://pmc.ncbi.nlm.nih.gov/articles/PMC10399955/ https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1016/j.ajcnut.2023.11.001 https://pmc.ncbi.nlm.nih.gov/articles/PMC12783075/ |
| family | Succinivibrionaceae | Succinivibrionaceae are found in low levels in the gastrointestinal tract of humans and other animals. They can ferment carbohydrates to create beneficial molecules for gut cells | Ferment carbohydrates to provide energy for gut cells | <0.01% | <10% | https://link.springer.com/rwe/10.1007/978-3-642-38922-1_368 https://pmc.ncbi.nlm.nih.gov/articles/PMC4664238/ https://doi.org/10.3390/microorganisms13010185 |
| family | Sutterellaceae | Some species in this family have been associated with diseases like inflamatory bowel disease, autism, and down syndrome, but they are also found in healthy gut microbiomes. They can stick to intestinal epthelial cells and modulate the immune system | Stick to intestinal cells and modulate the immune system | 0.19% | <2% | https://pmc.ncbi.nlm.nih.gov/articles/PMC5080374/ https://doi.org/10.1016/j.ajcnut.2023.11.001 |
| family | Synergistaceae | These bacteria can ferment carobydrates and proteins in anaerobic environments. They are normally found in the gut but can be used to create 'biogas' which can be used as a renewable energy source. | Create 'biogas', which can be used as renewable energy | <0.01% | <0.02% | https://www.sciencedirect.com/science/article/pii/S0723202025000293 https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1016/j.ajcnut.2023.11.001 |
| family | Tannerellaceae | Tannerellaceae is a family of bacteria found in the large intestine that helps protect against different chronic disease in the gut and the rest of the body | Implicated with some chronic diseases | 0.61% | 1-6% | https://pmc.ncbi.nlm.nih.gov/articles/PMC10244646/ https://doi.org/10.3390/life11070620 https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1371/journal.pone.0206484 |
| family | Tissierellia unclassified | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Found in human, animal, and environmental locations | <0.01% | No quantitative reference range identified | https://www.sciencedirect.com/science/article/pii/S0723202013001616 |
| family | Turicibacteraceae | A common gut family which has been linked to body weight and the metabolism of dietary fat. These bacteria are able to modify host bile acids and lipids, modulating host fat biology | Modify lipids and influence host fat biology | <0.01% | No quantitative reference range identified | https://www.nature.com/articles/s41467-023-39403-7 |
| family | Unclassified bacteria in the Actinobacteria phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Support gut barrier function | 1.70% | No quantitative reference range identified | https://www.sciencedirect.com/science/article/pii/S159086581830210X https://doi.org/10.1371/journal.pone.0206484 https://taylorandfrancis.com/knowledge/Medicine_and_healthcare/Medical_… https://doi.org/10.3389/fmicb.2017.01221 |
| family | Unclassified bacteria in the Bacteria unclassified phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Diverse bacteria that were not classified by our database | 0.07% | No quantitative reference range identified | |
| family | Unclassified bacteria in the Bacteroidetes phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Digest carbohydrates for gut cell use | 8.90% | No quantitative reference range identified | https://www.sciencedirect.com/science/article/pii/S1075996424000027 https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| family | Unclassified bacteria in the Candidatus Melainabacteria phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Produce vitamins B and K | 0.17% | No quantitative reference range identified | https://pubmed.ncbi.nlm.nih.gov/35454968/ |
| family | Unclassified bacteria in the Candidatus Thermoplasmatota phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Help other bacteria digest carbohydrates by producing methane | <0.01% | No quantitative reference range identified | https://www.researchgate.net/publication/285163735_Methanogens_in_Human… |
| family | Unclassified bacteria in the Elusimicrobia phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Associated with insects, ferment carbohydrates | <0.01% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC7785019/ |
| family | Unclassified bacteria in the Eukaryota unclassified phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Diverse eukaryotes that were not classified by our database | <0.01% | No quantitative reference range identified | |
| family | Unclassified bacteria in the Euryarchaeota phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Produce methane in the gut | 0.19% | No quantitative reference range identified | https://pubmed.ncbi.nlm.nih.gov/20079831/ https://doi.org/10.3389/fmicb.2017.01221 https://doi.org/10.1371/journal.pone.0206484 |
| family | Unclassified bacteria in the Firmicutes phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Maintain metabolic and immune balance in the gut | 29% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC7285218/ https://pmc.ncbi.nlm.nih.gov/articles/PMC7551767/ https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| family | Unclassified bacteria in the Fusobacteria phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Found in the mouth and at low levels in the gut | 0.01% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC6313651/ https://doi.org/10.3389/fmicb.2017.01221 |
| family | Unclassified bacteria in the Lentisphaerae phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Associated with sleep and neurological health | 0.02% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC7093326/ https://doi.org/10.3389/fmicb.2017.01221 |
| family | Unclassified bacteria in the Proteobacteria phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Abundance can correspond to environmental factors like diet and stress | 1.00% | No quantitative reference range identified | https://www.sciencedirect.com/science/article/pii/S0167779915001390 https://doi.org/10.1371/journal.pone.0206484 https://doi.org/10.3389/fmicb.2017.01221 |
| family | Unclassified bacteria in the Spirochaetes phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Spiral-shaped microbes that attach to gut cells | <0.01% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC2830567/ https://doi.org/10.3389/fmicb.2017.01221 |
| family | Unclassified bacteria in the Synergistetes phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Digest proteins in the gut | <0.01% | No quantitative reference range identified | https://link.springer.com/rwe/10.1007/978-3-642-38954-2_384 https://doi.org/10.3389/fmicb.2017.01221 |
| family | Unclassified bacteria in the Tenericutes phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Environmental bacteria that can be in the gut | 0.12% | No quantitative reference range identified | https://pmc.ncbi.nlm.nih.gov/articles/PMC7301438/ https://doi.org/10.3389/fmicb.2017.01221 |
| family | Unclassified bacteria in the unknown kingdom | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Diverse bacteria that were not classified by our database | 14% | No quantitative reference range identified | |
| family | Unclassified bacteria in the Verrucomicrobia phylum | These bacteria were not classified in our database. They highlight the diversity of the gut microbiome | Maintain a healthy mucus layer | 0.39% | No quantitative reference range identified | https://www.nature.com/articles/s41598-019-49081-5 https://doi.org/10.3389/fmicb.2017.01221 https://taylorandfrancis.com/knowledge/Medicine_and_healthcare/Medical_… |
| family | Veillonellaceae | Veillonellaceae are often found in the gut. They can break down sugars in diary, and research has shown that they are protective against lactose intolerance | Break down dairy-related sugars | 0.25% | 1-6% | https://pmc.ncbi.nlm.nih.gov/articles/PMC11333455/ https://doi.org/10.3390/microorganisms13010185 https://doi.org/10.1016/j.ajcnut.2023.11.001 https://pmc.ncbi.nlm.nih.gov/articles/PMC12783075/ https://doi.org/10.1371/journal.pone.0022109 |
| family | Victivallaceae | This family is found in the gut and is significantly associated with obesity. It helps regulate the immune system | Immune system regulator, depletions correlated with obesity | <0.01% | <0.002% | https://pmc.ncbi.nlm.nih.gov/articles/PMC11068179/ https://doi.org/10.1016/j.ajcnut.2023.11.001 |
RA: relative abundance; *average RA for each bacteria and rank within our study sample so far; **RA reference range for each bacteria and rank based on existing literature, if applicable and available; values <0.01% represent rare bacteria with values as low as 0.000008%
FAQ
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Why do I see “unclassified” or “other” bacteria in these results?
You may notice that some of the bacteria in this table are labeled "unclassified" or “other” rather than given a specific name. This is normal and doesn't mean anything is wrong with the samples or results.
The human gut is home to an extraordinary number of bacteria, far more than scientists have been able to fully catalog so far. To officially name and classify a new type of bacteria, researchers need to piece together its complete genetic blueprint, which requires collecting a large number of matching gene sequences. For many gut bacteria, especially rarer or less-studied ones, we simply don't have enough data yet to complete that process.
When this happens, we can usually still tell you which broader family or group the bacteria belongs to (kind of like knowing someone's last name without knowing their first name), but a more specific identification isn't available yet. As sequencing technology improves and more research is done, many of these "unclassified" groups will eventually be named. So this is really a reflection of the pace of scientific discovery, not a limitation specific to the results.
How does my gut microbiome change?
While the core of your gut microbiome tends to stay fairly stable over time, other parts of its composition can shift more frequently. As a result, your results offer a snapshot of your microbiome rather than a complete, fixed picture.
Visit our website and GitHub repository for a comprehensive table of all bacterial phyla and families identified so far in our cohort with reference ranges, study averages and additional resources.
Are study abundance averages expected to change during the life of the study?
Yes, we expect relative abundance averages to change as we sequence more samples during the study’s progression. We plan to regularly update these estimates on our website and GitHub repository as new data becomes available and will reach out to our CoVHORT GI community when we do so.
Disclaimers
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Research Context
The results above summarize early research findings from your biospecimen samples. These results are shared for informational purposes only and are not intended to diagnose, treat, cure, or prevent any disease.
Medical Use
These results come from a research laboratory and were generated solely for research purposes. They are not clinical laboratory results and have not been reviewed by a healthcare provider. These results are not intended to be used to make any medical or health-related decisions. Please contact your healthcare provider if you have questions about your health. You are not expected to take any action based on these results.
Privacy
These lab results are unique to you and should not be shared with unauthorized individuals. Results are stored in a HIPAA-compliant database and linked only to your unique study ID.
Questions? Let’s chat!
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