Streptococcus thermophilus
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Its ID gene: the stretch scientists read to tell microbes apart. Each bar is one letter of its DNA. Every species has its own order of letters, so the pattern works like a fingerprint. Close relatives share most of it.
16S rRNA gene, V4 region: the 252 letters between the standard primers (515F/806R), which are the same in every species. One reference sequence; strains can differ by a letter or two. NCBI NR_118998.1
Formerly Streptococcus salivarius subsp. thermophilus.
Among the smallest for a gut microbe: longer than 6% of the 2,354 we have genomes for.
39% G+C, higher than 25% of gut microbes.
To scale: if its ID gene were 1 cm long, its genome would stretch 12 meters. Yours would stretch 21 kilometers. One reference genome; strains vary. NCBI GCF_903886475.1
What it can do
- Can make lactic acid What yogurt bacteria make; other microbes turn it into butyrate.
- Can make B vitamins Folate, B12, riboflavin and others.
- Can ferment fiber Breaks down dietary fiber that our own enzymes can't. 2 of 16 strains can
- Can use lactose The sugar in milk and dairy.
Not seen in its genomes or lab tests: make butyrate, make propionate, eat inulin, eat resistant starch, eat pectin, feed on gut mucus, change bile acids, make hydrogen sulfide, make methane.
All 13 capabilities and their evidence
| Capability | Verdict | Genome analysis | Lab tests | Published research |
|---|---|---|---|---|
| Can make butyrate | Not seen | 0 of 6 genomes | — | No papers |
| Can make propionate | Not seen | 0 of 6 genomes | — | No papers |
| Can make lactic acid | Can | 6 of 6 genomes | — | Papers say yes |
| Can ferment fiber | Some strains | 0 of 6 genomes | 2 of 16 strains · strip test | No papers |
| Can eat inulin | Not seen | 0 of 6 genomes | 0 of 11 strains · strip test | No papers |
| Can eat resistant starch | Not seen | 0 of 6 genomes | — | No papers |
| Can eat pectin | Not seen | 0 of 6 genomes | — | No papers |
| Can use lactose | Can | 6 of 6 genomes | 16 of 16 strains | Papers say yes |
| Can feed on gut mucus | Not seen | 0 of 6 genomes | — | No papers |
| Can change bile acids | Not seen | 0 of 6 genomes | — | No papers |
| Can make B vitamins | Can | 6 of 6 genomes | — | Papers say yes |
| Can make hydrogen sulfide | Not seen | 0 of 6 genomes | — | No papers |
| Can make methane | Not seen | 0 of 6 genomes | — | No papers |
AGORA2 (Heinken et al. 2023) via VMH, CC BY 4.0 · BacDive (DSMZ), CC BY 4.0 · NJC19 (Lim et al., Scientific Data 2020), CC0
In healthy guts
Found in 35% of healthy people.
- largest Segatella copri 6.2%
- 2nd largest Phocaeicola vulgatus 5.0%
- 3rd largest Faecalibacterium prausnitzii 4.7%
- 4th largest Bacteroides uniformis 3.2%
- 5th largest Agathobacter rectalis 2.5%
- 6th largest Alistipes putredinis 2.3%
- 7th largest Bifidobacterium longum 2.1%
- 8th largest Ruminococcus bromii 1.8%
- top 5% Streptococcus thermophilus 0.1%
- 2,169 other microbes, each a sliver 56.5%
- 15.6%
On average, 0.1% of the microbes in a healthy gut: larger than 95% of species’ slices.
Every group, drawn the same way. Only some samples record age or sex, so each group says how many people it comes from. Tap one to see it above.
In conditions
Compared with healthy people in the same studies, it’s less common in none and more common in 1 condition. Only studies that had both are counted.
A difference is an association: it doesn’t mean this microbe causes, prevents or treats any of these.
Strongest first, then the biggest gap · Each figure is 10 peopleIn studies of how people live
- Diet patterns →
Streptococcus thermophilus, a dairy microbe, is higher in omnivores and vegetarians than in vegans.
omnivores vs vegans: 5 of 5 cohorts · vegetarians vs vegans: 5 of 5 cohorts · 21,561 people · Italy, UK, US Fackelmann 2025
A difference is an association: it doesn't mean how people live changes this microbe, or that the microbe affects health.
Recent research
Source: PubMed, U.S. National Library of Medicine · 665 linked papers, last 10 years
Strains studied
How much each strain has been studied in people, not whether it works. Many trials test a strain inside a blend, so those are counted apart, and reviews are summaries of trials, so they're never counted as more trials.
23 strains of S. thermophilus are named on product labels. 0 have human trials; 23 have none found yet, including St-21, which is in 98 products.
S. thermophilus St-21
In 98 products →No human trials found yet
S. thermophilus HA-110
In 23 products →No human trials found yet
S. thermophilus SD-5207
In 16 products →No human trials found yet
S. thermophilus UASt-09
In 14 products →No human trials found yet
S. thermophilus CUL 68
In 11 products →No human trials found yet
S. thermophilus Y08
In 8 products →No human trials found yet
S. thermophilus SD-5849
In 7 products →No human trials found yet
S. thermophilus PXN 66
In 4 products →No human trials found yet
S. thermophilus UASt-9
In 4 products →No human trials found yet
S. thermophilus Y-8
In 4 products →No human trials found yet
S. thermophilus YO8
In 4 products →No human trials found yet
S. thermophilus TH-4
In 3 products →No human trials found yet
S. thermophilus A336
In 2 products →No human trials found yet
S. thermophilus DSM 24731
In 2 products →No human trials found yet
S. thermophilus KB-19
In 2 products →No human trials found yet
S. thermophilus MAK34S24T
In 2 products →No human trials found yet
S. thermophilus NBRC 13957
In 2 products →No human trials found yet
S. thermophilus R0083
In 2 products →No human trials found yet
S. thermophilus ST1447
In 2 products →No human trials found yet
S. thermophilus VPro23
In 2 products →No human trials found yet
S. thermophilus W69
In 2 products →No human trials found yet
S. thermophilus DSM 20617
In 1 product →No human trials found yet
S. thermophilus ST075
In 1 product →No human trials found yet
Human trials, meta-analyses and systematic reviews naming the strain · animal and lab studies not counted · Data sources