Bifidobacterium longum
What's this?
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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 253 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_117506.1
Formerly Bifidobacterium infantis.
Small for a gut microbe: longer than 24% of the 2,354 we have genomes for.
60% G+C, higher than 76% of gut microbes.
To scale: if its ID gene were 1 cm long, its genome would stretch 16 meters. Yours would stretch 21 kilometers. One reference genome; strains vary. NCBI GCF_000196555.1
What it can do
- Mixed evidence Can make butyrate A short-chain fatty acid that feeds the cells lining the colon. Published research reports it; genome analysis found it in none of 28 genomes.
- Can make lactic acid What yogurt bacteria make; other microbes turn it into butyrate.
- Can ferment fiber Breaks down dietary fiber that our own enzymes can't.
- Can eat inulin A fiber in onions, garlic, leeks, chicory and bananas (also sold as FOS).
- Can use lactose The sugar in milk and dairy.
- Can feed on gut mucus Lives on mucin, the mucus that lines the gut.
Not seen in its genomes: make propionate, eat resistant starch, eat pectin, make hydrogen sulfide, make methane.
All 13 capabilities and their evidence
| Capability | Verdict | Genome analysis | Lab tests | Published research |
|---|---|---|---|---|
| Can make butyrate | Mixed evidence | 0 of 28 genomes | — | Papers say yes |
| Can make propionate | Not seen | 0 of 28 genomes | — | No papers |
| Can make lactic acid | Can | 28 of 28 genomes | — | Papers say yes |
| Can ferment fiber | Can | 28 of 28 genomes | 25 of 26 strains · strip test | Papers say yes |
| Can eat inulin | Can | 27 of 28 genomes | 1 of 7 strains · strip test Strip tests often miss fiber-eaters, so this doesn't override the genomes. | Papers say yes |
| Can eat resistant starch | Not seen | 0 of 28 genomes | — | No papers |
| Can eat pectin | Not seen | 0 of 28 genomes | — | No papers |
| Can use lactose | Can | 28 of 28 genomes | 24 of 24 strains | No papers |
| Can feed on gut mucus | Can | 1 of 28 genomes | — | Papers say yes |
| Can change bile acids | Can | 9 of 28 genomes | — | Papers say yes |
| Can make B vitamins | Can | 28 of 28 genomes | — | Papers say yes |
| Can make hydrogen sulfide | Not seen | 0 of 28 genomes | — | No papers |
| Can make methane | Not seen | 0 of 28 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 76% 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%
- 2,170 other microbes, each a sliver 56.7%
- 15.6%
On average, 2.1% of the microbes in a healthy gut: the 7th largest slice.
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 5 conditions and more common in none. 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
Higher in vegans than omnivores
Fackelmann 2025 · 21,561 people Landmark study
Higher in 4 of 5 cohorts
Higher in vegetarians than omnivores
Fackelmann 2025 · 21,561 people Landmark study
Higher in 4 of 5 cohorts
“Higher” is the study’s measure: on average, a bigger share of gut bacteria across everyone in the group, carriers or not. It isn’t how many people carry it. An association the authors report, measured once per person. It doesn’t mean a diet changes this microbe, or that the microbe affects health.
Recent research
Source: PubMed, U.S. National Library of Medicine · 1,682 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.
69 strains of B. longum are named on product labels. 0 have human trials; 69 have none found yet, including Bl-05, which is in 166 products.
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No human trials found yet
B. longum Bi-26
In 85 products →No human trials found yet
B. longum BB536
In 72 products →No human trials found yet
B. longum UABl-14
In 64 products →No human trials found yet
B. longum HA-135
In 53 products →No human trials found yet
B. longum BL-5
In 32 products →No human trials found yet
B. longum SD-6720
In 24 products →No human trials found yet
B. longum SD-5588
In 23 products →No human trials found yet
B. longum MM-2
In 16 products →No human trials found yet
B. longum BL-03
In 15 products →No human trials found yet
B. longum R0175
In 15 products →No human trials found yet
B. longum M-63
In 13 products →No human trials found yet
B. longum Rosell-175
In 13 products →No human trials found yet
B. longum BI02
In 11 products →No human trials found yet
B. longum HA-116
In 11 products →No human trials found yet
B. longum VPBI-6
In 11 products →No human trials found yet
B. longum VPBL-5
In 11 products →No human trials found yet
B. longum SD-6669
In 10 products →No human trials found yet
B. longum VP-114
In 10 products →No human trials found yet
B. longum VP-115
In 10 products →No human trials found yet
B. longum VP-117
In 10 products →No human trials found yet
B. longum VP-118
In 10 products →No human trials found yet
B. longum 35624
In 8 products →No human trials found yet
B. longum SD-5844
In 8 products →No human trials found yet
B. longum B12L
In 6 products →No human trials found yet
B. longum R0033
In 6 products →No human trials found yet
B. longum KABP-042
In 5 products →No human trials found yet
B. longum ATCC SD5588
In 4 products →No human trials found yet
B. longum ATCC SD6720
In 4 products →No human trials found yet
B. longum BL-3
In 4 products →No human trials found yet
B. longum DSM 16603
In 4 products →No human trials found yet
B. longum CUL-75
In 3 products →No human trials found yet
B. longum NI316
In 3 products →No human trials found yet
B. longum PXN 27
In 3 products →No human trials found yet
B. longum PXN 30
In 3 products →No human trials found yet
B. longum VPro53
In 3 products →No human trials found yet
B. longum A730
In 2 products →No human trials found yet
B. longum BI45
In 2 products →No human trials found yet
B. longum DSM 24736
In 2 products →No human trials found yet
B. longum DSM 24737
In 2 products →No human trials found yet
B. longum MAK22B04I
In 2 products →No human trials found yet
B. longum MAK34B12L
In 2 products →No human trials found yet
B. longum NI313
In 2 products →No human trials found yet
B. longum SD-5845
In 2 products →No human trials found yet
B. longum SP 07
In 2 products →No human trials found yet
B. longum UABi-13
In 2 products →No human trials found yet
B. longum Vpro 55
In 2 products →No human trials found yet
B. longum Bi-7
In 1 product →No human trials found yet
B. longum BI211
In 1 product →No human trials found yet
B. longum BINF-EXT-1
In 1 product →No human trials found yet
B. longum BK89
In 1 product →No human trials found yet
B. longum BL50
In 1 product →No human trials found yet
B. longum BL88
In 1 product →No human trials found yet
B. longum CECT 7347
In 1 product →No human trials found yet
B. longum EVC001
In 1 product →No human trials found yet
B. longum HRVD90b-US
In 1 product →No human trials found yet
B. longum KB31
In 1 product →No human trials found yet
B. longum LB21
In 1 product →No human trials found yet
B. longum NX 5845
In 1 product →No human trials found yet
B. longum R-175
In 1 product →No human trials found yet
B. longum Rosell-33
In 1 product →No human trials found yet
B. longum SP54
In 1 product →No human trials found yet
B. longum UABi-14
In 1 product →No human trials found yet
B. longum VP-87
In 1 product →No human trials found yet
B. longum VP-89
In 1 product →No human trials found yet
B. longum VP-91
In 1 product →No human trials found yet
B. longum VP-93
In 1 product →No human trials found yet
B. longum VP-95
In 1 product →No human trials found yet
B. longum VPro54
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