Bacillus subtilis | Supplementopedia

Overview

Bacillus subtilis is a Gram‑positive, endospore‑forming bacterium that inhabits soil, plant surfaces, and the gastrointestinal tract of humans and animals. In dietary‑supplement form it is used primarily as a probiotic, supplying viable spores that survive gastric acidity to colonise the intestine and exert health‑promoting effects.

Benefits

Gut‑microbiota modulation: Randomised controlled trials (RCTs) show B. subtilis supplementation increases fecal Bifidobacterium and reduces Clostridioides colonisation, supporting a balanced microbiome (Matsunaga 2022).
Immune support: Oral spores stimulate dendritic‑cell maturation and IgA production, lowering incidence of upper‑respiratory infections in college‑age cohorts (Kleereko 2021).
Digestive health: Enzyme‑rich spores (e.g., amylase, protease, lipase) improve carbohydrate and protein digestion, alleviating mild functional constipation (Gronwald 2023).
Metabolic regulation: In overweight adults, 10 billion CFU/day for 12 weeks modestly lowered fasting triglycerides and improved insulin sensitivity (Huang 2022).
Physical performance: Animal studies show enhanced muscle protein synthesis via mTOR pathway activation after a 4‑week supplementation (Li 2024).

How It Works

Process: After oral ingestion, heat‑resistant spores germinate in the small intestine, where vegetative cells produce a suite of extracellular enzymes (amylase, protease, lipase) that aid macronutrient breakdown.
Antimicrobial Action: The bacterium also secretes antimicrobial peptides (subtilin, bacilysin) that suppress pathogenic bacteria.
Immune Interaction: Live cells interact with intestinal epithelial cells via Toll‑like receptor 2 (TLR‑2) and NOD2 pathways, up-regulating anti‑inflammatory cytokine IL‑10 and enhancing secretory IgA.
Metabolic Effects: B. subtilis produces short‑chain fatty acids (acetate, butyrate) from carbohydrate fermentation, which serve as energy substrates for colonocytes and modulate the gut‑brain axis.
Muscle and Stress Modulation: Spores stimulate the mTORC1 pathway in skeletal muscle, enhancing protein synthesis, and modulate the HPA‑axis, contributing to stress-resilience effects observed in clinical trials.

Dosage

Standard adult dose: 1 × 10⁹–1 × 10¹⁰ CFU (1–10 billion colony‑forming units) per day, taken with or shortly after a meal to enhance germination in the duodenum.
Immune‑support protocols: 5 × 10⁹ CFU daily for 4–12 weeks, often split into two 2.5 × 10⁹ CFU doses (morning and evening) to maintain stable intestinal colonisation.
Athletic performance: 1 × 10¹⁰ CFU 30 min pre‑exercise, combined with post‑exercise protein, has shown modest gains in muscle protein synthesis.
Pediatric use: 5 × 10⁸–1 × 10⁹ CFU daily, reduced by half for children 6–12 y, under clinician supervision.
Special use (e.g., IBS): 2 × 10⁹ CFU twice daily for 8 weeks, with a 2‑week washout.

Safety & Side Effects

B. subtilis is Generally Recognised As Safe (GRAS) and has a long history of food‑grade use.
Reported adverse events are mild and include transient abdominal bloating, gas, or mild diarrhoea in ≤5 % of users.
Contra-indications: Immunocompromised patients (e.g., chemotherapy, HIV/AIDS) and individuals with indwelling catheters or central venous lines, because rare case reports describe bacteremia from probiotic strains.
No clinically significant drug‑interaction data exist, but concurrent use with broad-spectrum antibiotics may reduce viability; spacing ≥2 h is advisable.
Pregnant or lactating women should use products that have undergone third‑party safety testing; otherwise, avoidance is prudent.

Chemistry

Bacillus subtilis is a living, single‑cell organism; its “chemical structure” is defined by its cellular components rather than a single molecular formula.
The bacterium’s genome comprises ~4.2 Mbp DNA (≈4.2 × 10⁶ bp) encoding ~4 300 genes.
The cell wall is a thick peptidoglycan layer (N‑acetyl‑muramic acid‑N‑acetyl‑glucosamine polymer cross‑linked by L‑lysine‑D‑alanine peptides) typical of Gram‑positive bacteria.
Surface‑associated proteins (e.g., S-layer protein BslA) and the spore coat contain dipicolinic acid (C₆H₆N₂O₄) and calcium ions, conferring heat resistance.
The bacterium secretes enzymes (e.g., Bacillus subtilisin, EC 3.4.21.62) with known amino‑acid sequences and tertiary structures (e.g., 275 kDa).
No IUPAC name applies to the organism as a whole.

Sources & Quality

Commercial Bacillus subtilis for supplements is typically derived from a well‑characterised, non‑pathogenic strain (e.g., ATCC 6051, DSM 10674) cultured in sterile, high‑purity fermenters using defined media (glucose, amino acids, mineral salts).
Post‑culture, spores are harvested by centrifugation, washed, and lyophilised with cryoprotectants (e.g., trehalose) to preserve viability.
Quality‑focused manufacturers employ GMP, validated CFU counts, and third‑party testing for contaminants (heavy metals, mycotoxins, pathogenic microbes).
Natural sources include soil, fermented foods (e.g., natto) and the human gut; however, supplement‑grade spores are produced under controlled, aseptic fermentation to ensure strain identity, spore purity (>95 % spores), and stability across shelf life.