Bacillus indicus

Other Names

Bacillus cibiMetabacillus indicus

Synopsis

Bacillus indicus (HU36): A Comprehensive Reference

1. Identity, Classification, and Natural Source

Taxonomic Classification and Strain Designation

Bacillus indicus HU36 is a Gram-positive, spore-forming bacterium known for its probiotic properties and ability to produce carotenoids — pigments with antioxidant effects. HU36 is a pigmented isolate of B. indicus and is a member of a subgroup of Bacillus spp. that are rich in carotenoids (Duc et al., 2006). The species belongs to the family Bacillaceae, phylum Firmicutes. The strain designation "HU36" refers to its development at Holloway University (now Royal Holloway University of London), where it was assigned the thirty-sixth strain number in the research series.

Natural Source and Isolation

Bacillus indicus HU36 is isolated from human feces and used in dietary supplements and functional foods. B. indicus as a species has been isolated from human faeces, marine samples (water, sediment, plankton, mangroves), the Korean seafood dish Jeotgal, and various soil samples from a plethora of environments, including arsenic-contaminated sand, hot spring, salt pan, mangroves, and oily sludge. Six isolates of pigmented spore-forming bacteria were recovered from human faeces from subjects in Vietnam.

Commercial and Trade Names

The strain is commercially marketed as ColorsporeTM Bacillus indicus HU36 (Bacillus HU36), described as a unique patented strain of Gram-positive spore-forming bacterium that produces a distinct yellow-orange pigmentation. The European Union's COLOSPORE program-grant identified Bacillus indicus HU36 as gastric-stable and safe for consumption; these strains have been licensed exclusively to Viridis Biopharma for incorporation into foods.

2. Development History and Research Origins

The Royal Holloway University of London (RHUL) conducted an exhaustive study of these pigmented Bacillus species, identifying a diverse range of spore-forming Bacillus containing carotenoid pigments with potential probiotic properties and health benefits. Bacillus HU36 was developed at London University as a part of the Colorspore Project — a consortium funded by the European Union. Carotenoid extracts from Bacillus strains HU36 were provided by members of the Colorspore consortium (Small Collaborative Project No. 207948, funded by FP7 and coordinated by the Royal Holloway University of London).

The project comprehensively annotated Bacillus HU36, developed optimal bioprocess conditions for the production of carotenoid-containing bacterial spores, demonstrated bio-accessibility and bioavailability, and completed in-vivo and in-vitro toxicity and safety studies, as well as formulations for different food prototypes.

3. Traditional and Historical Use

No discrete, well-documented traditional or ethnopharmacological use of Bacillus indicus HU36 as a named or intentionally consumed substance has been identified in the published scientific literature. This strain was first characterized and developed for commercial use in the twenty-first century as a result of laboratory isolation from human fecal samples, and its commercial introduction as a dietary supplement ingredient post-dates this research. It does not appear in classical herbal or pharmaceutical traditions.

The broader Bacillus genus encompasses Gram-positive, rod-shaped, spore-forming, aerobic or facultatively anaerobic bacteria with the ability to produce a wide variety of enzymes, antimicrobial compounds, vitamins, and carotenoids. Bacillus species have been increasingly proposed for use as probiotics or feed additives because of advantages including heat-stability of spores, storage capacity at ambient temperature, and beneficial properties for health. The general concept of Bacillus-based fermented foods — such as natto (fermented soybean, Japan) and similar fermented staples — forms a broad historical backdrop for the genus, but no historical record specifically implicates B. indicus HU36 in any such tradition.

4. Key Constituents and Active Compounds

Carotenoid Profile

Recently isolated spore-forming pigmented marine bacteria Bacillus indicus HU36 are sources of oxygenated carotenoids with original structures — about fifteen distinct yellow and orange pigments with acylated d-glucosyl groups. Ultra-high performance liquid chromatography–mass spectrometry (UPLC-MS) analyses of the crude bacterial extract containing HU36 carotenoids identified two carotenoid glucosides as the parent structures of all subsequent peaks: O-glycosyl carotenoid and methylester O-glycosyl carotenoid.

Bacillus indicus HU36 is a spore-forming bacterium that produces various carotenoid pigments, such as astaxanthin, zeaxanthin, and α-carotene, which have a putative protective role against UV irradiation and oxygen-reactive forms. At least 11 different carotenoids are found in the walls of HU36 spores and the vegetative cells. Additional carotenoids reported in supplement literature include lycopene, lutein, and beta-carotene, though the precise quantitative composition of each specific carotenoid in HU36 has not been independently published in a detailed peer-reviewed study accessible via the sources reviewed here.

Other Bioactive Metabolites

The bacterium also co-produces the bacterial vitamin menaquinone MQ-7, the presence of which has been evaluated in combination with HU36 carotenoids for synergistic antioxidant effects. Supplement sources note the production of quinols and vitamins B and K2 by the vegetative cells, consistent with known metabolic capabilities of the Bacillus genus, though specific peer-reviewed data quantifying these outputs for HU36 specifically were not identified.

5. Established Mechanisms of Action

Carotenoid-Mediated Antioxidant Activity

In a study evaluating the stability and antioxidant activity of HU36 carotenoids in combination with the bacterial vitamin menaquinone MQ-7 and with phenolic antioxidants (vitamin E, chlorogenic acid, and rutin), MQ-7 was found to strongly improve the ability of HU36 carotenoids to inhibit iron-induced lipid peroxidation. The researchers proposed that this interaction modifies the carotenoid antioxidant mechanisms, possibly by allowing carotenoids to scavenge initiating radicals.

The carotenoid pigments produced by HU36 are described as gastric-stable, bio-accessible, and significantly more bioavailable than carotenoids from other sources. The carotenoids produced by Bacillus indicus HU36 are gastric-stable, enhancing their bioavailability and allowing them to exert antioxidant effects.

Immune Modulation via Pattern Recognition Receptors

Bacillus indicus HU36 primarily offers immune stimulation through the activation of Toll-like receptors, specifically TLR2, leading to cytokine induction. It modulates the immune system by activating TLR2, which triggers the release of cytokines like TNFα, and this interaction primarily occurs within the gut-associated lymphoid tissue (GALT), influencing the overall immune response.

Spore Germination and Gut Colonization

The bacterium can colonize the gut and remains stable in various food matrices without refrigeration, making it a convenient ingredient for diverse applications. Being a sporulating bacterium, HU36 offers advantages of better colonization and survival through the digestive tract when compared to non-sporulating probiotic organisms, with antioxidants and carotenoids as synthesized having high bioaccessibility.

Antimicrobial and Microbiome Modulation

Bacillus strains possess biotherapeutic potential connected with their ability to interact with the internal milieu of the host by producing a variety of antimicrobial peptides and small extracellular effector molecules. Secondary benefits of B. indicus HU36 may include the exclusion of harmful pathogens and the production of beneficial nutrients within the gut; however, the evidence supporting these benefits is largely derived from in vitro and animal studies.

6. Scientific Evidence by Area of Application

6.1 Antioxidant Activity and Carotenoid Bioavailability

Mechanism (in vitro): In a published study characterizing HU36 carotenoids, researchers evaluated the stability (sensitivity to iron-induced autoxidation) and antioxidant activity (inhibition of iron-induced lipid peroxidation) of combinations of bacterial HU36 carotenoids with menaquinone MQ-7 and phenolic antioxidants. Unexpectedly, MQ-7 was found to strongly improve the ability of HU36 carotenoids to inhibit FeII-induced lipid peroxidation, leading researchers to propose that this interaction modifies carotenoid antioxidant mechanisms, possibly by allowing carotenoids to scavenge initiating radicals.

Evidence strength: The antioxidant data for HU36 carotenoids is primarily in vitro. No published human randomized controlled trials (RCTs) specifically measuring carotenoid absorption or antioxidant status after administration of isolated B. indicus HU36 as a single agent were identified in this review. Evidence therefore remains preliminary and mechanistic at this time.

6.2 Gut Microbiota Composition and Activity

In vitro gut model study (2021): MegaSporeBiotic™ is an oral, spore-based probiotic comprised of five Bacillus species including Bacillus indicus HU36, Bacillus subtilis HU58, Bacillus coagulans SC208, Bacillus licheniformis SL307, and Bacillus clausii SC109. Treatment with this five-strain formula resulted in changes that could be beneficial to the gut microbiota: propionate levels increased, lactate and ammonium levels decreased, treatment increased Akkermansia muciniphila, Bifidobacteria, and Firmicutes levels, and bacterial diversity increased.

The effects on gut microbiota activity and community composition were evaluated for the first time using an in vitro model of the human gastrointestinal tract, the simulator of the human intestinal microbial ecosystem (SHIME®), under healthy conditions; following a stabilization period and a control period of two weeks each, the reactor feed was supplemented with daily MegaSporeBiotic™ for three weeks.

Limitation: High quality studies that elucidate the mechanisms by which Bacillus probiotics exert beneficial effects in both healthy and unhealthy individuals are needed, and studies using healthy donors may shed light on the mechanisms by which Bacillus probiotics support a healthy gut microbiome. Critically, HU36 was used as part of a five-strain blend in this study, and specific effects attributable to B. indicus HU36 alone cannot be isolated from these data.

6.3 Intestinal Permeability (Leaky Gut)

Human clinical evidence (multi-strain formula): In a 30-day clinical study, researchers gave subjects either a placebo or a combination of Bacillus spore probiotic strains (Bacillus indicus HU36®, Bacillus subtilis HU58®, Bacillus coagulans SC208, Bacillus licheniformis, and Bacillus clausii SC). Those who took the probiotics saw a 60% reduction in leaky gut compared to the placebo control group, and the probiotic group also saw a 24% reduction in triglyceride levels and a significant reduction in over six different systemic inflammation markers.

Researchers suggested that the strain Bacillus indicus HU36® may have been instrumental in the leaky gut study because oxidative stress is a major driver of intestinal permeability, and HU36® is the only probiotic strain that produces potent antioxidants in the intestines exactly where they can be absorbed, reducing inflammation and oxidative stress.

Evidence strength: This represents a published human clinical finding. However, the result is derived from a multi-strain combination product, making it impossible to attribute the outcome specifically to B. indicus HU36. The role of HU36 in the leaky gut finding is speculative and mechanistically proposed, not directly demonstrated by isolating this strain.

6.4 Gut Microbiota and Antibiotic-Associated Dysbiosis

In vitro model (infant gut): A study used MegaSporeBiotic™ — a probiotic comprising spores of five different Bacillus strains including B. indicus HU36 — and fecal microbiota from healthy 6–24-month-old babies from four individual donors to assess the effects on recovery of gut microbiota following antibiotic treatment in an in vitro model. This study used an in vitro model and should not be interpreted as human clinical evidence of efficacy.

6.5 Immune Function

Bacillus indicus HU36 primarily offers immune stimulation through the activation of Toll-like receptors, specifically TLR2, leading to cytokine induction, and this suggests a potential to modulate the gut-associated lymphoid tissue (GALT). The evidence supporting these benefits is largely derived from in vitro and animal studies. Human studies are needed to quantify the effect sizes and clinical significance, and the time course of these benefits in humans is also not well-established.

6.6 Aquaculture and Animal Studies

In a study testing novel probiotic blends (Bacillus subtilis and/or Bacillus indicus) as alternative health and/or colouration supplements to astaxanthin in two cyprinid species — mirror carp and Red Comet goldfish — researchers used experimental feed trials and 16S rRNA microbial profiling to assess the impact on fish growth and microbial community within the distal gastrointestinal tract, and in mirror carp, blood samples were tested for immunology and haematological parameters, while goldfish colouration was analyzed. Mirror carp fed astaxanthin showed significantly increased growth, whereas the B. subtilis/B. indicus supplementation had non-significant effects on growth performance. This animal-based research does not directly translate to human health outcomes.

6.7 Metabolic Health (Animal Studies)

A probiotic mixture composed of five different Bacillus spp. protected mice from high-fat diet-induced obesity, insulin resistance, and non-alcoholic fatty liver disease (NAFLD). Probiotic Bacillus treatment substantially attenuated body weight gain and enhanced glucose tolerance by sensitizing insulin action in skeletal muscle and epididymal adipose tissue of high-fat-diet-fed mice. Bacillus-treated mice also exhibited significantly suppressed chronic inflammation in the liver, adipose tissue, and skeletal muscle, associated with reduced intestinal permeability and enhanced adiponectin production. This study used a multi-species mixture and is animal-based; it cannot be directly extrapolated to human clinical outcomes for HU36 alone.

6.8 Food Applications Research

A 2016 peer-reviewed study (Erşan et al., International Journal of Dairy Technology, 69:81–88) examined the viability of Bacillus indicus HU36 in vegetative form in set-type recombined nonfat yoghurt during storage at 4°C. The number of B. indicus HU36 cells in yoghurt remained about 5 log CFU/mL after 14 days, but decreased to 3.5 log after 21 days. The bacterium resulted in increased yellowness but did not affect the rheological properties of the yoghurt, and sensorial properties were acceptable compared to a commercial probiotic yoghurt. The study also showed that B. indicus HU36 accelerates fermentation, achieving pH 4.5 thirty minutes faster than controls.

7. Body Systems and Health Areas Associated with Bacillus indicus HU36

Gastrointestinal system: The bacterium's ability to colonize the gut supports its probiotic action, contributing to a balanced gut microbiota and improved immune function.
Immune system: HU36 modulates the immune system by activating Toll-like receptors, particularly TLR2, which triggers the release of cytokines like TNFα; this interaction primarily occurs within the gut-associated lymphoid tissue (GALT).
Antioxidant/oxidative stress: The carotenoid pigments produced by HU36 have a putative protective role against UV irradiation and oxygen-reactive forms.
Intestinal barrier function: Multi-strain clinical data suggests a potential contribution to intestinal barrier integrity, though evidence attributable specifically to HU36 alone remains indirect.
Metabolic health (animal/in vitro only): Animal studies using Bacillus mixtures point toward potential effects on lipid metabolism and metabolic endotoxemia, but these cannot be specifically attributed to HU36 in the absence of isolated human data.

8. Dosage Forms and Reported Dosages

Common Supplemental Forms

B. indicus HU36 produces gastric-stable carotenoids that are bioavailable after oral consumption, and the bacterium remains stable in various food matrices without refrigeration, making it a convenient ingredient for diverse applications. The Bacillus HU36 spores can survive the harsh conditions associated with food processing and may be incorporated into a range of food matrices without the need for refrigeration; the strain is also uniquely stable in liquids at room temperature and will remain dormant in non-refrigerated beverages.

As a robust spore, it can be incorporated into food matrices without the need for refrigeration and is stable in a variety of beverages including fruit and dairy products, and is able to withstand heating at 235°C for up to eight minutes, allowing for incorporation into a number of cooked and baked food products.

Reported Dosages in Research

In published research using MegaSporeBiotic™, each capsule consists of 4 billion spores from Gram-positive, spore-forming Bacillus strains including B. indicus HU36. In one human clinical study, the spore-based probiotic Megasporebiotic™ included 4 billion spores from five strains including Bacillus indicus (HU36™), and participants were provided 4 capsules per day for a total of 45 days.

The minimum effective dose, optimal dosage ranges, and maximum safe dose of Bacillus indicus HU36 are not yet established in human studies. Timing considerations for administration are also not specified. It is available in various food matrices and supplements, and its gastric stability enhances absorption. Due to the limited human data, specific dosage recommendations cannot be provided.

9. Safety Considerations

Published Safety Assessment

The landmark safety study for HU36 (Hong et al., 2008, Journal of Applied Microbiology) aimed to conduct in vitro and in vivo assessments of the safety of two species of Bacillus, including B. indicus. Cultured cell lines — Caco-2, HEp-2, and the mucus-producing HT29-16E cell line — were used to evaluate adhesion, invasion, and cytotoxicity.

Neither species was able to adhere significantly to any cell line. No strain produced any of the known Bacillus enterotoxins. Disc-diffusion assays using a panel of antibiotics listed by the European Food Safety Authority (EFSA) showed that only Bacillus indicus carried resistance to clindamycin at a level above the minimum inhibitory concentration breakpoints set by the EFSA. In vivo assessments of acute and chronic dosing in guinea pigs and rabbits were made, and no toxicity was observed in animals under these conditions.

Conclusion of the safety study: Bacillus indicus and B. subtilis should be considered safe for oral use, although the resistance of B. indicus to clindamycin requires further study, and the results support the use of B. subtilis and B. indicus strains as food supplements.

Clindamycin Resistance: A Specific Safety Signal

Disc-diffusion assays showed that only Bacillus indicus carried resistance to clindamycin at a level above the minimum inhibitory concentration breakpoints set by the EFSA. A clindamycin MIC above the EFSA breakpoint was also identified in other Bacillus strains in later research, suggesting this may be an intrinsic characteristic of Bacillus species, and more work will be needed to demonstrate whether this resistance is of clinical concern. This resistance finding represents the most consistently noted safety consideration in the primary literature, though its clinical relevance has not been definitively established.

Evidence Quality Limitation

The current evidence base for B. indicus HU36 is primarily from in vitro and animal studies, with limited high-quality human clinical trials to fully validate its benefits and optimal usage. All published human clinical data for this strain involve it as a component of a multi-strain proprietary mixture, meaning effects cannot be isolated and attributed to HU36 specifically. The strain is generally considered safe, but its resistance to clindamycin requires further study.

References

Health Conditions

Health conditions that Bacillus indicus may help support.

No conditions available.

Body Systems

Body systems that Bacillus indicus may help support.

No body systems available.