IngredientsPriestia megaterium (previously known as Bacillus megaterium) is a Gram-positive, rod-shaped, spore-forming bacterium. The organism was first described and named by the German botanist Anton de Bary in 1884. B. megaterium, named for its large size (approximately 1.5 Ć 5 Āµm), was first discovered by Anton De Bary in 1884. The genus name Bacillus is well established, while the species epithet megaterium has a complex etymology: three hypotheses of the epithet "megaterium" are possible: unintentional orthographic error (unlikely given the fact that de Bary and his students consistently used the epithet "megaterium"), whereas it should have been megatherium, from therion (ĪøĪ·ĻĪÆĪæĪ½, meaning "beast"), to mean "great beast."
In more recent taxonomic revisions, the species has been reclassified. Since its discovery in 1884 (de Bary), Priestia megaterium (formerly known as Bacillus megaterium) has been studied extensively in the scientific literature. The full current taxonomic classification is: Phylum Bacillota (Firmicutes), Class Bacilli, Order Caryophanales, Family Bacillaceae, Genus Priestia. Despite the reclassification to Priestia megaterium, the name Bacillus megaterium remains dominant in the dietary supplement and probiotic literature and in older peer-reviewed work. Both names refer to the same organism and are used interchangeably in this article.
Bacillus megaterium is a rod-like, Gram-positive, mainly aerobic spore-forming bacterium found in widely diverse habitats. With a cell length of up to 4 Āµm and a diameter of 1.5 Āµm, B. megaterium is amongst the biggest known bacteria. The cells often occur in pairs and chains, where the cells are joined together by polysaccharides on the cell walls. It is considered aerobic, but is also capable of growing under anaerobic conditions when necessary.
One of the largest Eubacteria found in soil, the name "mega" means "relatively big"; it is a common soil saprophyte. It is motile, with the use of its flagella, and the cell wall has large amounts of peptidoglycan. The cell surface is a laminated structure that consists of a capsule, a proteinaceous surface layer (S-layer), and several layers of peptidoglycan sheeting. B. megaterium grows at temperatures from 3 Ā°C to 45 Ā°C, with the optimum around 30 Ā°C. Some isolates from an Antarctic geothermal lake were found to grow at temperatures up to 63 Ā°C. B. megaterium is also able to survive in extreme conditions such as desert environments due to the spores it forms.
Regarding spore morphology: spores are ellipsoidal or spherical, central, paracentral or subterminal, and do not swell the sporangia. Spores occur in soil, dust, water, and plants.
Bacillus megaterium does not have a widely recognized common name in the way botanical herbs do. In the supplement industry, it appears primarily under strain-specific trade names. One well-studied commercial strain is Bacillus megaterium MIT411, marketed as RenusporeĀ®, which has been characterized for general probiotic properties. The type strain DSM32 (ATCC14581) has been used to conduct basic genetic research and is also known as the source of the cytochrome P450-BM3 (CYP102A1).
Spores of B. megaterium occur in soil and feces, have been isolated from foods and clinical specimens, and have also been found in the gut of the termite Zootermopsis angusticollis. The species thrives as a soil saprophyte and is ubiquitous across diverse ecosystems. Rhizospheric strains have been isolated from metal-polluted soils, for example a strain designated HgT21 was isolated from soil in Zacatecas, Mexico. As a plant-growth promoting rhizobacterium (PGPR), it associates closely with plant root zones. Its wide distribution across soil, water, fermented food products, and the gastrointestinal tracts of insects and mammals underlies its relevance as both a biotechnological organism and a potential probiotic.
In the 1960s, prior to the utilization of Bacillus subtilis for this purpose, B. megaterium was the main model organism among Gram-positive bacteria for intensive studies on biochemistry, sporulation, and bacteriophages. This position in mid-20th century microbiology means the organism has an unusually deep scientific dossier. The single strain has been used for many studies on various aspects of spore physiology and cell wall structure.
Spore-forming bacilli have been explored for the production and preservation of food for many centuries. While B. megaterium specifically was not the subject of named traditional medical preparations in classical European, Chinese, or Ayurvedic medicine as a recognized ingredient, the broader genus Bacillus has been present in fermented foods across cultures for millennia. The species' long presence in soil and plant environments means it was consumed incidentally via fermented vegetables, traditional sourdoughs, natto-style fermented legumes, and similar preparations across Asia and elsewhere, though no traditional pharmacopeias isolated or named B. megaterium as a distinct therapeutic agent.
B. megaterium has been used as a biofertilizer in agriculture. This agricultural application likely dates to observations of soil health improvement associated with natural populations of the bacterium long before the scientific identification of the species. B. megaterium has been used in the past for the industrial production of vitamin B12 (cobalamin), historically known as the anti-pernicious anaemia factor.
B. megaterium is one of the vitamin B12 producers and an ideal host for many biotechnology applications, being one of the best tools for the industrial production of several enzymes. More recently, its popularity has started increasing in the field of biotechnology for its recombinant protein production capacity. These industrial applications ā vitamin B12 fermentation, enzyme production, and recombinant protein expression ā preceded its investigation as a human dietary supplement or probiotic by several decades.
The inherent ability of production of a large number of secretory proteins, enzymes, antimicrobial compounds, vitamins, and carotenoids specifies the importance of bacilli in the food chain. For B. megaterium specifically, several classes of enzymes are notable:
Vitamin B12 is a fascinating molecule which acts as a cofactor in the metabolism of many organisms, especially affecting DNA synthesis and regulation, fatty acid synthesis, and energy production. The synthesis of vitamin B12 is limited to a few bacteria and archaea. B. megaterium has been used in the past for the industrial production of vitamin B12 (cobalamin), the anti-pernicious anaemia factor. Cobalamin is a modified tetrapyrrole with a cobalt ion coordinated within its macrocycle.
Cobalamin (vitamin B12) production in Bacillus megaterium has served as a model system for the systematic evaluation of single and multiple directed molecular and genetic optimization strategies. Plasmid and genome-based overexpression of genes involved in vitamin B12 biosynthesis, including cbiX, sirA, modified hemA, the operons hemAXCDBL and cbiXJCDETLFGAcysGAcbiYbtuR, and the regulatory gene fnr, significantly increased cobalamin production.
B. megaterium is a natural PHB producer, functioning as an LPS-free and established industrial production host. It is the organism for which the accumulation of PHB was first reported in 1926. PHB is a biopolymer and is not itself a bioactive supplement compound, but its natural production in B. megaterium is relevant to its cellular physiology and has been exploited in biotechnology for vaccine and diagnostic bead applications.
B. megaterium is an antibiotic producer, specifically producing a bacteriocin called "megacin." This antimicrobial peptide represents one mechanism by which the bacterium may suppress pathogenic competitors in the gut and in agricultural settings.
Metabolic analysis of the RenusporeĀ® strain demonstrated strong enzymatic activity with a high release of amino acids and beneficial short-chain fatty acids (SCFAs). SCFAs such as butyrate, acetate, and propionate are recognized gut-health metabolites that support colonocyte nutrition, intestinal barrier function, and immunomodulation.
In silico studies of the MIT411 strain revealed genes associated with carbohydrate, protein, and lipid metabolism, xenobiotic chelation or degradation, and antioxidant properties. One studied strain contains an important set of genes related to a variety of operons associated with mercury, arsenic, copper, cobalt, cadmium, zinc, and aluminum resistance; additionally, halotolerance-, beta-lactam resistance-, phosphate solubilization-, and plant growth-promotion-related genes were identified.
Elementary attributes of native flora for survivability are not essential for spore-formers. Bacillus spores can survive in extreme acidity of the stomach and tolerate bile salts and other hostile conditions of the gastrointestinal tract. This spore-based resilience is the mechanistic foundation for using B. megaterium and related bacilli as oral probiotics: the dormant endospore form is highly resistant to gastric acid and enzymatic degradation, allowing live bacteria to reach the intestine where germination into vegetative cells occurs.
Fundamental attributes of the native bacterial microbiota that confer survival are not essential for Bacillus species, which show additional characteristics, such as tolerance of acids and bile salts in the hostile environment of the gastrointestinal tract, that support their use as probiotics. Bacilli are more stable during processing and storage of food and pharmaceutical preparations, making them more suitable candidates for health-promoting formulations.
B. megaterium MIT411 (RenusporeĀ®) demonstrated high levels of total antioxidant activities, in addition to antimicrobial activity against Escherichia coli, Salmonella enterica, Staphylococcus aureus, and Campylobacter jejuni in vitro. The production of megacin and possibly other antimicrobial peptides underlies this competitive exclusion of pathogens.
Probiotics possess health-promoting properties including antimicrobial activity, antioxidant and anti-inflammatory properties, immunomodulatory capacity, and production of bioactive molecules such as enzymes, short-chain fatty acids, and free amino acids. The antioxidant capacity of B. megaterium has been demonstrated in vitro but has not, as of the available literature, been confirmed in controlled human trials.
RenusporeĀ® effectively chelated the heavy metals mercury and lead, without negatively impacting the beneficial minerals iron, magnesium, or calcium, and degraded the environmental contaminants nitrite, ammonia, and 4-chloro-2-nitrophenol. B. megaterium has been studied for the elimination of environmental pollutants because of high levels of resistance to hostile conditions including exposure to heavy metals.
B. megaterium is a Gram-positive, endospore-forming rhizobacterium recognized for its high-efficiency solubilization of inorganic phosphate compounds. By producing organic acids and phosphatases, it enhances phosphorus bioavailability, promoting early crop establishment, accelerated phenological development, and improved root system architecture. This mechanism is primarily of agricultural relevance rather than directly applicable to human supplementation.
The cytochrome P450 BM-3 from B. megaterium can be regarded as a "one-enzyme-fits-all" oxidation catalyst. Catalytic activities of the variants are promiscuous towards non-natural substrates including human P450 substrates. The natural CYP enzyme repertoire of B. megaterium is primarily studied in the context of industrial biocatalysis and is not established as a direct mechanism of probiotic benefit in the human gut.
In the principal published in vitro study, B. megaterium MIT411 (RenusporeĀ®) was characterized for general probiotic properties including antimicrobial activity, dietary metabolism, and antioxidant activity, and for the capacity to detoxify several environmental contaminants that can be found in the food chain. In silico studies revealed genes associated with carbohydrate, protein, and lipid metabolism, xenobiotic chelation or degradation, and antioxidant properties. The metabolic analysis demonstrated strong enzymatic activity with a high release of amino acids and beneficial short-chain fatty acids (SCFAs).
Evidence strength: The gut health evidence for B. megaterium specifically is currently at the in vitro and genomic/in silico stage. No randomized controlled trials (RCTs) in humans evaluating B. megaterium as the sole probiotic ingredient for gut health were identified in the peer-reviewed literature. The available human-grade evidence is primarily extrapolated from studies on other Bacillus species (such as B. subtilis, B. coagulans, and B. clausii), which share the spore-forming phenotype but differ at the species and strain level. Characterization of probiotic properties for B. megaterium should therefore be considered preliminary and largely preclinical.
RenusporeĀ® effectively chelated the heavy metals mercury and lead without negatively impacting the beneficial minerals iron, magnesium, or calcium, and degraded the environmental contaminants nitrite, ammonia, and 4-chloro-2-nitrophenol. B. megaterium has been studied for the elimination of environmental pollutants because of high levels of resistance to hostile conditions including exposure to heavy metals, with some strains demonstrating efficacy in this context. Different spore probiotic species such as B. subtilis, B. megaterium, B. coagulans, and B. pumilus were also investigated for the removal of environmental contaminants using chelation or bioaccumulation principles.
Evidence strength: All detoxification evidence is in vitro. These findings suggest that RenusporeĀ® may play a beneficial role in supporting gut health metabolism and eliminating unwanted dietary contaminants, but this remains a hypothesis requiring confirmation in animal models and ultimately in human trials. No human clinical data on B. megaterium for detoxification endpoints were identified.
B. megaterium has previously been employed as an industrial producer of vitamin B12 (cobalamin), which is used intravenously or as a dietary supplement to treat pernicious anaemia. The scientific literature here is extensive, but it concerns the bacterium as a manufacturing platform for cobalamin rather than as an orally consumed probiotic that produces B12 in situ. Studies demonstrate that B. megaterium could be a good candidate for the industrial production of vitamin B12. Growth of engineered strains on minimal media supplemented with glycerol as a carbon source resulted in significant increases in cobalamin production (up to 200 Āµg Lā»Ā¹).
Evidence strength: The evidence that B. megaterium biosynthesizes cobalamin is robust and well-established at the microbiology level. Whether oral supplementation with live B. megaterium cells or spores substantially raises serum B12 levels in humans has not been demonstrated in clinical trials. This distinction is important: use of the bacterium as a production host is not equivalent to dietary supplementation with the bacterium itself.
B. megaterium is known to solubilize phosphorus (P) and potassium (K) in the soil, promote plant growth, as well as inhibit pathogens. The ability of studied strains to produce indole acetic acid (a phytohormone) and promote the growth of Arabidopsis thaliana seedlings in vitro has been demonstrated. This body of evidence is directed at agricultural biotechnology and not at human or animal health supplementation. The phosphate-solubilizing and plant growth-promoting properties are mentioned in dietary supplement contexts as markers of the organism's metabolic versatility, but they do not directly translate to human health claims.
One study demonstrated that B. megaterium 1259 (BM1259) at 1 Ć 10āø CFU/g may be a potentially useful probiotic in dairy cows, with a recommended dose of 10 or 15 g/day per head. Further research was noted as necessary to uncover the mechanism by which BM1259 improves nitrogen utilization in lactating dairy cows. Animal studies provide biological plausibility for probiotic effects but cannot be directly extrapolated to human outcomes.
The antioxidant properties of B. megaterium have been identified through in vitro assays. In silico studies revealed genes associated with carbohydrate, protein, and lipid metabolism, xenobiotic chelation or degradation, and antioxidant properties in the MIT411 strain. Demonstration of antioxidant activity in cell-free assays does not confirm clinically meaningful antioxidant effects in the human gastrointestinal tract. No human interventional data on antioxidant endpoints for B. megaterium were identified.
Bacilli are more stable during processing and storage of food and pharmaceutical preparations, making them more suitable candidates for health-promoting formulations. Bacillus strains with probiotic attributes are commercialized in the form of a diverse range of health supplements. B. megaterium is marketed in supplement form primarily as dried spores. Spore-forming Bacillus strains as constituents of foods and pharmaceutical preparations are stable during processing and storage.
Common dosage forms include:
Human dosage data specific to B. megaterium as a probiotic are sparse in the peer-reviewed literature. The only animal dosage data found in identified sources are from dairy cow research: BM1259 at 1 Ć 10āø CFU/g was studied in dairy cows at dosages of 5, 10, or 15 g/day per head. No established human dosing guidance from regulatory bodies (such as the EFSA or FDA) was identified for B. megaterium as a probiotic supplement in humans. Dosages used in the in vitro characterization studies (e.g., RenusporeĀ®) were not reported in terms of per-serving human equivalents in the available abstracts and summaries.
There is no evidence in the scientific literature to suggest that Bacillus megaterium strain ATCC 14581 is likely to have adverse effects on human health. In humans, Bacillus megaterium is generally considered to be non-pathogenic and is rarely isolated as an opportunistic pathogen in individuals with pre-existing health conditions. The species is considered to be not pathogenic or to have low virulence.
In spite of its widespread presence in the environment, B. megaterium has rarely been implicated in human infections. When it has been associated with infection, it was not always clear if the clinical isolates were opportunistic pathogens or contaminants. Documented cases from the literature include:
These reports consistently describe immunocompromised individuals or breaches in normal physical barriers (wounds, post-surgical states) as predisposing factors. B. megaterium is generally non-pathogenic; it can occasionally be associated with opportunistic infections, particularly in immunocompromised individuals.
In the unlikely event of infection, Bacillus megaterium strain ATCC 14581 is sensitive to a variety of antibiotics. In at least one documented case, the isolated organism was sensitive to all antibiotics against which it was tested, and the oral antibiotic therapy was set for 12 days with benefits. Antibiotics which appear especially useful in the treatment of Bacillus infections are clindamycin and vancomycin, to which a clear majority of strains are susceptible in vitro.
Some resistance profiles have been identified: examination of antibiotic resistance revealed that B. megaterium was highly resistant to streptomycin and cephalexin. These characteristics are relevant to the regulatory requirement, outlined by EFSA, that bacteria intentionally introduced to food or feed be evaluated for resistance genes. It is a requirement by the European Food Safety Authority (EFSA) that bacteria intentionally introduced to food or feed are free of acquired antimicrobial resistance genes conferring resistance toward antimicrobial compounds that are considered highly or critically important for treatment of infections in humans.
Five P. megaterium strains lack natural plasmids, while the remaining strains contain up to ten plasmids, consistent with studies already from the early 1980s which found plasmid-less strains to be an exception. The complex plasmid content of the species is relevant to safety, as plasmids are the primary vehicles for horizontal gene transfer of antibiotic resistance traits. Plasmid-less strains (such as DSM319) are preferred for biotechnological applications and, potentially, for supplement use from a safety standpoint.
The available literature does not include controlled clinical safety trials specifically evaluating B. megaterium supplementation in immunocompromised individuals. Given the reported opportunistic infection cases above, this population represents a theoretical area of concern, consistent with general guidance applicable to all live microbial supplements in immunocompromised patients.
The species is not listed on the EFSA Qualified Presumption of Safety (QPS) list specifically for human food use in the manner that, for example, Bacillus subtilis or Bacillus coagulans are. The Canadian government's Health Canada assessment concluded: there is no evidence in the scientific literature to suggest that Bacillus megaterium strain ATCC 14581 is likely to have adverse effects on human health. No information was identified implicating B. megaterium strain ATCC 14581 in adverse human health effects. The species is, however, subject to strain-by-strain evaluation, and regulatory classification may differ by jurisdiction and strain.
No peer-reviewed clinical data on drug-supplement interactions specific to oral B. megaterium supplementation in humans were identified in the available literature. As a spore-forming probiotic, the general theoretical interaction concern ā shared with all live bacterial supplements ā is that concurrent use of oral antibiotics may reduce viable counts and potentially diminish any beneficial effects. The practical significance of this for B. megaterium, given its demonstrated resistance to certain antibiotic classes, has not been formally studied in humans.
The evidence base for Bacillus megaterium as a human dietary supplement is at an early stage. The organism has an exceptionally well-developed scientific profile as a biotechnology and agricultural tool, and selected strains (particularly RenusporeĀ® MIT411) have been characterized in vitro for probiotic properties including antimicrobial activity, antioxidant capacity, SCFA production, and heavy metal chelation. Animal studies provide limited but suggestive data on probiotic effects in livestock. However, as of the available peer-reviewed literature, no published randomized controlled trials in healthy or diseased humans have evaluated B. megaterium as a dietary supplement for any health endpoint. Claims regarding its probiotic benefits in humans should therefore be understood as extrapolated from in vitro data, animal studies, and the wider literature on spore-forming Bacillus species. The safety record in humans is favorable ā the species is broadly considered non-pathogenic ā but with documented exceptions in specific clinical contexts. Further clinical research is required before evidence-based human supplementation recommendations can be made.
Health conditions that Bacillus megaterium may help support.
Body systems that Bacillus megaterium may help support.
Go back