Azomonas agilis

Azomonas agilis: Encyclopedic Reference

Overview and Important Preliminary Note

Azomonas agilis is a free-living, nitrogen-fixing bacterium with well-characterised biology in microbiology and agricultural science. Exhaustive searches of peer-reviewed databases (PubMed/PMC), government health body databases (NIH, NCCIH, WHO, EFSA), official pharmacopoeial monographs, and evidence-synthesis resources (Cochrane, Examine.com) return no records establishing Azomonas agilis as a dietary supplement ingredient, a traditional herbal or microbial medicine, or a substance evaluated in human clinical trials for any health outcome. The American Type Culture Collection (ATCC) — the definitive repository for type strains — explicitly states that its Azomonas agilis product "is not intended for any animal or human therapeutic use, any human or animal consumption, or any diagnostic use." The ATCC product is intended for laboratory research use only and is not intended for any animal or human therapeutic use, any human or animal consumption, or any diagnostic use.

Any representation of Azomonas agilis as a dietary supplement ingredient therefore currently lacks a scientific or regulatory foundation. The article below presents all verified scientific knowledge about the organism and explains why there is no supplement-relevant evidence base to report.

Identity and Taxonomy

Scientific Name and Nomenclatural History

Azomonas agilis is a species of motile, Gram-negative bacteria found in water and is capable of fixing atmospheric nitrogen. It is the type strain for the genus Azomonas.

The basonym of the species is Azotobacter agilis Beijerinck 1901. The accepted combination, Azomonas agilis (Beijerinck, 1901) Winogradsky, 1938, carries Taxonomic Serial No. 959624 in the Integrated Taxonomic Information System (ITIS). According to Bergey's Manual of Systematics of Archaea and Bacteria (Kennedy and Rudnick, 2015), Azomonas agilis (Beijerinck 1901) Winogradsky 1938 is the type species of the genus Azomonas.

According to the List of Prokaryotic names with Standing in Nomenclature (LPSN), the taxonomic status of the genus Azomonas is a correct name (last update, February 2025); its LPSN classification is Bacteria / Pseudomonadati / Pseudomonadota / Gammaproteobacteria / Pseudomonadales / Pseudomonadaceae / Azomonas.

The genus name carries classical etymological significance. The name derives from the Greek a (not) and zoê (life), hence azoê meaning "not sustaining life" — i.e., nitrogen — combined with monas (a unit, monad), giving the Modern Latin feminine noun Azomonas: "nitrogen monad."

Full Taxonomic Classification

• Domain: Bacteria
• Phylum: Proteobacteria
• Class: Gammaproteobacteria
• Order: Pseudomonadales
• Family: Pseudomonadaceae
• Genus: Azomonas
• Species: Azomonas agilis

The family formerly described as Azotobacteriaceae comprises two genera: Azomonas spp. (non-cyst-forming), with three species (Azomonas agilis, Azomonas insignis, and Azomonas macrocytogenes), and Azotobacter spp. Current molecular analysis has revised this picture; Pseudomonadaceae currently includes the following genera: Azomonas (3 species, but only 2 are available in culture collections), Azotobacter (7 species), Pseudomonas (252 species), and others.

There is ongoing molecular debate about the boundaries of the genus. A consideration of phenotypic determinative characteristics supports the possible synonymy of the genera Azomonas Winogradsky 1938 and Azotobacter Beijerinck 1901, as indicated by sequence data; an investigation with a wider selection of strains, including the type species Azomonas agilis, might support their synonymy, in which case Azotobacter would take priority over Azomonas. Phylogenomically, Azomonas is a genus whose members branch in between Pseudomonas species; the two Azomonas species included in phylogenomic analyses (A. agilis and A. macrocytogenes) formed a distinct cluster.

Type Strain and Culture Collection Designations

A. agilis was first isolated and described by Martinus Beijerinck in 1901, who obtained the species from Dutch canal water in Delft. Beijerinck's original strain has been lost, so the strain isolated by Albert Kluyver and van den Bout is now the neotype. The type strain is held in multiple international culture collections under the designations DSM 375, ATCC 7494, CCUG 53669, LMG 3842, IAM 15039, LMG 14901, LMG 8754, and NCIMB 12097. Azomonas agilis DSM 375 is a mesophilic bacterium of the family Pseudomonadaceae.

Morphology and Cellular Characteristics

A. agilis resembles protists with its ovoid, ellipsoidal, or coccoid cells. The cells are relatively large, usually 2.5–6.4 μm long and 2.0–2.8 μm wide, though giant cells that are 10.0–13.5 μm have been described. According to Bergey's Manual, cells are 2.0 μm or more in diameter, of variable length and shape, although usually 2.5–3.5 μm in length and generally ellipsoidal- to rod-shaped. They cannot easily be distinguished from cells of Azotobacter. Cells may occur singly, in pairs, or in clumps. They are motile by peritrichous, lophotrichous, or polar flagella, and are Gram-negative but sometimes Gram-variable, depending on culture age.

Motility is conferred by lophotrichous flagella that tend to bind together to form thick, whip-like structures. Cysts are not formed. This last point — the absence of cyst formation — is a key feature distinguishing Azomonas from the related genus Azotobacter, which does form environmentally resistant cysts.

The species also produces a diffusible yellow-green or red-violet pigment which fluoresces bluish-white under ultraviolet light. Some strains use glucose and produce a water-soluble green pigment, fluorescent under ultraviolet light, which are the main characteristics of Azomonas agilis.

Cysts are not formed and motility is very intense. Physiologically, isolates are strictly aerobic, catalase positive, and able to reduce acetylene, confirming their membership in the genus Azomonas.

Natural Sources and Ecology

Azomonas agilis is found in water and is capable of fixing atmospheric nitrogen. Unlike many related nitrogen-fixing bacteria that are primarily soil-dwelling, A. agilis is characteristically aquatic. In 1941, the presence of Azomonas agilis was reported in rivers near Buenos Aires City, with the bacterium studied for its possible influence on the nitrogen balance in waters.

The organism has also been isolated from terrestrial environments. Azomonas agilis, a nitrogen-fixing bacterium, was isolated from rhizospheric soil in central Myanmar. Salt tolerance of this species is up to 1.0%, and it is resistant to iodoacetate (1 μM); it is suggested that it may have the ability to live in contaminated water with relatively high concentrations of organic matter and mineral salts. In addition, A. agilis has been studied in the context of bioremediation of cadmium-polluted water.

Salt tolerance of this species is up to 1.0%, and it is resistant to iodoacetate (1 μM). The isolated A. agilis grew in media containing 3–12% of NaCl, although growth became poor when NaCl concentrations increased.

Key Biochemical Constituents and Known Metabolic Capacities

Nitrogenase System and Nitrogen Fixation

The defining biochemical feature of A. agilis is its capacity for biological nitrogen fixation, catalysed by the nitrogenase enzyme complex. All species of Azomonas fix atmospheric nitrogen under aerobic conditions. Nitrogen fixation is the biochemical reduction of atmospheric dinitrogen (N₂) to ammonia (NH₃), a form of nitrogen assimilable by living organisms. Among various carbon sources, sucrose is the best source for ammonium accumulation by A. agilis, whereas arabinose is not a suitable carbon source.

The nitrogenase of aerobic nitrogen-fixing bacteria must be protected against inactivation by oxygen. Obligate aerobes fix nitrogen under fully aerobic conditions that typically inactivate the nitrogenase enzyme; two known mechanisms for protecting nitrogenase against oxygen damage are (i) a high respiration rate that prevents diffusion of oxygen into the cells and consequently to the nitrogenase, and (ii) conformational protection of the enzyme or the switch-off of nitrogenase activity by Shethna or FeSII protein.

The nitrogen-fixing activity of A. agilis is highest after one week of incubation. Research has confirmed that Azomonas agilis is among the free-living nitrogen-fixing bacteria that can grow and fix N₂ using aromatic compounds as the sole carbon and energy source; all tested species grew and expressed nitrogenase activity on benzoate, catechol, 4-hydroxybenzoate, naphthalene, protocatechuate, and 4-toluate. Specific activity of nitrogenase in extracts of aromatic-grown cells often exceeded that in cells grown on non-aromatic substrates.

Cellulase Production

A. agilis also produces extracellular cellulase enzymes, conferring it with the ability to degrade cellulosic material. Cellulase enzyme production is highest after 2–3 days of incubation, and cellulase enzyme activity of A. agilis for cellulose and sodium carboxymethyl cellulose (CMC) are almost the same. In quantitative determination, the cellulase of the bacterium can convert some cellulosic residues into reducing sugar. Among five substrates, reducing sugars were recovered, indicating high potential as an effective bacterial strain for agricultural application and degradation of some agricultural residues.

Pigment Production

The species produces a diffusible yellow-green or red-violet pigment which fluoresces bluish-white under ultraviolet light. This fluorescent pigmentation is a characteristic used in species identification, but its biochemical significance has not been characterised in the context of any health application.

Relationship to Alginate Gene Sequences

Research into the broader Pseudomonas–Azomonas–Azotobacter lineage has examined alginate biosynthesis genes. Distribution of alginate gene sequences has been studied in the Pseudomonas rRNA homology group I–Azomonas–Azotobacter lineage of superfamily B prokaryotes. However, the capacity of A. agilis specifically to produce alginate as a functional exopolysaccharide has not been studied independently or evaluated for any health application.

Discovery and Scientific History

A. agilis was first isolated and described by Martinus Beijerinck in 1901, who obtained the species from Dutch canal water in Delft. Beijerinck's original strain has been lost, so the strain isolated by Albert Kluyver and van den Bout is now the neotype. Serge Winogradsky formally transferred the species to the genus Azomonas in 1938, creating the currently accepted combination. In 1901, Beijerinck extensively studied the extensive capsule-producing nitrogen fixer originally named Azotobacter agilis, which was found in Holland.

In 1941, the presence of Azomonas agilis in rivers near Buenos Aires City was first reported, extending the known geographic range of the species to South America. Estimations of bacterial density by the most probable number method indicated that this was very low, and no nitrogenase activity could be detected in the river water even after 48 hours of incubation.

The molecular placement of Azomonas within the Gammaproteobacteria was clarified in rRNA studies. Azomonas agilis, Azomonas insignis, and Azomonas macrocytogenes constitute independent branches about equidistant from Azotobacter and section I of Pseudomonas as presented in Bergey's Manual of Determinative Bacteriology. More recent phylogenomic work has confirmed this picture: Azomonas is a genus whose members branch in between Pseudomonas species; the two Azomonas species included in phylogenomic analyses formed a distinct cluster, a distinctness also supported by five conserved sequence indels (CSIs) identified in that work, which are exclusively shared by these two species.

Agricultural and Environmental Research Applications

The only documented applied research involving A. agilis relates to sustainable agriculture and environmental microbiology — not human health.

The isolated A. agilis has high potential as an effective bacterial strain to use in sustainable agriculture and degradation of some agricultural residues; keywords associated with its research include nitrogen fixation, cellulose degradation, and sustainable agriculture. The isolated A. agilis has high potential as an effective bacterial strain for agricultural application and degradation of some agricultural residues; however, it will not be suitable when applied in salt-affected agricultural soils, and more experiments on other important characteristics for agriculture should be studied.

The related genus Azotobacter has been studied as a component of biofertilisers in agriculture. Given their nitrogen-fixing capabilities and plant growth-promoting traits, Azotobacter species have great potential as biofertilisers, enhancing plant nutrition and soil fertility; Azotobacter-based biofertilisers stand out due to these bacteria's ability to form cysts, which confer resistance to environmental stresses and ensure stability under diverse conditions. Azomonas agilis does not form cysts, which is a notable difference limiting its suitability for similar applications.

Traditional and Historical Use

No traditional or historical use of Azomonas agilis as a medicine, dietary supplement, food ingredient, or therapeutic preparation in any culture or time period has been documented in any source retrieved. The species was not identified until 1901 by scientific microbiological methods, and its characterisation has remained entirely within the domain of laboratory and agricultural science. It does not appear in any pharmacopoeial monograph, traditional medicine compendium, herbalism literature, or ethnomedical record.

Scientific Evidence for Health-Related Applications

Human Clinical Evidence

There is no human clinical evidence of any kind for Azomonas agilis as a dietary supplement, functional food ingredient, probiotic, or therapeutic agent. No randomised controlled trials, observational studies, case series, or pilot studies involving human subjects have been identified in PubMed, PMC, or any other peer-reviewed database.

Animal Studies

No animal (in vivo) studies examining health outcomes from administration of Azomonas agilis to mammalian subjects have been identified.

In Vitro / Cell Culture Studies

The available in vitro literature on A. agilis is restricted to its enzyme biochemistry (nitrogenase, cellulase), its pigment production, and its nitrogen-fixing metabolism — none of which have been examined in the context of human physiological systems or health endpoints.

Summary of Evidence Strength

There is no evidence base — at any level of the research hierarchy (in vitro, animal, or human) — supporting the use of Azomonas agilis as a dietary supplement, health ingredient, or therapeutic agent for any health condition or body system. Any claim to the contrary cannot be grounded in verifiable, peer-reviewed, or regulatory scientific literature.

Dosage Forms and Reported Dosages

No dosage forms, dose ranges, or dosing regimens for human use have been described in any scientific or regulatory source. The organism is handled in culture collections as a research microorganism and is explicitly not intended for human consumption.

Safety Considerations

ATCC explicitly states that its Azomonas agilis product is intended for laboratory research use only and is not intended for any animal or human therapeutic use, any human or animal consumption, or any diagnostic use.

A. agilis is a Gram-negative bacterium. As with all Gram-negative bacteria, its outer membrane contains lipopolysaccharide (LPS), which is a potent endotoxin in mammalian systems. This is a structural feature of the bacterial cell wall and is not specific to any supplement application, but it is directly relevant to the unsuitability of whole-cell preparations for human consumption.

The ATCC classifies its Azomonas agilis (ATCC 12838) product at biosafety level 3, which represents a substantial containment requirement and is not consistent with consumer supplement use.

The broader Pseudomonadaceae family to which A. agilis belongs includes organisms with pathogenic potential. Pseudomonas can be important pathogens; Pseudomonas aeruginosa is an important opportunistic human pathogen, being a major cause of burn and eye infections and also causing severe lung disease in cystic fibrosis patients. While A. agilis is not P. aeruginosa, the phylogenetic proximity of these organisms, combined with the BSL-3 classification of the type strain, reinforces the absence of any basis for its use as a consumable product.

No drug interactions, contraindications, adverse event data, or safety pharmacology for Azomonas agilis as a consumed substance exist in the scientific literature, because no human exposure studies have been conducted.

Regulatory Status

Azomonas agilis does not appear on the European Food Safety Authority (EFSA) Qualified Presumption of Safety (QPS) list for microorganisms used in food or feed, nor is it listed in any NIH Office of Dietary Supplements database, the USP Dietary Supplements Compendium, or any other regulatory framework as a permitted food or supplement ingredient. It has not been reviewed by the WHO, EMA, ESCOP, or German Commission E in any health-relevant context.

Conclusion

Azomonas agilis is a well-characterised, free-living, nitrogen-fixing Gammaproteobacterium first isolated from Dutch canal water by Martinus Beijerinck in 1901. Its scientific significance lies in its role in the biogeochemical nitrogen cycle, its cellulolytic enzyme activity, and its potential applications in sustainable agriculture. It is the type species of the genus Azomonas within the family Pseudomonadaceae. It has no documented history of traditional medicinal use, no established identity as a dietary supplement ingredient, no human clinical evidence for any health application, no approved dosage or preparation for human consumption, and carries an ATCC biosafety level 3 designation with explicit warnings against human or animal consumption. The totality of available evidence — from microbiology, taxonomy, regulatory databases, and clinical research — does not support the characterisation of Azomonas agilis as a dietary supplement or natural health ingredient in any form.

References

• Wikipedia — Azomonas agilis
• Latt ZK et al. (2018). "Using Cellulolytic Nitrogen Fixing Bacterium, Azomonas agilis for Effective Degradation of Agricultural Residues." The Open Microbiology Journal. PMC5997855.
• PubMed abstract — Latt ZK et al. (2018). Using Cellulolytic Nitrogen Fixing Bacterium, Azomonas agilis for Effective Degradation of Agricultural Residues.
• ITIS — Azomonas agilis (Beijerinck, 1901) Winogradsky, 1938. Taxonomic Serial No. 959624.
• GBIF Backbone Taxonomy — Azomonas agilis (Beijerinck, 1901) Winogradsky, 1938.
• Encyclopedia of Life — Azomonas agilis.
• BacDive (DSMZ) — Azomonas agilis DSM 375. BacDiveID:12717.
• ATCC — Azomonas agilis (Beijerinck) Winogradsky. Product 12838.
• PubMed — Azomonas agilis in the surface water of the environs of Buenos Aires (1983).
• LPSN (DSMZ) — Genus Azomonas.
• Kennedy C, Rudnick P (2015). "Azomonas." In: Bergey's Manual of Systematics of Archaea and Bacteria. Wiley/Bergey's Manual Trust.
• Frontiers in Microbiology (2023) — Phylogenomics studies and molecular markers reliably demarcate genus Pseudomonas sensu stricto and twelve other Pseudomonadaceae species clades.
• ScienceDirect Topics — Azomonas overview.
• Archiv für Mikrobiologie — Utilization of aromatic compounds as carbon and energy sources during growth and N2-fixation by free-living nitrogen fixing bacteria (includes Azomonas agilis).
• PMC3465543 — Correlation between nitrogen fixation rate and alginate productivity of an indigenous Azotobacter vinelandii from Iran.
• PMC9866876 — Molecular Mechanism and Agricultural Application of the NifA–NifL System for Nitrogen Fixation.
• PMC12022260 — The c-di-GMP effector FleQ controls alginate production by repressing transcription of algD in Azotobacter vinelandii.