Bacillus velezensis · Paenibacillus polymyxa
Éra Boost Pro and Éra N-Fix sporulating consortia
PSB and PGPR Bacteria: Natural Drivers of Soil Fertility
Less than 5% of the phosphorus present in agricultural soils is directly available to plants. PSB and PGPR bacteria transform this immobilized phosphorus and much more into resources available for crops, in greenhouses and in the field.
<5%
available phosphorus
of total present in the soil
+20–40%
root biomass
with selected PSB strains
10⁴–10⁶
CFU/g or mL
effective window at application
What is a PSB bacterium?
PSB (Phosphate-Solubilizing Bacteria) are rhizospheric microorganisms capable of converting insoluble phosphorus into plant-available orthophosphate. This conversion relies on two complementary biochemical mechanisms.
Rhizosphere acidification
Secretion of organic acids (gluconic, citric, oxalic) that dissolve insoluble mineral phosphates. The mechanism involves the gcd/pqq genes encoding membrane glucose dehydrogenase.
García-Contreras et al., Front. Microbiol. 2026
Enzymatic mineralization
Production of phosphatases and phytases that hydrolyze organic soil phosphorus (phytates, nucleic acids, phospholipids) into available mineral forms.
Panda et al., 2025 · Bhattacharyya & Jha, 2012
The genera Bacillus and Paenibacillus are among the best-documented PSB for these two combined activities. Bacillus velezensis and related species (B. subtilis, B. amyloliquefaciens, B. pumilus, B. megaterium) rank among the commercially exploitable strains with the highest PSB activity, depending on the strain and substrate.
Key data — concentration at application
The effective window is between 10⁴ and 10⁶ CFU/g or mL depending on the substrate and strain. Beyond this threshold, intraspecific competition for carbon and substrate nutrients becomes a real barrier to root colonization the inoculant works against itself.
PGPR: a broader spectrum of action
PGPR (Plant Growth-Promoting Rhizobacteria) encompass PSB and act on several other agronomic levers simultaneously. A recent review identifies more than 30 distinct mechanisms documented for the genus Bacillus alone.
Atmospheric nitrogen fixation
Certain strains fix atmospheric N₂ in an associative manner, reducing dependence on synthetic nitrogen fertilizers.
Sun & Shahrajabian, Earth Syst. Environ. 2025
Root stimulation
Production of auxins (IAA) that increase the absorbent root surface area directly improving the efficiency of water and mineral uptake.
Vessey, Plant Soil 2003
Biocontrol
Synthesis of siderophores and antifungal lipopeptides. Induction of systemic resistance (ISR) against foliar and root pathogens.
Bhattacharyya & Jha, 2012
Improved nutrition
Mobilization of iron, zinc, manganese, boron and copper. ACC deaminase production reducing ethylene stress. Improvement of soil enzymatic activity.
Luiz Santos et al., Front. Plant Sci. 2026
Application in greenhouse horticulture
In greenhouse production, the rhizosphere is confined, the substrate volume is limited, the renewal is frequent (depending on the type of plants being produced), and they used precision irrigation. These conditions amplify the impact of PSB/PGPR: the phosphorus mobilized in a restricted volume is directly available to a dense root system.
Transplant inoculation is the most documented strategy. On substrates with low available phosphorus (peat, coco fibre, perlite) the PSB effect is particularly pronounced.
Tomato / pepper
Transplant inoculation. Benefit on root development and K/P uptake during the vegetative phase.
Aeroponic strawberry
PGPR with ISR activity strengthen resistance to pathogens without residues.
Lettuce / greens
PGPR auxins accelerate post-transplant rooting, reducing the time to first harvest.
Cucumber
PSB activity on coco substrate compensates for the naturally low P availability in this medium.
Cannabis / medicinals
Compatible with CanadaGAP and organic certification CGSB 32.311.
Seedlings and propagation
PGPR auxins stimulate cutting rhizogenesis and accelerate young plant establishment.
Greenhouse data — recent reference
Bacillus velezensis improves the growth of several horticultural crops (basil, cabbage, tomato, pepper) from nursery application. The combination of nursery + post-transplant inoculation produces the highest gains in survival and productivity.
Environ. Microbiome 2026 — Ohio State / USDA-ARS
Certification compatibility
Sporulating Bacillus consortia are compatible with CanadaGAP, HACCP and Ecocert Canada organic certification (CGSB 32.310 / 32.311). No residues, no pre-harvest interval.
Application in field crops
In corn, soy, canola and cereals, inoculation with well-characterized PSB/PGPR consortia optimizes the efficiency and quantity of fertilizers applied without replacing them. The effect is cumulative: solubilization of existing soil P + improved uptake of applied P fertilizer.
Reference data
Studies report root biomass gains of 20 to 40% with selected PSB strains. A recent study on sugarcane shows that B. velezensis alone delivers results comparable to 2/3 of the recommended MAP dose, with a 22% increase in bioavailable soil phosphorus.
Vessey 2003 · Bhattacharyya & Jha 2012 · Luiz Santos et al., Front. Plant Sci. 2026
Field performance remains variable depending on pedoclimatic context, competitive pressure from resident flora and timing of application.
Oli et al., World J. Microbiol. Biotechnol. 2025
Why sporulation is a decisive criterion
Non-sporulating bacteria rapidly lose viability during formulation, storage and exposure to field or greenhouse conditions. Bacillus spores are metabolically dormant and resistant to extreme conditions, a property directly linked to the efficacy of the formulated product in the field.
This stability determines the viable density at application, which must remain within the effective window (10⁴–10⁶ CFU/g) after the constraints of the logistics chain and storage at the producer's facility.
Éra products
Éra Boost Pro and Éra N-Fix incorporate Bacillus and Paenibacillus strains selected for their documented PSB/PGPR activity, formulated as spores to guarantee stability and efficacy at application in greenhouse horticulture and field crops alike.
Scientific references
Vessey, J.K. (2003). Plant growth promoting rhizobacteria as biofertilizers. Plant and Soil, 255, 571–586. doi:10.1023/A:1026037216893
Bhattacharyya, P.N. & Jha, D.K. (2012). Plant growth-promoting rhizobacteria (PGPR): emergence in agriculture. World Journal of Microbiology and Biotechnology, 28, 1327–1350. doi:10.1007/s11274-011-0979-9
Panda, J. et al. (2025). The role of phosphate-solubilizing bacteria (PSB) in sustainable agriculture. Environ. Sci. Proc., 4(6). ResearchGate
Sun, W. & Shahrajabian, M.H. (2025). Biostimulant and beyond: Bacillus spp., the important PGPR-based biostimulant. Earth Systems and Environment, 9, 1465–1498. doi:10.1007/s41748-024-00552-4
Oli, D. et al. (2025). The PGPB paradox: a critical review of field performance. World Journal of Microbiology and Biotechnology. doi:10.1007/s11274-025-04552-y
Environ. Microbiome (2026). Calcium phosphate-solubilizing bacteria promote growth in horticultural crops. Environmental Microbiome, 21:24. doi:10.1186/s40793-025-00844-w
García-Contreras et al. (2026). Phosphate-solubilizing ability of Lysinibacillus macroides. Frontiers in Microbiology, 17. doi:10.3389/fmicb.2026.1849362
Luiz Santos, H. et al. (2026). Enhancing soil health with Bacillus velezensis UFV 3918. Frontiers in Plant Science, 17:1805752. doi:10.3389/fpls.2026.1805752