Bacillus mucilaginosus: Rock-Weatherer and Soil-Enhancer for Sustainable Agriculture

Overview of the Microbe#

Taxonomy and Morphology#

Bacillus mucilaginosus (synonymously known as Paenibacillus mucilaginosus in some classifications) is a rod‐shaped, facultatively anaerobic bacterium belonging to the phylum Firmicutes and family Bacillaceae[9]. Cells measure approximately 0.8–1.0 µm in diameter and 2–4 µm in length, and produce oval endospores that confer resistance to desiccation and temperature extremes. Colonies on agar media are often slimy due to abundant extracellular polysaccharide (EPS) production, which plays key roles in soil aggregation and moisture retention.

Habitat and Ecology#

B. mucilaginosus is ubiquitously present in agricultural soils, particularly in weathered silicate‐rich regions where mineral weathering offers ecological niches[2]. It thrives in neutral to slightly alkaline pH (6.5–8.0) and temperatures between 20 °C and 37 °C, making it adaptable to tropical and temperate agroecosystems. As a model organism for microbe–mineral interactions, it often coexists with plant roots, forming beneficial associations characteristic of plant growth‑promoting rhizobacteria (PGPR)[9].

Rock Weathering and Mineral Solubilisation#

Mechanisms of Silicate Weathering#

B. mucilaginosus accelerates the dissolution of silicate minerals (e.g., feldspar, mica, and basalt) through organic acid secretion—primarily citric, oxalic and gluconic acids—that chelate and protonate mineral surfaces, disrupting crystal lattices and releasing Si, Al, Fe, Mg and other elements[1][2]. Experimental assays have demonstrated up to 40 % higher dissolution rates of feldspar in the presence of B. mucilaginosus cultures compared to abiotic controls, underscoring the bacterium’s weathering potency.

Mineral Nutrient Release#

Through weathering, macro‑ and micronutrients (e.g., K⁺, Ca²⁺, Mg²⁺, Fe²⁺/³⁺) become solubilised and bioavailable for plant uptake. Co‑inoculation studies combining crushed rock powder with B. mucilaginosus have reported yield increases of up to 25 % in maize and wheat, evidencing the agronomic benefits of microbial rock weathering[10]. Furthermore, laboratory incubations show that B. mucilaginosus can mobilise non‐exchangeable potassium from mica at rates comparable to chemical acid treatments, but without environmental hazards[5][4].

Phosphate Solubilisation and Nutrient Mobilisation#

Phosphate‑Solubilising Traits#

B. mucilaginosus solubilises inorganic phosphates by secreting organic acids that lower pH and chelate cations bound to phosphate, converting insoluble phosphates (e.g., Ca₃(PO₄)₂) into soluble H₂PO₄⁻/HPO₄²⁻ forms[3]. Typical acidification can reduce culture media pH from 7.0 to as low as 4.0, significantly enhancing phosphorus availability. Phosphatase enzymes further mineralise organic phosphorus compounds, completing the cycle of P mobilisation.

Agronomic Impacts#

Field trials in phosphorus‑deficient soils have shown that B. mucilaginosus inoculation increases plant P uptake by 20–35 %, leading to 10–20 % higher grain yields in cereals and legumes[8]. Enhanced root biomass and lateral root proliferation under P stress have been observed in tomato and maize seedlings treated with B. mucilaginosus, indicating its role in root architecture modulation[3].

Drought Tolerance and Soil Aggregation#

Exopolysaccharide‑Mediated Soil Structuring#

The high EPS output of B. mucilaginosus binds soil particles into macroaggregates, improving porosity, aeration and water retention. Inoculated soils show 15–25 % higher aggregate stability indices than uninoculated controls, mitigating erosion and compaction[6]. Laboratory studies report that EPS can hold up to five times their weight in water, buffering plants against drought spells.

Induction of Plant Stress Responses#

B. mucilaginosus inoculation enhances plant antioxidant enzyme activities—superoxide dismutase, catalase and peroxidase—under drought conditions, reducing oxidative damage and maintaining photosynthetic efficiency[13]. In maize and wheat, drought‑stressed seedlings treated with B. mucilaginosus maintain 25 % higher relative water content and exhibit delayed wilting compared to non‑inoculated counterparts[14].

Biocontrol and Plant Health Promotion#

Antagonism and Induced Systemic Resistance#

B. mucilaginosus produces lytic enzymes (chitinases, glucanases) and antimicrobial metabolites (phenazines, cyclic lipopeptides) that inhibit fungal pathogens such as Rhizoctonia solani and Fusarium oxysporum[13]. Seed and foliar applications have reduced disease incidence by 30–50 % in greenhouse trials, demonstrating its utility as a biocontrol agent[7].

Promotion of Plant Growth#

Beyond nutrient mobilisation, B. mucilaginosus synthesises phytohormones—indole‑3‑acetic acid (IAA), gibberellins and cytokinins—that stimulate root elongation and shoot development. Combined PGPR effects underpin 15–30 % increases in biomass and yield across horticultural and field crops when used as biofertiliser.

Challenges and Future Potential#

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Formulation and Field Performance#

Variability in field efficacy arises from soil physicochemical heterogeneity, native microbial competition and environmental stresses. Advanced carrier formulations—such as alginate beads and biochar matrices—are under development to enhance survival and shelf life of B. mucilaginosus inoculants.

Genetic and Systems Biology Insights#

Genome sequencing of Paenibacillus mucilaginosus strains has revealed clusters encoding acid production, EPS synthesis and stress‐tolerance factors, guiding targeted strain improvement via genetic or adaptive evolution approaches[12]. Systems biology integration promises refined inoculant consortia combining complementary PGPR traits for maximal agronomic benefit.

Regulatory and Adoption Pathways#

Clear regulatory frameworks and farmer education on biofertiliser benefits are critical for scaling B. mucilaginosus deployment. Collaborative initiatives between research institutions, industry and policy bodies are essential to validate and standardise application protocols across diverse cropping systems.

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Spotlight on Research: Bacillus mucilaginosus in Potato Production#

Brief Overview#

Bacillus mucilaginosus (also known as Paenibacillus mucilaginosus) is a well-researched potassium‑solubilising bacterium recognized for converting insoluble minerals into plant‑available nutrients—especially potassium, phosphorus, and silicon. It also enhances micronutrient availability (e.g. Ca, Mg, Fe, Zn), improves soil structure, and produces phytohormones like IAA and gibberellins to promote plant growth and stress resilience

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Key Insights#

In a comparative screening involving isolates for potassium solubilisation using waste mica as the potassium source, the reference strain B. mucilaginosus mobilized 40.53 mg/mL K, compared to 45.33 mg/mL by the top-performing isolate and 32 mg/mL by another Bacillus species. While some new isolates outperformed it, this confirmed B. mucilaginosus as a strong benchmark for potassium release in soil krishikosh.egranth.ac.in.

Additional literature identifies B. mucilaginosus as a potent silicate‑solubilising microbe, capable of releasing potassium and silicon, secreting organic acids and exopolysaccharides that aid in nutrient mobilization and soil aggregation—collectively improving crop growth and yield potential

Why This Matters#

Potassium is a critical nutrient for tuber development, water regulation, and enzyme activation in potatoes. Enhancing the availability of potassium via B. mucilaginosus supports stronger tuberisation, improved yield, and better tuber quality—especially in potassium‑deficient so

Summary Table: Spotlight Study#

Conclusion#

Category	Details
Lead Researchers	N. K. Altamimi, J. S. Alkobaisy & M. O. Sallume
Affiliations	Department of Soil Science and Water Resources, College of Agriculture, University of Anbar, Ramadi, Iraq[11]
Research Focus	Impact of B. mucilaginosus, mushroom farm residues and mineral K fertiliser on potato growth and yield.
Key Breakthroughs	Co‑application of B. mucilaginosus with mushroom waste achieved equivalent or superior growth and yield compared to full mineral fertiliser, demonstrating sustainable nutrient recycling.
Collaborative Efforts	Partnerships between microbiologists, agronomists and waste management specialists.
Published Work	IOP Conf. Series: Earth and Environmental Science 1449 (2025) 012099, doi:10.1088/1755-1315/1449/1/012099[11]
Perspective	Illustrates potential of integrating biofertiliser with agro‑waste to reduce chemical inputs while maintaining yields.
Publication Date	2025
Location	Ramadi, Iraq.
Key Findings	Potato tuber yield increased by 18 % under combined biofilm–waste treatment versus mineral fertiliser alone; soil K availability improved by 22 %; soil health indicators (aggregate stability and microbial respiration) were enhanced.

Bacillus mucilaginosus stands out as a versatile microbial ally for sustainable agriculture, capable of weathering minerals, solubilising essential nutrients, improving soil structure and enhancing plant resilience against biotic and abiotic stresses. Integrating its use as a biofertiliser and biocontrol agent can significantly reduce chemical fertiliser and pesticide inputs, fostering eco‑friendly crop production. Ongoing advances in genomics, formulation technology and field validation will further unlock its potential, aligning with global goals for sustainable intensification and soil health restoration.

References#

1. Wu X., et al. Preliminary study on the rock weathering effect of Bacillus mucilaginosus. Aloki Journal (2011). aloki.hu
2. Basak B.B., Biswas D.R. Natural efficiency of Bacillus mucilaginosus on the solubilization of silicate minerals. International Journal of Phyto­chemistry (2017). Phytojournal
   
3. Rodríguez H., Fraga R. Phosphate-solubilizing bacteria and their role in plant growth promotion. Biotechnology Advances (1999). PMC
   
4. Shen J., et al. Mechanisms of potassium solubilization by bacteria. Applied Soil Ecology (2013). ScienceDirect
   
5.  Indogulf Bioag. Bacillus mucilaginosus potassium solubilizing bacteria Manufacturer. [online] (2025). Indogulf BioAg
   
6. Dora Agri‑Tech. Advantages of Bacillus mucilaginosus Fertilizer. [online] (2024). Dora Agri-Tech
   
7. Frontiers in Plant Science. Bacillus and Paenibacillus as plant growth-promoting bacteria (2025). Frontiers
   
8. Universal Microbes. Bacillus Mucilaginosus: A Game‑Changer in Sustainable Agriculture. [online] (2024). universalmicrobes.com
9.  Sciencedirect Topics. Bacillus Mucilaginosus – an overview. [online] (2025). ScienceDirect
10. PMCID PMC7759553. Use of Mineral Weathering Bacteria to Enhance Nutrient Availability. (2020). PMC
    
11. Altamimi N.K., Alkobaisy J.S., Sallume M.O. The Role of Bacillus mucilaginosus, Mushroom Farm Residues, and Mineral Potassium in Some Characteristics of Potato Plants. IOP Conf. Ser.: Earth Environ. Sci. 1449 012099 (2025). ResearchGate
    
12. Wang, D., Poinsot, V., Li, W., Lu, Y., Liu, C., Li, Y., Xie, K., Sun, L., Shi, C., Peng, H., Li, W., Zhou, C., & Gu, W. (2023). Genomic insights and functional analysis reveal plant growth promotion traits of Paenibacillus mucilaginosus G78. Genes, 14(2), 392. https://doi.org/10.3390/genes14020392.
13. Han, X., Shen, Y., Sun, L., Shen, J., Mao, Y., Fan, K., Wang, S., Ding, Z., & Wang, Y. (2025). Phyllospheric application of Bacillus mucilaginosus mediates the recovery of tea plants exposed to low-temperature stress by alteration of leaf endophytic community and plant physiology. BMC Microbiology, 25, 177. https://doi.org/10.1186/s12866-025-03880-1.
    
14. Abdelaal, K. H. A., AlKahtani, M. D. F., Attia, K. A., Hafez, Y. M., Király, L., & Künstler, A. (2021). The role of plant growth-promoting bacteria in alleviating the adverse effects of drought on plants. Biology, 10(6), 520. https://doi.org/10.3390/biology10060520.