Bacillus megaterium: Versatile Powerhouse for Sustainable Biotechnological Applications

Overview of the Microbe#

Bacillus megaterium (recently reclassified as Priestia megaterium) is one of the largest known bacilli, with cells measuring up to 4 μm long and 1.5 μm across[1][3]. It is a rod‑shaped, Gram‑positive, primarily aerobic spore‑forming bacterium found in soil and diverse ecological niches[2]. Its genome, approximately 5.1 Mb in size, encodes a wide array of metabolic and stress‑response pathways, underpinning its environmental resilience and biotechnological utility.

Agricultural Sustainability and Plant Growth Promotion#

Nutrient Solubilisation#

Certain B. megaterium strains solubilise phosphate and other minerals, increasing nutrient availability to plants and improving soil fertility[5]. For example, strain HT517 possesses genes for organic acid production that mobilise bound phosphates[4].

Phytohormone Production#

B. megaterium synthesises gibberellins and cytokinins, stimulating seed germination and root elongation. In Arabidopsis mutants deficient in cytokinin perception, inoculation with B. megaterium enhanced shoot development, indicating active hormone secretion.

Stress Tolerance and Salinity Management#

In saline soils, inoculation with B. megaterium CDK25 improved maize growth by modulating the rhizosphere microbiome and reducing sodium uptake, demonstrating potential for crop cultivation under abiotic stress.

Industrial Biotechnology and Enzyme Production#

Recombinant Protein Host#

B. megaterium has been used for over 50 years as a host for extracellular protein secretion, owing to its low protease activity and high plasmid stability[6]. The xyl operon‑based expression system enables tight regulation and high yields of heterologous proteins[7].

Enzymatic Arsenal#

This species produces diverse enzymes, including subtilisins, amylases, and lipases, with applications in detergents, food processing, and pharmaceuticals. Recent reviews highlight its potential for industrial biocatalysis and bioprocess optimization[8].

Bioremediation and Heavy Metal Detoxification#

Bacillus megaterium tolerates and transforms heavy metals such as lead, cadmium, nickel, and chromium through biosorption, bioaccumulation, and bioprecipitation[9][10]]. It also produces extracellular polymeric substances (EPS) that sequester metals, aiding soil and water remediation[11]. Synergistic use with plants enhances phytoremediation efficiency by stimulating root uptake of contaminants[10].

Biopolymers and Bio‑based Material Synthesis#

Among its storage compounds, B. megaterium produces polyhydroxybutyrate (PHB), a biodegradable polyester with properties similar to polypropylene[12][13]. Utilising industrial by‑products such as glycerol, certain strains (e.g., DSM 32, saba.zh) can accumulate PHB up to 50% of cell dry weight, offering sustainable bioplastic production routes. Optimization of carbon/nitrogen ratios further enhances yields in bioprocessing settings[15].

Challenges and Future Potential#

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Despite its versatility, challenges remain in genetic tractability compared to model organisms like B. subtilis, requiring development of more efficient CRISPR and transformation systems. Scaling up fermentation while maintaining product consistency is nontrivial, and regulatory approval for environmental releases of large‑scale inoculants or genetically modified strains can be complex. However, advances in systems biology and synthetic biology are poised to unlock novel pathways for specialty chemicals, therapeutic proteins, and resilient biofertilisers.

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Spotlight on Research: Genomic Analysis of Bacillus megateriumHT517#

Brief Overview#

A recent study performed whole‑genome sequencing of strain HT517, a highly efficacious plant growth‑promoting rhizobacterium isolated from saline soils[4].

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Key Insights#

• Identification of gene clusters for phosphate solubilisation and indole‑3‑acetic acid synthesis.
• Discovery of salt‑tolerance genes, including Na⁺/H⁺ antiporters.
• Presence of novel two‑component regulatory systems linked to stress adaptation.

Why This Matters#

Understanding genetic determinants of plant‑microbe interactions enables rational strain improvement and formulation of bioinoculants tailored to marginal lands.

Summary Table: Spotlight Study#

Category	Details
Lead Researchers	Li et al.
Affiliations	South China Agricultural University
Research Focus	Genomic insights into HT517
Key Breakthroughs	Gene clusters for nutrient solubilisation; salt‑tolerance
Collaborative Efforts	Univ. of Alicante collaboration
Published Work	Front. Microbiol.
Perspective	Plant‑microbe genomics
Publication Date	2022
Location	China & Spain
Key Findings	Elucidated metabolic pathways for phosphate solubilisation and salinity resilience[4]

Conclusion#

Bacillus·megaterium stands out as a multifaceted workhorse for sustainable biotechnology, bridging agriculture, industry, environmental remediation, and materials science. Continued genomic and systems‑level studies, coupled with synthetic biology tools, promise to expand its repertoire of applications while addressing global challenges in food security, pollution, and plastic waste.

References#

1. The largest known Bacillus species, B. megaterium, is about 1.5 μm across by 4 μm long. Britannica. Encyclopedia Britannica
2. Priestia megaterium (Bacillus megaterium prior to 2020) is a rod-like, Gram-positive, mainly aerobic, spore forming bacterium. Gupta et al. 2020. Wikipedia
3. Bacillus megaterium is one of the biggest known bacteria, with a cell length of up to 4 μm and diameter of 1.5 μm. DOI:10.1371/journal.pbio.3026448. PMC
4. Genomic Analysis of Bacillus megaterium HT517 Reveals Plant Growth-Promotion and Salt Tolerance Mechanisms. Frontiers in Microbiology, 2022. PMC
5. Role of plant growth promoting Rhizobacteria in agricultural sustainability—a review. Molecules 21:573. 2016. Vejan et al. Frontiers
6. Bacillus megaterium has been industrially employed for more than 50 years, as it possesses useful enzymes and high exoenzyme capacity. J. Bacteriol. 176(11):3565–3573 (2007). PubMed
7. Bacillus megaterium protein production system based on the inducible promoter of the xyl operon (PxylA) was systematically optimized. Appl. Environ. Microbiol., 2010. ASM Journals
8. Practical Potential of Bacilli and Their Enzymes for Industrial Applications. Front. Bioeng. Biotechnol. 8:197. 2020. PMC
9. Microbial remediation of heavy metals contaminated media by Bacillus megaterium. Science of The Total Environment, 2020. ScienceDirect
10. Bioremediation of Heavy Metals by the Genus Bacillus. Microorganisms 11(2):274, 2023. PMC
11. Bioremediation of Heavy Metals by the Genus Bacillus. Int. J. Environ. Res. Public Health 20(8):4811, 2023. PubMed
12. Production of PHAs by Bacillus megaterium revealed PHB as the main polymer. Microb. Cell Factories 22:10, 2023. PMC
13. Recombinant production of PHB by Tadi, S. R. R., Ravindran, S. D., Balakrishnan, R., & Sivaprakasam, S. (2021). Recombinant production of poly-(3-hydroxybutyrate) by Bacillus megaterium utilizing millet bran and rapeseed meal hydrolysates. Bioresource Technology, 326, 124800. https://doi.org/10.1016/j.biortech.2021.124800
14. Amiri Kojuri, S., Issazadeh, K., Heshmatipour, Z., Mirpour, M., & Zarrabi, S. (2021). Production of bioplastic (polyhydroxybutyrate) with local Bacillus megaterium isolated from petrochemical wastewater. Iranian Journal of Biotechnology, 19(3), e2849. https://doi.org/10.30498/ijb.2021.244756.2849.
15. Optimization of PHB production by Priestia megaterium ASL11 achieved 49.6% accumulation. J. Microbiol. Methods 215:106744, 2023. ScienceDirect