Bacillus mucilaginosus
1. Classification
a. Higher order taxa
Higher order taxa: Domain: Bacteria Phylum: Firmicutes Class: Bacilli Order: Bacillales Family: Bacillaceae Genus: Bacillus Species: Bacillus mucilaginosus
2. Introduction
Bacillus mucilaginosus is a Gram-negative, rod-shaped bacteria commonly found in soil.1 It has several properties which make it useful as an agricultural biofertilizer. For example, Bacillus mucilaginosus has the ability to solubilize potassium from minerals in soil so that plants, such as food crops, are able to use it.2 Bacillus mucilaginosus is also useful in wastewater treatment due to its role in microbial flocculation: it helps aggregate bacteria and minerals into large clumps that can be more easily removed from liquids such as sewage and industrial wastewater.3 It has been shown to have the ability to break down silicate materials, but more research is needed on the specific metabolic processes of Bacillus mucilaginosus.1
3. Morphology
Bacillus mucilaginosus is a rod-shaped bacterium measuring 0.8–1.2 μm × 3–9 μm in size.3 This bacteria also has thick capsules surrounding cells, and these capsules can link individual cells together to form zoogloea, a gelatinous matrix of cells with greatly polymerized exocellular material.3, 4 The capsules are 2-5 times larger in size than the cells are.3 The bacterium produces spores that are elliptical or circular.1 The negative Gram staining of Bacillus mucilaginosus indicates that the bacterium has a thin inner peptidoglycan layer and a thick plasma membrane.5
4. Ecology
Bacillus mucilaginosus is most commonly found in the rhizosphere region of soils.6 The bacterium can grow in temperatures from 10℃ to 45℃, with an optimal temperature from 35℃ to 40℃, and its optimal pH range is from 7.5 to 8.0.7 Its proximity to plant roots in its natural habitat suggests that it aids in plant growth; research has been studying the growth patterns of this bacteria and using this information to explore ways to use it as a biofertilizer.7,8
5. Significance and Application
Bacillus mucilaginosus shows potential as a fertilizer that people could use for crops to produce food and other plant-based goods.8 It aids in plant growth by solubilizing phosphorus and potassium, both macronutrients required by plants for growth. 6 It releases these nutrients from soil minerals such as feldspar and mica into soluble forms that plants can uptake.1, 6, 8 Crops grown in soils with Bacillus mucilaginosus have greater potassium and phosphorus uptake and more biomass than crops grown without this microbe.6, 8 It is also useful for cleaning up waste. It plays a part in microbial flocculation in wastewater by aggregating bacteria and minerals into large clumps that can be more easily removed from liquids such as sewage and industrial wastewater.3
6. Current Research
The current research surrounding Bacillus mucilaginosus is focused on its use as a fertilizer by releasing key nutrients. Silicate bacteria such as Bacillus circulans has been shown to release phosphorus for use by plants. Bacillus circulans is inefficient in this process, however a strain of related Bacillus mucilaginosus was engineered to increase the ability of phosphorus liberation.1 In a 2005 study, a plasmid was transformed into Bacillus mucilaginosus and its presence was confirmed by Southern blotting. Bacillus mucilaginosus expressed the phyA gene, which is present in some plants as a way to utilize phosphorus. The engineered strain showed phyA high activity, confirming the ability of Bacillus mucilaginosus to be a microbial fertilizer.9 Since this finding, researchers have focused their studies on ways to further increase the efficacy of Bacillus mucilaginosus in the agricultural field. In a 2017 study, biochar was used to enhance the fertilizing effects of Bacillus mucilaginosus. Biochar is a soil amendment used to improve the quality of soil.10 When incubated with Bacillus mucilaginosus, biochar absorbs Bacillus mucilaginosus. The absorption both increased the survival of Bacillus mucilaginosus, and increased the potassium-releasing properties of biochar.10 Further research can be done to determine the safest and most efficacious strain of Bacillus mucilaginosus to use a biofertilizer.
7. References
[1]Zhang, L., Sun, D., Bo, Y. (2011). Physiological and biochemical characteristics and desilication ability of Bacillus mucilaginosus screened from Poyang Lake area of Jiandxi province. Advanced Materials Research. 308-310(1):1604-1608. Retrieved from: https://doi.org/10.4028/www.scientific.net/AMR.308-310.1604 [2]Yang, X., Li, Y., Lu, A., Wang, H., Zhu, Y., Ding, H., Wang, X. (2016). Effect of Bacillus mucilaginosus D4B1 on the structure and soil-conservation-related properties of montmorillonite. Applied Clay Science. 119(1):141-145. Retrieved from: https://doi.org/10.1016/j.clay.2015.08.033. [3]Lian, B., Chen, Y., Zhao, J., Teng, HH., Zhu, L., Yuan, S. (2008). Microbial flocculation by Bacillus mucilaginosus: Applications and mechanisms. Bioresource Technology. 99(11):4825-31. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/17967531. [4]Friedman, B.A. and Dugan, P.R. (1968). Identification of Zooglea species and the Relationship to Zoogleal Matrix and Floc Formation. Journal of Bacteriology. 95(5):1903-1909. Retrieved from: https://jb-asm-org.ezproxy.bu.edu/content/95/5/1903. [5]Moyes R.B., Reynolds J., Breakwell D.P. (2009). Differential staining of bacteria: gram stain. Current Protocols in Microbiology. 15(1). Retrieved from: https://currentprotocols.onlinelibrary.wiley.com/doi/abs/10.1002/9780471729259.mca03cs15. [6]Li, X., Wu, Z., Li, W., Yan, R., Li, Y., Li, M. (2007). Growth promoting effect of a transgenic Bacillus mucilaginosus on tobacco planting. Applied Microbiology and Biotechnology. 74(5):1120-1125. Retrieved from: https://link-springer-com.ezproxy.bu.edu/article/10.1007/s00253-006-0750-6. [7]Zhao, Y., Zhang, X., Guo, W., Hong, J. (2009). Study on culture condition of Bacillus mucilaginosus isolated from rhizosphere of Kentucky bluegrass. 17(6):822-825. Retrieved from: https://www.cabdirect.org/cabdirect/abstract/20103008714. [8]Basak, B.B. and Biswas, D.R. (2009). Influence of potassium solubilizing microorganism (Bacillus mucilaginosus) and waste mica on potassium uptake dynamics by sudan grass (Sorghum vulgare Pers.) grown under two Alfisols. Plant and Soil. 317: 235-255. Retrieved from: https://doi.org/10.1007/s11104-008-9805-z [9]Li, X., Yang, S.H., Yu, X.C., Jin, Z.X., Li, W.D., Li, L., Li, J., Li, M.G. (2005). Construction of transgenic Bacillus mucilaginosus strain with improved phytase secretion. Journal of Applied Microbiology. 99(4):878-884. Retrieved from: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-2672.2005.02683.x. [10]Liu, S., Tang, W., Yang, F., Meng, J., Chen, W., Li, X. (2017). Influence of biochar application on potassium-solubilizing Bacillus mucilaginosus as potential biofertilizer. Preparative Biochemistry and Biotechnology. 47(1):32-37. Retrieved from: https://www.ncbi.nlm.nih.gov/pubmed/26914283.
