Use of Bacillus as a Plant Growth-Promoting Rhizobacteria to Improve Phosphate and Potassium Availability in Acidic and Saline Soils


Bacillus is a rhizobacterium that can help with the nutrient cycle in the soil. Plant growth-promoting rhizobacteria (PGPR) can be found in the rhizosphere of many plants. This research was divided into two parts: (1) a test of the ability of Bacillus genus isolates to withstand various NaCl concentrations in saline and acidic soils; and (2) quantification of the secondary metabolites produced by the rhizobacteria in the form of hormones and organic acids. Bacillus valezensis (BPF2), which can dissolve phosphate, Bacillus sp (BPK1), and Bacillus subtilis (BPK2), which can dissolve potassium, were the isolates tested. Bacillus increased the availability of phosphate and potassium in the saline and acidic soils and the secondary metabolites produced, such as organic acids and the hormone indole acetic acid. The results showed that the three isolates could still dissolve phosphorous and potassium with a 3% NaCl addition, but the concentration decreased as the incubation time increased to H+15. On the 30th day, Bacillus valezensis inoculation improved soil phosphate availability by up to 88% in the acidic soil and 73% in the saline soil compared to the control. On the other hand, Bacillus sp. and Bacillus subtilis raised the potassium concentration in the acidic soil until day 10, reaching a maximum of 0.37 me.100g−1. The three PGPRs (Bacillus valezensis, Bacillus sp., and Bacillus subtilis) produced 13.25, 11.97, and 14.97 g.mL−1 of indole acetic acid metabolites, respectively. Acetic, lactic, citric, malic, and oxalic acids were among the organic acids produced. Bacillus valezensis produced the most lactic acid at 4.94 mg.L−1, while Bacillus sp. and Bacillus subtilis produced the most acetic acid, at 2.91 and 2.55 mg,L−1, respectively.

Keywords: Bacillus, Organic acid, Indole acetic acid

[1] Lagos L, Maruyama F, Nannipieri P, Mora ML, Ogram A, Jorquera MA. Current overview on the study of bacteria in the rhizosphere by modern molecular techniques: A mini–review. Journal of Soil Science and Plant Nutrition. 2015;15(2):504- 523.

[2] Dworkin M, Falkow S, Rosenberg E, Schleifer K-H, Stackebrandt E, editors. The prokaryotes. A handbook on the biology of bacteria. New York: Springer-Verlag; 2006.

[3] Roesch LFW, Fulthorpe RR, Riva A et al. Pyrosequencing enumerates and contrasts soil microbial diversity. The Isme Journal. 2007;1:283-290.

[4] Saxena AK, Kumar M, Chakdar H, Anuroopa N, Bagyaraj DJ. Bacillus species in soil as a natural resource for plant health and nutrition. Journal of Applied Microbiology. 2019;128:1583—1594.

[5] Goswami D, Thakker JN, Dhandhukia PC. Portraying mechanics of plant growthpromoting rhizobacteria (PGPR): A review. Cogent Food & Agriculture. 2016;2: issue 1: 1127500-1127518

[6] Sharma SB, Sayyed RZ, Trivedi MH, Gobi TA. Phosphate solubilizing microbes: Sustainable approach for managing phosphorus deficiency in agricultural soils. Springerplus. 2013;2:587–600.

[7] Shim J, Kim J-W, Shea PJ, Oh B-T. IAA production by Bacillus sp. JH 2-2 promotes Indian mustard growth in the presence of hexavalent chromium. Journal of Basic Microbiology. 2015;55:652–658

[8] Chen Y, Ye J, Kong Q. Potassium-solubilizing activity of Bacillus aryabhattai SK1-7 and its growth-promoting effect on Populus alba L. Forests. 2020;11:1348-1356.

[9] Bahadir PS, Liaqat F, Eltem R. Plant growth-promoting properties of phosphate solubilizing Bacillus species isolated from the Aegean region of Turkey. Turkish Journal of Botany. 2018;42:183-196.

[10] Xiao-Hua C, Koumoutsi A, Scholz R, Borriss R. More than anticipated - Production of antibiotics and other secondary metabolites by Bacillus amyloliquefaciens FZB42. Journal of Molecular Microbiology and Biotechnology. 2009;16:14–24

[11] Rajawat MVS, Singh S, Tyagi SP, Saxena AK. A Modified plate assay for rapid screening of potassium solubilizing bacteria. Pedosphere. 2016;26(5):768–773.

[12] Gravel V, Antoun AH, Tweddell ARJ. Effect of indole-acetic acid (IAA) on the development of symptoms caused by Pythium ultimum on tomato plants. European Journal of Plant Pathology. 2007;119:457–462.

[13] Khakipour N, Khavazi K., Mojallali H, Pazira E, Asadirahmani H. Production of auxin hormone by fluorescent pseudomonads. American-Eurasian Journal of Agricultural and Environmental Sciences 2008;4(6):687-692.

[14] Aleksandrov VG, Blagodyr RN, Ilev IP. Liberation of phosphoric acid from apatite by silicate bacteria. Mikrobiol Zhurnal (Kiev). 1967;29:111–114.

[15] Sugumaran P, and Janarthanam B. Solubilization of potassium containing minerals by bacteria and their effect of plant growth. World Journal of Agricultural Sciences. 2007;3(3):350-355.

[16] Setiawati TC, Mutmainnah L. Solubilization of potassium containing mineral by microorganisms from sugarcane rhizosphere. Agriculture and Agricultural Science Procedia. 2016;9:108-117.

[17] Vreeland RH. Mechanisms of halotolerance in microorganisms. CRC Critical Reviews in Microbiology. 1987;14(4):311–356.

[18] Lopes-Assad ML, Avansini SH, Rosa MM, Carvalho JRP, Ceccato Antonini SR. The solubilization of potassium-bearing rock powder by Aspergillus niger in small-scale batch fermentations. Canadian Journal of Microbiology. 2010;56:598-605.

[19] Meena VS, Maurya BR, Verma JP. Does a rhizospheric microorganism enhance K+ availability in agricultural soils? Microbiol Research. 2014;169:337–347.

[20] Macias-Benitez S, Garcia-Martinez AM, Caballero-Jimenez P, Gonzalez JM, Tejada Moral M, Parrado-Rubio J. Rhizospheric organic acids as biostimulants: Monitoring feedbacks on soil microorganisms and biochemical properties. Frontiers in Plant Sci. 2020;11:633-648.

[21] Iyamuremye F, Dick,R.P., Baham J. Organic amendments and phosphorus dynamics: I. phosphorus chemistry and sorption. Soil Science. 1996;161:426-435.

[22] Srivastava S, Kausalya MT, Archana G, Rupela OP, Naresh-Kumar G. Efficacy of organic acid-secreting bacteria insolubilization of rock phosphate in acidic alfisols. First International Meeting on Microbial Phosphate Solubilization. 16-19 July 2002. Salamanca, Spain, 2007.

[23] Violante A, Gianfreda L. Role of biomolecules in the formation of variable charge minerals and organo-mineral complexes and their reactivity with plant nutrients and organic in soil. Bollag JB, Stotzky G, editors. Soil Biochemistry. 2000;10:207-270.

[24] Setiawati TC. Peran bakteri pelarut fosfat dalam media organik terhadap dinamika fosfat pada oxisol [Dissertation]. Universitas Brawijaya, Malang. Indonesia; 2008.

[25] Dey G, Banerjee P, Sharma RK et al. Management of phosphorus in salinity-stressed agriculture for sustainable crop production by salt-tolerant phosphate-solubilizing bacteria—A review. Agronomy. 2021;11:1552-1578.

[26] Dhaliwal AK, Gupta RK, Singh Y, Singh B. Potassium fixation and release characteristics of some benchmark soil series under rice-wheat cropping system in the Indo-Gangetic Plains of northwestern India. Communications in Soil Science and Plant Analysis. 2006;37:827–845.

[27] Azadi A, Baghernejad M, Abtahi A. Kinetics of potassium desorption from some calcareous soil (Fars province, Southern Iran). International Journal of Forest Soil and Erosion. 2015;5(2):46-51.

[28] Widyawati, A. Bacillus sp. asal rhizosfer kedelai yang berpotensi sebagai pemacu pertumbuhan tanaman dan biokontrol fungi patogen akar [Thesis]. Bogor: Program Studi Biologi Sekolah Pascasarjana Institut Pertanian Bogor; 2008.

[29] Wagi S, Ahmed A. Bacillus spp.: Potent microfactories of bacterial IAA. PeerJ. Life and Environment. 2019;7:7258-7272.