EFFECT OF TRYPTOPHAN AND PH LEVEL ON INDOLE-3-ACETIC ACID (IAA) PRODUCTION BY Bacillus spp.
DOI:
https://doi.org/10.24246/agric.2026.v38.i1.p15-26Keywords:
Tryptophan, Indole-3-acetic acid (IAA), Bacillus sppAbstract
Tryptophan and pH are environmental factors that convincingly influence microbial growth, metabolism, and metabolite production. This study aimed to find out how tryptophan and pH affect the production of Indole-3-acetic acid (IAA) by Bacillus spp. in Nutrient Broth (NB) medium. A Completely Randomized Design (CRD) with six treatments and three replications was used. The confirmation bacterial strains were Brevibacillus agri, Brevibacillus borstelensis (2 isolates), and Bacillus subtilis. The NB medium was adjusted to four pH levels (5, 6, 7, and 8) and supplemented with different concentrations of tryptophan: 0, 102, 150, 300, 450, and 600 mg/ml. The results after incubated showed that Brevibacillus agri was detected the highest IAA content at pH level 7.0 with 600 mg/ml of tryptophan (204 µg/ml). Whereas Brevibacillus borstelensis and Bacillus subtilis caused the maximum of IAA contents at pH level 8.0 with 600 mg/ml of tryptophan at 79.31 µg/ml and 35.82 µg/ml respectively.
Downloads
References
Agrawal, M., Sharma, A., Sundaram, S. 2026. Biosynthesis of auxin under Cr (VI) stress conditions by thermophilic Brevibacillus borstelensis SSAU-3T. Folia Microbiologica. Advance online publication. https://doi.org/10.1007/s12223-025-01412-y
Ait Bessai, S., Bensidhoum, L., Nabti, E. 2022. Optimization of IAA production by telluric bacteria isolated from northern Algeria. Biocatalysis and Agricultural Biotechnology. 41: 102246. https://doi.org/10.1016/j.bcab.2022.102246
Ali, S., Akhtar, M. S., Siraj, M., Zaman, W. 2024. Molecular communication of microbial plant biostimulants in the rhizosphere under abiotic stress conditions. International Journal of Molecular Sciences. 25(22): 12424. https://doi.org/10.3390/ijms252212424
Bai, Y., Miaomiao, C., Changhong ,M., Wenlong, C., Huifang, Z., Zhanchao ,C. Juan, L., Shaohua M. Jian, G. 2022. New Insights Into the Local Auxin Biosynthesis and Its Effects on the Rapid Growth of Moso Bamboo (Phyllostachys Edulis). Frontiers in Plant Science. 13. https://doi:10.3389/fpls.2022.858686.
Chuaboon, W., Athinuwat, D. 2014. Plant Hormone Produced from Pseudomonas Fluorescens SP007s to Enhance Growth of Organic Kale. Thai Journal of Science and Technology. 3(3): 197–205. DOI: 10.14456/tjst.2014.21.
Costacurta, A., Paulo. M., Yoko B. R. 1998. Indole-3-Acetic Acid Biosynthesis by Xanthomonas Axonopodis Pv. Citri Is Increased in the Presence of Plant Leaf Extracts. FEMS Microbiology Letters. 159(2): 215–20. https://doi:10.1111/j.1574-6968.1998.tb12863.x.
Dixit, V. K., Misra, S., Mishra, S. K., Tewari, S. K., Joshi, N., Chauhan, P. S. 2020. Characterization of plant growthpromoting alkalotolerant Alcaligenes and Bacillus strains for mitigating the alkaline stress in Zea mays. Antonie van Leeuwenhoek. 113(6): 789–805. https://doi.org/10.1007/s10482-020-01399-1
Espinosa-Palomeque, B., Jiménez-Pérez, O., Ramírez-Gottfried, R. I., PreciadoRangel, P., Buendía-García, A., Sifuentes, G. Z., Sariñana Navarrete, M. A., RivasGarcía, T. 2025. Biocontrol of phyto pathogens using plant growth promoting rhizobacteria: Bibliometric analysis and systematic review. Horticulturae. 11(3):27 1 .https://doi.org/10.3390/horticulturae11030271
Etesami, H., Glick, B. R. 2020. Bacterial indole-3-acetic acid: A key regulator for plant growth, plant-microbe interactions, and agricultural adaptive resilience. Microbiological Research. 239: 126547. https://doi.org/10.1016/j.micres.2020.126547
Feng, Y., Tian, B., Xiong, J., Lin, G., Cheng, L., Zhang, T., Lin, B., Ke, Z., Li, X. 2024. Exploring IAA biosynthesis and plant growth promotion mechanism for tomato root endophytes with incomplete IAA synthesis pathways. Chemical and Biological Technologies in Agriculture. 11: 187. https://doi.org/10.1186/s40538-024-00712-8
Gondek, K., Mierzwa-Hersztek, M. 2021. Effect of soil-applied L-tryptophan on the amount of biomass and nitrogen and sulfur utilization by maize. Agronomy.11(12): 2582. https://doi.org/10.3390/agronomy11122582
Guo, D., Sijia,K. , Xu, C., Xun, L., Hong, P. 2019. De Novo Biosynthesis of Indole-3-Acetic Acid in Engineered Escherichia Coli. Journal of Agricultural and Food Chemistry. 67(29): 8186–90. https://doi:10.1021/acs.jafc.9b02048.
Idris, E. E. S., Bochow, H., Ross, H., and Borriss, R. 2004. Use of Bacillus subtilis as biocontrol agent. VI. Phytohormone like action of culture filtrates prepared from plant growth-promoting Bacillus amyloliquefaciens FZB24, FZB42, FZB45 and Bacillus subtilis FZB37. J. Plant Dis. Prot. 111: 583-597. https://www.jstor.org/stable/43215615.
Inthasan ,J., Dechjiraratthanasiri ,C., Boonmee, P. 2017. Effect of Bacteria-Producing Indole-3-Acetic Acid (IAA) on Growth and Nutrient Contents of Bird Chili (Capsicum Annuum L.). Journal of Agricultural. 33(3): 333–44.
Khan, N., Bano, A., Rahman, M. A. 2023. Indole-3 acetic acid production by plant growth-promotingbacteria:mechanisms and agricultural applications. Frontiers in Microbiology. 14: 1187342.
Khianngam, S., Meetum, P., Na Chiangmai, P., Tanasupawat, S. 2023. Identification and optimisation of indole-3-acetic acid production of endophytic bacteria and their effects on plant growth. Tropical Life Sciences Research 34(1): 219–239. https://doi.org/10.21315/tlsr2023.34.1.12
Kumar, A., Maurya, B. R., Raghuwanshi, R. 2019. Isolation and characterization of PGPR and their effect on growth, yield and nutrient content in wheat. Rhizosphere. 9: 1–7. https://doi.org/10.1016/j.rhisph.2018.11.002
Lastochkina, O., Yuldashev, R., Avalbaev, A., Allagulova, C., Veselova, S. 2023. The contribution of hormonal changes to the protective effect of endophytic bacterium Bacillus subtilis on two wheat genotypes with contrasting drought sensitivities under osmotic stress. Microorganisms. 11(12): 2955. https://doi.org/10.3390/microorganisms11122955
Luo, P., Dong-Wei, D. 2023. Precise Regulationof the TAA1/TAR-YUCCA Auxin Biosynthesis Pathway in Plants. International Journal of Molecular Sciences. 24(10): 8514. https://doi:10.3390/ijms24108514.
Munné-Bosch, S., Müller, M. 2013. Hormonal cross-talk in plant development and stress responses. Frontiers in Plant Science. 4: 52. https://doi.org/10.3389/fpls.2013.00052
Mustafa, A., Imran, M., Ashraf, M., Mahmood, K. 2018. Perspectives of using L-tryptophan for improving productivity of agricultural
crops: A review. Pedosphere. 28(1): 16–34. https://doi.org/10.1016/S1002-0160(18)60002-5
Naz, M., Dai, Z., Hussain, S., Tariq, M., Danish, S., Khan, I. U., Qi, S., Du, D. 2022. The soil pH and heavy metals revealed their impact on soil microbial community. Journal of Environmental Management. 321: 115770. https://doi.org/10.1016/j.jenvman.2022.115770
Patten, C. L., Glick, B. R. 2002. Role of Pseudomonas putida indoleacetic acid in development of the host plant root system. Applied and Environmental Microbiology. 68: 3795–3801.
Pollmann, S., Düchting, P., Weiler, E. W. 2009. Tryptophan-dependent indole-3-acetic acid biosynthesis by ‘IAA-synthase’ proceeds via indole-3-acetamide. Phytochemistry. 70(4): 523–531. https://doi.org /10.1016/j.phytochem.2009.01.014
Queiroz, R. B., Layara A. B., Roniel, G. Á., Damiana, S. S. A., Marilene, S. O., Luciana C.V. 2023. Effect of Exogenous Tryptophan on Primary Metabolism and Oxidative Stress and Their Relationship with Seedling Germination and Vigor of Glycine Max L. Agronomy. 13(6):1609.
https://doi:10.3390/agronomy13061609.
Sachdev, D. P., Chaudhari, H. G., Kasture, V. M.,Dhavale, D. D., Chopade, B. A. 2009. Isolation and characterization of indole acetic acid (IAA) producing Klebsiella pneumoniae strains from rhizosphere of wheat (Triticum aestivum) and their effect on plant growth. Indian Journal of Experimental Biology. 47(12): 993–1000.
Seangsanga, T. 2015. Biosynthesis of Indole-3-Acetic Acid (IAA) of Nitrogen Fixing Bacteria Isolated from Rubber Tree Hevea Brasiliensis Mull-Arg. P. 31 (in Thai).
Spaepen, S., Vanderleyden, J., Remans, R. 2007. Indole-3-acetic acid in microbial and microorganism–plant signaling. FEMS Microbiology Reviews. 31: 425–448. https://doi.org/10.1111/j.1574-6976.2007.00072.x
Swarnakar, S., Chakraborty, A.P. 2025. Bacillus Pumilus: A Potent IAA Producing Plant Growth-Promoting Rhizobacteria with In Vitro PGP Traits and Antagonism against Fusarium Equiseti. Discover Plants. 2(1): 183. https://doi:10.1007/s44372-025-00277-2.
Tsavkelova, E. A., Klimova, S. Yu., Cherdyntseva, T. A., Netrusov, A. I. 2006. Microbial producers of plant growth stimulators and their practical use. Applied Biochemistry and Microbiology. 42:117–126. https://doi.org/10.1134/S0003683806020013.
Vashi, J. D. 2023. Plant Hormones- Natural Growth Regulators. Journal of Experimental Agriculture International. 45(11):30–38. https://doi:10.9734/jeai/2023/v45i112232.
Wahyudi, A. T., Astuti, R. P., Widyawati, A., Meryandini, A., Nawangsih, A. A. 2011. Characterization of Bacillus sp. strains isolated from rhizosphere and their potential for plant growth promotion. Microbiological Research. 166: 285–294. https://doi.org/10.1016/j.micres.2010.05.004
Wagi, S., Ahmed, A. 2019. Bacillus spp.: Potent microfactories of bacterial IAA. PeerJ. 7: e7258. https://doi.org/10.7717/peerj.7258
Wang, X., Zhang, J., An, X., You, J., Zhou, C., Hao, Y. 2022. The growth-promoting mechanism of Brevibacillus laterosporus AMCC100017 on apple rootstock Malus robusta. Horticultural Plant Journal. 8(1): 22–34.https://doi.org /10.1016/j.hpj.2021.11.002
Downloads
Published
How to Cite
Issue
Section
License
Copyright (c) 2026 Agric
This work is licensed under a Creative Commons Attribution 4.0 International License.
This work is licensed under a Creative Commons Attribution 4.0 International License.
