Potassium is an essential macronutrient for living creatures on earth and in plants, it plays a very significant role in determining the overall health of the plants. Although potassium is present in the soil, it is present in a form that is inaccessible to the plants, and hence synthetic harmful non-eco-friendly potassium fertilizers are used. To overcome this problem, the use of eco-friendly potassium-solubilizing bacteria comes into play. The goal of the present study was to assess the potassium-solubilizing bacteria that inhabit the farm rhizosphere, which demonstrate the presence of enzymes associated with plant growth promotion and antagonistic properties. A total of thirty-four isolates were isolated from the rhizosphere. All these isolates were subjected to a potassium solubilization test on Aleksandrov agar medium, out of which fourteen were found to possess potassium solubilizing ability. On the basis of the 16S rRNA gene sequencing, the most potential potassium-solubilizing bacterium was identified as Proteus mirabilis PSCR17. The plant growth promoting abilities and production of biocontrol enzymes of this isolate were evaluated, and the results indicated, in addition to potassium solubilization, the isolate was positive for indole acetic acid production, hydrogen cyanide production, amylase, catalase, cellulase, chitinase, and protease. The use of potassium fertilizers is harmful to the environment and ecosystem; hence, this study concludes that P. mirabilis PSCR17 can be used as a substitute for chemical potassium fertilizers to improve the growth and biocontrol traits of the plants in a sustainable manner after further research.

1.         Johnson R, Vishwakarma K, Hossen MS, et al. Potassium in plants: Growth regulation, signaling, and environmental stress tolerance. Plant Physiology and Biochemistry. 2022; 172: 56–69. doi: 10.1016/j.plaphy.2022.01.001

2.         Xu X, Du X, Wang F, et al. Effects of potassium levels on plant growth, accumulation and distribution of carbon, and nitrate metabolism in apple dwarf rootstock seedlings. Frontiers in Plant Science. 2020; 11. doi: 10.3389/fpls.2020.00904

3.         Sardans J, Peñuelas J. Potassium control of plant functions: Ecological and agricultural implications. Plants. 2020; 10(2): 419. doi: 10.3390/plants10020419

4.         Dhiman S, Dubey RC, Baliyan N, et al. Application of potassium-solubilising Proteus mirabilis MG738216 inhabiting cattle dung in improving nutrient use efficiency of Foeniculum vulgare Mill. Environmental Sustainability. 2019; 2: 401–409. doi: 10.1007/s42398-019-00088-8

5.         Jacob SM, Paranthaman S. Biofertilizers: An advent for eco-friendly and sustainable agriculture development. Vegetos. 2023; 36: 1141–1153. doi: 10.1007/s42535-022-00550-9

6.         Zia R, Nawaz MS, Yousaf S, et al. Seed inoculation of desert‐plant growth‐promoting rhizobacteria induce biochemical alterations and develop resistance against water stress in wheat. Physiologia Plantarum. 2021; 172(2): 990–1006. doi: 10.1111/ppl.13362

7.         Jacob SM, Lelapalli S, Paranthaman S. Characterization of phosphate solubilizing rhizobacteria Lysinibacillus boronitolerans PSLR2. Vegetos. 2025; doi: 10.1007/s42535-025-01185-2

8.         Drzewiecka D. Significance and roles of Proteus spp. bacteria in natural environments. Microbial Ecology. 2016; 72: 741–758. doi: 10.1007/s00248-015-0720-6

9.         Survery S, Ahmad S, Subhan SA, et al. Hydrocarbon degrading bacteria from Pakistani soil: Isolation, identification, screening and genetical studies. Pakistan Journal of Biological Sciences. 2004; 7: 1518–1522.

10.      Lutz G, Chavarría M, Arias ML, Mata-Segreda JF. Microbial degradation of palm (Elaeis giuneensis) biodiesel (Indonesian). Revista de Biología Tropical. 2006; 54(1): 59–63. doi: 10.15517/rbt.v54i1.13994

11.      Hernández-Rivera MA, Ojeda-Morales ME, Martinez-Vazquez JG, et al. Optimal parameters for in vitro development of the hydrocarbonoclastic microorganism Proteus sp. Journal of Soil Science and Plant Nutrition. 2011; 11(1): 29–43. doi: 10.4067/S0718-95162011000100003

12.      Ibrahim ML, Ijah UJJ, Manga SB, et al. Production and partial characterization of biosurfactant produced by crude oil degrading bacteria. International Biodeterioration & Biodegradation. 2013; 81: 28–34. doi: 10.1016/j.ibiod.2012.11.012

13.      Correa IE, Steen WC. Degradation of propanil by bacterial isolates and mixed populations from a pristine lake. Chemosphere. 1995; 30(1): 103–116. doi: 10.1016/0045-6535(94)00380-D

14.      Chen KC, Huang WT, Wu JY, Houng JY. Microbial decolorization of azo dyes by Proteus mirabilis. Journal of Industrial Microbiology & Biotechnology. 1999; 23(1): 686–690. doi: 10.1038/sj.jim.2900689

15.      Foght J, April T, Biggar K, Aislabie J. Bioremediation of DDT-contaminated soils: A review. Bioremediation Journal. 2001; 5(3): 225–246. doi: 10.1080/20018891079302

16.      Olukanni OD, Osuntoki AA, Kalyani DC, et al. Decolorization and biodegradation of Reactive Blue 13 by Proteus mirabilis LAG. Journal of Hazardous Materials. 2010; 184(1–3): 290–298. doi: 10.1016/j.jhazmat.2010.08.035

17.      Barthakur M, Bezbaruah B. Plant beneficial effect of two strains of Proteus vulgaris isolated from tea plantations. Indian Journal of Experimental Biology. 1999; 37(9): 919–924.

18.      Rau N, Mishra V, Sharma M, et al. Evaluation of functional diversity in rhizobacterial taxa of a wild grass (Saccharum ravennae) colonizing abandoned fly ash dumps in Delhi urban ecosystem. Soil Biology and Biochemistry. 2009; 41(4): 813–821. doi: 10.1016/j.soilbio.2009.01.022

19.      Yu SM, Lee YH. Plant growth promoting rhizobacterium Proteus vulgaris JBLS202 stimulates the seedling growth of Chinese cabbage through indole emission. Plant and Soil. 2013; 370: 485–495. doi: 10.1007/s11104-013-1652-x

20.      Islam F, Yasmeen T, Riaz M, et al. Proteus mirabilis alleviates zinc toxicity by preventing oxidative stress in maize (Zea mays) plants. Ecotoxicology and Environmental Safety. 2014; 110: 143–152. doi: 10.1016/j.ecoenv.2014.08.020

21.      Bhattacharyya D, Garladinne M, Lee YH. Volatile indole produced by rhizobacterium Proteus vulgaris JBLS202 stimulates growth of Arabidopsis thaliana through auxin, cytokinin, and brassinosteroid pathways. Journal of Plant Growth Regulation. 2015; 34: 158–168. doi: 10.1007/s00344-014-9453-x

22.      Verma S, Verma R, Verma P, et al. Salt tolerant endophytic and diazotrophic strain of Proteus mirabilis PD25 and its effect on the growth of wheat under saline conditions. Natural Volatiles and Essential Oils. 2021; 8: 13172–13183.

23.      Musa SI. Seed bio-priming with phosphate-solubilizing bacteria strains to improve rice (Oryza sativa L. var. FARO 44) growth under ferruginous ultisol conditions. BioTechnologia. 2023; 104(1): 33–51. doi: 10.5114/bta.2023.125084

24.      Abiala MA, Odebode AC, Hsu SF, Blackwood CB. Phytobeneficial properties of bacteria isolated from the rhizosphere of maize in Southwestern Nigerian soils. Applied and Environmental Microbiology. 2015; 81(14): 4736–4743. doi: 10.1128/AEM.00570-15

25.      Raji M, Thangavelu M. Isolation and screening of potassium solubilizing bacteria from saxicolous habitat and their impact on tomato growth in different soil types. Archives of Microbiology. 2021; 203: 3147–3161. doi: 10.1007/s00203-021-02284-9

26.      Setiawati TC, Mutmainnah L. Solubilization of potassium containing mineral by microorganisms from sugarcane rhizosphere. Agriculture and Agricultural Science Procedia. 2016; 9: 108–117. doi: 10.1016/j.aaspro.2016.02.134

27.      Ramlath L, Keerthana PP, Fathima SP, Mashhoor K. Bacteria from coral ecosystem of Kiltan Island, Lakshadweep: Resource for hydrolytic enzymes. International Journal of Cell Science and Biotechnology. 2018; 7: 1–9.

28.      Divakaran JS, Philip JS, Chereddy P, et al. Insights into the bacterial profiles and resistome structures following the severe 2018 flood in Kerala, South India. Microorganisms. 2019; 7: 474. doi: 10.3390/microorganisms7100474

29.      Sharon MJ, Srilakshmi L, Sripriya P. Proteus mirabilis strain PSCR17 16S ribosomal RNA gene, partial sequence. Available online: https://www.ncbi.nlm.nih.gov/nuccore/OR782201.1/ (accessed on 10 December 2024).

30.      Behera BC, Yadav H, Singh SK, et al. Phosphate solubilization and acid phosphatase activity of Serratia sp. isolated from mangrove soil of Mahanadi river delta, Odisha, India. Journal of Genetic Engineering and Biotechnology. 2017; 15: 169–178. doi: 10.1016/j.jgeb.2017.01.003

31.      Whitman WB, Goodfellow M, Kämpfer P, et al. Bergey’s Manual of Systematic Bacteriology: The Actinobacteria. Springer-Verlag; 2012. Volume 5.

32.      Kovacs N. Identification of Pseudomonas pyocyanea by the Oxidase Reaction. Nature. 1956; 703. doi: 10.1038/178703a0

33.      Reiner K. Catalase test protocol. American Society for Microbiology. 2010; 1–9.

34.      Simmons JS. A culture medium for differentiating organisms of typhoid-colon Aerogenes groups and for isolation of certain fungi. The Journal of Infectious Diseases. 1926; 209–214. doi: 10.1093/infdis/39.3.209

35.      Dahanayake PS, De Silva BCJ, Hossain S, et al. Occurrence, virulence factors, and antimicrobial susceptibility patterns of Vibrio spp. isolated from live oyster (Crassostrea gigas) in Korea. Journal of Food Safety. 2018; 38: e12490. doi: 10.1111/jfs.12490

36.      Christensen WB. Urea decomposition as a means of differentiating Proteus and Paracolon cultures from each other and from Salmonella and Shigella types. Journal of Bacteriology. 1946; 52: 461–466. doi: 10.1128/jb.52.4.461-466.1946

37.      Skillern JK, Overman TL. Oxidase testing from Kligler’s iron agar and Triple Sugar Iron agar slants. Current Microbiology. 1983; 8: 269–271. doi: 10.1007/BF01577726

38.      McDevitt S. Methyl Red and Voges-Proskauer test protocols. American Society for Microbiology. 2009; 1–9.

39.      Muleta D, Assefa F, Börjesson E, Granhall U. Phosphate-solubilising rhizobacteria associated with Coffea arabica L. in natural coffee forests of southwestern Ethiopia. Journal of the Saudi Society of Agricultural Sciences. 2013; 12: 73–84. doi: 10.1016/j.jssas.2012.07.002

40.      Mumtaz MZ, Ahmad M, Jamil M, Hussain T. Zinc solubilizing Bacillus spp. potential candidates for biofortification in maize. Microbiological Research. 2017; 202: 51–60. doi: 10.1016/j.micres.2017.06.001

41.      Ahmad F, Ahmad I, Khan MS. Screening of free-living rhizospheric bacteria for their multiple plant growth promoting activities. Microbiological Research. 2008; 163: 173–181. doi: 10.1016/j.micres.2006.04.001

42.      Lelapalli S, Baskar S, Jacob SM, Paranthaman S. Characterization of phosphate solubilizing plant growth promoting rhizobacterium Lysinibacillus pakistanensis strain PCPSMR15 isolated from Oryza sativa. Current Research in Microbial Sciences. 2021; 2: 100080. doi: 10.1016/j.crmicr.2021.100080

43.      Bódalo A, Borrego R, Garrido C, et al. In Vitro Studies of endophytic bacteria isolated from ginger (Zingiber officinale) as potential plant-growth-promoting and biocontrol agents against Botrytis cinerea and Colletotrichum acutatum. Plants. 2023; 12: 4032. doi: 10.3390/plants12234032

44.      Amaresan N, Jayakumar V, Kumar K, Thajuddin N. Plant growth-promoting effects of Proteus mirabilis isolated from tomato (Lycopersicon esculentum Mill) plants. National Academy Science Letters. 2021; 44: 453–455. doi: 10.1007/s40009-020-01038-3

45.      Jha V, Purohit H, Dafale NA. Designing an efficient consortium for improved crop productivity using phosphate stress adapted bacteria with multiple growth-promoting attributes. Geomicrobiology Journal. 2022; 39: 925–938. doi: 10.1080/01490451.2022.2097340

46.      Bano N, Musarrat J. Isolation and characterization of phorate degrading soil bacteria of environmental and agronomic significance. Letters in Applied Microbiology. 2003; 36: 349–353. doi: 10.1046/j.1472-765X.2003.01329.x

47.      Pino NJ, Domínguez MC, Peñuela GA. Isolation of a selected microbial consortium capable of degrading methyl parathion and p-nitrophenol from a contaminated soil site. Journal of Environmental Science and Health, Part B. 2011; 46: 173–180. doi: 10.1080/03601234.2011.539142

48.      Pino N, Peñuela G. Simultaneous degradation of the pesticides methyl parathion and chlorpyrifos by an isolated bacterial consortium from a contaminated site. International Biodeterioration & Biodegradation. 2011; 65: 827–831. doi: 10.1016/j.ibiod.2011.06.001