Document Type : Original Paper


1 Department of Cell and Molecular Biology & Microbiology, Faculty of Biological Science and Technology, University of Isfahan, Isfahan, Islamic Republic of Iran

2 Department of Microbiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Islamic Republic of Iran


Application of metal-resistant plant growth-promoting bacteria is an efficient method for enhancing crop yields by improving biomass accumulation and plant tolerance to heavy metals. The present study aimed to isolate and characterize these bacteria from rhizosphere soil and root exudates of plants grown on agricultural soils contaminated with heavy metals. Plant growth-promoting properties of isolated strains were assayed by evaluating their abilities to solubilize insoluble phosphate, produce indole-3-acetic acid (IAA), and fix nitrogen. Resistance to metals toxicity and metal removal potential of the selected strains were investigated by MIC and MBC values determination and atomic absorption spectroscopy (AAS), respectively. Pantoea agglomeransexhibited the maximum solubilization of insoluble phosphate and IAA production. In the case of Cd2+, the highest MIC value belonged to Enterobacter ludwigi. Pseudomonas taiwanensis, P. agglomerans, and E. ludwigi exhibited the greatest MIC value (8mM) in the case of Pb2+. P. agglomerans and E. ludwigi showed the highest MBC of Pb2+(>120mM) and the greatest MBC of Cd2+ (30mM) belonged to P. agglomerans. Also, E. ludwigi exhibited the highest metal removal percentage for Pb2+ as 31.81% and Cd2+ as 37.58%. As results showed, these four isolated strains can be used as novel and efficient agents for improving plant growth, especially in heavy metals polluted agricultural soils.


  1. Briffa J, Sinagra E, Blundell R. Heavy metal pollution in the environment and their toxicological effects on humans. Heliyon. 2020;6(9):e04691.
  2. Mitra S, Chakraborty AJ, Tareq AM, Emran TB, Nainu F, Khusro A, et al. Impact of heavy metals on the environment and human health: Novel therapeutic insights to counter the toxicity. J King Saud Univ Sci. 2022:101865.
  3. Wuana RA, Okieimen FE. Heavy metals in contaminated soils: a review of sources, chemistry, risks and best available strategies for remediation. Int Sch Res Notices. 2011;2011.
  4. Jan AT, Azam M, Siddiqui K, Ali A, Choi I, Haq QM. Heavy metals and human health: mechanistic insight into toxicity and counter defense system of antioxidants. Int J Mol Sci. 2015;16(12):29592-630.
  5. Rai PK, Lee SS, Zhang M, Tsang YF, Kim K-H. Heavy metals in food crops: Health risks, fate, mechanisms, and management. Environ Int. 2019;125:365-85.
  6. Khashei S, Etemadifar Z, Rahmani HR. Immobilization of Pseudomonas putida PT in resistant matrices to environmental stresses: A strategy for continuous removal of heavy metals under extreme conditions. Ann Microbiol. 2018;68(12):931-42.
  7. Ali H, Khan E, Sajad MA. Phytoremediation of heavy metals—concepts and applications. Chemosphere. 2013;91(7):869-81.
  8. Azubuike CC, Chikere CB, Okpokwasili GC. Bioremediation techniques–classification based on site of application: principles, advantages, limitations and prospects. World J Microbiol Biotechnol. 2016;32(11):180.
  9. Ayangbenro AS, Babalola OO. A new strategy for heavy metal polluted environments: a review of microbial biosorbents. Int J Environ Res Public Health. 2017;14(1):94.
  10. Ahemad M. Remediation of metalliferous soils through the heavy metal resistant plant growth promoting bacteria: paradigms and prospects. Arab J Chem. 2014.
  11. Ahemad M, Kibret M. Mechanisms and applications of plant growth promoting rhizobacteria: current perspective. J King Saud Univ Sci. 2014;26(1):1-20.
  12. Olanrewaju OS, Glick BR, Babalola OO. Mechanisms of action of plant growth promoting bacteria. World J Microbiol Biotechnol. 2017;33(11):197.
  13. Bhattacharyya PN, Jha DK. Plant growth-promoting rhizobacteria (PGPR): emergence in agriculture. World J Microbiol Biotechnol. 2012;28(4):1327-50.
  14. Mohite B. Isolation and characterization of indole acetic acid (IAA) producing bacteria from rhizospheric soil and its effect on plant growth. J Plant Nutr Soil Sci. 2013;13(3):638-49.
  15. Walpola BC, Yoon MH. Isolation and characterization of phosphate solubilizing bacteria and their co-inoculation efficiency on tomato plant growth and phosphorous uptake. Afr J Microbiol Res. 2013;7(3):266-75.
  16. Kifle MH, Laing MD. Isolation and screening of bacteria for their diazotrophic potential and their influence on growth promotion of maize seedlings in greenhouses. Front Plant Sci. 2016;6:1225.
  17. Yilmaz EI, Ensari N. Cadmium biosorption by Bacillus circulans strain EB1. World J Microbiol Biotechnol. 2005;21(5):777-9.
  18. Yahaghi Z, Shirvani M, Nourbakhsh F, De La Pena TC, Pueyo JJ, Talebi M. Isolation and characterization of Pb-solubilizing bacteria and their effects on Pb uptake by Brassica juncea: implications for microbe-assisted phytoremediation. J Microbiol Biotechnol. 2018;28(7):1156-67.


  1. Tirry N, Joutey NT, Sayel H, Kouchou A, Bahafid W, Asri M, et al. Screening of plant growth promoting traits in heavy metals resistant bacteria: prospects in phytoremediation. J Genet Eng Biotechnol. 2018;16(2):613-9.
  2. He ZL, Yang XE. Role of soil rhizobacteria in phytoremediation of heavy metal contaminated soils. J Zhejiang Univ Sci B. 2007;8(3):192-207.
  3. Igiri BE, Okoduwa SI, Idoko GO, Akabuogu EP, Adeyi AO, Ejiogu IK. Toxicity and bioremediation of heavy metals contaminated ecosystem from tannery wastewater: a review. J Toxicol. 2018;2018.
  4. Yu X, Li Y, Zhang C, Liu H, Liu J, Zheng W, et al. Culturable heavy metal-resistant and plant growth promoting bacteria in V-Ti magnetite mine tailing soil from Panzhihua, China. PloS One. 2014;9(9):e106618.
  5. Ghosh A, Pramanik K, Bhattacharya S, Mondal S, Ghosh SK, Maiti TK. A potent cadmium bioaccumulating Enterobacter cloacae strain displays phytobeneficial property in Cd-exposed rice seedlings. Curr Res Micro Sci. (CRMICR). 2022;3:100101.
  6. Rashed RO, Muhammed SM. Evaluation of heavy metal content in water and removal of metals using native isolated bacterial strains. Biodivers J Biol Divers. 2021;22(8).