Screening and Molecular Identification of a Salt-Tolerant Streptomyces Isolate with Plant Growth-Promoting Traits and Evaluation of Its Biofertilizer Potential for Catharanthus roseus L.

Articles in Press

Document Type : Original Article- Persian

Authors

1 Department Of Microbiology, Qo.C., Islamic Azad University, Iran.

2 Infectious Diseases Research Center, AJA University of Medical Sciences, Tehran, Iran

3 Department of Basic Medical Sciences, QoMS.C, Islamic Azad University, Qom,Iran Applied Physiology Research Center, Qom Medical Sciences, Islamic Azad University, Qom, Iran

10.22108/bjm.2026.150550.1698

Abstract

This study aimed to screen, molecularly identify, and evaluate the plant growth-promoting characteristics of indigenous salt-adapted actinobacteria isolated from the rhizosphere of Lake Namak in Qom, Iran, and to investigate the potential of the selected isolate to improve the growth of periwinkle (Catharanthus roseus L.). A total of 100 rhizospheric soil samples were collected from the surrounding areas of Lake Namak in Qom. Following initial isolation and screening, the selected isolates were evaluated for salt tolerance; growth under different pH and temperature conditions; production of indole-3-acetic acid (IAA), hydrogen cyanide (HCN), and ammonia; siderophore production; phosphate solubilization; biosurfactant production; resistance to heavy metals Cobalt (Co), silver (Ag) and lead (Pb); and antagonistic activity against Erwinia carotovora and Fusarium oxysporum. The superior isolate was identified by sequencing the 16S rRNA gene, and its effect on the morphological parameters of periwinkle plants was evaluated under greenhouse conditions. Among the screened isolates, isolate No. 54 exhibited the highest number of plant growth-promoting traits and was identified as belonging to the genus Streptomyces, with 99% sequence similarity. This isolate was capable of growing in the presence of 10% NaCl and demonstrated the production of IAA, HCN, ammonia, and siderophores, as well as phosphate solubilization. In addition, biofilm formation was maintained in the presence of heavy metals at concentrations of 0, 5, 10, 15, and 20 mM, although the amount of biofilm formation gradually decreased with increasing metal concentrations. Inoculation with the selected isolate under greenhouse conditions resulted in increases in stem length, leaf number, and leaf width of periwinkle plants compared with the control group. The findings of this study demonstrated that the indigenous Streptomyces isolate possesses a combination of plant growth-promoting traits and heavy-metal tolerance and may be considered a promising candidate for the development of biofertilizers.

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Journal of Microbial Biology

Articles in Press, Accepted Manuscript
Available Online from 05 October 2026

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