The ability of microorganisms to reduce inorganic metals has launched an exciting eco-friendly approach towards developing green nanotechnology. Thus, the synthesis of metal nanoparticles through a biological approach is an important aspect of current nanotechnology. In this study, Streptomyces aizuneusis ATCC 14921 gave the small particle of silver nanoparticles (AgNPs) a size of 38.45 nm, with 1.342 optical density. AgNPs produced by Streptomyces aizuneusis were characterized by means of UV-VIS spectroscopy and transmission electron microscopy (TEM). The UV-Vis spectrum of the aqueous solution containing silver ion showed a peak between 410 to 430. Moreover, the majority of nanoparticles were found to be a spherical shape with variables between 11 to 42 nm, as seen under TEM. The purity of extracted AgNPs was investigated by energy dispersive X-ray analysis (EDXA), and the identification of the possible biomolecules responsible for the reduction of Ag⁺ ions by the cell filtrate was carried out by Fourier Transform Infrared spectrum (FTIR). High antimicrobial activities were observed by AgNPs at a low concentration of 0.01 ppm, however, no deleterious effect of AgNPs was observed on the development and occurrence of Drosophila melanogaster phenotype. The highest reduction in the viability of the human lung carcinoma and normal cells was attained at 0.2 AgNPs ppm.

Indole-3-acetic acid (IAA), a key phytohormone widely synthesized by soil bacteria, plays a vital role in root development and stress resilience. This study aimed to optimize the culture conditions for IAA production by Kocuria rosea SS1 and to evaluate the efficacy of bacterial derived IAA on the micropropagation of potato ( Solanum tuberosum L. cv. Spunta). Maximum IAA production (10.83 mg 100 mL ^− 1 , as quantified by HPLC) was achieved in nutrient broth at pH 7 and 30 °C, supplemented with 1 mM tryptophan and incubated under shaking conditions for three days. Filter-sterilized bacterial supernatant containing IAA (0.0–1.0 mgL ^− 1 ) was incorporated into Murashige and Skoog (MS) medium and compared to commercial IAA in potato tissue culture. After 28 days, plantlets treated with bacterial IAA, particularly at 0.25 mgL ^− 1 ; showed significant enhancements in fresh weight (1.5-fold), roots number (69.9%), leaves number (100%) and shoot length (50%) compared to the control, outperforming equivalent doses of synthetic IAA. Biochemical analyses revealed increased levels of total sugars, chlorophylls, carotenoids, and endogenous IAA and gibberellins. These findings demonstrate that the bacterial supernatant serves as a potent, eco-friendly biostimulant that enhances the growth and biochemical quality of in vitro-propagated potato plantlets, offering a sustainable alternative to synthetic growth regulators.