Harnessing plant growth-promoting bacteria for nanoparticle biosynthesis: a systematic review of mechanisms, agricultural applications, and biomedical potential.

The rapid expansion of nanotechnology has opened novel opportunities to share for addressing global challenges related to food security, environmental sustainability, and human health. Conventional physical and chemical methods for the synthesis of nanoparticles (NPs) often involve hazardous chemicals, high energy demands, and poor biocompatibility. In contrast, bacterial-synthesized NPs are considered eco-friendly and multifunctional with their enormous potential in agriculture, bioremediation, and biomedical applications. The study highlights the importance of Bacteriogenic NPs as a sustainable alternative to chemically and physically produced NPs due to their reduced toxicity and lower energy consumption. Hence, bacteriogenic NPs, particularly those derived from Bacillus and Pseudomonas species, exhibit remarkable stability, biocompatibility, and multifunctional spectrum due to inherent reducing and capping biomolecules secreted by those bacteria. This review highlights the biosynthetic mechanisms, characterization techniques, and diverse applications of bacterial-based NPs. Initially, in agriculture, silver NPs synthesized by Bacillus xiamenesis enhanced rice growth while suppressing Xanthomonas oryzae, the causal agent of bacterial blight. Then, in environmental remediation, Bacillus pumilus-derived silver nanoparticles demonstrated 96.99% degradation of Congo red dye, underscoring their catalytic efficiency. And, in biomedical sciences, selenium NPs biosynthesized from Streptomyces minutiscleroticus exhibited antiviral activity against dengue virus type 1, highlighting their therapeutic promise. Key findings reveal that these NPs can enhance stress tolerance, nutrient uptake, and disease resistance, along with remediating harmful pollutants from the environment. They also exhibit strong antimicrobial and anticancer properties. Despite all these advancements, much work is still needed to optimize NPs' yield, uniformity, and functionality, as well as environmental and health safety assessment. Integrating omics approaches and nanobiotechnology innovations may unlock new opportunities for precision agriculture, environmental restoration, and advanced therapeutics. In a nutshell, bacterially mediated nanotechnology emerges as a sustainable and transformative tool to address pressing societal and ecological concerns.