The Sustainable Synthesis of Silver and Gold Nanoparticles and Their Effect on the Growth of Metal Resistant Microorganisms

Silver and gold nanoparticles (NPs) have gained considerable attention in recent years due to their wide-ranging applications in medicine, agriculture, industry, and other fields where they may interact with the environment. Green synthesis of NPs supports sustainability by reducing chemical waste and energy use while improving their biocompatibility through plant phytochemicals. Accordingly, it is important to assess the effects of metal NPs on microorganisms, which play vital roles in ecosystems and biogeochemical cycles. This study aimed to investigate microbial growth dynamics in the presence of green-synthesized silver and gold NPs (using an aqueous extract of Mentha × piperita leaves) and to evaluate potential mechanisms of their interaction. Microorganisms were cultivated in 96-well microtiter plates, and growth curves were analyzed alongside bacterial enumeration on Petri plates. Silver NPs affected the growth of Brevundimonas vesicularis USM1, Pseudarthrobacter oxydans USM2, and Pseudomonas putida USM4, although these strains exhibited partial resistance. In contrast, gold NPs did not inhibit the growth of the tested strains. The ability of Brevundimonas vesicularis USM1 to precipitate metal NPs highlights its potential for sustainable bioremediation applications. The findings contribute to a better understanding of the environmental impact and sustainability aspects of silver and gold NPs in microbial systems.