Nanoparticles (1 to 100 nm) have unique physical and chemical properties, which makes them suitable for application in a vast range of scientific and technological fields. In particular, metal nanoparticle (MNPs) research has been showing promising antimicrobial activities, paving the way for new applications. However, despite some research into their antimicrobial potential, the antimicrobial mechanisms are still not well determined. Nanoparticles’ biosynthesis, using plant extracts or microorganisms, has shown promising results as green alternatives to chemical synthesis; however, the knowledge regarding the mechanisms behind it is neither abundant nor consensual. In this review, findings from studies on the antimicrobial and biosynthesis mechanisms of MNPs were compiled and evidence-based mechanisms proposed. The first revealed the importance of enzymatic disturbance by internalized metal ions, while the second illustrated the role of reducing and negatively charged molecules. Additionally, the main results from recent studies (2018–2022) on the biosynthesis of MNPs using microorganisms were summarized and analyzed, evidencing a prevalence of research on silver nanoparticles synthesized using bacteria aiming toward testing their antimicrobial potential. Finally, a synopsis of studies on MNPs applied to cultural heritage materials showed potential for their future use in preservation.

The study performed on the stone materials from the Convent of Christ revealed the presence of a complex microbial ecosystem, emphasizing the determinant role of microorganisms on the biodecay of this built cultural heritage. In this case study, the presence of Rubrobacter sp., Arthrobacter sp., Roseomonas sp., and Marinobacter sp. seems to be responsible for colored stains and biofilm formation while Ulocladium sp., Cladosporium sp., and Dirina sp. may be related to structural damages. The implementation of high‐throughput sequencing approaches on the Convent of Christ's biodecay assessment allowed us to explore, compare, and characterize the microbial communities, overcoming the limitations of culture‐dependent techniques, which only identify the cultivable population. The application of these different tools and insights gave us a panoramic view of the microbiota thriving on the Convent of Christ and signalize the main biodeteriogenic agents acting on the biodecay of stone materials. This finding highlighted the importance of performing metagenomic studies due to the improvements and the reduced amount of sample DNA needed, promoting a deeper and more detailed knowledge of the microbiota present on these dynamic repositories that support microbial life. This will further enable us to perform prospective studies in quarry and applied stone context, monitoring biogenic and nonbiogenic agents, and also to define long‐term mitigation strategies to prevent biodegradation/biodeterioration processes.

The identification of microorganisms involved in biodeterioration/biodegradation process is determinant to understand their effects on cultural assets, and furthermore, it is a crucial step to define an efficient strategy to protect monuments and artworks from microbiological recolonisation, in order to promote its preservation. The renaissance mural paintings from the garden of the Inquisition Palace in Évora, classified by UNESCO as World Heritage, were analysed in order to find the microbial population involved in the biodeterioration process, and, to assist and develop an efficient intervention, by biocides application to control the propagation of microbial communities responsible for biodegradation. The biocides tested revealed good inhibition results against the microbial communities isolated from the paintings, whose action spectrum was noticeably enlarged when the application was carried out combining two different commercial biocides. In vitro antifungal assays performed with new natural biocompounds revealed efficient inhibition capacity, suggesting the potential of these compounds to be used as a great and safe alternative to the chemical compounds usually used on cultural assets microbial treatments