Scheme 1. Schematic illustration of microbial taxonomic identification through biosynthetic AuNPs and machine learning. 1) Microorganism-mediated biosynthesis of AuNPs in solution. 2) Characterizations of biosynthetic AuNPs including diameter, SPR spectrum, surface potential, and transmission electron microscopy (TEM). 3) Features of the biosynthetic AuNPs as a data set of input for machine-learning-based analysis. 4) Data processing and analysis including PCA, LDA, and RF. 5) Output of the data analysis for visualization, including scatter charts, histograms, and line charts. 6) Taxonomic identification and the clustering tree through machine-learning-based analysis of biosynthetic AuNPs.