1：Experimental Design and Method Selection:

The study used SERS with silver colloidal nanoparticles synthesized by microwave heating as substrates for detecting bacteria. The rationale was to leverage the enhancement of Raman signals for sensitive and rapid detection.

2：Sample Selection and Data Sources:

Bacterial strains (Escherichia coli O157:H7 ATCC 43895, Staphylococcus aureus ATCC 27664, Salmonella ATCC 13076) were obtained from the American Type Culture Collection and cultured in TSB broth.

3：List of Experimental Equipment and Materials:

Silver nitrate, sodium citrate, double distilled water, microwave oven, UV-Vis spectrophotometer (UV-1800, Shimadzu), laser particle size analyzer (ZEN3690 Malvern), transmission electron microscope (JEOL JEM 1200EX), zeta potential analyzer (Zetasizer Nano ZS Malvern), portable Raman spectrometer (I0785MM0350MF, Ocean Optics), glass capillary tubes, and software (Origin 9.0, SPSS 11.5.0).

4：0, SPSS 0). Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Silver nanoparticles were synthesized by microwave heating AgNO3 with sodium citrate. Bacteria were cultured, washed, and resuspended with AgNPs. SERS measurements were performed using a Raman spectrometer with 785 nm laser excitation. Data were analyzed using PCA and HCA.

5：Data Analysis Methods:

Spectra were processed with smoothing, normalization, and second-derivative transformation. PCA and HCA were used for classification and differentiation of bacterial strains based on SERS spectra.