Amplification of the bacterial 16S rRNA gene V4 region and the fungal ITS1 region was performed using the universal prokaryotic and fungal primers 515F/806R and the ITS5–1737F/ITS2-2043R (Supplementary Table 3), respectively, with barcodes attached that were unique to each sample33,34. All PCR reactions were carried out using Phusion® High-Fidelity PCR Master Mix with GC Buffer (New England Biolabs, UK). Amplifications were carried out in a 50 μL reaction mixture including 25 μL of Master Mix (2X), a 0.5 μM final concentration of the forward and reverse primers, 10 ng of template DNA and nuclease-free water to 50 μL. The PCR conditions were 98 °C for 1 min, followed by 30 cycles of 10 s at 98 °C, 30 s at 50 °C for 16S rRNA gene amplification or 55 °C for ITS region amplification, and 30 s at 72 °C, with a final extension of 5 min at 72 °C.