DNA extraction
Soil metagenomic DNA was extracted using a FastDNA spin kit for
soil (MP Biomedical, Carlsbad, CA, USA) following the manufacturer's
instructions and precipitated with 100% ethanol and 0.3 M NaOAc.
DNA purity was assessed by UV absorbance ratios of A260/A280
(N1.8) and A260/A230 (N1.7), and DNA concentrations were measured
with a PicoGreen method