Modified methods obtain high-quality DNA and RNA from anaerobic activated sludge at a wide range of temperatures.

Anaerobic activated sludge is rich in humic substances and water, leading to significant differences in the stability of metagenomic DNA and metatranscriptomic RNA. Thus, it is of great difficulty to exact high-quality and high-yield DNA and RNA from them, especially those cultured at a wide range of temperatures. Here, we established fast and effective DNA and RNA extraction methods based on current commercial kits. The modified methods combined liquid nitrogen grinding with kits, achieving notable improvements in concentrations, yields, purity and integrities for both DNA and RNA. The ratios of OD260/280 of the metagenomic DNA were between 1.81 ± 0.03 and 1.83 ± 0.02, while OD260/280 and OD260/230 of the metatranscriptomic RNA ranged from 1.96 ± 0.01 to 2.13 ± 0.03 and from 1.94 ± 0.02 to 2.30 ± 0.03 respectively. Metagenomic DNA and metatranscriptomic RNA obtained by the modified methods perfectly met the requirements of second- and third-generation sequencing, providing valuable reference for extracting high-quality metagenomic DNA and metatranscriptomic RNA from environmental samples of high water content and humic substances under temperatures ranging from 18 °C to 52 °C.