[Objective] The objective of this study was to report an improved method for rapid DNA extraction from black-order sediments, without any purification step. [Methods] Sediments in eutrophic lake are complex ecosystems and soil microbes involved in anthropogenic nutrient cycling are very important. DNA-based molecular methods offer new tools for characterization of these mixed communities of mi- croorganisms. However, it is very difficult to remove humic substances, heavy met- als that co-existed with genome DNA representing the microbial community directly from these complex systems and can interfere with subsequent genetic analysis. The potassium dichromate solution was firstly used to remove humic substances. [Results] The steps of removing humic substances and DNA extraction were per- formed simultaneously that improved the speed of extraction to approximately 1 hour and the nucleic acids that were obtained with this method did not need to be washed with 70% ethanol and dissolved directly in sterile water for total bacterial 16S rDNA, nosZ gene of denitrifying bacteria, pmoA of methanotrophs, nifH of nitro- gen-fixing bacteria, amoA of ammonia-oxidizing bacteria and ammonia-oxidizing ar- chaea molecular ecology analyses. [Conclusion] This method could provide a plat- form for preparing a fast sediments DNA extraction.
