Effect of DNA Extraction Methods on the Apparent Structure of Yak Rumen Microbial Communities as Revealed by 16S rDNA Sequencing

To more efficiently identify the microbial community of the yak rumen, the standardization of DNA extraction is key to ensure fidelity while studying environmental microbial communities. In this study, we systematically compared the efficiency of several extraction methods based on DNA yield, purity, and 16S rDNA sequencing to determine the optimal DNA extraction methods whose DNA products reflect complete bacterial communities. The results indicate that method 6 (hexadecyltrimethylammomium bromide-lysozyme-physical lysis by bead beating) is recommended for the DNA isolation of the rumen microbial community due to its high yield, operational taxonomic unit, bacterial diversity, and excellent cell-breaking capability. The results also indicate that the bead-beating step is necessary to effectively break down the cell walls of all of the microbes, especially Gram-positive bacteria. Another aim of this study was to preliminarily analyze the bacterial community via 16S rDNA sequencing. The microbial community spanned approximately 21 phyla, 35 classes, 75 families, and 112 genera. A comparative analysis showed some variations in the microbial community between yaks and cattle that may be attributed to diet and environmental differences. Interestingly, numerous uncultured or unclassified bacteria were found in yak rumen, suggesting that further research is required to determine the specific functional and ecological roles of these bacteria in yak rumen. In summary, the investigation of the optimal DNA extraction methods and the preliminary evaluation of the bacterial community composition of yak rumen support further identification of the specificity of the rumen microbial community in yak and the discovery of distinct gene resources.