The effect of soil-sample size for practical DNA extraction on soil microbial diversity in different taxonomic rank

In this study, we investigated effects of changes of sample soil volume on microbial diversity using amplicon sequence analysis. Five samples of three different sample sizes (0.2, 1, and 5 g) were prepared for each. Microbial community structure analysis in different taxonomic rank was carried out to evaluate the effect of the taxonomic rank applied. DNA extraction from 1 g using 15-mL tubes was superior for both alpha and beta diversity, and thus the results were highly reproducible. When the taxonomic level was changed from order to phylum, minor taxa identified at the order level were aggregated into major taxa at the phylum level, although differences in microbial community structure were preserved. In the consideration of beta-diversity, When the presence or absence of minor taxa is assessed, as in the case of the Sorensen-Dice index, the results may vary depending on the taxonomic level.