The taxon-specific degradation of soil extracellular 16S rRNA genes: rates, influential factors, and implications Metagenome

The taxon-specific degradation rates of extracellular 16S rRNA genes play a crucial role in determining the impact of extracellular DNA on soil microbial analysis, yet the related understanding remains limited. Here, we investigated the overall and taxon-specific degradation rates of extracellular 16S rRNA genes in soils collected across China, based on primer labeling, microcosmic incubation, qPCR, and amplicon sequencing. The results revealed substantial variations in the overall degradation rates of extracellular 16S rRNA genes across the study sites, with their half-life time ranging from 4.33 to 12.15 days. The overall degradation rates showed significant correlations with multiple environmental factors such as mean annul precipitation, soil moisture content, and soil pH values. Furthermore, significant differences in the degradation rates of extracellular 16S rRNA genes among prokaryotic taxa were also observed. The taxon-specific half-life time ranged from several hours to decades, with the majority falling within 1 to 14 days. The profiles of extracellular 16S rRNA gene taxon-specific degradation rates significantly correlated with soil pH and mean annual temperature. The removal of extracellular16S rRNA genes decreased soil prokaryotic abundance and richness by 59.7% and 13.5%, respectively, and it significantly changed prokaryotic community profiles. Interestingly, the sizes of taxon-specific extracellular 16S rRNA gene pools also showed significant correlations with the degradation rates of these genes. This study established a methodological system for determining the taxon-specific degradation rates of extracellular 16S rRNA genes, highlighting the strong influences of extracellular DNA on the analysis of soil microbial diversity and abundance.