Impact on the microbiome of soils treated with a novel reconstruction technique, assessed by 16S rDNA multi-amplicon sequencing

The microbial diversity is, among soil key factors, responsible for soil fertility and nutrient biogeochemical cycles, and can be modified upon changes in main soil physicochemical properties and soil pollution. Over the years, many restoration techniques have been applied to restore degraded soils. However, the effect of these approaches on soil microbial diversity profile is less understood and thus requires more investigation. In this study, we investigated the impact of patented novel technology, used to restore degraded soils, on the soil microbial diversity. Soil samples were collected from three nearby sites located in Borgotrebbia, Piacenza, Italy, and categorized as reconstituted, degraded, and agricultural soils. After total soil DNA extraction, the 16S rDNA multi-amplicon sequencing was carried out using an Ion GeneStudio S5 System to compare soils' bacterial profile. Sequenced reads were processed to assign taxonomy and then the key microbial community differences were identified across the sampling sites. In parallel, the abundance of genes involved in the nitrogen (N) biogeochemical cycle was assessed using quantitative Real-Time PCR (qPCR). Total DNA content was significantly higher (p<0.05) in degraded (µ=12.69±2.58 µg·g-1) and reconstituted (µ=11.73±1.65 µg·g-1) soil samples when compared to the agricultural soil samples (µ=2.39±0.50 µg·g-1). The taxonomic diversity of each soil site was significantly different, with some instances unique of the agricultural soil even at phylum level. The analysis of N functional genes showed that the relative abundance of bacterial amoA (p<0.05) and nosZ (p<0.01) genes were significantly lower in the agricultural than in the reconstituted and degraded soils. We concluded that the application of the soil reconstitution technique seemed to enhance the active microbial community, with distinct diversity and functionality towards genes involved in N biogeochemical cycle, as compared to both the degraded and the agricultural soil.