Effect of experimental soil disturbance and recovery on structure and function of soil community: a metagenomic and metagenetic approach.

There has been little study of effects of disturbance on soil biota combining closely controlled experimental conditions and DNA-based methods. We sampled pots of soil at varying times following an initial simulated mass mortality event. Soil DNA was extracted at intervals up to 24 weeks after the event, and shotgun metagenomes sequenced using NextSeq. Compared to initial conditions, we found: consistent, sequential changes in functional metagenome and community structure over time, indicating successional niche differentiation amongst soil biota. As predicted, early successional systems had greater abundance of genes associated with motility, but fewer genes relating to DNA/RNA/protein metabolism, cell division and cell cycle. Contrary to predictions, there were no significant differences in cell signaling, virulence and defense-related genes. Also, stress related genes were less abundant in later succession. The early successional system had lower taxonomic diversity but higher functional gene diversity. Over time, community characteristics changed progressively, but by the end of the experiment had not returned to the 'original' state of the system before disturbance. Results indicated a predictable sequence of gene functions and taxa following disturbance, analogous to ecosystem succession for large organisms. It is unclear if and when the system would return to its pre-disturbance state.