Sustainable reuse of treated wastewater sludge, commonly known as biosolids, is a key activity in developing circular economies of nutrients. Application of biosolids to soils amounts to a collision of two distinct microbial communities adapted to vastly different matrices, however taxonomic and functional dynamics of this process have not been adequately characterised.
To address this, we applied metagenomics and metatranscriptomics to a lab-based incubation experiment with biosolids-amended soils. Briefly, biosolids (10 t-1 ha-1) were added to soil microcosms and incubated under controlled conditions for six-months. Both soils-only and biosolids-only controls were included to assess the relative contribution of each matrix to outcomes in the treatments. Samples for metagenomic and metatranscriptomic sequencing were taken at six weeks and six months, and a MAG-based analysis was performed to identify differentially expressed functions in key organisms originating from each matrix. A suite of biogeochemical measurements was also taken.
We hypothesise that overall transcriptional profiles of treatments will differ significantly from controls, primarily driven by the biosolids addition of organic matter. This is likely to be reflected in the differential expression of various functional categories including organic matter breakdown, central carbon metabolism, and nitrogen and phosphorus cycling. We expect differentially expressed functional groups to be associated with, and favour the expansion of, copiotrophs originating in both the soils and the biosolids.
These results will provide fundamental insights into the functional landscape of microbial communities as they assemble in biosolids-amended soils and inform future pot experiments to characterise their influence on relevant agricultural crops.