Loss in microbial diversity affects nitrogen cycling in soil

Abstract

Microbial communities have a central role in ecosystem processes by driving the Earth's biogeochemical cycles. However, the importance of microbial diversity for ecosystem functioning is still debated. Here, we experimentally manipulated the soil microbial community using a dilution approach to analyze the functional consequences of diversity loss. A trait-centered approach was embraced using the denitrifiers as model guild due to their role in nitrogen cycling, a major ecosystem service. How various diversity metrics related to richness, eveness and phylogenetic diversity of the soil denitrifier community were affected by the removal experiment was assessed by 454 sequencing. As expected, the diversity metrics indicated a decrease in diversity in the 1/10 3 and 1/10 5 dilution treatments compared with the undiluted one. However, the extent of dilution and the corresponding reduction in diversity were not commensurate, as a dilution of five orders of magnitude resulted in a 75% decrease in estimated richness. This reduction in denitrifier diversity resulted in a significantly lower potential denitrification activity in soil of up to 4-5 folds. Addition of wheat residues significantly increased differences in potential denitrification between diversity levels, indicating that the resource level can influence the shape of the microbial diversityfunctioning relationship. This study shows that microbial diversity loss can alter terrestrial ecosystem processes, which suggests that the importance of functional redundancy in soil microbial communities has been overstated.

Elucidating the impact of microbial community biodiversity on pharmaceutical biotransformation during wastewater treatment

“…A gradient in microbial biodiversity in an activated sludge community was established using a dilution‐to‐extinction approach (Szabó et al ., 2007; Peter et al ., 2010; Philippot et al ., 2013; Ylla et al ., 2013). In this approach, each dilution theoretically removes the least abundant species from the previous culture, resulting in a less diverse subset of the original community.…”

“…Dilution‐induced reductions in diversity have been used in numerous previous studies to understand structure–function relationships in mixed microbial communities (e.g. Franklin and Mills, 2006; Hernandez‐Raquet et al ., 2013; Philippot et al ., 2013). Before serial dilution, disaggregation of macroflocs in the activated sludge sample was achieved by blending approximately 500 ml of mixed liquor in an industrial blender (Waring Commercial Blender, Model 516L31) at maximum speed for 10 min.…”

Cutting Edge: IL-17–Secreting Innate Lymphoid Cells Are Essential for Host Defense against Fungal Infection

“…Some complex microbial functional traits (e.g., photosynthesis and nitrogen fixation) are strongly linked to specific phylogenetic groups and decreases in microbial diversity have been linked to declines in denitrification, nitrification, and methane oxidation (20,21). For widespread functions like simple carbon substrate degradation, redundancy within the microbiome may mean similar functioning by very different microbial assemblages, reducing the importance of microbial diversity.…”

Influence Mechanisms of Rainfall and Terrain Characteristics on Total Nitrogen Losses from Regosol

“…Microbes have effects on the forms of nitrogen in soil. For example, the existence of nitrogenfixing bacteria and phosphorus bacteria could add available nitrogen content in soil, denitrifying bacteria could slow the conversion of available nitrogen to ineffective nitrogen, and, in soil, some bacteria activate nitrogen and turns it into nutrients that plants can absorb [34]. Furthermore, other soil components have effects of the background value of nitrogen; for instance, the content of clay particles in soil could affect the mass fraction of TN in soil [35].…”