The pH optimum of soil exoenzymes adapt to long term changes in soil pH

• Published in: Soil biology & biochemistry Vol. 138; p. 107601
• Main Authors: Puissant, Jérémy, Jones, Briony, Goodall, Tim, Mang, Dana, Blaud, Aimeric, Gweon, Hyun Soon, Malik, Ashish, Jones, Davey L., Clark, Ian M., Hirsch, Penny R., Griffiths, Robert
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2019
• Subjects: Actinobacteria; Adaptation; beta-glucosidase; Carbon degradation; community structure; environmental factors; Enzyme activity; extracellular enzymes; fungal communities; grasses; isozymes; Liming; long term experiments; Metagenomics; Microbial community; nucleotide sequences; organic matter; soil bacteria; soil pH; Metagenomics; Liming; Enzyme activity; Carbon degradation; Microbial community; Adaptation
• ISSN: 0038-0717; 1879-3428
• DOI: 10.1016/j.soilbio.2019.107601

Soil exoenzymes released by microorganisms break down organic matter and are crucial in regulating C, N and P cycling. Soil pH is known to influence enzyme activity, and is also a strong driver of microbial community composition; but little is known about how alterations in soil pH affect enzymatic activity and how this is mediated by microbial communities. To assess long term enzymatic adaptation to soil pH, we conducted enzyme assays at buffered pH levels on two historically managed soils maintained at either pH 5 or 7 from the Rothamsted Park Grass Long-term experiment. The pH optima for a range of exoenzymes involved in C, N, P cycling, differed between the two soils, the direction of the shift being toward the source soil pH, indicating the production of pH adapted isoenzymes by the soil microbial community. Soil bacterial and fungal communities determined by amplicon sequencing were clearly distinct between pH 5 and soil pH 7 soils, possibly explaining differences in enzymatic responses. Furthermore, β-glucosidase gene sequences extracted from metagenomes revealed an increased abundance of Acidobacterial producers in the pH 5 soils, and Actinobacteria in pH 7 soils. Our findings demonstrate that the pH optimum of soil exoenzymes adapt to long term changes in soil pH, the direction being dependent on the soil pH shift; and we provide further evidence that changes in functional microbial communities may underpin this phenomena, though new research is now needed to directly link change in enzyme activity optima with microbial communities. More generally, our new findings have large implications for modelling the efficiency of different microbial enzymatic processes under changing environmental conditions. -The pH optima of exoenzymes differed between pH 5 and pH 7 soils-The direction of the shift in exoenzymes pH optima was toward the source soil pH-Bacterial and fungal communities were clearly distinct between pH5 and pH7 soils-Presence of unique β-glucosidase gene sequences at both pH soils-The majority of β-glucosidase Acidobacteria sequences were classed as pH 5 specialists-Implications for modelling the efficiency and adaptation of soil microbial community