Microbial Key Players Involved in P Turnover Differ in Artificial Soil Mixtures Depending on Clay Mineral Composition

Irina Tanuwidjaja,Mirna Mrkonjic Fuka,Cordula Vogel,Geertje J Pronk,Michael Schloter,Ingrid Kögel-Knabner,Stefanie Schulz,Anne Schöler,Gisle Vestergaard,Susanne Kublik

doi:10.1007/s00248-020-01635-1

Abstract

Nutrient turnover in soils is strongly driven by soil properties, including clay mineral composition. One main nutrient is phosphorus (P), which is known to be easily immobilized in soil. Therefore, the specific surface characteristics of clay minerals might substantially influence P availability in soil and thus the microbial strategies for accessing P pools. We used a metagenomic approach to analyze the microbial potential to access P after 842 days of incubation in artificial soils with a clay mineral composition of either non-expandable illite (IL) or expandable montmorillonite (MT), which differ in their surface characteristics like soil surface area and surface charge. Our data indicate that microorganisms of the two soils developed different strategies to overcome P depletion, resulting in similar total P concentrations. Genes predicted to encode inorganic pyrophosphatase (ppa), exopolyphosphatase (ppx), and the pstSCAB transport system were higher in MT, suggesting effective P uptake and the use of internal poly-P stores. Genes predicted to encode enzymes involved in organic P turnover like alkaline phosphatases (phoA, phoD) and glycerophosphoryl diester phosphodiesterase were detected in both soils in comparable numbers. In addition, Po concentrations did not differ significantly. Most identified genes were assigned to microbial lineages generally abundant in agricultural fields, but some were assigned to lineages known to include oligotrophic specialists, such as Bacillaceae and Microchaetaceae.

Highlights

In soils, minerals and microbiota are tightly associated and form highly reactive interfaces [1, 2], which represent activity hotspots
The predicted key players involved in P transformation in our study were among the dominant taxa, which underlines the importance of P acquisition in both artificial soil mixtures
Our data indicate that organic P is an important source in both artificial soil mixtures, as many reads were assigned to genes potentially involved in the effective use of organic P sources, including different alkaline phosphatases and glycerophosphoryl diester phosphodiesterase

Summary

Introduction

Minerals and microbiota are tightly associated and form highly reactive interfaces [1, 2], which represent activity hotspots. These hotspots can be considered highly structured, heterogeneous, and discontinuous [3]. Swelling clay minerals like montmorillonite are characterized by large specific surface areas, which result in water and nutrient retention. The importance of soil mineral composition as a driver for the formation of interfaces in soils has been proven in experiments with artificial soil mixtures where different combinations of clay minerals (illite and montmorillonite), iron and aluminum oxides (ferrihydrite and boehmite), and charcoal were investigated, while texture and incubation conditions were the same [5,6,7]. The authors concluded that functionally redundant microbes were present in the different soil mixtures, at least those involved in organic matter degradation

Results

Discussion

Conclusion