This is the dataset for the manuscript entitled "Temperature controls the relation between soil organic carbon and microbial carbon use efficiency".

This is the dataset for the manuscript entitled "Temperature controls the relation between soil organic carbon and microbial carbon use efficiency".

Metatranscriptomics holds the prospect of predicting fungal phenotypes based on patterns of gene expressions, providing new opportunities to obtain information about metabolic processes without disturbance of natural systems, and with taxonomic resolution. Acquisition of fungal metabolic carbon and its subsequent partitioning between biomass production and respiration, i.e. the carbon-use efficiency, are central parameters in biogeochemical modelling. However, current available techniques for estimating these parameters in natural systems are all associated with practical and theoretical shortcomings, making assessments unreliable. We cultured four different fungal isolates (Chalara longipes, Laccaria bicolor, Serpula lacrymans, and Trichoderma harzianum) in liquid media with contrasting nitrogen availability and measured growth rates and respiration to calculate carbon-use efficiency. By relating expression of gene markers to measured carbon fluxes, we identified genes coding for 1,3-β-glucan synthase and 2-oxoglutarate dehydrogenase as good markers for growth and respiration, respectively, capturing both intraspecific variation as well as within-strain variation dependent on growth medium. A gene expression index based on these markers correlated significantly with differences in carbon-use efficiency between the fungal isolates. Our study paves the way for use of these markers to assess differences in growth, respiration, and carbon-use efficiency in natural fungal communities, using metatranscriptomic or RT-qPCR approach.

Here leveraging decades of experimental data on growth of microbial isolates, we study in depth the non-equilibrium thermodynamics of microbial growth to shed light on the relation between mass and energy constraints on growth. Our results show that there exist universal scaling laws relating the thermodynamic efficiency of microbial growth to the electron donor uptake rate and to the growth yield, which tightly couple mass and energy conversion in microbial growth. This resource contains an excel file with original data from Smeaton and Van Cappellen (2018) and the thermodynamic calculations for the article associated to this resource, and a Mathematica code used for drawing the Figures.

1. In boreal forest soils, mycelium of mycorrhizal fungi is pivotal for regulating soil carbon (C) cycling and storage. The carbon use efficiency (CUE), a key parameter in C cycling models, can inform on the partitioning of C between microbial biomass, and potential soil storage, and respiration. Here we test the dependency of mycorrhizal mycelial CUE on stand age and seasonality in managed boreal forest stands. 2. Based on mycelial production and respiration estimates, derived from sequentially incubated ingrowth mesh bags, we estimated CUE on an ecosystem-scale during a seasonal cycle and across a chronosequence of eight, 12- to 158-years-old, managed Pinus sylvestris forest stands characterised by decreasing pH and nitrogen (N) availability with increasing age. Mycelial respiration was related to total soil respiration, and by using eddy covariance flux measurements, primary production (GPP) was estimated in the 12- and 100-years-old forests, and related to mycelial respiration and CUE. 3. As hypothesized, mycelial CUE decreased significantly with increasing forest age by c. 65%, supposedly related to a shift in mycorrhizal community composition and a metabolic adjustment to reduce their own biomass N demand with declining soil N availability. Furthermore, mycelial CUE increased by a factor of five over the growing season; from 0.03 in May to 0.15 in November, and we propose that the seasonal change in CUE is regulated by a decrease in photosynthate production and temperature. The respiratory contribution of mycorrhizal mycelium ranged from 14 to 26% of total soil respiration, and was on average 17% across all sites and occasions. 4. Synthesis: Carbon is retained more efficiently in mycorrhizal mycelium late in the growing season, when fungi have access to a more balanced C and nutrient supplies. Earlier in the growing season, at maximum host plant photosynthesis, when belowground C availability is high in relation to N, the fungi respire excess C resulting in lower mycelial CUE. Additionally, C is retained less efficiently in mycorrhizal fungal biomass in older forest stands characterized by more nutrient depleted soils than younger forest stands.