Carbon availability affects already large species-specific differences in chemical composition of ectomycorrhizal fungal mycelia in pure culture
Data files
Oct 05, 2023 version files 1.93 MB
Abstract
Although ectomycorrhizal (ECM) contribution to soil organic matter processes receives increased attention, little is known about fundamental differences in chemical composition among species, and how that may be affected by carbon (C) availability. Here we study how 16 species (incl. 19 isolates) grown in pure culture at three different C:N ratios (10:1, 20:1 and 40:1) vary in chemical structure, using Fourier transform infrared (FTIR) spectroscopy. We hypothesised that C availability impacts directly on chemical composition, expecting increased C availability to lead to more carbohydrates and less proteins in the mycelia. There were strong and significant effects of ECM species (R2 = 0.873 and P = 0.001) and large species-specific differences in chemical composition. Chemical composition also changed significantly with C availability, and increased C led to more polysaccharides and less proteins for many species, but not all. Understanding how chemical composition change with altered C availability is a first step towards understanding their role in organic matter accumulation and decomposition.
README: Title of Dataset:
Carbon availability affects already large species-specific differences in chemical composition of ectomycorrhizal fungal mycelia in pure culture
Abstract
Although ectomycorrhizal (ECM) contribution to soil organic matter processes receives increased attention, little is known about fundamental differences in chemical composition among species, and how that may be affected by carbon (C) availability. Here we study how 16 species (incl. 19 isolates) grown in pure culture at three different C:N ratios (10:1, 20:1 and 40:1) vary in chemical structure, using Fourier transform infrared (FTIR) spectroscopy. We hypothesised that C availability impacts directly on chemical composition, expecting increased C availability to lead to more carbohydrates and less proteins in the mycelia. There were strong and significant effects of ECM species (R2 = 0.873 and P = 0.001) and large species-specific differences in chemical composition. Chemical composition also changed significantly with C availability, and increased C led to more polysaccharides and less proteins for many species, but not all. Understanding how chemical composition change with altered C availability is a first step towards understanding their role in organic matter accumulation and decomposition.
Materials and methods
Spectral characterisation of fungal samples was performed by FTIR spectroscopy. Ectomycorrhizal (ECM) fungal isolates (a total of 19 fungal isolates, covering 16 different ECM species) were grown in duplicates in liquid pure culture at 25° C for three weeks at three different C:N ratios (10:1, 20:1 and 40:1), in effect moving from conditions of C limitation (C:N 10:1) to conditions of N limitation (C:N 40:1). At harvest, mycelia were washed in double distilled H2O, freezedried and homogenised. IR spectra were recorded on a Bruker Vertex 70 FTIR spectrometer (Bruker, Ettlingen, Germany) fitted with a potassium bromide beam splitter and a deutroglycine sulphate detector for two replicates of each species. A Diamond Attenuated Total Reflectance (DATR) sampling accessory, with a single reflectance system, was used to produce transmission-like spectra, then the IR transmittance spectra were converted to absorbance spectra. Samples were placed directly on a DATR/KRS-5 crystal, and a flat tip powder press was used to achieve even distribution and contact. Spectra were acquired by averaging 200 scans at 4 cm-1 resolution over the range 4000 - 370cm-1. A correction was made to the ATR spectra to allow for differences in depth of beam penetration at different wavelengths, using OPUS software (Bruker, Ettlingen, Germany, version 6.0). The spectra were also baseline corrected. No correction was required for water vapour and CO2 as the spectrometer is continuously flushed with dry air. Deposited data shows raw data output, from .csv files.FTIR data was then normalised by subtraction of the minimum value and subsequent division by the average of all data points per sample prior to statistical analyses.
Description of the Data and file structure
Raw data from FTIR spectroscopy in excel spread sheet. Column A shows wave numbers for IR spectra, ranging from 349 to 4000. Row 1 (columns B-DH) shows sample-IDs. A sample-ID consists of the ectomycorrhizal fungal species name followed by the C:N ratio treatment (10:1, 20:1 and 40:1), and the replicate number (n=2). Fungal species names have isolate identifiers for the species with more than one isolate included (Suillus bovinus = 3 isolates, Suillus variegatus = 2 isolates). One of the two Hebeloma species was unidentified and is labelled Hebeloma sp. 1. A total of 19 isolates includes 16 different species.
Data set includes one spread sheet. Hebeloma sp. 1 = Hebeloma species 1. C:N ratio = carbon:nitrogen ratio. Species Piloderma fallax has one replicate for treatment C:N ratio 10:1. Suillus variegatus UP60 has one replicate for treatments C:N ratio 20:1 and one for treatment 40:1.
Sharing/access Information
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Was data derived from another source?
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Methods
Spectral characterisation of fungal samples was performed by FTIR spectroscopy. Ectomycorrhizal (ECM) fungal isolates (a total of 19 fungal isolates, covering 16 different ECM species) were grown in duplicates in liquid pure culture at 25° C for three weeks at three different C:N ratios (10:1, 20:1 and 40:1), in effect moving from conditions of C limitation (C:N 10:1) to conditions of N limitation (C:N 40:1). At harvest, mycelia were washed in double distilled H2O, freezedried and homogenised. IR spectra were recorded on a Bruker Vertex 70 FTIR spectrometer (Bruker, Ettlingen, Germany) fitted with a potassium bromide beam splitter and a deutroglycine sulphate detector for two replicates of each species. A Diamond Attenuated Total Reflectance (DATR) sampling accessory, with a single reflectance system, was used to produce “transmission-like” spectra, then the IR transmittance spectra were converted to absorbance spectra. Samples were placed directly on a DATR/KRS-5 crystal, and a flat tip powder press was used to achieve even distribution and contact. Spectra were acquired by averaging 200 scans at 4 cm-1 resolution over the range 4000 - 370cm-1. A correction was made to the ATR spectra to allow for differences in depth of beam penetration at different wavelengths, using OPUS software (Bruker, Ettlingen, Germany, version 6.0). The spectra were also baseline corrected. No correction was required for water vapour and CO2 as the spectrometer is continuously flushed with dry air. Deposited data shows raw data output. FTIR data was then normalised by subtraction of the minimum value and subsequent division by the average of all data points per sample prior to statistical analyses.