DOI: 10.5061/dryad.rbnzs7hhb
title: Carbon availability affects already large species-specific differences in chemical composition of ectomycorrhizal fungal mycelia in pure culture

description: 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.
description: 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
 H<sub>2</sub>O, 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<sup>-1</sup> resolution over the range 4000 -
 370cm<sup>-1</sup>. 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 CO<sub>2</sub> 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.
description: # 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 (R<sup>2</sup> = 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 H<sub>2</sub>O, 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<sup>-1</sup> resolution over the range 4000 -
 370cm<sup>-1</sup>. 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 CO<sub>2</sub> 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 Links to other publicly accessible
 locations of the data: no Was data derived from another source? If yes,
 list source(s): no