Methodology:

The field experiment was set up in December 2007, at Mars Oasis. 64 circular plots (1 m diameter) were established, half of which were covered with open top chambers. In December 2007, 2009, 2010, 2011 and 2012, each of the 64 plots was assigned to one of four groups (16 plots in each group) and the soil underwent four different treatments: unamended; received glucose; received glycine (amino acid); received powdered tryptic soy broth (mix of amino acids and protein). Half of the chambered and half of the unchambered plots were then raised to 100% water holding capacity. The experimental layout resulted in 16 open top chamber-irrigation-substrate treatment combinations, each replicated four times in a randomised design.

Temperature was monitored in three chambered and three unchambered plots between December 2009 and December 2012. Frozen soil samples were returned to the UK, where water potentials were measured. Laboratory experiments were also undertaken. Three Pseudogymnoascus roseus isolates were obtained from Mars Oasis soil using the soil plate method and identified by sequencing of ribosomal DNA. Quantitative-PCR assays were used to estimate the concentration of Pseudogymnoascus DNA present in soil. The hyphal extension rate analyses were undertaken in the lab, where isolates were grown for 10 weeks on soil extract medium at temperatures cycling daily from 2-18 ° C, 2-21 ° C and 2-24 ° C and at water potentials of -1.06 MPa, -3.60 MPa, -6.00 MPa and -10.80 MPa. At the end of the growth rate experiments, extracellular enzymes were extracted from colonies and the activities of β -1,4-glucosidase (cellulase), N-acetyl- β -glucosaminidase (chitinase), leucine aminopeptidase and alkaline and acid phosphatases were measured using p-nitrophenyl substrates. The impact of temperature cycle and water potential treatments on numbers of P. roseus conidia produced per colony was measured. The treatment effects on conidial germination were also quantified at modified water potentials.

Complete methods can be downloaded with the data via the Get Data link.

Data collection:

Soil temperatures: TinyTag Plus 2 TGP-4017, Gemini Data Loggers Ltd., Chichester, UK

Soil water potentials: WP4C, Decagon Devices, Inc., Pullman, WA, USA

Q-PCR thermocycler: Eco 48 machine, PCRMax Ltd., Witford, UK

Image analysis: ImageJ, National Institute of Health, Bethesda, MD, USA

Plant growth cabinets: MCR-350 Versatile Environmental Test Chamber, Sanyo, Osaka, Japan

Plate reader: Sunrise, TECAN, Austria

Data quality:

Raw data are shown. The data have not been cleaned. Missing data are indicated by NA. There are 1-2 missing data points in the water potential, DNA concentration, conidial density and hyphal extension rate data, caused principally by lack of material or analysis failure. 22 values are missing from the specific enzyme activity data, all of which were caused by analysis failure.