To make the fungal hyphae burst and release the ICNO3 into the NaCl solution, the tube was alternately cooled down to −196°C in GANT61 nmr liquid nitrogen and heated up to +90°C in a water bath for 5 min each. Cell disruption was additionally

Bucladesine promoted by a 1-min treatment with an ultrasonic probe (UW70, Bandelin, Germany). The homogenized hyphae were pelleted by centrifugation at 3000× g for 10 min and the supernatant (S2) was stored at −20°C for later analysis. Aggregates intended for protein analysis were suspended in 4 mL 0.5 M NaOH, sonicated for 1 min, and incubated at +90°C for 15 min for hot alkaline extraction of cellular proteins. The hyphae were pelleted by centrifugation selleck chemical at 3000× g for 5 min and the supernatant was stored at −20°C for later protein analysis according to [60]. Protein extraction was repeated with the pelleted hyphae and the results of the analysis of the two supernatants were combined. A conversion factor

(wet weight → protein content) was derived and used for calculating the biomass-specific ICNO3 contents as the difference between NO3 – concentrations in S1 and S2 divided by the protein contents of the hyphae. Production of biomass and cellular energy The production of biomass and cellular energy by An-4 was studied during aerobic and anaerobic cultivation in the presence or absence of NO3 – (Experiment 4). For this purpose, the time courses of protein and ATP contents of An-4 mycelia and of NO3 – and NH4 + concentrations in the liquid media were followed. Twelve replicate liquid cultures were prepared as described for Experiment Adenosine triphosphate 1, but in six cultures NO3 – addition was omitted. Six cultures (3 cultures each with and without NO3 -) were incubated aerobically, whereas the other six cultures (3 cultures each with and without NO3 -) were incubated anaerobically. Subsamples of the liquid media (1.5 mL) and An-4 mycelia (4–6 aggregates) were taken after defined time intervals using aseptic techniques. Samples were immediately frozen

at −20°C for later analysis of NO3 – and NH4 + concentrations and protein and ATP contents. The NO3 –amended cultures received additional NO3 – (to a nominal concentration of 50 μmol L-1) after 1, 3, 7, and 9 days of incubation to avoid premature nitrate depletion. Nitrogen analyses Nitrate and NO2 – were analyzed with the VCl3 and NaI reduction assay, respectively [61, 62]. In these methods, NO3 – and/or NO2 – are reduced to nitric oxide that is quantified with the chemiluminescence detector of an NOx analyzer (CLD 60, Eco Physics, Munich, Germany). Ammonium was analyzed with the salicylate method [63]. Nitrous oxide was analyzed on a gas chromatograph (GC 7890, Agilent Technologies) equipped with a CP-PoraPLOT Q column and a 63Ni electron capture detector.