Comparison of Aspergillus fumigatus transcriptome grown on selected nitrogen sources

Transcriptome of A. fumigatus shifted from ammoniumtartrate to different nitrogen sources and incubated for a defined time was compared. After 16h preculture, the fungus was transferred into fresh medium containing ammonium tartrate, sodium nitrate, proline or bsa as nitrogen source. After 1h, fungus was reisolated, RNA was prepared from fungus, transcriptome was assessed and used for further analysis. Ammoniumtartrate, sodiumnitrate, BSA and proline as nitrogen sources, 2 biological replicates for each source. A. fumigatus liquid media shifts were performed according to ref. (Narendja et al.,2002) with minor modifications: 200 ml minimal medium base with 5 mM ammonium tartrate was inoculated with 10^8 conidia freshly harvested. A. fumigatus ATCC 46645 conidia were grown at 37°C and 150 rpm for 16 hours. This pre-culture was then harvested, washed liberally with sterile saline and divided into mycelial masses of equal size on a sterile surface. The portions were then added to 100 ml of minimal medium base without nitrogen source. When a defined carbon source was needed, 1% glucose was added. Flasks were incubated for 20 min at 37°C. Thereafter, one of the following sterile nitrogen sources was added: ammonium tartrate to a final concentration of 5 mM, Sodiumnitrate to a final concentration of 10 mM, 1 g proline suspended in 2 ml minimal medium base, or 0.5 g BSA (Albumin Fraktion V, Roth), suspended in 15 ml minimal medium base. The cultures were incubated for another 60 minutes, harvested by filtering through Miracloth, snap frozen in liquid nitrogen, and ground using a cooled mortar to obtain a fine powder.