Cell function is related to cell composition. Hyphal composition can change substantially over a few tens of microns, and spores have different composition from hyphae. Most biochemical analyses are restricted to studying a few components at high spatial resolution (e.g. histochemistry) or many compounds at low spatial resolution (e.g. GC-MS). We are using synchrotron Fourier transform infrared (sFTIR) spectromicroscopy to study fungal cell composition by fingerprinting varieties of carbohydrate, protein and lipid at 3-10 μm spatial resolution. The diffraction limit depends on wavelength, which in the mid-IR spans 3-30 μm. We have previously shown (Szeghalmi et al 2007 Analyt Bioanalyt Chem 387:1779-89) that sFTIR can distinguish fungal species, near-isogenic strains, and apical vs subapical regions in single cells. Aspergillus and Neurospora hyphae had similar sFTIR profiles (rich in protein) which were different from Rhizopus (rich in carbohydrate). For all three fungi, the biochemical content near the tips was substantially less than at 50 μm or 100 μm subapically. Fungi grown under optimal vs mildly stressed (e.g. a change of 2 pH units or less, in either direction) differed in sFTIR profile despite typically exhibiting few morphological effects. Here we compare hypha and spore composition of Neurospora and Rhizopus. There were biochemical profile changes when Neurospora hyphae committed to spore development, during spore maturation, and following germination. Many of these are consistent with results from molecular genetics, but had not been shown before at high spatial resolution. Notably, although Neurospora hyphal carbohydrate content was reduced by growth at sub-optimal pH, the spores formed at optimal and sub-optimal pH levels had remarkably similar composition. Germinated Neurospora spores retained a nutrient dowry even after the germ tube was >100 μm long, presumably to support the growth of additional germ tubes. Developing Rhizopus spores had similar protein content and significantly more carbohydrate than hyphae, and spores had different composition from the sporangial fluid that surrounds them during maturation.
Full conference title:
9th EUROPEAN CONFERENCE ON FUNGAL GENETICS
- ECFG 9th (2008)