Mycelial pellet intrastructure and visualization of mycelia and intracellular lipid in a culture of Mortierella alpina.

The intrastructure of mycelial pellets of Mortierella alpina, which accumulate fatty acids in mycelia, was visualized following labeling with fluorescein isothiocyanate (FITC) and Nile red using fluorescence microscopy. The pellet was an ellipse shape, but its intrastructure was shaped as a doughnut with a cave inside. Using three-dimensional image analysis, it was shown that the lipid was produced on the edge of the pellet, which corresponded to the area where the mycelial density was high. The cavity ratio of the pellet section was determined on the basis of the FITC fluorescence intensity, and in the early culture stage remained at 0.2 in a 10-kl fermentor culture, but finally increased to 0.35. Mycelial pellet volume paralleled the cavity ratio. Application of the technique used here allows analysis of the intrastructure of fungal pellets and new types of fungal biological study.