Fig. 2

Autophagic processes in P. pastoris approaching stationary phase in glycerol batch cultures and during methanol-induced IP production in fed-batch cultures. a–c Cells were first grown in a 15 L bioreactor in batch mode with 95 g/L glycerol as carbon source as described previously [19]. Directly after depletion of glycerol and prior to methanol feeding cells were examined by transmission electron microscopy. Representative images of cells from the morphologically diverse population are shown. d After depletion of glycerol IP production was induced by methanol feeding as described before [19]. Representative image taken 48 h after the onset of methanol feeding. N: nucleus, AB: autophagic body, P: peroxisome, open arrows: membranous structures with the typical features of the delimiting ER membranes (ER-phagy), black arrow: ribosomes (ribophagy). For typical features of ER-phagy in electron micrographs of S. cerevisiae [32,33,34] and P. pastoris [29] please consult figures in indicated references. Bars represent 200 nm