Extracellular peroxidase reaction at hyphal tips of white-rot fungus Phanerochaete crassa WD1694 and in fungal slime

The distribution of an extracellular peroxidase reaction by white-rot fungus Phanerochaete crassa WD1694 was visualized by peroxidase activity staining. The extracellular peroxidase reaction occurred at the hyphal tips and in the fungal slime filling the gaps between the hyphae. We investigated whether the peroxidase reaction occurred from the hyphal tips or in the slime. The hyphal tips were observed by phase-contrast microscopy, which showed that slime did not exist around the hyphal tips. Time-course observation of hyphal tips showed that peroxidase staining became thick and intense at the tips that did not have fungal slime. Daily observation of the peroxidase staining revealed that the staining was first observed at the hyphal tips. Furthermore, strongly stained hyphae were observed in the stained slime. These results suggested that an active species that oxidizes a peroxidase substrate is first produced at the tips of the hyphae, and then occurs in the slime via diffusion when slime exists around the hyphae. Our results show that the extracellular peroxidase reaction that is important to lignin biodegradation by white-rot fungi occurs directly at the tips of the hyphae and in the slime. Part of this report was presented at the 50th Lignin Symposium, October 19–20, 2005, Nagoya, Japan