Lysis of an Aspergillus nidulans mutant blocked in chitin synthesis and its relation to wall assembly and wall metabolism.

Abstract

1. Mutant Aspergillus nidulans hyphae containing 7–15% of the normal chitin complement did not lyse in dilute buffer but lysed on continued incubation in growth medium without osmotic stabiliser. Distortion and lysis could occur anywhere along the hypha and were not confined to the apex. 2. Hyphae with a normal chitin content started to distort and lyse 90 min after transfer to medium lacking osmotic stabiliser and at the temperature inhibiting chitin synthesis. Lysis was not confined to the growing tips. 3. Hyphae lacking wall chitin and transferred to conditions where chitin synthesis could proceed, formed stable mycelium at the growing tips and distorted in the older, chitin-poor, regions. Pulse-labelling with N-acetylglucosamine and radioautography showed that, in such hyphae, chitin was incorporated into the wall in the older regions undergoing distortion. 4. The relation between growth—dependent distortion and lysis and the activity and location of autolytic enzymes is discussed.