Stress management: Filamentous fungi as exemplary survivors

Abstract

Consideration of examples of the filamentous fungi, a major group of so‐called ‘lower organisms’, highlights some advantages that their simple organization has over the often extreme fragility of apparently more advanced organisms such as the supposed pinnacle of the evolutionary process thus far, Homo sapiens. Severe trauma resulting in extensive cytoplasmic loss as a consequence of hyphal tip bursting or the severing of intercalary compartments rarely has catastrophic effects but simply delays hyphal extension for a short period of time, less than one hour in many cases such as Sordaria brevicollis growing at 25°C. Less disruptive stress, such as nutrient deprivation, may give rise to severely aberrant morphology, but recovery may be very rapid upon simple addition of the required nutrient as in the case of choline‐requiring strains of Aspergillus nidulans. Under stress, many filamentous fungi inducing A. nidulans and Neurospora crassa exhibit the phenomenon of multiple tip‐formation, often near the hyphal apex. This may simply be due to disturbance of the process of tip extension by the adverse conditions, but the potential benefit to the fungus of a sudden dramatic increase in the number of exploratory branches emanating from a mycelium in an inhomogenous environment would be an increased likehood of locating regions of reduced stress.