Autolysis of <i>Penicillium chrysogenum-A </i>Holistic Approach

Abstract

Despite of its biotechnological significance, the autolysis of filamentous fungi is a poorly studied and understood

area of fungal physiology. The autolysis of 13-lactam producing fungus, <i>Penicillium chrysogenum </i>shares some similarities

with the apoptosis of higher eukaryotes. For example, the biosynthesis and processing of age-related hydrolases

were highly regulated in carbon-depleted cultures. The <i>in vivo </i>inhibition of autolytic chitinase activity hindered

considerably the disintegration of pelleted structures that are typical of the exponential growth phase. In the absence

of conidiation, round-ended "yeast-like" hyphal fragments were the dominant surviving morphological forms, which

were characterised with decreasing total respiration, increasing cyanide-resistant respiration, intracellular accumulation

of reactive oxygen species (ROS) and declining viability in the autolytic and post-autolytic phases of growth.

The term "ageing" was used to describe these physiological changes, and the surviving fragments may undergo oxidative-

stress induced programmed cell death. Although variations in oxygen tension and extracellular ROS concentrations

are key elements in the initiation of morphological changes, the genomic expression programmes of fungi

governing morphological transitions including autolysis are likely to be activated by different kinds of environmental

stress and signal transduction pathways. The glutathione (GSH) and ROS metabolisms of <i>P. chrysogenum </i>were influenced

by many extrinsic and intrinsic factors in each growth phase studied. As a consequence, no firm correlation

was found between the GSHIglutathione disulphide (GSSG) redox status, the intracellular ROS levels and the observed

morphological and physiological characteristics of the cells.