Fungal heterogeneity; from zones to compartments

Abstract

Heterogeneity in fungi is ubiquitous with respect to many variables. In this thesis it is shown that 3D micro-colonies are heterogeneous with respect to protein expression. Showing a peripheral shell where the glucoamylase gene, the feruloyl esterase gene and the α-glucuronidase gene are expressed. This expression zone is relatively stable, enabling human intervention to control micro-colony size and thereby increasing protein production efficiency. Moving from zones to hyphae it is shown that environmental factors impact occlusion of septa, enabling heterogeneity to arise between hyphae and hyphal compartments. It is shown that fungal hyphae can be divided into secretor and persistor categories, demonstrating the positive impact of heterogeneity on fungal fitness. Hyphal apical compartments in turn are shown to be heterogeneous in their capacity to maintain their growth rate after they have been severed from their originating mycelium. The ability to occlude the apical septum is not a predictor of survival of apical compartments after dissection. In contrast, the relative cytoplasmic volume remaining in an apical compartment could predict the maintaining of growth rate. The parental hypha of a severed compartment was shown to be able to continue growth after the apical zone of a hypha was lost. However, parental hyphae that were reduced in their capability to plug septal pores showed reduced ability to reinitiate growth. The ability of fungal apical compartments to maintain their growth rate after separation from their originating mycelium seems to be commonplace. Single second compartment are severely reduced in their capacity to reinitate growth at the same rate as apical compartments, nevertheless functioning as a back-up in case of catastrophic loss of mycelium.