21st Century Guidebook to Fungi

Although their mode of nutrition is important in defining members of Kingdom Fungi, the fundamental aspect of cell biology that sets the majority of fungi apart from most members of the other major kingdoms is the apical extension of their tubular hyphae. These possess controls which ensure that hyphae normally grow away from one another to form the typical ‘colony’ with an outwardly migrating growing front. Extension growth of the hypha is limited to the apex and this pattern of growth makes the vegetative fungal mycelium an exploratory, invasive organism; and exploration and invasion is the fundamental lifestyle of fungi. This lifestyle allows filamentous fungi to dominate their ecosystems because it gives them the tools they need to find and colonise new substrates rapidly. The success of this growth habit can be judged from the extraordinary diversity of fungal species, their distribution in virtually every habitat on the planet and the parallel evolution of a similar growth strategy by other important soil microorganisms, the prokaryotic streptomycetes and some of the Oomycota in Kingdom Chromista (e.g. Saprolegnia and Achlya).

In this chapter we will discuss the hyphal mode of growth in some detail, explaining how hyphae emerge during spore germination and how hyphae contribute to colony formation. Mycelium growth kinetics is a key topic in understanding the nature of fungi; here we show how that understanding has been built from experiments with living fungi.