Insights on the Structural and Functional Attributes of Melanin from Termitophilic Agaricales (Chapter 15)

Abstract

The mutualistic genus, Termitomyces Heim, maintained as exosymbionts by fungus growing termites with its complex life cycle having a distinct common hypogeal anamorph and morphologically extremely diverse epigeal teleomorphs is well distinguished from all other Agaricales in having biomechanically specialised organ, called pseudorrhiza (except for Termitomyces microcarpus). These Agaricales are distributed throughout the tropical and subtropical Afro-Asia. Several taxonomists have described Termitomyces fruit bodies without much attention to its black-brown, grey pigmentation / colour indication of its various fruit body parts. In this chapter we review mainly the chromatic taxonomic characters observed in Termitomyces species, indicating the presence of black, brown or grey pigmentation. Along with literature, field studies in Goa (India) aided in better understanding of melanogenesis in Termitomyces during its developmental stages. Several studies were carried out related to melanin in fruit body as well as in culture. We also postulated and correlated the functional role of pseudorrhiza with respect to its ecological, chemical aspects as a powerful biomechanical organ with predisposition to melanisation in response to injuries. Analysis of Termitomyces fruit body parts demonstrated a sulphur-rich melanin pool and implied important biogeochemical role in sulphur turnover in termite-Termitomyces mutualistic association. Characterisation of melanin from mycelial cultures indicated Termitomyces melanin as a sulphur-rich pheomelanin.