Thermotolerant fungi erroneously reported in applied research work as possessing thermophilic attributes

Abstract

In applied research work dealing with heat-tolerant fungi, currently classified into two groups: namely thermotolerants and thermophiles, information on levels of thermotolerance is generally scant. Cited binomials are often referred to as representatives of thermophilic taxa. The present contribution attempts to specify proper heat-tolerance levels of species cited in biotechnological papers of academic and applied research types published in the last four decades. This assessment integrates relevant available information concerning well defined thermotolerant taxa. Distinction between both groups of heat-tolerant fungi is a mean to optimize investigations of temperature-dependent physiological processes. The nomenclatural status of the binomials retrieved was also re-appraised following the International Code of Botanical Nomenclature. Articles of the code govern the legal validity of fungal names. The goal is to deter `ghost names' that have no status of any kind. Their use in the literature is not only a source of confusion but also hinders the preparation of sound reviews and reference documents. The intention was also to detect names which do not fulfill all criteria for a valid legal publication. Their status could then be validated if the taxonomic position of the fungus justifies this procedure. The taxonomic status of these thermotolerants was also re-examined following present-day knowledge of their respective genera. Integration of warranted taxonomic decisions in the literature of applied research is crucial. These decisions consider the status of a fungus as a valid species (proposed synonymies) or the nature of its generic affinities (name change). Strict application of these decisions severly reduces levels of heterogeneity regarding names used for the same organism. It also clarifies its generic affinities with other thermotolerant fungi. The present note is not an exhaustive assessment on the nomenclatural and taxonomic positions of known thermotolerant fungi, an ecological group for which a global document remains to be produced. It only deals with those taxa most commonly cited in the literature examined. Over 130 fungi are here considered. The group manifests a diversity of taxonomic characters since it includes members of the following systematic groupings: Oomycetes, Zygomycetes, Ascomycetes, anamorphic fungi and Holobasidiomycetes. Few new taxonomic synonyms and invalid binomials are introduced in the present contribution. The former concern the following taxa: Gilmaniella thermophila, Mucor thermoaerospora, Sporotrichum lignicola and Zalerion thermophylii. Three binomials proved to have no taxonomic status of any sort: Acremonium cellulophilum, Nodulisporium microsporum and N. thermoroseum.