Microsporidia: accumulating molecular evidence that a group of amitochondriate and suspectedly primitive eukaryotes are just curious fungi

Microsporidia are obligate intracellular parasites that have long been cons idered to be primitive eukaryotes, both on the basis of morphological featu res and on the basis of molecular, mainly ribosomal RNA-based, phylogenies. However, accumulating sequence data and the use of more sophisticated tree construction methods now seem to suggest that microsporidia share a common origin with fungi and are therefore most probably just curious fungi. In t his paper, we describe the current views on the phylogenetic position of th e microsporidia and present additional evidence for a close relationship be tween fungi and microsporidia on the basis of reanalysed ribosomal RNA data . In this respect, the importance of incorporating detailed knowledge of th e substitution pattern of sequences into phylogenetic methods is discussed. (C) 2000 Elsevier Science B.V. All rights reserved.