A new genus and family for the misclassified chytrid, Rhizophlyctis harderi

Abstract

A chytrid first discovered in Mediterranean sands and called Rhizophlyctis harderi was classified in the genus Rhizophlyctis based on its interbiotic vegetative thalli with multiple rhizoidal axes and resting thalli with tufts of rhizoid-like appendages. Developmental, electron microscopic and molecular analyses, however, have brought into question the proper placement of this chytrid. Because its original description was in German and not Latin, the name R. harderi is not validly published. We found that this chytrid produces three thallus forms that could place it in three different morpho-genera: Rhizophydium, Phlyctochytrium or Rhizophlyctis. The ultrastructural architecture of its zoospore is different from that of zoospores of Rhizophlyctis rosea, the type species for Rhizophlyctis, and shares zoospore ultrastructural characteristics with the Rhizophydiales. Zoospores of this chytrid exhibit a distinctive kinetosome-associated structure (KAS), a curved shield bridged to two of the kinetosomal triplets and a layered cap anterior to the kinetosome. Phylogenetic analyses of nuc rDNA also support the placement of this chytrid in the Rhizophydiales and not in the Rhizophlyctidales. Given its molecularly based phylogenetic placement and its distinctive zoospore architecture, we describe this chytrid in a new genus, Uebelmesseromyces, in the Rhizophydiales and erect Uebelmesseromycetaceae as a new family to accommodate it.

• Chytridiomycota
• flagellar apparatus
• morphological plasticity
• nomenclature
• phylogeny
• Rhizophydiales
• ultrastructure

Acknowledgments

This study was supported by a National Science Foundation PEET Grant ( DEB-9978094), NSF REVSYS grants ( DEB-0516173, DEB-0949305) and through the undergraduate researcher component of a grant from the Howard Hughes Medical Institute Undergraduate Biological Sciences Program to the University of Alabama. We express our appreciation to Dr Thomas Booth (Univ. Manitoba) for sharing collection information on his culture No. 63, deposited at The American Type Culture Collection under the number 24053.