The importance of pneumocandin B0 as the fermentation-derived
starting material for the antifungal drug candidate, MK-991, along
with the identification of our production strain as Z. arboricola
(ATCC 20868) as CBS prompted a search for other strains of Z.
arboricola or Zalerion species with improved titres or that
might produce natural pneumocandin analogues. Analysis of morphology,
secondary metabolites profiles, and DNA fingerprinting demonstrated that
ATCC 20868 was not congeneric with Z. arboricola.
Ribosomal DNA sequences were compared among Zalerion species and
pneumocandin-producing fungi and with rDNA sequences in
GenBank. No good matches with sequences in GenBank were obtained for Z.
arboricola or Z. maritimum, but for Z. varium, P.
carpinea and ATCC 20868, relevant similarities were observed with
ITS1 sequences from fungi of Leotiales. ATCC 20868 was
phylogenetically more akin to P. carpinea, another pneumocandin
producer, than initially suspected. The closest relative of ATCC
20868 seemed to be Hymenoscyphus monotropae. We conclude that
the genus Zalerion is artificial; its species bear no phylogenetic
relation among themselves. ATCC 20868 and Z. varium were related
to fungi of the Leotiales. We propose a new anamorph genus
and species, Glarea lozoyensis, to accommodate ATCC 20868.