Euryhaline Black Yeasts From the Arabian Gulf: Descriptions of Salinomyces qatarensis sp. nov. and Hortaea werneckii Genotypic Variations

Abstract

The Arabian Gulf surrounding Qatar is an oligotrophic marine environment characterized by extreme conditions, such as increased water temperatures and high salinity compared to other semi-enclosed seas, such as the Mediterranean Sea. Thirty-six black yeast-like isolates were obtained from marine waters surrounding Qatar, representing 4% of all isolated yeasts. DNA sequence analysis of the internal transcribed spacers (ITS1, ITS2), the 5.8S rRNA gene, and the D1/D2 domains of the LSU rDNA identified 20 isolates as Hortaea werneckii, and 15 (75%) of them represent previously unknown genotypes with a wide NaCl tolerance at 37°C. In addition, 16 meristematic black yeast-like cultures were isolated that grew as multi-cellular bodies and reproduced by endoconidiation. Phylogenetic analysis based on the D1/D2 domains of LSU rDNA, partial sequences of the second largest subunit of RNA polymerase II (RPB2) and translation elongation factor 1-alpha (TEF) of selected representative strains of Dothideomycetes and of morphologically similar taxa, Pseudotaeniolina globosa and Trimmatostroma salinum, supported the proposal of meristematic black yeast-like cultures as a new species, Salinomyces qatarensis sp. nov., within Teratosphaeriaceae, Mycosphaerellales. The holotype is designated as CBS 150510, with ex-type strains EXF-15246 and QCC/Y38/18, and the species is registered in Mycobank as MB#848869. In addition, based on the above molecular analysis, a new combination was proposed for an euryhaline fungus from Mediterranean salterns, Trimmatostroma salinum, into the genus Verrucocladosporium as V. salinum, MB#856063. This study increases our knowledge of the distribution and genetic diversity of Hortaea werneckii, the etiological agent of tinea nigra. In addition, the description of S. qatarensis and the combination of euryhaline T. salinum to Verrucocladosporium provides support for halotolerance as one of the traits in Dothideomycetes.