Description of Wickerhamia europaea sp. nov. and revisitation of the ascospore number of W. fluorescens

During the course of two independent studies, six conspecific yeast strains were recovered from flowers, soil, bird faeces and wood of different geographical origins. The six strains share identical DNA sequences in two barcoding regions, the D1/D2 domain of the LSU rRNA gene and the internal transcribed spacer (ITS) region (ITS1-5.8S rRNA gene-ITS2). According to sequence comparisons and phylogenetic analysis, they represent an undescribed Wickerhamia species. The novel species is not only genetically distinct from W. fluorescens, the single species of the genus but can also be distinguished from it by some phenotypic characters. We propose Wickerhamia europaea sp. nov. (holotype: NCAIM Y.01938; isotype: CBS 18675; MycoBank no.: 856571) to accommodate the above noted strains. Under certain fermentation conditions, we detected the production of phenyllactic acid, a potential broad-spectrum antimicrobial compound against food-borne pathogens, by the type strain of the novel species, although in smaller concentrations than in the case of W. fluorescens. Comparing our observations on the formation and properties of the ascospores of Wickerhamia europaea sp. nov. and the ambiguous data on the number of ascospores per ascus of W. fluorescens, we suggest a possible explanation to reconcile the different data regarding the number of ascospores per ascus formed by W. fluorescens.