Taxogenomic placement of Rasporella oleae and Rasporella dianae gen. and spp. nov., two insect associated yeast species.

During the course of independent studies in Europe, North America, and Africa, seven yeast strains were isolated from insect frass, decaying wood, tree flux, and olive oil sediment. Phylogenetic analysis of two barcoding DNA regions (internal transcribed spacer and the D1/D2 domain of the LSU rRNA gene) revealed that they belong to two closely related undescribed species distinct from all genera in the family Debaryomycetaceae. For reliable taxonomic placement the genomes of four strains of the two novel species and six type strains of closely related species were sequenced. Orthologous genes from 54 genomes of representatives of the Pichiomycetes and 23 outgroup taxa were concatenated to construct a fully supported phylogenetic tree. Consistent with the assumptions, we found that the two new species belong to a novel genus. In addition, the delimitation of the novel species was supported by genetic distance calculations from average nucleotide identity (ANI) and digital DNA:DNA hybridization (dDDH) values. The physiological characterization of the novel species was generally consistent with their genomic content. All strains had two alleles encoding secretory lipase in either two or three copies depending on the species. However, lipolytic activity was detected only in strains with three copies of the secretory lipase gene. Nevertheless, lipolytic activity might be related to their association with the insect gut. Based on these results, formal descriptions of the new genus Rasporella gen. nov. and of two new species Rasporella dianae sp. nov. (holotype UCDFST 68-643T , MycoBank no.: 850238) and Rasporella oleae sp. nov. (holotype ZIM 2471T , MycoBank no.: 850126) are provided.

Diddensiella parasantjacobensis f.a., sp. nov., a yeast species from forest habitats.

Six conspecific yeast strains, representing an undescribed species, were isolated from rotten wood collected in different locations in Hungary and Germany and an additional one from fungal fruiting body in Taiwan. The seven strains share identical nucleotide sequences in the D1/D2 domain of the nuclear large subunit (LSU) rRNA gene. The Hungarian and Taiwanese isolates share identical internal transcribed spacer (ITS) sequences as well, while the two German isolates differ from them merely by three substitutions and four indels in this region. The investigated strains are very closely related to Diddensiella santjacobensis. Along their LSU D1/D2 domain they differ only by one substitution from the type strain of D. santjacobensis. However, in the ITS region of Hungarian and Taiwanese strains we detected 3.5 % divergence (nine substitutions and nine indels) between the undescribed species and D. santjacobensis, while the German strains differed by 13 substitutions and nine indels from D. santjacobensis. This ITS sequence divergence has raised the possibility that the strains investigated in this study may represent a different species from D. santjacobensis. This hypothesis was supported by comparisons of partial translation elongation factor 1-α (EF-1α) and cytochrome oxidase II (COX II) gene sequences. While no difference and 1-2 substitutions among the partial EF-1α and COX II gene sequences of the strains of the undescribed species, respectively, were detected; the undescribed species differ by about 4 % (36 substitutions) and 10 % (50-51 substitutions) from D. santjacobensis in these regions. Parsimony network analysis of the partial COX II gene sequences also separated the investigated strains from the type strain of D. santjacobensis. In this paper we propose Diddensiella parasantjacobensis f.a., sp. nov. (holotype: NCAIM Y.02121; isotypes: CBS 17819, DSM 114156) to accommodate the above-noted strains.

Description of Crinitomyces reliqui gen. nov., sp. nov. and Reassignment of Trichosporiella flavificans and Candida ghanaensis to the Genus Crinitomyces.

The systematic position of 16 yeast strains isolated from Thailand, Hungary, The Netherlands, and the Republic of Poland were evaluated using morphological, physiological, and phylogenetic analyses. Based on the similarity of the D1/D2 domain of the LSU rRNA gene, the strains were assigned to two distinct species, Trichosporiella flavificans and representatives of a new yeast species. Phylogenetic analyses revealed that Candida ghanaensis CBS 8798T showed a strong relationship with the aforementioned two species. The more fascinating issue is that Candida and Trichosporiella genera have been placed in different subphyla, Saccharomycotina and Pezizomycotina, respectively. The close relationship between Trichosporiella flavificans, Candida ghanaensis and the undescribed species was unexpected and needed to be clarified. As for morphological and physiological characteristics, the three yeast species shared a hairy colony appearance and an ability to assimilate 18 carbon sources. Based on phylogenetic analyses carried out in the present study, Crinitomyces gen. nov. was proposed to accommodate the new yeast species, Crinitomyces reliqui sp. nov. (Holotype: TBRC 15054, Isotypes: DMKU-FW23-23 and PYCC 9001). In addition, the two species Trichosporiella flavificans and Candida ghanaensis were reassigned to the genus Crinitomyces as, Crinitomyces flavificans (Type: CBS 760.79) comb. nov. and Crinitomyces ghanaensis (Type: CBS 8798) comb. nov., respectively.

Novakomyces olei sp. nov., the First Member of a Novel Taphrinomycotina Lineage.

Taphrinomycotina is the smallest subphylum of the phylum Ascomycota. It is an assemblage of distantly related early diverging lineages of the phylum, comprising organisms with divergent morphology and ecology; however, phylogenomic analyses support its monophyly. In this study, we report the isolation of a yeast strain, which could not be assigned to any of the currently recognised five classes of Taphrinomycotina. The strain of the novel budding species was recovered from extra virgin olive oil and characterised phenotypically by standard methods. The ultrastructure of the cell wall was investigated by transmission electron microscopy. Comparisons of barcoding DNA sequences indicated that the investigated strain is not closely related to any known organism. Tentative phylogenetic placement was achieved by maximum-likelihood analysis of the D1/D2 domain of the nuclear LSU rRNA gene. The genome of the investigated strain was sequenced, assembled, and annotated. Phylogenomic analyses placed it next to the fission Schizosaccharomyces species. To accommodate the novel species, Novakomyces olei, a novel genus Novakomyces, a novel family Novakomycetaceae, a novel order Novakomycetales, and a novel class Novakomycetes is proposed as well. Functional analysis of genes missing in N. olei in comparison to Schizosaccharomyces pombe revealed that they are biased towards biosynthesis of complex organic molecules, regulation of mRNA, and the electron transport chain. Correlating the genome content and physiology among species of Taphrinomycotina revealed some discordance between pheno- and genotype. N. olei produced ascospores in axenic culture preceded by conjugation between two cells. We confirmed that N. olei is a primary homothallic species lacking genes for different mating types.

Cyberlindnera sylvatica sp. nov., a yeast species isolated from forest habitats.

Five yeast strains isolated from forest habitats in Hungary and Germany were characterized phenotypically and by sequencing of the D1/D2 domain of the large subunit rRNA gene and the ITS1-5.8S-ITS2 (ITS) region of the rRNA gene. The strains have identical D1/D2 domain and ITS region sequences. By sequence comparisons, Candida mycetangii and Candida maritima were identified as the closest relatives among the currently recognized yeast species. The DNA sequences of the investigated strains differ by 1.2 % (six substitutions) in the D1/D2 domain and by 3.5 % (12 substitutions and eight indels) in the ITS region from the type strain of C. mycetangii (CBS 8675T) while by 1.2 % (six substitutions and one indel) in the D1/D2 domain and by 7 % (32 substitutions and seven indels) in the ITS region from the type strain of C. maritima (CBS 5107T). Because the intraspecies heterogeneity seems to be very low and the distance to the most closely related species is above the commonly expected level for intraspecies variability Cyberlindnera sylvatica sp. nov. (holotype, CBS 16335T; isotype, NCAIM Y.02233T; MycoBank no., MB 835268) is proposed to accommodate the above-noted five yeast strains. Phenotypically the novel species can be distinguished from C. mycetangii and C. maritima by the formation of ascospores. Cyberlindnera sylvatica forms one or two hat-shaped ascospores per ascus on many different media as well as well-developed pseudohyphae and true hyphae. Additionally, we propose the transfer of three anamorphic members of the Cyberlindnera americana sub-clade to the genus Cyberlindnera as the following new taxonomic combinations Cyberlindnera maritima f.a., comb. nov., Cyberlindnera mycetangii f.a., comb. nov. and Cyberlindnera nakhonratchasimensis f.a., comb. nov.

Starmerella vitis f.a., sp. nov., a yeast species isolated from flowers and grapes.

A novel yeast species of Starmerella vitis f.a. sp. nov. is proposed to accommodate five strains isolated from flowers, grapes and an insect in the Azores, Canada, Hungary, Palau and Taiwan. As the strains were genetically distinct, we used parsimony network analysis based on ITS-D1/D2 sequences to delineate the species in a statistically objective manner. According to sequence comparisons and phylogenetic analysis, the novel species is most closely related to Starmerella lactis-condensi. The two species cannot be distinguished by conventional physiological tests. The type strain of Starmerella vitis f.a., sp. nov. is CBS 16418T; Mycobank number MB 835251.

Hyphopichia lachancei, f.a., sp. nov., a yeast species from diverse origins.

Three strains originating from insect frass in South Africa, yellow foxglove in Hungary and soil in France, were characterised phenotypically and by sequencing of the D1/D2 domain of the large subunit and the ITS1-5.8S-ITS2 (ITS)-region of the rRNA gene. The strains have identical D1/D2 domain sequences and only one strain shows a 1 bp indel in a 9 bp homopolymer A/T repeat within the ITS-region. Based on sequence analysis Hyphopichia burtonii is the closest related species. The investigated strains differ from the type strain of H. burtonii by 1.9% (9 substitutions and an indel) in the D1/D2 domain and by 23 substitutions and 21-22 indels in the ITS-region. Since the sequence variability is very low among the three strains and the sequence divergence with the closely related H. burtonii exceeds the level generally encountered between species we propose the new species Hyphopichia lachancei f.a., sp. nov. to accommodate the three novel strains. From H. burtonii the new species can be distinguished phenotypically by its inability to ferment cellobiose and by the formation of endospores (Holotype: CBS 5999T; Isotype: NCAIM Y.02228T; MycoBank no.: MB833616).

Cutaneotrichosporon suis sp. nov., a lipolytic yeast species from food and food-related environment.

Two conspecific yeast strains, which based on DNA sequence comparisons represented an undescribed species in the order Trichosporonales were isolated during two independent studies in Hungary and France. One of them (NCAIM Y.02224) was recovered from minced pork in Hungary while the other one (UBOCC-A-218003) was isolated from the air of a dairy plant in France. The two strains shared identical nucleotide sequences in the D1/D2 domain of the nuclear large subunit (LSU) rRNA gene and in the internal transcribed spacer (ITS) region. Analysis of the concatenated DNA sequences for the ITS region and D1/D2 domain of the LSU rRNA gene indicated that the novel species belongs to the recently erected genus Cutaneotrichosporon. According to sequence comparisons and phylogenetic analysis, the novel species is most closely related to Cutaneotrichosporon curvatum (formerly Cryptococcus curvatus), which is often associated with humans and warm-blooded animals. The physiological characteristics of this novel species are also very similar to that of Cutaneotrichosporon curvatum. The only clear-cut difference is that, unlike C. curvatum, the novel species does not utilize imidazole as a nitrogen-source. The species name Cutaneotrichosporon suis sp. nov. is proposed to accommodate the above-noted two strains.

Schizosaccharomyces osmophilus sp. nov., an osmophilic fission yeast occurring in bee bread of different solitary bee species.

Eight yeast strains that asexually reproduce by cell fission were isolated from bee bread of different solitary bees in Germany. DNA sequence analysis revealed that the strains shared the same sequence in the D1/D2 domain of the nuclear large subunit (LSU) rRNA gene with a strain that was previously isolated from a fig snack from Spain. The closest related type strain was that of Schizosaccharomyces octosporus, which showed 98.2% sequence similarity (11 substitutions) with the new strains. By clone sequence analysis of the internal transcribed spacer (ITS) region (ITS1, 5.8S rDNA, and ITS2) a total of nine different copy types were identified. The new strains differed from S. octosporus by approximately 31% in the ITS region. Sequence analysis of the RNAse P gene further supported the description of a new species. The strains isolated during this study show some phenotypic characteristics that separate them from the closest related species, S. octosporus and S. cryophilus. Since all strains showed true osmophily the name of the new species is S. osmophilus (holotype: CBS 15793T; isotype: CLIB 3267 T = NCAIM Y.02225 T, MycoBank no.: MB829586).

Kuraishia mediterranea sp. nov., a methanol-assimilating yeast species from olive oil and its sediment.

Six yeast strains isolated from olive oil sediments and spoiled olive oils originating from Slovenia and Portugal, respectively, proved to represent an undescribed yeast species based on DNA sequence comparisons. The analysis of gene sequences for internal transcribed spacer regions and the large subunit rRNA gene D1/D2 domain placed the novel species in the genus Kuraishia in a subclade containing Kuraishiacapsulata, the type species of the genus. Although the novel species is well separated genetically from the recognized species of the genus, only a minor phenotypic difference differentiating it from Kuraishia capsulata and K. molischiana was observed. Relevant to its isolation source, no lipolytic activity was detected in the strains of the novel species. To accommodate the above-noted strains, Kuraishia mediterranea sp. nov. (holotype: ZIM 2473T; isotype: CBS 15107T; MycoBank no.: MB 822817) is proposed.

Meyerozyma amylolytica sp. nov. from temperate deciduous trees and the transfer of five Candida species to the genus Meyerozyma.

In the course of two independent studies three yeasts have been isolated from temperate deciduous trees in Hungary and Germany. Analyses of nucleotide sequences of D1/D2 domains of the 26S rRNA gene (LSU) suggested that these strains belong to the Meyerozyma clade in Debaryomycetaceae (Saccharomycetales). The phylogenetic analysis of a concatenated alignment of the ITS region and LSU gene sequences confirmed the placement of the three strains in the Meyerozyma clade close to Candida elateridarum. If mixed in proper combinations, the strains formed one to two hat shaped ascospores in deliquescent asci. In addition to the ascospore formation, the three studied strains differed from Candida elateridarum and other members of the Meyerozyma clade in terms of ribosomal gene sequence and some physiological properties. To accommodate the above-noted strains, we describe the new species as Meyerozyma amylolytica sp. nov. (holotype: DSM 27310T; ex-type cultures: NCAIM Y.02140T=MUCL 56454T, allotype: NCAIM Y.01955A; ex-allotype culture: DSM 27468), MB 821663. Additionally, we propose the transfer of five non-ascosporic members of the Meyerozyma clade to the genus Meyerozyma as the following new taxonomic combinations Meyerozyma athensensis f.a., comb. nov. (MB 821664), Meyerozyma carpophila f.a., comb. nov. (MB 821665), Meyerozyma elateridarum f.a., comb. nov. (MB 821666), Meyerozyma neustonensis f.a., comb. nov. (MB 821667), and Meyerozyma smithsonii f.a., comb. nov. (MB 821668).

Brettanomyces acidodurans sp. nov., a new acetic acid producing yeast species from olive oil.

Two yeast strains representing a hitherto undescribed yeast species were isolated from olive oil and spoiled olive oil originating from Spain and Israel, respectively. Both strains are strong acetic acid producers, equipped with considerable tolerance to acetic acid. The cultures are not short-lived. Cellobiose is fermented as well as several other sugars. The sequences of their large subunit (LSU) rRNA gene D1/D2 domain are very divergent from the sequences available in the GenBank. They differ from the closest hit, Brettanomyces naardenensis by about 27%, mainly substitutions. Sequence analyses of the concatenated dataset from genes of the small subunit (SSU) rRNA, LSU rRNA and translation elongation factor-1α (EF-1α) placed the two strains as an early diverging member of the Brettanomyces/Dekkera clade with high bootstrap support. Sexual reproduction was not observed. The name Brettanomyces acidodurans sp. nov. (holotype: NCAIM Y.02178T; isotypes: CBS 14519T = NRRL Y-63865T = ZIM 2626T, MycoBank no.: MB 819608) is proposed for this highly divergent new yeast species.

Apiotrichum terrigenum sp. nov., a soil-associated yeast found in both the UK and mainland Europe.

Five arthroconidium-producing yeast strains representing a novel Trichosporon-like species were independently isolated from the UK, Hungary and Norway. Two strains (Bio4T and Bio21) were isolated from biogas reactors used for processing grass silage, with a third strain (S8) was isolated from soil collected at the same UK site. Two additional strains were isolated in mainland Europe, one from soil in Norway (NCAIM Y.02175) and the other from sewage in Hungary (NCAIM Y.02176). Sequence analyses of the D1/D2 domains of the LSU rRNA gene and internal transcribed spacer (ITS) region indicated that the novel species belongs to the recently reinstated genus Apiotrichum and is most closely related to Apiotrichum scarabaeorum, a beetle-associated species first found in South Africa. Despite having similar physiological characteristics, the two species can be readily distinguished from one another by ITS sequencing. The species name Apiotrichum terrigenum sp. nov. is proposed to accommodate these strains, with Bio4T (=CBS 11373T=NCYC 3540T) designated as the type strain. The Mycobank deposit number is MB817431.

Spencermartinsiella silvicola sp. nov., a yeast species isolated from rotting wood.

Three strains of a new xylanase-producing yeast species were isolated from rotting wood samples collected in the Atlantic Rain Forest of Brazil. The sequences of the internal transcribed spacer region and D1/D2 domains of the large subunit of the rRNA gene showed that this novel yeast species belongs to the genus Spencermartinsiella, and its closest relatives among recognized species are Spencermartinsiella europaea and Spencermartinsiella ligniputridi. A novel species, named Spencermartinsiella silvicola sp. nov., is proposed to accommodate these isolates. The type strain is UFMG-CM-Y274T ( = CBS 13490T). The MycoBank number is MB 813053. In addition, Candida cellulosicola is reassigned to the genus Spencermartinsiella as a new combination.

Zygosaccharomyces favi sp. nov., an obligate osmophilic yeast species from bee bread and honey.

Five yeast strains representing a hitherto undescribed yeast species were isolated from bee bread and honey in Hungary. They are obligate osmophilic, i.e. they are unable to grow in/on high water activity culture media. Following isogamous conjugation, they form 1-4 spheroid or subspheroid ascospores in persistent asci. The analysis of the sequences of their large subunit rRNA gene D1/D2 domain placed the new species in the Zygosaccharomyces clade. In terms of pairwise sequence similarity, Zygosaccharomyces gambellarensis is the most closely related species. Comparisons of D1/D2, internal transcribed spacer and translation elongation factor-1α (EF-1α) gene sequences of the five strains with that of the type strain of Z. gambellarensis revealed that they represent a new yeast species. The name Zygosaccharomyces favi sp. nov. (type strain: NCAIM Y.01994(T) = CBS 13653(T) = NRRL Y-63719(T) = ZIM 2551(T)) is proposed for this new yeast species, which based on phenotype can be distinguished from related Zygosaccharomyces species by its obligate osmophilic nature. Some intragenomic sequence variability, mainly indels, was detected among the ITS copies of the strains of the new species.

Yarrowia porcina sp. nov. and Yarrowia bubula f.a. sp. nov., two yeast species from meat and river sediment.

Eleven yeast strains representing two hitherto undescribed species were isolated from different kinds of meat samples in Hungary and one from the sediment of a tropical freshwater river in Southeastern Brazil. The analysis of the sequences of their large subunit rRNA gene D1/D2 domain and the internal transcribed spacer (ITS) regions placed the two new species in the Yarrowia clade. Some of the seven strains representing the first new species can mate and give rise to asci and form ascospores embedded in capsular material, which qualifies it as the third teleomorph species of the Yarrowia clade. The name Yarrowia porcina sp. nov. (type strain: NCAIM Y.02100(T) = CBS 12935(T) = NRRL Y-63669(T), allotype strain UFMG-RD131(A) = CBS 12932(A)) is proposed for this new yeast species, which, based on physiological characters, is indistinguishable from Yarrowia lipolytica and some other species of the genus. Considerable intraspecific variability was detected among the sequences of the large subunit rRNA gene D1/D2 domains of the seven strains. The variability among the D1/D2 sequences exceeded the divergence observed among the ITS sequences and in some cases more than 1 % substitution among the D1/D2 sequences was detected. The conspecificity of these strains was supported by the low (0-3 substitutions) sequence divergence among their ITS sequences, the result of a parsimony network analysis utilizing the concatenated ITS and D1/D2 sequences and also by the fingerprint patterns generated by microsatellite primed PCR. No ascospore formation was observed in the group of the other five strains representing the second new species. These strains shared identical D1/D2 and ITS sequences. Yarrowia bubula f.a., sp. nov. (type strain: NCAIM Y.01998(T) = CBS 12934(T) = NRRL Y-63668(T)) is proposed to accommodate these strains.

Yarrowia divulgata f.a., sp. nov., a yeast species from animal-related and marine sources.

Five yeast strains, phenotypically indistinguishable from Yarrowia lipolytica and Yarrowia deformans, were recovered from different animal-related samples. One strain was isolated from a bacon processing plant in Denmark, two strains from chicken liver in the USA, one strain from chicken breast in Hungary and one from minced beef in Hungary. Comparisons of the sequences of their large subunit rRNA gene D1/D2 domain and the internal transcribed spacer (ITS) regions revealed that, despite their phenotypic similarity, they represent a novel yeast species of the Yarrowia clade with Y. deformans being the genotypically closest relative (LSU rRNA gene D1/D2 and ITS region similarity of 97.0 and 93.7 %, respectively). Yarrowia divulgata f.a., sp. nov. is proposed to accommodate these strains with F6-17(T) ( = CBS 11013(T) = CCUG 56725(T)) as the type strain. Some D1/D2 sequences of yeasts from marine habitats were found in the GenBank database that were identical to those of the strains of Y. divulgata f.a., sp. nov. Unfortunately, these strains were not available for our study.

Ogataea kolombanensis sp. nov., Ogataea histrianica sp. nov. and Ogataea deakii sp. nov., three novel yeast species from plant sources.

Nine methanol-assimilating yeast strains isolated from olive oil sediments in Slovenia, extra virgin olive oil from Italy and rotten wood collected in Hungary were found to form three genetically separated groups, distinct from the currently recognized yeast species. Sequence analysis from genes of the small subunit (SSU) rRNA, internal transcribed spacer region/5.8S rRNA, large subunit (LSU) rRNA D1/D2 domains and translational elongation factor-1α (EF-1α) revealed that the three closely related groups represent three different undescribed yeast species. Sequence analysis of the LSU rRNA gene D1/D2 domains placed the novel species in the Ogataea clade. The three novel species are designated as Ogataea kolombanensis sp. nov. (type strain: ZIM 2322(T) = CBS 12778(T) = NRRL Y-63657(T)), Ogataea histrianica sp. nov. (type strain: ZIM 2463(T) = CBS 12779(T) = NRRL Y-63658(T)) and Ogataea deakii sp. nov. (type strain: NCAIM Y.01896(T) = CBS 12735(T) = NRRL Y-63656(T)).

Bandoniozyma gen. nov., a genus of fermentative and non-fermentative tremellaceous yeast species.

BACKGROUND: Independent surveys across the globe led to the proposal of a new basidiomycetous yeast genus within the Bulleromyces clade of the Tremellales, Bandoniozyma gen. nov., with seven new species. METHODOLOGY/PRINCIPAL FINDINGS: The species were characterized by multiple methods, including the analysis of D1/D2 and ITS nucleotide sequences, and morphological and physiological/biochemical traits. Most species can ferment glucose, which is an unusual trait among basidiomycetous yeasts. CONCLUSIONS/SIGNIFICANCE: In this study we propose the new yeast genus Bandoniozyma, with seven species Bandoniozyma noutii sp. nov. (type species of genus; CBS 8364(T)  =  DBVPG 4489(T)), Bandoniozyma aquatica sp. nov. (UFMG-DH4.20(T)  =  CBS 12527(T)  =  ATCC MYA-4876(T)), Bandoniozyma complexa sp. nov. (CBS 11570(T)  =  ATCC MYA-4603(T)  =  MA28a(T)), Bandoniozyma fermentans sp. nov. (CBS 12399(T)  =  NU7M71(T)  =  BCRC 23267(T)), Bandoniozyma glucofermentans sp. nov. (CBS 10381(T)  =  NRRL Y-48076(T)  =  ATCC MYA-4760(T)  =  BG 02-7-15-015A-1-1(T)), Bandoniozyma tunnelae sp. nov. (CBS 8024(T)  =  DBVPG 7000(T)), and Bandoniozyma visegradensis sp. nov. (CBS 12505(T)  =  NRRL Y-48783(T)  =  NCAIM Y.01952(T)).

Diddensiella caesifluorescens gen. nov., sp. nov., a riboflavin-producing yeast species of the family Trichomonascaceae.

Four strains of a novel heterothallic yeast species were isolated from rotten wood collected in or near the Pilis Mountains in Hungary. The strains produced riboflavin in liquid culture. Analysis of gene sequences for the D1/D2 domains of the LSU nuclear rRNA, as well as analysis of concatenated gene sequences for the D1/D2 nuclear LSU rRNA, mitochondrial SSU rRNA and cytochrome oxidase II placed the novel species in a small clade including only two recognized species, Candida santjacobensis and Candida transvaalensis, in the family Trichomonascaceae. DNA sequence analyses demonstrated that the novel species was distinct from all currently recognized teleomorphic yeast genera. The name Diddensiella caesifluorescens gen nov., sp. nov. is proposed to accommodate the novel genus and species. The new genus proposed here can be recognized only from gene sequence analysis, because the characters of its asexual reproduction and ascospore formation are shared by several members of the genera Trichomonascus, Sugiyamaella and Spencermartinsiella. The type and isotype strains of D. caesifluorescens are NCAIM Y.01949(T) ( = NRRL Y-48781(T) = CBS 12613(T)) and NCAIM Y.01956(I) ( = NRRL Y-48782(I) = CBS 12614(I)), respectively. In view of their close relatedness to D. caesifluorescens, C. santjacobensis and C. transvaalensis are transferred to the genus Diddensiella as new combinations in accordance with changes in the International Code of Nomenclature for algae, fungi and plants.