Wickerhamiella lachancei f.a. sp. nov., a novel ascomycetous yeast species isolated from flowers of Lantana camara in India

Two isolates representing a novel species of the genus Wickerhamiella were obtained in India from nectar of flowers of Lantana camara, an ornamental exotic species native to Central and South America. Phylogenetic analyses of the D1/D2 domain of the 26S large subunit (LSU) rRNA gene, internal transcribed spacer (ITS) region, and physiological characteristics, supported the recognition of the novel species, that we designate Wickerhamiella lachancei sp. nov (MycoBank no. MB851709), with MCC 9929T as the holotype and PYCC 10003T as the isotype. Considering pairwise sequence similarity, the type strain of the novel species differs from the type strain of the most closely related species, Wickerhamiella drosophilae CBS 8459T, by 16 nucleotide substitutions and two gaps (3.9 % sequence variation) in the D1/D2 region (560 bp compared) and 28 nucleotide substitutions and five gaps (7.22 % sequence variation) in the ITS region (444 bp compared).

Taxogenomic analyses of Starmerella gilliamiae f.a, sp. nov. and Starmerella monicapupoae f.a., sp. nov., two novel species isolated from plant substrates and insects

Four yeast isolates collected from flowers from different ecosystems in Brazil, one from fruit of Nothofagus alpina in Argentina, three from flowers of Neltuma chilensis in Chile and one obtained from the proventriculus of a female bumblebee in Canada were demonstred, by analysis of the sequences of the internal transcribed spacer (ITS) region and D1/D2 domains of the large subunit rRNA gene, to represent two novel species of the genus Starmerella. These species are described here as Starmerella gilliamiae f.a, sp. nov. (CBS 16166T; Mycobank MB 851206) and Starmerella monicapupoae f.a., sp. nov. (PYCC 8997T; Mycobank MB 851207). The results of a phylogenomic analysis using 1037 single-copy orthogroups indicated that S. gilliamiae is a member of a subclade that contains Starmerella opuntiae, Starmerella aceti and Starmerella apicola. The results also indicated that S. monicapupoae is phylogenetically related to Starmerella riodocensis. The two isolates of S. monicapupoae were obtained from flowers in Brazil and were probably vectored by insects that visit these substrates. Starmerella gilliamiae has a wide geographical distribution having been isolated in flowers from Brazil and Chile, fruit from Argentina and a bumblebee from Canada.

Starmerella kisarazuensis f.a., sp. nov., a novel yeast isolated from Trifolium pratense flowers

Three yeast isolates, NBRC 115909T, NBRC 115910 and NBRC 116270, were isolated from Trifolium pratense (red clover) flowers collected from Kisarazu, Chiba, Japan. Analysis of the sequences of the D1/D2 domains of the large subunit (LSU) rRNA gene and the internal transcribed spacer (ITS) regions revealed that these isolates represent a single novel species within the genus Starmerella. Also, no ascospore formation was observed. The yeast isolates were closely related to Starmerella vitae UWOPS 00-107.2T and Starmerella bombi NRRL Y-17081T. They differed from S. vitae, the most closely related species with a validly published name, by ten nucleotide substitutions with two gaps in the D1/D2 domains and 20 nucleotide substitutions in the ITS region. Moreover, the three isolates exhibited distinct phenotypic characteristics from the closely related species. Therefore, we suggest that these three isolates represent a novel species, designated as Starmerella kisarazuensis f.a., sp. nov. The holotype is NBRC 115909T (isotype: CBS 18485T).

Microbial communities of a variety of 75 homemade fermented vegetables

Fermentation is an ancient practice of food preservation. Fermented vegetables are popular in Eastern European and Asian countries. They have received a growing interest in Western countries, where they are mainly manufactured at domestic and artisanal scales and poorly characterized. Our aim was to investigate the microbial communities and the safety of French homemade fermented vegetables, in the frame of a citizen science project. Fermented vegetables and the data associated with their manufacture were collected from citizens and characterized for pH, NaCl concentration, and microbiology by culturomics and 16S DNA metabarcoding analysis. Lactic acid bacteria (LAB) and yeast isolates were identified by 16S rRNA gene sequencing and D1/D2 domains of the large subunit of the rRNA gene, respectively. The 75 collected samples contained 23 types of vegetables, mainly cabbage, followed by carrots and beets, and many mixtures of vegetables. They were 2 weeks to 4 years old, and their median pH was 3.56, except for two samples with a pH over 4.5. LAB represented the dominant viable bacteria. LAB concentrations ranged from non-detectable values to 8.7 log colony-forming units (CFU)/g and only depended on the age of the samples, with the highest most frequently observed in the youngest samples (<100 days). The 93 LAB isolates identified belonged to 23 species, the two mains being Lactiplantibacillus pentosus/plantarum and Levilactobacillus brevis. The other microbial groups enumerated (total aerobic bacteria, halotolerant bacteria, Gram-negative bacteria, and acetic acid bacteria) generally showed lower concentrations compared to LAB concentrations. No pathogenic bacteria were detected. Viable yeasts were observed in nearly half the samples, at concentrations reaching up to 8.0 log CFU/g. The 33 yeast clones identified belonged to 16 species. Bacterial metabarcoding showed two main orders, namely, Lactobacillales (i.e., LAB, 79% of abundance, 177 of the 398 total ASVs) and Enterobacterales (19% of abundance, 191 ASVs). Fifteen LAB genera were identified, with Lactiplantibacillus and Levilactobacillus as the most abundant, with 41 and 12% of total reads, respectively. Enterobacterales members were mainly represented by Enterobacteriaceae and Yersiniaceae. This study is the first wide description of the microbiota of a large variety of homemade fermented vegetables and documents their safety.

Harnessing dual applications of a novel ascomycetes yeast, Starmerella cerana sp. nov., as a biocatalyst for stereoselective ketone reduction and biosurfactant production

Introduction: New bioresources for catalytic application and fine chemical synthesis are the need of the hour. In an effort to find out new biocatalyst for oxidation-reduction reaction, leading to the synthesis of chiral intermediates, novel yeast were isolated from unique niche and employed for the synthesis of value added compounds. Methods: To determine the genetic relatedness of the isolated strain, HSB-15T, sequence analysis of the internal transcribed spacer (ITS) and D1/D2 domains of the 26S rRNA gene sequence was carried out. The distinctive features of the strain HSB-15T were also identified by phenotypic characterization. The isolated strain HSB-15T was employed for the reduction of selected naphthyl ketones to their corresponding alcohols and a biosurfactant was isolated from its culture broth. Results: The analysis of the ITS and D1/D2 domains of the 26S rRNA gene revealed that strain HSB-15T is closely related to the type strain of Starmerella vitae (CBS 15147T) with 96.3% and 97.7% sequence similarity, respectively. However, concatenated sequences of the ITS gene and D1/D2 domain showed 94.6% sequence similarity. Phenotypic characterization indicated significant differences between strain HSB-15T and its closely related species and consequently, it was identified as a novel species, leading to the proposal of the name Starmerella cerana sp. nov. The strain was able to reduce selected naphthyl ketones to their corresponding alcohols with remarkable efficiency, within a 12-hours. The strain HSB-15T also produced a surfactant in its culture broth, identified as sophorolipid upon analysis. Discussion: The study explored the potential of the novel strain, HSB-15T, as a whole-cell biocatalyst for the reduction of naphthyl ketones to their corresponding alcohols and also reports its capability to produce sophorolipid, a biosurfactant, in its culture broth. This dual functionality of HSB-15T both as biocatalyst and biosurfactant producer enhances its applicability in biotechnology and environmental science.

Metabolome Exploration by High-Resolution Mass Spectrometry Methodologies of Two New Yeast Species: Starmerella reginensis and Starmerella kourouensis

Nature is harnessed since ancient times to fulfill human needs, and yeast culture has been mastered for bakery, brewery, or the preparation of beverages. In this context, the two recently discovered yeast species Starmerella reginensis and Starmerella kourouensis, belonging to a genus related to fermentative activities in the literature, were explored via untargeted metabolomics approaches. Ultrahigh-performance liquid chromatography hyphenated with tandem mass spectrometry and a deep investigation of molecular networks and spectral data allowed the annotation of, respectively, 439 and 513 metabolites for S. reginensis and S. kourouensis, with approximatively 30% compound annotations and 40% chemical class annotations for both yeast strains. These analyses and Fourier transform ion cyclotron resonance mass spectrometry accurate metabolic profiles unveiled a rich content of alkaloids, lipids, amino acids, and terpenoids for S. reginensis. S. kourouensis presents a similar profile with more sulfated compounds. In short, these results enrich the current knowledge about Starmerella yeast secondary metabolites and reveal their significant structural diversity of small molecules.

Candida metrosideri pro tempore sp. nov. and Candida ohialehuae pro tempore sp. nov., two antifungal-resistant yeasts associated with Metrosideros polymorpha flowers in Hawaii

Flowers produce an array of nutrient-rich exudates in which microbes can thrive, making them hotspots for microbial abundance and diversity. During a diversity study of yeasts inhabiting the flowers of Metrosideros polymorpha (Myrtaceae) in the Hawai’i Volcanoes National Park (HI, USA), five isolates were found to represent two novel species. Morphological and physiological characterization, and sequence analysis of the small subunit ribosomal RNA (rRNA) genes, the D1/D2 domains of the large subunit rRNA genes, the internal transcribed spacer (ITS) regions, and the genes encoding the largest and second largest subunits of the RNA polymerase II (RPB1 and RPB2, respectively), classified both species in the family Metschnikowiaceae, and we propose the names Candida metrosideri pro tempore sp. nov. (JK22^T = CBS 16091 = MUCL 57821) and Candida ohialehuae pro tempore sp. nov. (JK58.2^T = CBS 16092 = MUCL 57822) for such new taxa. Both novel Candida species form a well-supported subclade in the Metschnikowiaceae containing species associated with insects, flowers, and a few species of clinical importance. The ascosporic state of the novel species was not observed. The two novel yeast species showed elevated minimum inhibitory concentrations to the antifungal drug amphotericin B (>4 μg/mL). The ecology and phylogenetic relationships of C. metrosideri and C. ohialehuae are also discussed.

Towards a better understanding of the role of nectar-inhabiting yeasts in plant-animal interactions

Flowers offer a wide variety of substrates suitable for fungal growth. However, the mycological study of flowers has only recently begun to be systematically addressed from an ecological point of view. Most research on the topic carried out during the last decade has focused on studying the prevalence and diversity of flower-inhabiting yeasts, describing new species retrieved from floral parts and animal pollinators, and the use of select nectar yeasts as model systems to test ecological hypotheses. In this primer article, we summarize the current state of the art in floral nectar mycology and provide an overview of some research areas that, in our view, still require further attention, such as the influence of fungal volatile organic compounds on the foraging behavior of pollinators and other floral visitors, the analysis of the direct and indirect effects of nectar-inhabiting fungi on the fitness of plants and animals, and the nature and consequences of fungal-bacterial interactions taking place within flowers.

Large biodiversity of yeasts in French Guiana and the description of Suhomyces coccinellae f.a. sp. nov. and Suhomyces faveliae f.a. sp. nov

The extent of the diversity of yeasts in tropical rain forest and different environments from French Guiana was investigated. A total of 365 samples were collected from various substrates, such as plants, fruits and insects, at 13 locations, yielding 276 pure yeast isolates. Sequence analysis of the D1/D2 domains of the large subunit rRNA gene indicated that 210 isolates out of 276 belonged to 82 described species (67 Saccharomycotina, 14 Basidiomycota and 1 Pezizomycotina). In addition to these, a total of 54 Saccharomycotina isolates could not be assigned to a known species. These belonged to 14 genera and should be studied further from a taxonomic point of view. In addition, among the 43 Basidiomycotina isolates found, 12 could not be assigned to a known species. This report shows an unexpected biodiversity and indicates that oversea territories, such as French Guiana, constitute a largely unexplored reservoir for yeast diversity. Two Saccharomycotina strains, CLIB 1706 and CLIB 1725, isolated from an insect and from a fern respectively, were characterized further and were shown to belong to the Suhomyces clade on the basis of the rDNA sequence comparison. CLIB 1706^TrDNA sequences showed nine substitutions and three indels out of 556 bp (D1/D2 domains) and 32 substitutions and 12 indels out of 380 bp [internal transcribed spacer (ITS)] with that of the most closely related species Suhomyces guaymorum CBS 9823^T. CLIB 1725^T rDNA sequences presented 18 substitutions and one indel out of 549 bp (D1/D2 domains) and 48 substitutions and 11 indels out of 398 bp (ITS) with that of its closest relative Suhomyces vadensis CBS 9454^T. Two novel species of the genus Suhomyces were described to accommodate these two strains: Suhomyces coccinellae f.a. sp. nov. (CLIB 1706^T=CBS 14298^T) and Suhomyces faveliae f.a. sp. nov. (CLIB 1725^T=CBS 14299^T).