Accurate, rapid taxonomic classification of fungal large-subunit rRNA genes

Updated RDP taxonomy and RDP Classifier for more accurate taxonomic classification

The RDP Classifier is one of the most popular machine learning approaches for taxonomic classification due to its robustness and relatively high accuracy. Both the RDP taxonomy and RDP Classifier have been updated to incorporate newly described taxa and recent changes to prokaryotic nomenclature.

Niche-dependent sponge hologenome expression profiles and the host-microbes interplay: a case of the hawaiian demosponge Mycale Grandis

BACKGROUND

Most researches on sponge holobionts focus primarily on symbiotic microbes, yet data at the level of the sponge hologenome are still relatively scarce. Understanding of the sponge host and its microbial gene expression profiles and the host-microbes interplay in different niches represents a key aspect of sponge hologenome. Using the Hawaiian demosponge Mycale grandis in different niches as a model, i.e. on rocks, on the surface of coral Porites compressa, under alga Gracilaria salicornia, we compared the bacterial and fungal community structure, functional gene diversity, expression pattern and the host transcriptome by integrating open-format (deep sequencing) and closed-format (GeoChip microarray) high-throughput techniques.

RESULTS

Little inter-niche variation in bacterial and fungal phylogenetic diversity was detected for M. grandis in different niches, but a clear niche-dependent variability in the functional gene diversity and expression pattern of M. grandis host and its symbiotic microbiota was uncovered by GeoChip microarray and transcriptome analyses. Particularly, sponge host genes related to innate immunity and microbial recognition showed a strong correlation with the microbial symbionts' functional gene diversity and transcriptional richness in different niches. The cross-niche variability with respect to the symbiont functional gene diversity and the transcriptional richness of M. grandis holobiont putatively reflects the interplay of niche-specific selective pressure and the symbiont functional diversity.

CONCLUSIONS

Niche-dependent gene expression profiles of M. grandis hologenome and the host-microbes interplay were suggested though little inter-niche variation in bacterial and fungal diversity was detected, particularly the sponge innate immunity was found to be closely related to the symbiotic microbes. Altogether, these findings provide novel insights into the black box of one sponge holobiont in different niches at the hologenome level.

Characterization of the Cassava Mycobiome in Symptomatic Leaf Tissues Displaying Cassava Superelongation Disease

Superelongation disease (SED) is a fungal disease that affects cassava in the Caribbean. The symptoms include the appearance of dry necrotic spots and lesions on the leaves, which may severely affect the plant yield. However, the primary causal pathogen is difficult to culture and isolate in the lab because of its slow growth and potential contamination from faster-growing organisms. In addition, the leaf symptoms can be confused with those caused by other pathogens that produce similar necrotic spots and scab-like lesions. There is also little or no information on the contribution of endophytes, if any, to disease symptoms in cassava, a plant where the disease is prevalent. Therefore, this study aimed to characterize the fungal communities in cassava associated with SED symptoms by analyzing gross fungal morphology and performing metagenomics profiling. First, several individual pathogenic fungi were isolated and cultured from diseased cassava leaf tissues from seven locations in Barbados (BB). Both culture isolation and molecular community analyses showed the presence of several other fungi in the disease microenvironment of symptomatic cassava leaves. These included Fusarium, Colletotrichum, and Alternaria species and the suspected species Elsinoë brasiliensis synonym Sphaceloma manihoticola. Additionally, a community analysis using ITS2 amplicon sequencing of 21 symptomatic leaf tissues from BB, St. Vincent and the Grenadines (SVG), Trinidad and Tobago (TT), and Jamaica (JA) revealed that the disease symptoms of superelongation may also result from the interactions of fungal communities in the mycobiome, including Elsinoë species and other fungi such as Colletotrichum, Cercospora, Alternaria, and Fusarium. Therefore, we suggest that examining the pathobiome concept in SED in the future is necessary.

Soil Alveolata diversity in the undisturbed steppe and wheat agrocenoses under different tillage

Microeukaryotes are vital for maintaining soil quality and ecosystem functioning, however, their communities are less studied than bacterial and fungal ones, especially by high throughput sequencing techniques. Alveolates are important members of soil microbial communities, being consumers and/or prey for other microorganisms. We studied alveolate diversity in soil under the undisturbed steppe (US) and cropped for wheat using two tillage practices (conventional, CT, and no-till, NT) by amplifying the ITS2 marker with ITS3_KYO2/ITS4 primers and sequencing amplicons using Illumina MiSeq. A total of 198 Alveolata OTUs were identified, with 158 OTUs attributed to the Ciliophora phylum, containing five classes: Litostomatea, Spirotrichea and Oligohymenophorea, Nassophorea and Phyllopharyngea. Litostomatea and Phyllopharyngea were more abundant in US as compared with CT and NT. The observed OTU richness was higher in US than in CT and NT. The β-biodiversity of soil ciliates also very distinctly differentiated the US field from CT and NT. In the US, Nassophorea and Spirotrichea correlated positively with sand and negatively with clay, silt and SOM contents. This is the first report about soil ciliates diversity in Siberia as assessed by metabarcoding technique. The revealed clear effect of land use on the relative abundance of some taxa and a lack of tillage effect suggest the importance of the quantity and quality of plant material input for shaping the prey for ciliates. The ITS-metabarcoding technique was used for the first time in the research of ciliates diversity; further studies, embracing diverse aspects of soil ciliates by combining -omics methodology with the traditional one, are needed to get a better insight on the ecological roles of the main ciliate taxa in the complex soil system.

Rapid and accurate taxonomic classification of cpn60 amplicon sequence variants

The "universal target" region of the gene encoding the 60 kDa chaperonin protein (cpn60, also known as groEL or hsp60) is a proven sequence barcode for bacteria and a useful target for marker gene amplicon-based studies of complex microbial communities. To date, identification of cpn60 sequence variants from microbiome studies has been accomplished by alignment of queries to a reference database. Naïve Bayesian classifiers offer an alternative identification method that provides variable rank classification and shorter analysis times. We curated a set of cpn60 barcode sequences to train the RDP classifier and tested its performance on data from previous human microbiome studies. Results showed that sequences accounting for 79%, 86% and 92% of the observations (read counts) in saliva, vagina and infant stool microbiome data sets were classified to the species rank. We also trained the QIIME 2 q2-feature-classifier on cpn60 sequence data and demonstrated that it gives results consistent with the standalone RDP classifier. Successful implementation of a naïve Bayesian classifier for cpn60 sequences will facilitate future microbiome studies and open opportunities to integrate cpn60 amplicon sequence identification into existing analysis pipelines.

MetaWorks: A flexible, scalable bioinformatic pipeline for high-throughput multi-marker biodiversity assessments

Multi-marker metabarcoding is increasingly being used to generate biodiversity information across different domains of life from microbes to fungi to animals such as for molecular ecology and biomonitoring applications in different sectors from academic research to regulatory agencies and industry. Current popular bioinformatic pipelines support microbial and fungal marker analysis, while ad hoc methods are often used to process animal metabarcode markers from the same study. MetaWorks provides a harmonized processing environment, pipeline, and taxonomic assignment approach for demultiplexed Illumina reads for all biota using a wide range of metabarcoding markers such as 16S, ITS, and COI. A Conda environment is provided to quickly gather most of the programs and dependencies for the pipeline. Several workflows are provided such as: taxonomically assigning exact sequence variants, provides an option to generate operational taxonomic units, and facilitates single-read processing. Pipelines are automated using Snakemake to minimize user intervention and facilitate scalability. All pipelines use the RDP classifier to provide taxonomic assignments with confidence measures. We extend the functionality of the RDP classifier for taxonomically assigning 16S (bacteria), ITS (fungi), and 28S (fungi), to also support COI (eukaryotes), rbcL (eukaryotes, land plants, diatoms), 12S (fish, vertebrates), 18S (eukaryotes, diatoms) and ITS (fungi, plants). MetaWorks properly handles ITS by trimming flanking conserved rRNA gene regions as well as protein coding genes by providing two options for removing obvious pseudogenes. MetaWorks can be downloaded from https://github.com/terrimporter/MetaWorks and quickstart instructions, pipeline details, and a tutorial for new users can be found at https://terrimporter.github.io/MetaWorksSite.

Effects of operational taxonomic unit inference methods on soil microeukaryote community analysis using long-read metabarcoding

Long amplicon metabarcoding has opened the door for phylogenetic analysis of the largely unknown communities of microeukaryotes in soil. Here, we amplified and sequenced the ITS and LSU regions of the rDNA operon (around 1500 bp) from grassland soils using PacBio SMRT sequencing. We tested how three different methods for generation of operational taxonomic units (OTUs) effected estimated richness and identified taxa, and how well large-scale ecological patterns associated with shifting environmental conditions were recovered in data from the three methods. The field site at Kungsängen Nature Reserve has drawn frequent visitors since Linnaeus's time, and its species rich vegetation includes the largest population of Fritillaria meleagris in Sweden. To test the effect of different OTU generation methods, we sampled soils across an abrupt moisture transition that divides the meadow community into a Carex acuta dominated plant community with low species richness in the wetter part, which is visually distinct from the mesic-dry part that has a species rich grass-dominated plant community including a high frequency of F. meleagris. We used the moisture and plant community transition as a framework to investigate how detected belowground microeukaryotic community composition was influenced by OTU generation methods. Soil communities in both moisture regimes were dominated by protists, a large fraction of which were taxonomically assigned to Ciliophora (Alveolata) while 30%-40% of all reads were assigned to kingdom Fungi. Ecological patterns were consistently recovered irrespective of OTU generation method used. However, different methods strongly affect richness estimates and the taxonomic and phylogenetic resolution of the characterized community with implications for how well members of the microeukaryotic communities can be recognized in the data.

Detection and diversity of the mannosylerythritol lipid (MEL) gene cluster and lipase A and B genes of Moesziomyces antarcticus isolated from terrestrial sites chronically contaminated with crude oil in Trinidad

BACKGROUND

Mannosylerythritol lipids (MELs) belong to the class of glycolipid biosurfactants and are produced by members of the Ustilago and Moesziomyces genera. Production of MELs is regulated by a biosynthetic gene cluster (MEL BGC). Extracellular lipase activity is also associated with MEL production. Most microbial glycolipid-producers are isolated from oil-contaminated environments. MEL-producing yeast that are capable of metabolizing crude oil are understudied, and there is very limited data on indigenous strains from tropical climates. Analysis of the MEL BGC and lipase genes in Trinidad M. antarcticus strains, using a gene-targeted approach, revealed a correlation between their intrinsic capability to degrade crude oil and their adaptation to survive in a chronically polluted terrestrial environment.

RESULTS

M. antarcticus was isolated from naturally-occurring crude oil seeps and an asphaltic mud volcano in Trinidad; these are habitats that have not been previously reported for this species. Genus identification was confirmed by the large-subunit (LSU) and the small-subunit (SSU) sequence comparisons and species identification was confirmed by ITS sequence comparisons and phylogenetic inference. The essential genes (Emt1, Mac1, Mac2, Mmf1) of the MEL BGC were detected with gene-specific primers. Emt1p, Mac1p and Mmf1p sequence analyses confirmed that the Trinidad strains harboured novel synonymous amino acid (aa) substitutions and structural comparisons revealed different regions of disorder, specifically for the Emt1p sequence. Functionality of each protein sequence was confirmed through motif mining and mutation prediction. Phylogenetic relatedness was inferred for Emt1p, Mac1p and Mmf1p sequences. The Trinidad strains clustered with other M. antarcticus sequences, however, the representative Trinidad M. antarcticus sequences consistently formed a separate, highly supported branch for each protein. Similar phylogenetic placement was indicated for LipA and LipB nucleotide and protein sequences. The Trinidad strains also demonstrated lipolytic activity in culture, with an ability to utilize different carbon sources. Comparative evolution of MEL BGC and LipA gene suggested early and late duplication events, depending on the gene, followed by a number of speciation events within Ustilaginaceae. M. antarcticus and M. aphidis were separated from all other members of Ustilaginaceae and two gene homologues were detected, one for each species.

CONCLUSIONS

Sequence analyses was based on a novel gene-targeted approach to analyze the essential genes of the MEL BGC and LipA and LipB genes of M. antarcticus strains from Trinidad. The findings indicated that these strains accumulated nucleotide mutations to a threshold level that did not affect the function of specific proteins encoded by the MEL BGC and LipA and LipB genes. The biosurfactant and lipase enzymes secreted by these Trinidad M. antarcticus strains facilitated their survival in oil-contaminated terrestrial environments. These findings suggest that the Trinidad strains should be explored as promising candidates for the commercial production of MEL biosurfactants and lipase enzymes.

The search for Schizosaccharomyces fission yeasts in environmental meta-transcriptomes

Fission yeast is an important model organism in evolutionary genetics and cell biology research. Nevertheless, most research is limited to a single laboratory strain and knowledge of its natural occurrence is limited, which reduces our understanding of its life history and hinders isolation of new strains from nature. Understanding the natural diversity of fission yeast can provide insight into its genetic and phenotypic diversity and the evolutionary processes that shaped these. Here we aimed to identify candidate natural habitats of fission yeasts by searching through a large collection of publicly available environmental metatranscriptomic datasets. Using a custom pipeline, we processed over 13,000 NCBI SRA accessions, from a wide range of 34 different environmental categories. Overall, we found a very low abundance of putative yeast transcripts, with most fission yeast signatures coming from the categories of 'food' and 'terrestrial arthropods'. Additionally, a signal could be found in a variety of marine and fresh aquatic habitats. Our results do not provide a conclusive answer on the natural habitat of fission yeasts, but our analysis further narrows the range of locations where fission yeasts naturally occur.

Rhizospheric pathogen proliferation and ROS production are associated with premature senescence of the osvha-a1 rice mutant

Root-pathogen interactions influence premature senescence in rice, however, few studies have addressed the underlying mechanism. In this study, when premature senescence significantly occurred in the osvha-a1 mutant (loss of tonoplast H+-ATPase activity), the relative abundance of rhizospheric bacterial communities was similar between the mutant and its wild type, while the fungi in the rhizosphere of the osvha-a1 mutant significantly differed from the wild type. Furthermore, one key fungal strain in the rhizospheric soil of the osvha-a1 mutant, Gibberella intermedia, increased substantially during the late growing phase, resulting in severe accumulation of reactive oxygen species (ROS). By contrast, the wild type showed much lower levels of ROS when infected by G. intermedia. Using high performance liquid chromatography, sugars in root exudates were identified to be different between osvha-a1 mutant and the wild type. G. intermedia could use mannose and rhamnose in root exudates from the mutant more efficiently than any other sugar. Finally, antagonistic bacteria could be employed for limiting the proliferation of G. intermedia in the rhizosphere, thereby alleviating the early senescent phenotypes of the osvha-a1 mutant, and improving grain yield.

Understudied, underrepresented, and unknown: Methodological biases that limit detection of early diverging fungi from environmental samples

Metabarcoding is an important tool for understanding fungal communities. The internal transcribed spacer (ITS) rDNA is the accepted fungal barcode but has known problems. The large subunit (LSU) rDNA has also been used to investigate fungal communities but available LSU metabarcoding primers were mostly designed to target Dikarya (Ascomycota + Basidiomycota) with little attention to early diverging fungi (EDF). However, evidence from multiple studies suggests that EDF comprise a large portion of unknown diversity in community sampling. Here, we investigate how DNA marker choice and methodological biases impact recovery of EDF from environmental samples. We focused on one EDF lineage, Zoopagomycota, as an example. We evaluated three primer sets (ITS1F/ITS2, LROR/LR3, and LR3 paired with new primer LR22F) to amplify and sequence a Zoopagomycota mock community and a set of 146 environmental samples with Illumina MiSeq. We compared two taxonomy assignment methods and created an LSU reference database compatible with AMPtk software. The two taxonomy assignment methods recovered strikingly different communities of fungi and EDF. Target fragment length variation exacerbated PCR amplification biases and influenced downstream taxonomic assignments, but this effect was greater for EDF than Dikarya. To improve identification of LSU amplicons we performed phylogenetic reconstruction and illustrate the advantages of this critical tool for investigating identified and unidentified sequences. Our results suggest much of the EDF community may be missed or misidentified with "standard" metabarcoding approaches and modified techniques are needed to understand the role of these taxa in a broader ecological context.

Disturbance alters the forest soil microbiome

Billions of microorganisms perform critical below-ground functions in all terrestrial ecosystems. While largely invisible to the naked eye, they support all higher lifeforms, form symbiotic relationships with ~90% of terrestrial plant species, stabilize soils, and facilitate biogeochemical cycles. Global increases in the frequency of disturbances are driving major changes in the structure and function of forests. However, despite their functional significance, the disturbance responses of forest microbial communities are poorly understood. Here, we explore the influence of disturbance on the soil microbiome (archaea, fungi and bacteria) of some of the world's tallest and most carbon-dense forests, the Mountain Ash forests of south-eastern Australia. From 80 sites, we identified 23,277 and 19,056 microbial operational taxonomic units from the 0-10 cm and 20-30 cm depths of soil respectively. From this extensive data set, we found the diversity and composition of these often cryptic communities has been altered by human and natural disturbance events. For instance, the diversity of ectomycorrhizal fungi declined with clearcut logging, the diversity of archaea declined with salvage logging, and bacterial diversity and overall microbial diversity declined with the number of fires. Moreover, we identified key associations between edaphic (soil properties), environmental (slope, elevation) and spatial variables and the composition of all microbial communities. Specifically, we found that soil pH, manganese, magnesium, phosphorus, iron and nitrate were associated with the composition of all microbial communities. In a period of widespread degradation of global forest ecosystems, our findings provide an important and timely insight into the disturbance responses of soil microbial communities, which may influence key ecological functions.

Strobiloscyphones A-F, 6-Isopentylsphaeropsidones and Other Metabolites from Strobiloscypha sp. AZ0266, a Leaf-Associated Fungus of Douglas Fir

Six new 6-isopentylsphaeropsidones, strobiloscyphones A-F (1-6), and a new hexadecanoic acid, (2Z,4E,6E)-8,9-dihydroxy-10-oxohexadeca-2,4,6-trienoic acid (7), together with sphaeropsidone (8) and its known synthetic analogue 5-dehydrosphaeropsidone (9) were isolated from Strobiloscypha sp. AZ0266, a fungus inhabiting the leaf litter of Douglas fir (Pseudotsuga menziesii). The structures of 1-7 were established on the basis of their high-resolution mass and 1D and 2D NMR spectroscopic data, and their relative and/or absolute configurations were determined by NOE, comparison of experimental and calculated ECD spectra, and application of the modified Mosher's ester method. Of these, strobiloscyphone F (6) contains a novel highly oxygenated tetracyclic oxireno-octahydrodibenzofuran ring system. Natural products 1, 6, and 9 and the semisynthetic analogue 12 derived from 8 exhibited cytotoxic activity, whereas 9 and 12 showed antimicrobial activity. Possible biosynthetic pathways to 1-6, 8, and 9 are proposed.

Using High-Throughput Amplicon Sequencing to Evaluate Intragenomic Variation and Accuracy in Species Identification of Cordyceps Species

While recent sequencing technologies (third generation sequencing) can successfully sequence all copies of nuclear ribosomal DNA (rDNA) markers present within a genome and offer insights into the intragenomic variation of these markers, high intragenomic variation can be a source of confusion for high-throughput species identification using such technologies. High-throughput (HT) amplicon sequencing via PacBio SEQUEL I was used to evaluate the intragenomic variation of the ITS region and D1-D2 LSU domains in nine Cordyceps species, and the accuracy of such technology to identify these species based on molecular phylogenies was also assessed. PacBio sequences within strains showed variable level of intragenomic variation among the studied Cordyceps species with C. blackwelliae showing greater variation than the others. Some variants from a mix of species clustered together outside their respective species of origin, indicative of intragenomic variation that escaped concerted evolution shared between species. Proper selection of consensus sequences from HT amplicon sequencing is a challenge for interpretation of correct species identification. PacBio consensus sequences with the highest number of reads represent the major variants within a genome and gave the best results in terms of species identification.

Ribovore: ribosomal RNA sequence analysis for GenBank submissions and database curation

Background

The DNA sequences encoding ribosomal RNA genes (rRNAs) are commonly used as markers to identify species, including in metagenomics samples that may combine many organismal communities. The 16S small subunit ribosomal RNA (SSU rRNA) gene is typically used to identify bacterial and archaeal species. The nuclear 18S SSU rRNA gene, and 28S large subunit (LSU) rRNA gene have been used as DNA barcodes and for phylogenetic studies in different eukaryote taxonomic groups. Because of their popularity, the National Center for Biotechnology Information (NCBI) receives a disproportionate number of rRNA sequence submissions and BLAST queries. These sequences vary in quality, length, origin (nuclear, mitochondria, plastid), and organism source and can represent any region of the ribosomal cistron.

Results

To improve the timely verification of quality, origin and loci boundaries, we developed Ribovore, a software package for sequence analysis of rRNA sequences. The ribotyper and ribosensor programs are used to validate incoming sequences of bacterial and archaeal SSU rRNA. The ribodbmaker program is used to create high-quality datasets of rRNAs from different taxonomic groups. Key algorithmic steps include comparing candidate sequences against rRNA sequence profile hidden Markov models (HMMs) and covariance models of rRNA sequence and secondary-structure conservation, as well as other tests. Nine freely available blastn rRNA databases created and maintained with Ribovore are used for checking incoming GenBank submissions and used by the blastn browser interface at NCBI. Since 2018, Ribovore has been used to analyze more than 50 million prokaryotic SSU rRNA sequences submitted to GenBank, and to select at least 10,435 fungal rRNA RefSeq records from type material of 8350 taxa.

Conclusion

Ribovore combines single-sequence and profile-based methods to improve GenBank processing and analysis of rRNA sequences. It is a standalone, portable, and extensible software package for the alignment, classification and validation of rRNA sequences. Researchers planning on submitting SSU rRNA sequences to GenBank are encouraged to download and use Ribovore to analyze their sequences prior to submission to determine which sequences are likely to be automatically accepted into GenBank.

Long- and short-read metabarcoding technologies reveal similar spatiotemporal structures in fungal communities

Fungi form diverse communities and play essential roles in many terrestrial ecosystems, yet there are methodological challenges in taxonomic and phylogenetic placement of fungi from environmental sequences. To address such challenges, we investigated spatiotemporal structure of a fungal community using soil metabarcoding with four different sequencing strategies: short-amplicon sequencing of the ITS2 region (300-400 bp) with Illumina MiSeq, Ion Torrent Ion S5 and PacBio RS II, all from the same PCR library, as well as long-amplicon sequencing of the full ITS and partial LSU regions (1200-1600 bp) with PacBio RS II. Resulting community structure and diversity depended more on statistical method than sequencing technology. The use of long-amplicon sequencing enables construction of a phylogenetic tree from metabarcoding reads, which facilitates taxonomic identification of sequences. However, long reads present issues for denoising algorithms in diverse communities. We present a solution that splits the reads into shorter homologous regions prior to denoising, and then reconstructs the full denoised reads. In the choice between short and long amplicons, we suggest a hybrid approach using short amplicons for sampling breadth and depth, and long amplicons to characterize the local species pool for improved identification and phylogenetic analyses.

DNA Metabarcoding for the Characterization of Terrestrial Microbiota-Pitfalls and Solutions

Soil-borne microbes are major ecological players in terrestrial environments since they cycle organic matter, channel nutrients across trophic levels and influence plant growth and health. Therefore, the identification, taxonomic characterization and determination of the ecological role of members of soil microbial communities have become major topics of interest. The development and continuous improvement of high-throughput sequencing platforms have further stimulated the study of complex microbiota in soils and plants. The most frequently used approach to study microbiota composition, diversity and dynamics is polymerase chain reaction (PCR), amplifying specific taxonomically informative gene markers with the subsequent sequencing of the amplicons. This methodological approach is called DNA metabarcoding. Over the last decade, DNA metabarcoding has rapidly emerged as a powerful and cost-effective method for the description of microbiota in environmental samples. However, this approach involves several processing steps, each of which might introduce significant biases that can considerably compromise the reliability of the metabarcoding output. The aim of this review is to provide state-of-the-art background knowledge needed to make appropriate decisions at each step of a DNA metabarcoding workflow, highlighting crucial steps that, if considered, ensures an accurate and standardized characterization of microbiota in environmental studies.

Greater local diversity under older species pools may arise from enhanced competitive equivalence

Ecological communities typically contain more species when located within geologically older regions. This pattern is traditionally attributed to the long-term accumulation of species in the regional species pool, with local species interactions playing a minor role. We provide evidence suggesting a more important role of local species interactions than generally assumed. We assembled 320 communities of root-associated fungi under 80 species pools, varying species pool richness and the mean age of the sites from which the fungi were collected across a 4-myr soil chronosequence. We found that local diversity increased more with increasing species pool richness when species were from older sites. We also found that older species pools had lower functional and phylogenetic diversity, indicating greater competitive equivalence among species. Our results suggest that older regions have higher local richness not simply because older pools are more speciose but also because species have evolved traits that allow them to locally co-occur.

Teratopyrones A-C, Dimeric Naphtho-γ-Pyrones and Other Metabolites from Teratosphaeria sp. AK1128, a Fungal Endophyte of Equisetum arvense

Bioassay-guided fractionation of a cytotoxic extract derived from a solid potato dextrose agar (PDA) culture of Teratosphaeria sp. AK1128, a fungal endophyte of Equisetum arvense, afforded three new naphtho-γ-pyrone dimers, teratopyrones A–C (1–3), together with five known naphtho-γ-pyrones, aurasperone B (4), aurasperone C (5), aurasperone F (6), nigerasperone A (7), and fonsecin B (8), and two known diketopiperazines, asperazine (9) and isorugulosuvine (10). The structures of 1–3 were determined on the basis of their spectroscopic data. Cytotoxicity assay revealed that nigerasperone A (7) was moderately active against the cancer cell lines PC-3M (human metastatic prostate cancer), NCI-H460 (human non-small cell lung cancer), SF-268 (human CNS glioma), and MCF-7 (human breast cancer), with IC₅₀s ranging from 2.37 to 4.12 μM while other metabolites exhibited no cytotoxic activity up to a concentration of 5.0 μM.

An epigenetic modifier induces production of 3-(4-oxopyrano)-chromen-2-ones in Aspergillus sp. AST0006, an endophytic fungus of Astragalus lentiginosus

Incorporation of the epigenetic modifier suberoylanilide hydroxamic acid (SAHA) into a potato dextrose broth culture of the endophytic fungus Aspergillus sp. AST0006 affected its polyketide biosynthetic pathway providing two new 3-(4-oxopyrano)-chromen-2-ones, aspyranochromenones A (1) and B (2), and the isocoumarin, (-)-6,7-dihydroxymellein (3). Eight additional metabolites (4-11) and two biotransformation products of SAHA (12-13) were also encountered. The planar structures and relative configurations of the new metabolites 1-2 were elucidated with the help of high-resolution mass, 1D and 2D NMR spectroscopic data and the absolute configurations of 1-3 were determined by comparison of experimental and calculated ECD data. Possible biosynthetic pathways to 1 and 2 are presented.

Assessing anaerobic gut fungal diversity in herbivores using D1/D2 large ribosomal subunit sequencing and multi-year isolation

The anaerobic gut fungi (AGF, Neocallimastigomycota) reside in the alimentary tracts of herbivores where they play a central role in the breakdown of plant material. Here, we report on the development of the hypervariable domains D1/D2 of the large ribosomal subunit (D1/D2 LSU) as a barcoding marker for the AGF. We generated a reference D1/D2 LSU database for all cultured AGF genera, as well as the majority of candidate genera encountered in prior internal transcribed spacer 1 (ITS1)-based surveys. Subsequently, a D1/D2 LSU-based diversity survey using long read PacBio SMRT sequencing was conducted on faecal samples from 21 wild and domesticated herbivores. Twenty-eight genera and candidate genera were identified, including multiple novel lineages that were predominantly, but not exclusively, identified in wild herbivores. Association between certain AGF genera and animal lifestyles, or animal host family was observed. Finally, to address the current paucity of AGF isolates, concurrent isolation efforts utilizing multiple approaches to maximize recovery yielded 216 isolates belonging to 12 different genera, several of which have no prior cultured-representatives. Our results establish the utility of D1/D2 LSU and PacBio sequencing for AGF diversity surveys, the culturability of multiple AGF taxa, and demonstrate that wild herbivores represent a yet-untapped reservoir of AGF diversity.

Increase in abundance and decrease in richness of soil microbes following Hurricane Otto in three primary forest types in the Northern Zone of Costa Rica

Little is known of how hurricane-induced deposition of canopy material onto tropical forest floors influences the soil microbial communities involved in decomposition of these materials. In this study, to identify how soil bacterial and fungal communities might change after a hurricane, and their possible roles in the C and N cycles, soils were collected from five 2000 m² permanent plots in Lowland, Upland and Riparian primary forests in Costa Rica 3 months before and 7 months after Hurricane Otto damaged the forests. The soil Water, inorganic N and Biomass C increased and total organic C decreased Post-Hurricane, all of which best predicted the changes in the Post-Hurricane soil microbial communities. Post-Hurricane soils from all forest types showed significant changes in community composition of total bacteria, total fungi, and five functional groups of microbes (i.e., degrading/lignin degrading, NH₄⁺-producing, and ammonium oxidizing bacteria, and the complex C degrading/wood rot/lignin degrading and ectomycorrhizal fungi), along with a decrease in richness in genera of all groups. As well, the mean proportion of DNA sequences (MPS) of all five functional groups increased. There were also significant changes in the MPS values of 7 different fungal and 7 different bacterial genera that were part of these functional groups. This is the first evidence that hurricane-induced deposition of canopy material is stimulating changes in the soil microbial communities after the hurricane, involving changes in specific taxonomic and functional group genera, and reduction in the community richness while selecting for dominant genera possibly better suited to process the canopy material. These changes may represent examples of taxonomic switching of functionally redundant microbial genera in response to dramatic changes in resource input. It is possible that differences in these microbial communities and genera may serve as indicators of disturbed and recovering regional soil ecosystems, and should be evaluated in the future.

Convolutional neural networks improve fungal classification

Sequence classification plays an important role in metagenomics studies. We assess the deep neural network approach for fungal sequence classification as it has emerged as a successful paradigm for big data classification and clustering. Two deep learning-based classifiers, a convolutional neural network (CNN) and a deep belief network (DBN) were trained using our recently released barcode datasets. Experimental results show that CNN outperformed the traditional BLAST classification and the most accurate machine learning based Ribosomal Database Project (RDP) classifier on datasets that had many of the labels present in the training datasets. When classifying an independent dataset namely the "Top 50 Most Wanted Fungi", CNN and DBN assigned less sequences than BLAST. However, they could assign much more sequences than the RDP classifier. In terms of efficiency, it took the machine learning classifiers up to two seconds to classify a test dataset while it was 53 s for BLAST. The result of the current study will enable us to speed up the taxonomic assignments for the fungal barcode sequences generated at our institute as ~ 70% of them still need to be validated for public release. In addition, it will help to quickly provide a taxonomic profile for metagenomics samples.

Mushroom DNA barcoding project: Sequencing a segment of the 28S rRNA gene

DNA barcoding is an important molecular methodology for species identification that was developed over the last two decades and it should be covered in the biology bachelor curriculum. Here, we present an example of DNA barcoding by sequencing a segment of the 28S nuclear ribosomal large subunit rRNA gene of wild mushrooms and framing the education in a project form for undergraduate students in biology. Students perform this project in 6-8 weeks, which also includes preparing a poster, writing a report and presenting a paper related to the work in a journal club format. First, fieldwork in the Netherlands was carried out, during which students collected mushrooms under supervision of a professional mycologist with the goal to (a) verify morphologically based identifications with a molecular method and (b) assess phylogenetic relationships of the different species collected. Next, DNA extractions and quantitation were performed, PCR amplification was done, and samples were sent out for Sanger sequencing. Students aligned and analyzed the sequences using BLAST and Geneious and subsequently created a phylogenetic tree. In case of collecting DNA barcodes of an earlier sequenced species, students could upload the data to a repository established for facilitation of future research projects. The method described is very robust, reagents and equipment are readily available, and costs are relatively low. In addition, the results can be compared to published fungal phylogenetic trees.

Gongronella eborensis sp. nov., from vineyard soil of Alentejo (Portugal)

This study describes a novel fungal species belonging to the genus Gongronella. During a previous work focusing on metalaxyl degradation by Mucorales strains, two isolates from vineyard soil samples collected in the Alentejo region, south Portugal, were identified as a putative novel species based on combined molecular and MALDI-TOF MS data. This new species is described here using a polyphasic approach that combines morphology, internal transcribed spacer of ribosomal DNA (ITS) and 28S ribosomal DNA (LSU) sequence data analysis and proteomic profiling by MALDI-TOF MS. Phenotypic and molecular data enabled this novel species to be clearly distinguished from other Gongronella species with results of combined ITS+LSU analysis showing that the Gongronella species is related to Gongronella butleri and Gongronella brasiliensis. Therefore, from the results of morphological and molecular analyses, isolates MUM 10.262 and MUM 10.263 seem to represent a new Gongronella species and the name Gongronella eborensis sp. nov. is proposed, with the ex-type strain MUM 10.262 (=CCMI 1100=CBS 128763).

Mollisiaceae: An overlooked lineage of diverse endophytes

Mollisia is a taxonomically neglected discomycete genus (Helotiales, Leotiomycetes) of commonly encountered saprotrophs on decaying plant tissues throughout temperate regions. The combination of indistinct morphological characters, more than 700 names in the literature, and lack of reference DNA sequences presents a major challenge when working with Mollisia. Unidentified endophytes, including strains that produced antifungal or antiinsectan secondary metabolites, were isolated from conifer needles in New Brunswick and placed with uncertainty in Phialocephala and Mollisia, necessitating a more comprehensive treatment of these genera. In this study, morphology and multigene phylogenetic analyses were used to explore the taxonomy of Mollisiaceae, including Mollisia, Phialocephala, and related genera, using new field collections, herbarium specimens, and accessioned cultures and sequences. The phylogeny of Mollisiaceae was reconstructed and compared using the nuc internal transcribed spacer rDNA (ITS) barcode and partial sequences of the 28S nuc rDNA (LSU) gene, largest subunit of RNA polymerase II (RPB1), DNA topoisomerase I (TOP1), and the hypothetical protein Lipin/Ned1/Smp2 (LNS2). The results show that endophytism is common throughout the Mollisiaceae lineage in a diverse range of hosts but is infrequently attributed to Mollisia because of a paucity of reference sequences. Generic boundaries within Mollisiaceae are poorly resolved and based on phylogenetic evidence the family included species placed in Acephala, Acidomelania, Barrenia, Bispora, Cheirospora, Cystodendron, Fuscosclera, Hysteronaevia, Loramyces, Mollisia, Neopyrenopeziza, Obtectodiscus, Ombrophila, Patellariopsis, Phialocephala, Pulvinata, Tapesia (=Mollisia), and Trimmatostroma. Taxonomic novelties included the description of five novel Mollisia species and five novel Phialocephala species and the synonymy of Fuscosclera with Phialocephala, Acidomelania with Mollisia, and Loramycetaceae with Mollisiaceae.

Spatial and temporal turnover of soil microbial communities is not linked to function in a primary tropical forest

The spatial and temporal linkages between turnover of soil microbial communities and their associated functions remain largely unexplored in terrestrial ecosystems. Yet defining these relationships and how they vary across ecosystems and microbial lineages is key to incorporating microbial communities into ecological forecasts and ecosystem models. To define linkages between turnover of soil bacterial and fungal communities and their function we sampled fungal and bacterial composition, abundance, and enzyme activities across a 3-ha area of wet tropical primary forest over 2 yr. We show that fungal and bacterial communities both exhibited temporal turnover, but turnover of both groups was much lower than in temperate ecosystems. Turnover over time was driven by gain and loss of microbial taxa and not changes in abundance of individual species present in multiple samples. Only fungi varied over space with idiosyncratic variation that did not increase linearly with distance among sampling locations. Only phosphorus-acquiring enzyme activities were linked to shifts in septate, decomposer fungal abundance; no enzymes were affected by composition or diversity of fungi or bacteria. Although temporal and spatial variation in composition was appreciable, because turnover of microbial communities did not alter the functional repertoire of decomposing enzymes, functional redundancy among taxa may be high in this ecosystem. Slow temporal turnover of tropical soil microbial communities and large functional redundancy suggests that shifts in abundance of particular functional groups may capture ecosystem function more accurately than composition in these heterogeneous ecosystems.

A rapid approach to profiling diverse fungal communities using the MinION™ nanopore sequencer

The Oxford Nanopore Technologies MinION™ sequencer holds the capability to generate long amplicon reads; however, only a small amount of information is available regarding methodological approaches and the ability to identify a broad diversity of fungal taxa. To assess capabilities, three fungal mock communities were sequenced, each of which had varying ratios of 16 taxa. The data were processed through our selected pipeline. The MinION recovered all mock community members, when mixed at equal ratios. When a taxon was represented at a lower ratio, it was not recovered or decreased in relative abundance. Despite high error rates, highly accurate consensus sequences can be derived. This methodological approach identified all mock community taxa, demonstrating the MinION can be used as a practical alternative to profile fungal communities.

Anthropogenic N deposition alters soil organic matter biochemistry and microbial communities on decaying fine roots

Fine root litter is a primary source of soil organic matter (SOM), which is a globally important pool of C that is responsive to climate change. We previously established that ~20 years of experimental nitrogen (N) deposition has slowed fine root decay and increased the storage of soil carbon (C; +18%) across a widespread northern hardwood forest ecosystem. However, the microbial mechanisms that have directly slowed fine root decay are unknown. Here, we show that experimental N deposition has decreased the relative abundance of Agaricales fungi (-31%) and increased that of partially ligninolytic Actinobacteria (+24%) on decaying fine roots. Moreover, experimental N deposition has increased the relative abundance of lignin-derived compounds residing in SOM (+53%), and this biochemical response is significantly related to shifts in both fungal and bacterial community composition. Specifically, the accumulation of lignin-derived compounds in SOM is negatively related to the relative abundance of ligninolytic Mycena and Kuehneromyces fungi, and positively related to Microbacteriaceae. Our findings suggest that by altering the composition of microbial communities on decaying fine roots such that their capacity for lignin degradation is reduced, experimental N deposition has slowed fine root litter decay, and increased the contribution of lignin-derived compounds from fine roots to SOM. The microbial responses we observed may explain widespread findings that anthropogenic N deposition increases soil C storage in terrestrial ecosystems. More broadly, our findings directly link composition to function in soil microbial communities, and implicate compositional shifts in mediating biogeochemical processes of global significance.

Antibiotic resistant bacteria and commensal fungi are common and conserved in the mosquito microbiome

The emerging and increasing prevalence of bacterial antibiotic resistance is a significant public health challenge. To begin to tackle this problem, it will be critical to not only understand the origins of this resistance but also document environmental reservoirs of antibiotic resistance. In this study we investigated the possibility that both colony and field caught mosquitoes could harbor antibiotic resistant bacteria. Specifically, we characterized the antibiotic resistant bacterial populations from colony-reared Aedes aegypti larvae and adults and two field caught mosquito species Coquillettidia perturbans and Ochlerotatus canadensis. The cultured bacterial populations were dominated by isolates belonging to the class Gammaproteobacteria. Among the antibiotic resistant populations, we found bacteria resistant to carbenicillin, kanamycin, and tetracycline, including bacteria resistant to a cocktail of all three antibiotics in combination. The antibiotic resistant bacteria were numerically rare, at most 5% of total cell counts. Isolates were characterized by 16S rRNA gene sequencing, and clustering into Operational Taxonomic Units (OTUs; 99% sequence identity). 27 antibiotic resistant OTUs were identified, although members of an OTU did not always share the same resistance profile. This suggests the clustering was either not sensitive enough to distinguish different bacteria taxa or different antibiotic resistant sub-populations exist within an OTU. Finally, the antibiotic selection opened up a niche to culture mosquito-associated fungi, and 10 fungal OTUs (28S rRNA gene sequencing) were identified. Two fungal OTUs both classified to the class Microbotryomycetes were commonly identified in the field-caught mosquitoes. Thus, in this study we demonstrate that antibiotic resistant bacteria and certain fungi are common and conserved mosquito microbiome members. These observations highlight the potential of invertebrates to serve as vehicles for the spread of antibiotic resistance throughout the environment.

Salivary mycobiome dysbiosis and its potential impact on bacteriome shifts and host immunity in oral lichen planus

The biodiversity of the mycobiome, an important component of the oral microbial community, and the roles of fungal–bacterial and fungal–immune system interactions in the pathogenesis of oral lichen planus (OLP) remain largely uncharacterized. In this study, we sequenced the salivary mycobiome and bacteriome associated with OLP. First, we described the dysbiosis of the microbiome in OLP patients, which exhibits lower levels of fungi and higher levels of bacteria. Significantly higher abundances of the fungi Candida and Aspergillus in patients with reticular OLP and of Alternaria and Sclerotiniaceae_unidentified in patients with erosive OLP were observed compared to the healthy controls. Aspergillus was identified as an “OLP-associated” fungus because of its detection at a higher frequency than in the healthy controls. Second, the co-occurrence patterns of the salivary mycobiome–bacteriome demonstrated negative associations between specific fungal and bacterial taxa identified in the healthy controls, which diminished in the reticular OLP group and even became positive in the erosive OLP group. Moreover, the oral cavities of OLP patients were colonized by dysbiotic oral flora with lower ecological network complexity and decreased fungal–Firmicutes and increased fungal–Bacteroidetes sub-networks. Third, several keystone fungal genera (Bovista, Erysiphe, Psathyrella, etc.) demonstrated significant correlations with clinical scores and IL-17 levels. Thus, we established that fungal dysbiosis is associated with the aggravation of OLP. Fungal dysbiosis could alter the salivary bacteriome or may reflect a direct effect of host immunity, which participates in OLP pathogenesis.

Imbalance in the oral fungal community could lead to the development of oral lichen planus (OLP), a chronic inflammatory disease that affects the mucous membranes in the mouth. The exact cause of OLP is uncertain, which is a major obstacle to therapeutic development. Using salivary samples, a team headed by Xuedong Zhou at Sichuan University in China investigated the composition and diversity of the fungal community in OLP patients and healthy individuals. The authors found that the oral fungal community was less diverse and that there were higher levels of bacteria in OLP patients. The team concluded that fungal community imbalance could affect the bacterial community in the saliva and the host immunity in the mucous membrane, thereby constituting a direct or indirect cause of the development of OLP.

DNA extraction and amplicon production strategies deeply inf luence the outcome of gut mycobiome studies

Microbial ecology studies are often performed through extraction of metagenomic DNA followed by amplification and sequencing of a marker. It is known that each step may bias the results. These biases have been explored for the study of bacterial communities, but rarely for fungi. Our aim was therefore to evaluate methods for the study of the gut mycobiome. We first evaluated DNA extraction methods in fungal cultures relevant to the gut. Afterwards, to assess how these methods would behave with an actual sample, stool from a donor was spiked with cells from the same cultures. We found that different extraction kits favour some species and bias against others. In terms of amplicon sequencing, we evaluated five primer sets, two for ITS2 and one for ITS1, 18S and 28S rRNA. Results showed that 18S rRNA outperformed the other markers: it was able to amplify all the species in the mock community and to discriminate among them. ITS primers showed both amplification and sequencing biases, the latter related to the variable length of the product. We identified several biases in the characterisation of the gut mycobiome and showed how crucial it is to be aware of these before drawing conclusions from the results of these studies.

Effects of agricultural management on phyllosphere fungal diversity in vineyards and the association with adjacent native forests

Agriculture is one of the main drivers of land conversion, and agriculture practices can impact on microbial diversity. Here we characterized the phyllosphere fungal diversity associated with Carménère grapevines under conventional and organic agricultural management. We also explored the fungal diversity present in the adjacent sclerophyllous forests to explore the potential role of native forest on vineyard phyllosphere. After conducting D2 and ITS2 amplicon sequencing, we found that fungal diversity indices did not change between conventional and organic vineyards, but community structure was sensitive to the agricultural management. On the other hand, we found a high proportion of shared fungal OTUs between vineyards and native forests. In addition, both habitats had similar levels of fungal diversity despite forest samples were derived from multiple plant species. In contrast, the community structure was different in both habitats. Interestingly, the native forest had more unidentified species and unique OTUs than vineyards. Forest dominant species were Aureobasidium pullulans and Endoconidioma populi, whereas Davidiella tassiana, Didymella sp., and Alternaria eichhorniae were more abundant in vineyards. Overall, this study argues that a better understanding of the relationship native forests and agroecosystems is needed for maintaining and enhancing ecosystem services provided by natural ecosystems. Finally, knowledge of microbial communities living in the Chilean Mediterranean biome is needed for appropriate conservation management of these biomes and their classification as biodiversity hotspots.

IDTAXA: a novel approach for accurate taxonomic classification of microbiome sequences

BACKGROUND

Microbiome studies often involve sequencing a marker gene to identify the microorganisms in samples of interest. Sequence classification is a critical component of this process, whereby sequences are assigned to a reference taxonomy containing known sequence representatives of many microbial groups. Previous studies have shown that existing classification programs often assign sequences to reference groups even if they belong to novel taxonomic groups that are absent from the reference taxonomy. This high rate of "over classification" is particularly detrimental in microbiome studies because reference taxonomies are far from comprehensive.

RESULTS

Here, we introduce IDTAXA, a novel approach to taxonomic classification that employs principles from machine learning to reduce over classification errors. Using multiple reference taxonomies, we demonstrate that IDTAXA has higher accuracy than popular classifiers such as BLAST, MAPSeq, QIIME, SINTAX, SPINGO, and the RDP Classifier. Similarly, IDTAXA yields far fewer over classifications on Illumina mock microbial community data when the expected taxa are absent from the training set. Furthermore, IDTAXA offers many practical advantages over other classifiers, such as maintaining low error rates across varying input sequence lengths and withholding classifications from input sequences composed of random nucleotides or repeats.

CONCLUSIONS

IDTAXA's classifications may lead to different conclusions in microbiome studies because of the substantially reduced number of taxa that are incorrectly identified through over classification. Although misclassification error is relatively minor, we believe that many remaining misclassifications are likely caused by errors in the reference taxonomy. We describe how IDTAXA is able to identify many putative mislabeling errors in reference taxonomies, enabling training sets to be automatically corrected by eliminating spurious sequences. IDTAXA is part of the DECIPHER package for the R programming language, available through the Bioconductor repository or accessible online ( http://DECIPHER.codes ).

RNA-based analyses reveal fungal communities structured by a senescence gradient in the moss Dicranum scoparium and the presence of putative multi-trophic fungi

Diverse plant-associated fungi are thought to have symbiotrophic and saprotrophic states because they can be isolated from both dead and living plant tissues. However, such tissues often are separated in time and space, and fungal activity at various stages of plant senescence is rarely assessed directly in fungal community studies. We used fungal ribosomal RNA metatranscriptomics to detect active fungal communities across a natural senescence gradient within wild-collected gametophytes of Dicranum scoparium (Bryophyta) to understand the distribution of active fungal communities in adjacent living, senescing and dead tissues. Ascomycota were active in all tissues across the senescence gradient. By contrast, Basidiomycota were prevalent and active in senescing and dead tissues. Several fungi were detected as active in living and dead tissues, suggesting their capacity for multi-trophy. Differences in community assembly detected by metatranscriptomics were echoed by amplicon sequencing of cDNA and compared to culture-based inferences and observation of fungal fruit bodies in the field. The combination of amplicon sequencing of cDNA and metatranscriptomics is promising for studying symbiotic systems with complex microbial diversity, allowing for the simultaneous detection of their presence and activity.

The fallopian tube microbiome: implications for reproductive health

Objective

There is a paucity of data characterizing the microbiota of the female upper genital tract, which controversially is described as a sterile site. We examine whether the fallopian tube harbours an endogenous microbial community.

Design

This prospective study collected from women undergoing total hysterectomy or salpingectomy-oophorectomy.

Setting

Private hospital gynaecology department.

Patients

Fallopian tubes were collected from women diagnosed with benign disease or for prophylaxis.

Interventions

Samples were interrogated for the presence of microbial DNA using a next generation sequencing technology approach to exploit the V5 to V9 regions of the 16S rRNA gene.

Main outcome measures

The fallopian tube microbiota was characterized using traditional culture techniques and next generation sequencing.

Results

Bacteria were isolated from 50% of cultured samples, and 100% of samples returned positive PCR results. Only 68% of the culture isolates could be confidently identified using automated diagnostic equipment in a clinical microbiology laboratory. Monomicrobial communities were identified only for cultured isolates (50%). Pyrosequencing revealed that all communities were polymicrobial. Lactobacillus spp. were not present in all groups, nor were they the most dominant isolates. Distinct differences in the microbial communities were evident for left compared to right fallopian tubes, ampulla versus isthmus, pre- and post- menopausal tissue, and in secretory phase fallopian tubes with and without Mirena intrauterine devices in situ (all p < 0.05).

Conclusion

The female upper genital tract is not sterile. Distinct microbial community profiles in the fallopian tubes of healthy women suggest that this genital tract site supports an endogenous microbiota.

Cytotoxic and Noncytotoxic Metabolites from Teratosphaeria sp. FL2137, a Fungus Associated with Pinus clausa

A new naphthoquinone, teratosphaerone A (1), four new naphthalenones, namely, teratosphaerone B (2), structurally related to 1, iso-balticol B (3), iso-balticol B-4,9-acetonide (4), and (+)-balticol C (5), a new furanonaphthalenone, (3a S,9 R,9a S)-1(9a),3(3a),9-hexahydromonosporascone (6), and the known metabolite monosporascone (7) were isolated from Teratosphaeria sp. FL2137, a fungal strain inhabiting the internal tissue of recently dead but undecomposed foliage of Pinus clausa. The structures of 1-6 were elucidated on the basis of their spectroscopic data including 2D NMR, and absolute configurations of 2, 3, and 6 were determined by the modified Mosher's ester method. When evaluated in a panel of five tumor cell lines, metabolites 1 and 7 isolated from a cytotoxic fraction of the extract exhibited moderate selectivity for metastatic breast adenocarcinoma cell line MDA-MB-231. Of these, 1 showed cytotoxicity to this cell line with an IC₅₀ of 1.2 ± 0.1 μM.

Automated high throughput animal CO1 metabarcode classification

We introduce a method for assigning names to CO1 metabarcode sequences with confidence scores in a rapid, high-throughput manner. We compiled nearly 1 million CO1 barcode sequences appropriate for classifying arthropods and chordates. Compared to our previous Insecta classifier, the current classifier has more than three times the taxonomic coverage, including outgroups, and is based on almost five times as many reference sequences. Unlike other popular rDNA metabarcoding markers, we show that classification performance is similar across the length of the CO1 barcoding region. We show that the RDP classifier can make taxonomic assignments about 19 times faster than the popular top BLAST hit method and reduce the false positive rate from nearly 100% to 34%. This is especially important in large-scale biodiversity and biomonitoring studies where datasets can become very large and the taxonomic assignment problem is not trivial. We also show that reference databases are becoming more representative of current species diversity but that gaps still exist. We suggest that it would benefit the field as a whole if all investigators involved in metabarocoding studies, through collaborations with taxonomic experts, also planned to barcode representatives of their local biota as a part of their projects.

Scaling up: A guide to high-throughput genomic approaches for biodiversity analysis

The purpose of this review is to present the most common and emerging DNA-based methods used to generate data for biodiversity and biomonitoring studies. As environmental assessment and monitoring programmes may require biodiversity information at multiple levels, we pay particular attention to the DNA metabarcoding method and discuss a number of bioinformatic tools and considerations for producing DNA-based indicators using operational taxonomic units (OTUs), taxa at a variety of ranks and community composition. By developing the capacity to harness the advantages provided by the newest technologies, investigators can "scale up" by increasing the number of samples and replicates processed, the frequency of sampling over time and space, and even the depth of sampling such as by sequencing more reads per sample or more markers per sample. The ability to scale up is made possible by the reduced hands-on time and cost per sample provided by the newest kits, platforms and software tools. Results gleaned from broad-scale monitoring will provide opportunities to address key scientific questions linked to biodiversity and its dynamics across time and space as well as being more relevant for policymakers, enabling science-based decision-making, and provide a greater socio-economic impact. As genomic approaches are continually evolving, we provide this guide to methods used in biodiversity genomics.

Intraspecific functional and genetic diversity of Petriella setifera

The aim of the study was an analysis of the intraspecific genetic and functional diversity of the new isolated fungal strains of P. setifera. This is the first report concerning the genetic and metabolic diversity of Petriella setifera strains isolated from industrial compost and the first description of a protocol for AFLP fingerprinting analysis optimised for these fungal species. The results showed a significant degree of variability among the isolates, which was demonstrated by the clearly subdivision of all the isolates into two clusters with 51% and 62% similarity, respectively. For the metabolic diversity, the BIOLOG system was used and this analysis revealed clearly different patterns of carbon substrates utilization between the isolates resulting in a clear separation of the five isolates into three clusters with 0%, 42% and 54% of similarity, respectively. These results suggest that genetic diversity does not always match the level of functional diversity, which may be useful in discovering the importance of this fungus to ecosystem functioning. The results indicated that P. setifera strains were able to degrade substrates produced in the degradation of hemicellulose (D-Arabinose, L-Arabinose, D-Glucuronic Acid, Xylitol, γ-Amino-Butyric Acid, D-Mannose, D-Xylose and L-Rhamnose), cellulose (α-D-Glucose and D-Cellobiose) and the synthesis of lignin (Quinic Acid) at a high level, showing their importance in ecosystem services as a decomposer of carbon compounds and as organisms, which make a significant contribution to carbon cycling in the ecosystem.The results showed for the first time that the use of molecular biology techniques (such as AFLP and BIOLOG analyses) may allow for the identification of intraspecific diversity of as yet poorly investigated fungal species with favourable consequences for our understanding their ecosystem function.

PacBio metabarcoding of Fungi and other eukaryotes: errors, biases and perspectives

Second-generation, high-throughput sequencing methods have greatly improved our understanding of the ecology of soil microorganisms, yet the short barcodes (< 500 bp) provide limited taxonomic and phylogenetic information for species discrimination and taxonomic assignment. Here, we utilized the third-generation Pacific Biosciences (PacBio) RSII and Sequel instruments to evaluate the suitability of full-length internal transcribed spacer (ITS) barcodes and longer rRNA gene amplicons for metabarcoding Fungi, Oomycetes and other eukaryotes in soil samples. Metabarcoding revealed multiple errors and biases: Taq polymerase substitution errors and mis-incorporating indels in sequencing homopolymers constitute major errors; sequence length biases occur during PCR, library preparation, loading to the sequencing instrument and quality filtering; primer-template mismatches bias the taxonomic profile when using regular and highly degenerate primers. The RSII and Sequel platforms enable the sequencing of amplicons up to 3000 bp, but the sequence quality remains slightly inferior to Illumina sequencing especially in longer amplicons. The full ITS barcode and flanking rRNA small subunit gene greatly improve taxonomic identification at the species and phylum levels, respectively. We conclude that PacBio sequencing provides a viable alternative for metabarcoding of organisms that are of relatively low diversity, require > 500-bp barcode for reliable identification or when phylogenetic approaches are intended.

Host Specificity for Bacterial, Archaeal and Fungal Communities Determined for High- and Low-Microbial Abundance Sponge Species in Two Genera

Sponges are engaged in intimate symbioses with a diversity of microorganisms from all three domains of life, namely Bacteria, Archaea and Eukarya. Sponges have been well studied and categorized for their bacterial communities, some displaying a high microbial abundance (HMA), while others show low microbial abundance (LMA). However, the associated Archaea and Eukarya have remained relatively understudied. We assessed the bacterial, archaeal and eukaryotic diversities in the LMA sponge species Dysidea avara and Dysidea etheria by deep amplicon sequencing, and compared the results to those in the HMA sponges Aplysina aerophoba and Aplysina cauliformis. D. avara and A. aerophoba are sympatric in the Mediterranean Sea, while D. etheria and A. cauliformis are sympatric in the Caribbean Sea. The bacterial communities followed a host-specific pattern, with host species identity explaining most of the variation among samples. We identified OTUs shared by the Aplysina species that support a more ancient association of these microbes, before the split of the two species studied here. These shared OTUs are suitable targets for future studies of the microbial traits that mediate interactions with their hosts. Even though the archaeal communities were not as rich as the bacterial ones, we found a remarkable diversification and specificity of OTUs of the family Cenarchaeaceae and the genus Nitrosopumilus in all four sponge species studied. Similarly, the differences in fungal communities were driven by sponge identity. The structures of the communities of small eukaryotes such as dinophytes and ciliophores (alveolates), and stramenopiles, could not be explained by either sponge host, sponge genus or geographic location. Our analyses suggest that the host specificity that was previously described for sponge bacterial communities also extends to the archaeal and fungal communities, but not to other microbial eukaryotes.

Forgotten fungi-the gut mycobiome in human health and disease

The human body is home to a complex and diverse microbial ecosystem that plays a central role in host health. This includes a diversity of fungal species that is collectively referred to as our 'mycobiome'. Although research into the mycobiome is still in its infancy, its potential role in human disease is increasingly recognised. Here we review the existing literature available on the human mycobiota with an emphasis on the gut mycobiome, including how fungi interact with the human host and other microbes. In doing so, we provide a comprehensive critique of the methodologies available to research the human mycobiota as well as highlighting the latest research findings from mycological surveys of different groups of interest including infants, obese and inflammatory bowel disease cohorts. This in turn provides new insights and directions for future studies in this burgeoning research area.

How to boost marine fungal research: A first step towards a multidisciplinary approach by combining molecular fungal ecology and natural products chemistry

Marine fungi have attracted attention in recent years due to increased appreciation of their functional role in ecosystems and as important sources of new natural products. The concomitant development of various "omic" technologies has boosted fungal research in the fields of biodiversity, physiological ecology and natural product biosynthesis. Each of these research areas has its own research agenda, scientific language and quality standards, which have so far hindered an interdisciplinary exchange. Inter- and transdisciplinary interactions are, however, vital for: (i) a detailed understanding of the ecological role of marine fungi, (ii) unlocking their hidden potential for natural product discovery, and (iii) designing access routes for biotechnological production. In this review and opinion paper, we describe the two different "worlds" of marine fungal natural product chemists and marine fungal molecular ecologists. The individual scientific approaches and tools employed are summarised and explained, and enriched with a first common glossary. We propose a strategy to find a multidisciplinary approach towards a comprehensive view on marine fungi and their chemical potential.

Multiple Approaches Detect the Presence of Fungi in Human Breastmilk Samples from Healthy Mothers

Human breastmilk contains a variety of bacteria that are transmitted to the infant and have been suggested to contribute to gut microbiota development and immune maturation. However, the characterization of fungal organisms in milk from healthy mothers is currently unknown although their presence has been reported in the infant gut and also in milk from other mammals. Breastmilk samples from healthy lactating mothers (n = 65) within 1 month after birth were analyzed. Fungal presence was assessed by different techniques, including microscopy, growth and identification of cultured isolates, fungal load estimation by qPCR, and fungal composition using 28S rRNA gene high-throughput sequencing. In addition, milk macronutrients and human somatic cells were quantified by spectrophotometry and cytometry. qPCR data showed that 89% of samples had detectable levels of fungal DNA, at an estimated median load of 3,5 × 10⁵ cells/ml, potentially including both viable and non-viable fungi. Using different culture media, 33 strains were isolated and identified, confirming the presence of viable fungal species. Pyrosequencing results showed that the most common genera were Malassezia (44%), followed by Candida (19%) and Saccharomyces (12%). Yeast cells were observed by fluorescence microscopy. Future work should study the origin of these fungi and their potential contribution to infant health.