Metagenomic and Bioinformatics Analysis of Sebacina vermifera for Next-Generation Biofertilizer Development

The genome, transcriptome and metabolome of Aspergillus welwitschiae Ocstreb1 from wild halophytic rice, Oryza coarctata, indicates its distinctiveness.

Aspergillus welwitschiae is a widespread fungus with diverse roles as a plant mutualist, opportunistic human pathogen and industrial enzyme producer. The endophytic strain AwOcstreb1, isolated from halophytic rice (Oryza coarctata), promotes growth in commercial rice under normal and saline conditions. Despite its significance, genomic and metabolic resources for A. welwitschiae remain limited, with no complete genome information available for endophytic strains within the species. Moreover, the close relationship of this species to Aspergillus niger complicates its taxonomic resolution. We performed whole-genome and transcriptomic sequencing of AwOcstreb1 cultured on potato dextrose agar, along with -MS-based volatile metabolite profiling. Comparative analyses included simple sequence repeat (SSR), transposable element (TE; including starships) and carbohydrate-active enzyme (CAZyme) profiling across A. welwitschiae strains. Evolutionary relationships with A. niger were examined using average nucleotide identity (ANI) and orthologous gene clustering, supported by phylogenomic reconstruction. Genes for mycotoxin production and plant growth-promoting traits were also searched in this strain. The AwOcstreb1 genome is 37.7 Mb with 13,242 predicted genes, of which 66.6% were actively expressed under potato dextrose agar growth. The genome harbours 5,126 SSRs, 19,434 TEs and a CAZyme composition similar to other A. welwitschiae strains. Although established marker genes such as CaM and β-tubulin identify AwOcstreb1 as A. welwitschiae, whole-genome ANI and orthologous gene-based analyses place A. welwitschiae strains within the broader A. niger species complex, suggesting that it represents a population-level group rather than a clearly separated species, a view that is still not widely adopted. Synteny analysis showed that the AwOcstreb1 genes are highly collinear with those of A. niger. Genes involved in phosphate and zinc solubilization and siderophore biosynthesis were detected, whereas ochratoxin A biosynthetic genes were absent. Although the presence of fumonisin genes was detected, only a trace amount of the toxin was detected both in culture as well as rice grains. Among 172 strain-specific orthogroups, several encode intrinsically disordered, secreted or membrane-associated proteins that are potentially linked to endophytic lifestyle adaptations. Volatile metabolite profiling identified compounds such as 17-pentatriacontene, eicosane and octanal, each linked to known biological sources and potential functions, such as antifungal, antibacterial and anti-inflammatory activities. Several additional metabolites were also identified, whose biological roles need further investigation. This integrated omics study provides foundational insights into the endophytic potential and genomic distinctiveness of AwOcstreb1. This work opens new avenues for exploring A. welwitschiae for sustainable agriculture and fungal biology.

Single-cell genomics, metagenomics, and transcriptomics of Rhizophydium megarrhizum, an obligate fungal parasite of Planktothrix agardhii

Chytrids (phylum Chytridiomycota) are zoosporic fungi that play key roles as parasites of aquatic microorganisms, yet they are understudied and genomic resources for algal-infecting chytrids remain scarce. Here, we present the first comparative genomic analysis of multiple isolates of a single chytrid species (order Rhizophydiales) infecting the cyanobacterium Planktothrix agardhii. Isolates were collected from Sandusky Bay, Lake Erie, across two bloom years (2018 and 2019). Using single cell sequencing and metagenomic assembly, we generated individual genomes averaging 15.36 ± 0.12 Mbp in size with ~ 75% completeness, and a pangenome. Gene ontology analyses highlighted the presence of categories related to cellular structure, biosynthetic regulation, and interspecies interactions. As a preliminary exploration of gene expression during infection, we also performed RNA sequencing on a subset of size-sorted samples. These data suggest that chytrids consistently express high levels of cytoskeletal genes, alongside numerous hypothetical proteins, and that zoospores may upregulate carbohydrate-binding proteins implicated in host recognition. On the host side, P. agardhii showed transcriptional shifts in pathways associated with buoyancy and nutrient acquisition, patterns that could represent defensive adjustments or parasite-driven manipulation. Together, this study generates reference genomes for Planktothrix-infective chytrids, identifies conserved gene content across isolates from different bloom years, and provides preliminary transcriptomic insights into parasite and host responses. These resources lay the foundation for deeper investigations into chytrid genome evolution, infection biology, and their ecological roles in shaping cyanobacterial bloom dynamics.

From diversity to function: microbiome-mediated plant growth promotion, secondary metabolism, and antimicrobial resistance in Rauwolfia serpentina

Introduction This study presents the first metagenomic analysis of the root and rhizosphere microbiomes of Rauvolfia serpentina, an endangered medicinal plant. Metagenomic sequencing and bioinformatics analysis were used to characterize the diverse microbial communities and their functional attributes to assess the ecological and biotechnological potential of this plant-associated microbiome. Methods High-throughput Illumina sequencing and bioinformatics analysis were used to profile the microbial communities. Functional annotation was performed to identify plant growth-promoting traits using PLABASE, to predict pathways for the biosynthesis of novel bioactive compounds using antiSMASH, and to identify antimicrobial resistance genes using ResFinder. Results The analysis revealed highly diverse microbial communities in both habitats, predominantly composed of Pseudomonadota, Bacillota, and Actinomycetota, with minor but consistent contributions from archaea and eukaryotes. Functional annotation identified extensive PGPTs, including genes associated with phosphate solubilization, nitrogen fixation, siderophore-mediated iron acquisition, and stress tolerance. The rhizosphere microbiome exhibited greater metabolic versatility and stress tolerance, characterized by a higher copy number of heavy metal efflux pumps, whereas the root microbiome was enriched in genes involved in plant hormone regulation and plant-microbe interactions. A diverse array of non-ribosomal peptide synthase, polyketide synthase, and lasso peptide pathways were predicted, underscoring the potential to produce novel bioactive compounds. These distinct functional profiles demonstrates that the protected root endomicrobiome specializes in plant signalling and nutrient assimilation, while the rhizosphere microbiome, facing higher competition, specializes in nutrient acquisition and stress resilience. Conclusion These findings provide novel insights into the ecological specialization and biotechnological potential of the R. serpentina microbiome, offering significant implications for the sustainable utilization and conservation of this endangered medicinal plant.

Genome-scale insights into the metabolic landscape and evolutionary development of Bifidobacterium bifidum

Background: Bifidobacterium bifidum (B. bifidum) is an infant gut symbiont specialized in degrading host-derived glycans. Despite its relevance in early life, the species’ genomic diversity has not yet been comprehensively surveyed, and current reference collections capture only a fraction of the global B. bifidum pangenome. Methods: In this study, we reconstructed the first comprehensive pangenome of B. bifidum using 1,351 high-quality genomes, including metagenome-assembled genomes. This dataset was used for in silico comparative genomics analyses to identify species-specific genetic and functional features. In vitro transcriptomics analyses were further performed to validate and functionally characterize selected species-specific traits. Results: Comparative genomic analysis with other human-associated bifidobacteria species identified 667 B. bifidum-specific clusters of orthologous genes mostly involved in carbohydrate utilization, osmotic regulation, and host interaction. Notably, B. bifidum displays the most extensive enzymatic repertoire for host-glycan degradation, dedicating 43% of its conserved glycoside hydrolases to these substrates. We identified significant gain-of-function events, including two unique phosphotransferase systems (PTS) for disaccharide uptake. Transcriptomic profiling corroborated the functional relevance of these PTS clusters, which were significantly up-regulated during growth on human milk oligosaccharides, mucin, and N-acetylglucosamine. While the species exhibits high genomic stability, a localized divergence (average nucleotide identitiy, ANI < 98.5%) was identified in rural, non-Westernized populations, reflecting niche-specific adaptations. Conclusion: The identified genomic framework highlighted a distinct evolutionary path of B. bifidum, placing this taxon as a metabolic cornerstone in the neonatal gut via extensive metabolic specialization toward glycan hosts.

Whole genome sequencing and annotation of a non-pathogenic Fusarium brachygibbosum TZ1MST22 strain isolated from Medicago sativa in Southern Tunisian oases

MeioBIOME: A snakemake workflow for the parallel analysis of meiofaunal genomes and host-associated bacteria/archaea

Microbes closely interact with every living organism, including meiofauna (i.e., microbial eukaryotes 38 μm – 1 mm in length), and influence the development, life cycle, and evolution of diverse metazoans. Together, meiofauna and their microbiomes, collectively referred to as the holobiont, underpin biogeochemical cycles and drive decomposition of organic matter. However, our understanding of the ecological and evolutionary dynamics of meiofauna microbiomes are limited, typically owed to low-resolution 16S rRNA surveys, which cannot accurately delineate bacterial taxa. Single-specimen holobiont sequencing can help overcome the limitations of metabarcoding approaches by 1) generating metagenome-assembled genomes (MAGs) of the host microbiome and 2) recovering host single-copy genes (SCGs) to phylogenetically confirm the identity of the host organism. However, most bioinformatics pipelines for the assembly of metagenomic datasets have been developed for the assembly of high-complexity microbial communities of bulk sediment or soil samples (and cannot be used for the assembly of host genomes), rely on co-assembly approaches (which collapses strain-level genomic information of bacterial taxa), and focus on binning either prokaryotic or eukaryotic taxa. Therefore, there is a tremendous need for a computational workflow for the dual analysis of host genomes and their microbiomes. Here, we developed MeioBIOME, a modular Snakemake pipeline for the reproducible analysis of holobiont metagenomes obtained from individually sequenced microbial metazoa. We analyze publicly available single-specimen metagenomics datasets to show the utility of MeioBIOME and recover host-associated symbiont MAGs and host SCGs. Additionally, we integrate state-of-the-art binning algorithms which generate more MAGs than the DOE Joint Genome Institute metagenomic pipeline. We anticipate that MeioBIOME will facilitate studies of phylosymbiosis by generating high-quality host genome skims (to build well-supported host phylogenetic trees) and host-associated prokaryotic MAGs obtained from single specimens.