Nanopore sequencing as a revolutionary diagnostic tool for porcine viral enteric disease complexes identifies porcine kobuvirus as an important enteric virus

Enteric diseases in swine are often caused by different pathogens and thus metagenomics are a useful tool for diagnostics. The capacities of nanopore sequencing for viral diagnostics were investigated here. First, cell culture-grown porcine epidemic diarrhea virus and rotavirus A were pooled and sequenced on a MinION. Reads were already detected at 7 seconds after start of sequencing, resulting in high sequencing depths (19.2 to 103.5X) after 3 h. Next, diarrheic feces of a one-week-old piglet was analyzed. Almost all reads (99%) belonged to bacteriophages, which may have reshaped the piglet's microbiome. Contigs matched Bacteroides, Escherichia and Enterococcus phages. Moreover, porcine kobuvirus was discovered in the feces for the first time in Belgium. Suckling piglets shed kobuvirus from one week of age, but an association between peak of viral shedding (10(6.42)-10(7.01) copies/swab) and diarrheic signs was not observed during a follow-up study. Retrospective analysis showed the widespread (n = 25, 56.8% positive) of genetically moderately related kobuviruses among Belgian diarrheic piglets. MinION enables rapid detection of enteric viruses. Such new methodologies will change diagnostics, but more extensive validations should be conducted. The true enteric pathogenicity of porcine kobuvirus should be questioned, while its subclinical importance cannot be excluded

Beyond Homopolymer Errors: a Systematic Investigation of Nanopore-based DNA Sequencing Characteristics Using HLA-DQA2

Electronic, nanopore based single molecule real-time DNA sequencing technology offers very long, albeit lower accuracy reads in sharp contrast to existing next-generation sequencing methods, which offer short, high-accuracy reads in abundance. We provide a systematic review of the error characteristics of this new sequencing platform, and demonstrate the most challenging aspects in the field of whole gene sequencing through the human HLA-DQA2 gene using long-range PCR products on multiplexed samples. We consider the limitations of these errors for the applications of this technology, and also indicate prospective improvements and expected thresholds with respect to these errors

Nanopore sequencing of native adeno-associated virus (AAV) single-stranded DNA using a transposase-based rapid protocol

Radukic M, Brandt D, Haak M, Müller K, Kalinowski J. Nanopore sequencing of native adeno-associated virus (AAV) single-stranded DNA using a transposase-based rapid protocol. NAR Genomics and Bioinformatics. 2020;2(4): lqaa074.Next-generation sequencing of single-stranded DNA (ssDNA) enables transgene characterization of gene therapy vectors such as adeno-associated virus (AAV), but current library generation uses complicated and potentially biased second-strand synthesis. We report that libraries for nanopore sequencing of ssDNA can be conveniently created without second-strand synthesis using a transposase-based protocol. We show for bacteriophage M13 ssDNA that the MuA transposase has unexpected residual activity on ssDNA, explained in part by transposase action on transient double-stranded hairpins. In case of AAV, library creation is additionally aided by genome hybridization. We demonstrate the power of direct sequencing combined with nanopore long reads by characterizing AAV vector transgenes. Sequencing yielded reads up to full genome length, including GC-rich inverted terminal repeats. Unlike short-read techniques, single reads covered genome-genome and genome-contaminant fusions and other recombination events, whilst additionally providing information on epigenetic methylation. Single-nucleotide variants across the transgene cassette were revealed and secondary genome packaging signals were readily identified. Moreover, comparison of sequence abundance with quantitative polymerase chain reaction results demonstrated the technique's future potential for quantification of DNA impurities in AAV vector stocks. The findings promote direct nanopore sequencing as a fast and versatile platform for ssDNA characterization, such as AAV ssDNA in research and clinical settings

Detailed evaluation of data analysis tools for subtyping of bacterial isolates based on whole genome sequencing : Neisseria meningitidis as a proof of concept

Whole genome sequencing is increasingly recognized as the most informative approach for characterization of bacterial isolates. Success of the routine use of this technology in public health laboratories depends on the availability of well-characterized and verified data analysis methods. However, multiple subtyping workflows are now often being used for a single organism, and differences between them are not always well described. Moreover, methodologies for comparison of subtyping workflows, and assessment of their performance are only beginning to emerge. Current work focuses on the detailed comparison of WGS-based subtyping workflows and evaluation of their suitability for the organism and the research context in question. We evaluated the performance of pipelines used for subtyping of Neisseria meningitidis, including the currently widely applied cgMLST approach and different SNP-based methods. In addition, the impact of the use of different tools for detection and filtering of recombinant regions and of different reference genomes were tested. Our benchmarking analysis included both assessment of technical performance of the pipelines and functional comparison of the generated genetic distance matrices and phylogenetic trees. It was carried out using replicate sequencing datasets of high- and low-coverage, consisting mainly of isolates belonging to the clonal complex 269. We demonstrated that cgMLST and some of the SNP-based subtyping workflows showed very good performance characteristics and highly similar genetic distance matrices and phylogenetic trees with isolates belonging to the same clonal complex. However, only two of the tested workflows demonstrated reproducible results for a group of more closely related isolates. Additionally, results of the SNP-based subtyping workflows were to some level dependent on the reference genome used. Interestingly, the use of recombination-filtering software generally reduced the similarity between the gene-by-gene and SNP-based methodologies for subtyping of N. meningitidis. Our study, where N. meningitidis was taken as an example, clearly highlights the need for more benchmarking comparative studies to eventually contribute to a justified use of a specific WGS data analysis workflow within an international public health laboratory context

A simple path to complexity: horizontal gene transfer in microbial communities

This thesis delves into the pivotal role of Horizontal Gene Transfer (HGT) in microbial communities, which are vital components of ecosystems, impacting the health of organisms. Genetic variation, significantly driven by HGT, is crucial for ecosystem functioning. The study applied Quistad et al.'s established method for tracking HGT in complex microbial communities. This entailed cultivating compost-derived microbial communities on cellulose paper with the host model organism Caenorhabditis elegans. These communities were then repeatedly treated with Mobile Genetic Elements (MGEs) from other communities to facilitate HGT tracking. Following this, a streamlined and improved pipeline was successfully employed to trace HGT events between these paper-grown communities, utilizing metagenomics data. The research showed that fueling communities with MGEs influenced the fitness of their eukaryotic host, with both positive and negative effects. Microbial composition of host-associated communities remained unaffected. Although metagenomics faced challenges in tracking HGT within the nematode gut, dominant genera like Ochrobactrum and Pseudochrobactrum showed a notable inclination for gene acquisition in this environment. These genomes were effectively monitored and identified as recipients of recent HGT events facilitated by MGEs. This work highlights the value of simplified experimental setups in understanding complex microbial community dynamics and advances our knowledge of HGT's role in shaping community function