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Performance of the IR Biotyper, Nanopore, and Illumina sequencing to discriminate Escherichia coli strains originating from poultry.

UNLABELLED: Escherichia coli is a highly diverse bacterial species that includes avian pathogenic E. coli (APEC), one of the most prevalent causative agents of disease in poultry worldwide. Rapid and accurate discrimination of E. coli strains is essential for outbreak management, antimicrobial resistance surveillance, and vaccine development. In this study, we compared the performance of Fourier Transform Infrared (FTIR) spectroscopy using the IR Biotyper system with Nanopore and Illumina whole-genome sequencing (WGS) for typing 200 E. coli isolates, originating from four poultry rearing farms in the Netherlands. From each farm, we sampled 10 one-day-old meat type rearing chicks, and from every chick, we isolated 5 E. coli strains. FTIR clustering showed strong concordance with WGS-based classifications, particularly serotyping and core-genome similarity determined by PopPUNK analysis (Adjusted Rand Index 0.75-0.92). While Nanopore and Illumina sequencing provided the highest genetic resolution, FTIR offered a faster (max 6 vs 12-28 days for 200 isolates) and more cost-effective alternative for assessing clonality. Across all methods, multiple strains were detected per farm, whereas most birds carried a single dominant E. coli strain. Our findings demonstrate that FTIR provides a reliable and scalable phenotypic method for rapid strain discrimination in E. coli, complementing WGS in diagnostic, surveillance, and epidemiological settings where speed and throughput are critical. IMPORTANCE: Escherichia coli is a major pathogen in poultry and a potential zoonotic risk for humans. Rapid and accurate discrimination of avian pathogenic E. coli (APEC) strains is critical for outbreak management, antimicrobial resistance surveillance, and the design of effective autogenous vaccines. In this study, we compared Fourier Transform Infrared (FTIR) spectroscopy with Nanopore and Illumina whole-genome sequencing for strain typing of E. coli isolates originating from poultry. The results show that FTIR provides comparable clustering accuracy to genomic approaches at a fraction of the time and costs. This work demonstrates that FTIR can serve as a practical, high-throughput alternative for routine monitoring of E. coli in veterinary diagnostics and food safety of poultry meat, enabling faster decision-making and more targeted interventions across the poultry production chain.

Animals

TGIRT-seq to profile tRNA-derived RNAs and associated RNA modifications.

RNA modifications are key regulators for RNA processes. tRNA-derived RNAs are small RNAs with size between 15 and 50 bases long that are processed from mature or precursor tRNAs. Despite their more recent discovery, tRNA-derived RNAs have been found to play regulatory roles in many cellular processes including gene silencing, protein synthesis, stress response, and transgenerational inheritance. Furthermore, tRNA-derived RNAs are highly abundant in bodily fluids, posing as potential biomarkers. A unique feature of tRNA-derived RNAs is that they are rich in RNA modifications. Many of the RNA modifications on tRNA-derived RNAs disrupt Watson-Crick base pairing and will thus stall reverse transcriptase, such as N1-methyladenosine (m1A), N1-methylguanosine (m1G) and N2, N2-dimethylguanosine (m22G). These RNA modifications add another layer of regulation onto tRNA-derived RNAs' functions and are of interests for future research. However, these RNA modifications could also lead to lower detection of modification-containing RNAs in genome-wide small RNA sequencing analysis due to reverse transcriptase stall. To circumvent this bias, TGIRT (Thermostable Group II Intron Reverse Transcriptase) has been used to readthrough RNA modifications inserting mismatches. These mismatch signatures can then be used to precisely map the modification sites at base resolution. Here we describe the step-by-step experimental protocol to start with purified RNAs from cells or tissues and use TGIRT to make small RNA sequencing library for Illumina sequencing to profile the abundance of tRNA-derived RNAs and the associated RNA modifications.

RNA, Transfer

Genomic and functional characterization of ST11-KL64 hypervirulence-associated carbapenem-resistant Klebsiella pneumoniae co-harboring bla KPC-2 and bla NDM-13.

BACKGROUND: Hypervirulence-associated carbapenem-resistant Klebsiella pneumoniae (hv-CRKP) is a major clinical and public health threat. However, ST11-KL64 hv-CRKP co-harboring bla KPC-2 and bla NDM-13 remains poorly characterized, particularly regarding genomic relatedness, plasmid dynamics, and attenuated virulence-associated phenotypes. METHODS: We retrospectively investigated clinical K. pneumoniae isolates collected at a tertiary hospital in Chengdu, China, between January and December 2024. Hypervirulence-associated markers were screened by PCR, followed by antimicrobial susceptibility testing and carbapenemase inhibitor enhancement assay to identify genotype-defined hv-CRKP. All isolates were subjected to molecular typing. ST11-KL64 isolates co-harboring bla KPC-2 and bla NDM-13 were subjected to Illumina sequencing, with the representative isolate K3 undergoing hybrid whole-genome sequencing and functional characterization. RESULTS: Among the 46 hvKP isolates recovered from 43 patients, 35 were identified as hv-CRKP, predominantly ST11-KL64. Three ST11-KL64 hv-CRKP isolates co-harbored bla KPC-2/bla NDM-13, and Illumina sequencing coupled with core-genome SNP (cgSNP) typing revealed minimal genetic variation. The expanded cgSNP analysis supported close relatedness between K3 and Beijing isolate K56649. K3 carried a pLVPK-like virulence plasmid, a bla KPC-2-bearing IncFII/IncR plasmid, and a bla NDM-13-bearing IncI1 plasmid. Relative to pK2044, K3 exhibited an rmpA-proximal ISKpn26-associated insertion and a complex alteration of the 5'-terminal coding region of rmpA. The bla NDM-13 plasmid was conjugatively transferred to Escherichia coli C600 with a mean conjugation frequency of 5.213 × 10-3 transconjugants per recipient cell and bla NDM-13 maintained high stability following approximately 100 generations of antibiotic-free passage, whereas bla KPC-2 was not detected under the tested conditions. Phenotypically, K3 showed a negative string test, low mucoviscosity, and attenuated virulence-associated phenotypes. CONCLUSION: Our results reveal that the three isolates formed a closely related local genomic cluster, among which K3 was closely related to the K56649 clone. In addition, K3 exhibited conjugative transfer capacity of the bla NDM-13-bearing IncI1 plasmid, and alterations at the rmpA locus accompanied by reduced rmpA transcript abundance were associated with low mucoviscosity.

IncI1 plasmid

A chromosome-level reference genome assembly of the Small snakehead (Channa asiatica).

The Small snakehead (Channa asiatica) is an economically important species in both aquaculture and ornamental trade, mainly distributed in South China and Southeast Asia. Despite its significance, limited genomic resources have impeded in-depth genetic studies and breeding programs. In this study, we used PacBio HiFi long-read sequencing, Illumina short-read sequencing, and Hi-C technologies to generate a high-quality chromosome-level genome of the C. asiatica. The final genome spans 659.44 Mb, with an impressive 98.18% anchored to 23 chromosomes. Notably, the contig N50 and scaffold N50 are 23.92 Mb and 29.61 Mb, validated by a BUSCO completeness score of 98.93%. Genome annotation identified 26,603 protein-coding genes, 99.29% of which were confirmed by BUSCO analysis, and 93.68% were functionally annotated. Approximately 27.72% of the genome sequences were classified as repeat elements. This high-fidelity genome assembly provides a robust foundation for advancing molecular breeding, comparative genomics, and evolutionary studies of C. asiatica and related species.

Animals

The chromosome-level genome assembly and annotation of the silver-lipped pearl oyster, Pinctada maxima.

The silver-lipped pearl oyster (Pinctada maxima) is a valuable tropical aquaculture species, playing a crucial economic role in the global pearl industry. However, the lack of genomic reference limits our in-depth understanding of this species in genome-based breeding, conservation, evolution and adaptation. Here, annotated chromosome-level reference genome for P. maxima was generated by integrating PacBio long-read sequencing, Illumina short-read sequencing, and Hi-C sequencing data. The total genome size is 1,264.93&#x2009;Mb, with contig N50 and scaffold N50 of 649&#x2009;kb and 89.19&#x2009;Mb, respectively. The majority (97.94%) of the assembled genome was anchored to the 14 chromosomes by Hi-C analysis. The relatively high genome completeness was observed, with 97.38% (metazoa_odb10 database) and 95.26% (mollusca_odb10 database) in BUSCO analysis. Genome annotation revealed approximately 65.46% of the repeat sequences and 26,315 protein-coding genes. Comparative genome analysis revealed 28 expanded and 48 contracted families (p&#x2009;<&#x2009;0.05) in P. maxima, with 3.2% of genes (894) being species-specific. This chromosome-level genome serves as an essential resource for research in evolutionary genomics, phylogenetics, and biomineralization.

Animals

Genomic signatures of cold adaptation in a Himalayan drosophilid.

Drosophila nepalensis is a cold-adapted drosophilid endemic to the Himalayan region. Its ability to survive in harsh, cold conditions makes it a valuable Drosophila model for investigating how adaptation to thermal extremes may influence species persistence under future climate change. Here, we report the first de novo genome assembly of D. nepalensis, based on a hybrid sequencing strategy that combines Illumina short reads and Oxford Nanopore long reads. Illumina sequencing generated 49.88 million 150&#x2005;bp paired-end reads (&#x223c;14.96&#x2005;Gbp), while Nanopore sequencing produced 1.35 million long reads totaling &#x223c;0.76&#x2005;Gbp. The assembled genome spanned &#x223c;178&#x2005;Mb with an N50 of 83.6&#x2005;kb and 98% BUSCO completeness, comparable to other well-annotated Drosophila genomes. Annotation identified 10,560 protein-coding genes, including transcription factor-rich and stress-related domains such as zinc fingers, WD40 repeats, and ankyrin motifs. Comparative orthology analysis across 6 Drosophila species identified 14,168 orthologous clusters, of which 9,173 were shared among all 6 species, indicating a conserved core genomic set across the sampled taxa. D. nepalensis showed 83 unique orthogroups and 50 singletons, suggesting some lineage-specific gene expansions associated with cold adaptation and endemicity, including families encoding caspase-family apoptotic regulators, chromatin remodeling proteins (HMGB/protamine-like), and SNARE-domain vesicle trafficking factors. Gene family evolution analysis revealed the highest expansions in the cold-tolerant Himalayan drosophilid, D. nepalensis, including significant expansions in serine protease, chaperone, and neurotransmitter transporter families, alongside dramatic contractions of core histone gene families, suggesting lineage-specific chromatin remodeling and ecological specialization.

Drosophila nepalensis

Chromosome-Level Genome Assembly of Solanum carolinense.

Horsenettle (Solanum carolinense L.) is a noxious weed widely distributed across North America and increasingly invasive in other regions. Its strong environmental adaptability, complex defense strategies, and distinctive reproductive traits make it an important model for studying plant-herbivore coevolution. However, the absence of high-quality genomic resources has limited deeper investigation into its adaptive evolutionary mechanisms. In this study, we generated a chromosome-level reference genome assembly for S. carolinense using an integrated approach combining PacBio HiFi long-read sequencing, Illumina second-generation sequencing, and Hi-C chromatin interaction scaffolding. The final genome assembly had a total length of 915.40 Mb, with a contig N50 of 51.06 Mb and a scaffold N50 of 73.17 Mb; 96.05% of the sequences were successfully anchored onto 12 pseudochromosomes. The genome was characterized by a high proportion of repetitive sequences (73.64%) and substantial heterozygosity (1.13%), consistent with a highly repetitive and moderately high heterozygous genome. BUSCO analysis indicated that the chromosome-level genome assembly of S. carolinense reached a completeness score of 94.8%. A total of 32,206 protein-coding genes were annotated, of which 97.95% received functional annotations. The evaluation of the annotated protein-coding gene set returned a completeness value of 94.9%. This reference genome provides a valuable resource for advancing research on the adaptive evolution of weedy Solanaceae species, supports the development of more effective management strategies for this troublesome species, and offers a technical reference for assembling other highly heterozygous weed genomes.

Solanum carolinense

Next-Generation Sequencing Methods for Sensitive Hepatitis B Viral Genome Analysis: A European Study.

This multicentre study investigated the utility of next-generation sequencing (NGS) to detect and generate hepatitis B virus (HBV) genomes in samples of low viral load (from 0.2 to 6207 IU/mL). 23 HBV DNA-positive plasma samples of genotypes A-E and one HBV-negative control sample were assayed blindly via 9 established NGS methods from 6 European laboratories. Methods included untargeted metagenomics, pre-enrichment by probe-capture followed by Illumina sequencing, and HBV-specific PCR pre-amplification followed by sequencing with Nanopore or Illumina. Full HBV genomes were obtained only from samples with viral loads >&#x2009;1000 IU/mL using probe-capture methods, >&#x2009;200 IU/mL using PCR-Illumina methods, >&#x2009;10 IU/mL using PCR-Nanopore methods, and in no samples using metagenomic methods. Contamination was observed in the negative control and samples with very low viral loads in PCR-based methods. Probe-capture and metagenomic methods detected additional viruses not routinely screened in blood donations, including polyomaviruses and herpesviruses; positive results were confirmed by PCR. In conclusion, NGS may delineate whole-genome sequences at low viral loads if supported by a PCR pre-amplification step. Probe-capture methods also reliably detect HBV without pre-amplification but show limited genome coverage for samples with low viral loads; they may additionally detect a wide range of blood-borne viruses.

Humans

RadiSeq: a single- and bulk-cell whole-genome DNA sequencing simulator for radiation-damaged cell models.

Objective.To build and validate a simulation framework to perform single-cell and bulk-cell whole genome sequencing simulation of radiation-exposed Monte Carlo (MC) cell models to assist radiation genomics studies.Approach.Sequencing the genomes of radiation-damaged cells can provide useful insight into radiation action for radiobiology research. However, carrying out post-irradiation sequencing experiments can often be challenging, expensive, and time-consuming. Although computational simulations have the potential to provide solutions to these experimental challenges, and aid in designing optimal experiments, the absence of tools currently limits such application. MC toolkits exist to simulate radiation exposures of cell models but there are no tools to simulate single- and bulk-cell sequencing of cell models containing radiation-damaged DNA. Therefore, we aimed to develop a MC simulation framework to address this gap by designing a tool capable of simulating sequencing processes for radiation-damaged cells. Main results.We developed RadiSeq-a multi-threaded whole-genome DNA sequencing simulator written in C++. RadiSeq can be used to simulate Illumina sequencing of radiation-damaged cell models produced by MC simulations. RadiSeq has been validated through comparative analysis, where simulated data were matched against experimentally obtained data, demonstrating reasonable agreement between the two. Additionally, it comes with numerous features designed to closely resemble actual whole-genome sequencing. RadiSeq is also highly customizable with a single input parameter file.Significance.RadiSeq enables the research community to perform complex simulations of radiation-exposed DNA sequencing, supporting the optimization, planning, and validation of costly and time-intensive radiation biology experiments. This framework provides a powerful tool for advancing radiation genomics research.

Monte Carlo Method

Chromosomal-level genome assembly of Trypanosoma carassii, the etiologic agent of a recent outbreak of trypanosomiasis in cage-cultured large yellow croaker (Larimichthys crocea) in China.

Trypanosoma carassii, a typical freshwater fish trypanosome, has recently been identified as the etiological agent of a trypanosomiasis outbreak in cage-cultured large yellow croaker (Larimichthys crocea) in China and has been designated as T. c. larimichthys. To date, publicly available genomic data for trypanosomes have been limited to terrestrial species, particularly those of medical importance. Here, we present a chromosome-level genome assembly of T. carassii, the first genome of an aquatic trypanosome, generated using PacBio HiFi long-read sequencing and Hi-C scaffolding technologies. A preliminary genome survey based on Illumina sequencing data estimated the genome size at 56.38&#x2009;Mb with a heterozygosity of 1.17%. The final assembled genome spans 48.55&#x2009;Mb, with contig N50 and scaffold N50 values of 139.15 Kb, and achieves 100.00% BUSCO completeness. Hi-C data resolved the assembly into 34 chromosomes and 9 unanchored scaffolds. Repetitive elements account for 53.29% of the genome (approximately 25.87&#x2009;Mb). A total of 11,584 protein-coding genes were predicted, 95.36% of which were functionally annotated. Synonymous substitution rates analysis of paralogous genes indicates a recent burst of gene duplication, which likely corresponds to a whole-genome duplications. This high-quality genome assembly provides invaluable resources for understanding the evolution and host adaptation of aquatic trypanosomes.

Animals

The complete chloroplast genomes of Rhamnus arguta Maxim. and R. parvifolia Bunge (Rhamnaceae).

The genus Rhamnus L. (Rhamnaceae) has high medicinal, ecological, and ornamental value, but its infrageneric classification remains unclear. Here, we sequenced, assembled, and annotated the complete chloroplast genomes of Rhamnus arguta and R. parvifolia using Illumina sequencing. Both plastomes exhibit the typical quadripartite structure, with lengths of 160,566&#x2009;bp and 161,243&#x2009;bp, containing 128 and 129 genes, respectively. Phylogenetic analyses support the monophyly of Rhamnus and its close relationship with Frangula. This study provides genomic resources for further phylogenetic and comparative studies within Rhamnaceae.

Chloroplast genome

Whole-genome sequence of the type strain and two field strains of Arsenicicoccus dermatophilus causing pododermatitis in greater flamingos (Phoenicopterus roseus).

The complete genome sequence of the type strain KM894/11T and two field strains of Arsenicicoccus dermatophilus (KM18/12; KM9/12) isolated from foot skin lesions of captive greater flamingos was determined using Oxford Nanopore and Illumina sequencing technologies. The genomes differ structurally by a large ~650 kb inverted chromosomal fragment and plasmid content.

dermatitis

Oxford Nanopore Sequencing of Clinical DNA for Identification and Comparative Genomic Analysis of Erysipelothrix piscisicarius.

The genus Erysipelothrix comprises facultative anaerobic, nonspore-forming, gram-positive bacteria that can cause skin infections and severe diseases such as septicemia and endocarditis in humans. Although E. rhusiopathiae is the primary pathogen, other species may also be involved, necessitating accurate identification. However, 16S rDNA sequencing lacks sufficient resolution to differentiate among Erysipelothrix species. In this study, we used Oxford Nanopore Technology (ONT) to directly sequence low-quality DNA extracted from heart valve tissue of a 66-year-old female patient with a fatal case of septicemia and aortic endocarditis. In contrast to 16S rDNA Illumina sequencing and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), which incorrectly identified the pathogen as E. rhusiopathiae, direct sequencing via ONT precisely identified E. piscisicarius as the cause of infection. About 1.47&#x2009;Mb genome was retrieved from nanopore direct sequencing. Within the E. piscisicarius genome, we detected genes associated with virulence. Phylogenetic analysis showed that our strain clustered with a human-derived E. piscisicarius strain from China and swine-derived strains from Brazil. In conclusion, this study demonstrated that ONT can be used to sequence low-quality DNA extracted directly from patient specimens, obtain a draft bacterial genome, and reliably distinguish between pathogenic species.

Aged

Detecting Meiotic Crossing-Overs in Maize Using Chromatin Immunoprecipitation-Sequencing (ChIP-seq).

During meiosis, homologous chromosomes engage in reciprocal exchanges of segments in a process known as crossing over (CO). About 85% of CO events in maize are products of the class I pathway. Class I COs are interference-sensitive, meaning that the formation of one CO reduces the likelihood of another CO forming close by. This protocol describes a chromatin immunoprecipitation-sequencing (ChIP-seq)-based method for mapping meiotic COs in maize, using an antibody against MutL Homolog 3 (MLH3), a key component of the class I CO pathway. CO sites are determined by Illumina sequencing of DNA isolated from MLH3-associated chromatin fragments. Traditionally, COs have been identified through genetic mapping, which relies on the segregation of genetic markers in the progeny of hybrid plants. However, conventional genetic mapping provides limited resolution and requires large numbers of progeny individuals. The MLH3 ChIP-seq approach enables direct detection of COs, providing high-resolution and genome-wide coverage, including genome regions with low DNA sequence polymorphism, which are inaccessible to genetic CO mapping. Furthermore, MLH3 ChIP-seq enables screening of thousands of CO events, greatly accelerating the analysis and reducing its cost. This protocol can also be used to examine any chromatin-bound meiotic proteins and adapted to studying chromatin-associated proteins in somatic cells.

Journal Article

Whole genome sequencing-based detection of extensively drug-resistant tuberculosis from Ethiopia.

BACKGROUND: Rapid and accurate detection of extensively drug-resistant tuberculosis is crucial for effective intervention. Next-generation sequencing technologies have been recommended to rapidly and accurately detect resistance to second-line anti-TB drugs. We deployed whole-genome sequencing to detect mutations associated with drug resistance in pre-extensively drug-resistant tuberculosis and extensively drug-resistant tuberculosis strains in Ethiopia. METHODS: This report is part of the routine laboratory-based drug-resistance surveillance in Ethiopia. Among 15 pre-extensively drug-resistant tuberculosis and extensively drug-resistant tuberculosis isolates identified during the study period, eleven isolates were retrieved by Whole-genome sequencing. Illumina NextSeq 550 instruments were used to generate genomic data. Lineage and drug-resistance prediction were performed with Tuberculosis Profiler, while phylogeny was conducted by IQ-tree. RESULTS: Of the genotyped isolates, whole-genome sequencing identifies five extensively drug-resistant tuberculosis and four pre-extensively drug-resistant tuberculosis strains. It detects fluoroquinolone resistance mutations gyrA (Ala90Val, Asp94Tyr, Asp94Gly). Bedaquiline resistance mutations are found in atpE (Glu61Asp) and Rv0678 (139dupG, 141 and 142dupTC). Cross-resistance is identified between bedaquiline and clofazimine (n&#x2009;=&#x2009;4) and delamanid and pretomanid (n&#x2009;=&#x2009;1). Concordance result is observed between phenotypic drug-susceptibility testing and whole-genome sequencing for eight cases, while three cases are discordant (fluoroquinolones, delamanid, and pretomanid). Phylogenetic analysis reveals three major lineages: Lineage 4 (Euro-American, n&#x2009;=&#x2009;6 isolates), Lineage 3 (East African-Indian, n&#x2009;=&#x2009;3 isolates), and Lineage 1 (Indo-Oceanic, n&#x2009;=&#x2009;2 isolates). CONCLUSIONS: Whole-genome sequencing identifies dominant mutations in genes such as gyrA, atpE, and Rv067 that are associated with resistance to second-line anti-tuberculosis drugs. Significant cross-resistance is observed between key second-line drugs, bedaquiline and clofazimine, as well as delamanid and pretomanid. This finding highlights the need for routine genomic surveillance to detect drug resistance early, improve treatment outcomes, and prevent transmission.

Journal Article

Complete genome sequence and genomic characterization of the probiotic Limosilactobacillus reuteri PSC102.

BACKGROUND: Gut microbiota are potential sources of probiotics and play an essential role in maintaining intestinal health. Limosilactobacillus reuteri PSC102 (L. reuteri PSC102), which was isolated from the feces of healthy pigs, exhibited health-beneficial properties. AIM: We aimed to conduct a whole-genome sequencing analysis of L. reuteri PSC102 to determine its molecular characteristics as a probiotic strain. METHODS: Limosilactobacillus reuteri PSC102 cells were cultured in De Man-Rogosa-Sharpe medium, followed by DNA extraction for genomic analysis using the PacBio-Illumina sequencing platform. The EzBioCloud software was used to perform gene assembly, and the genes were interpreted by the National Center for Biotechnology Information (NCBI) and the Glimmer program. Core and pan-genomic analyses were performed to assess the extent of functional conservation in the genomic sequence. Moreover, the NCBI database and the Basic Local Alignment Search Tool software were used to identify antimicrobial resistance genes and virulence factors. RESULTS: Limosilactobacillus reuteri PSC102 consists of a single circular chromosome with 2,048,626 bp, a guanine- cytosine of 38.9%, 18 rRNA genes, and 69 tRNA genes. Among the 1,846 protein-coding sequences, genes associated with probiotic characteristics were identified, including genes involved in host-microbe interactions, stress tolerance, biogenesis, and defense mechanisms. Furthermore, the genome of L. reuteri PSC102 comprises 2,446 pan-genome and 1,222 core-genome orthologous gene clusters. A total of 74 unique genes were identified in L. reuteri PSC102 genome. These genes mostly encode proteins potentially involved in the transport and metabolism of amino acids and carbohydrates. Moreover, antibacterial resistance genes and virulence factors were absent in L. reuteri PSC102. CONCLUSION: The results of the molecular insight into L. reuteri PSC102 corroborates its use as a probiotic in humans and other animals.

Limosilactobacillus reuteri

Evaluation of one-step amplicon-based targeted enrichment for SARS-CoV-2 whole-genome sequencing using the Midnight amplicon scheme.

Genomic surveillance proved invaluable during the COVID-19 pandemic for tracking SARS-CoV-2 variants and guiding outbreak responses, underscoring the ongoing need to reduce whole-genome sequencing (WGS) costs and improve workflow efficiency to ensure accessibility in resource limited settings. Here, we evaluated a one-step reverse transcription polymerase chain reaction (RT-PCR) approach using the Midnight V2 primer scheme for targeted amplification of the SARS-CoV-2 genome, assessed its compatibility with Illumina sequencing, and compared its performance to a well-established two-step method. Initially, we determined optimal RT-PCR reaction conditions using the Midnight V2 primer panel for the one-step RT-PCR kit and scaled reaction volumes for both RT-PCR and library preparation. Clinical specimens (n&#x202f;=&#x202f;53) that had undergone routine WGS for surveillance purposes using the established two-step RT-PCR method were compared using the one-step RT-PCR assay. For samples with genome completeness greater than 70%, both methods gave comparable results with similar sequence coverage and 100% concordance for lineage assignment. Further investigation revealed a higher percentage of reads aligning to the SARS-CoV-2 genome with a greater depth of coverage using the one-step method compared to the two-step method. Finally, analysis of scaled one-step and library reaction volumes revealed significant cost savings for samples undergoing WGS. Overall, the results presented here verify the accuracy and reproducibility of one-step targeted amplification and offer an efficient and cost-effective workflow for routine SARS-CoV-2 genomic surveillance.

Humans

Columba: fast approximate pattern matching with optimized search schemes.

MOTIVATION: Aligning sequencing reads to reference genomes is a fundamental task in bioinformatics. Aligners can be classified as lossy or lossless: lossy aligners prioritize speed by reporting only one or a few high-scoring alignments, whereas lossless aligners output all optimal alignments, ensuring completeness and sensitivity. RESULTS: This paper introduces Columba, a high-performance lossless aligner tailored for Illumina sequencing data. Columba processes single or paired-end reads in FASTQ format and outputs alignments in SAM format. By utilizing advanced search schemes and bit-parallel alignment techniques, Columba achieves exceptional speed. Columba is available in two variants. The first, based on the bidirectional FM-index, prioritizes speed. The second, Columba RLC, uses run-length compression using a bidirectional move structure, significantly reducing memory usage for large, repetitive datasets like pan-genomes. Benchmarks on the human genome, as well as bacterial and human pan-genome datasets, demonstrate that Columba is much faster than existing lossless aligners and even competitive with lossy tools. We integrated Columba into the OptiType HLA genotyping pipeline, where it substantially reduced computational time while maintaining accuracy. These results position Columba as a versatile, state-of-the-art tool for high-sensitivity genomic analyses. AVAILABILITY AND IMPLEMENTATION: The source code of Columba is available at https://github.com/biointec/columba under AGPL license. Scripts to reproduce the benchmarks and analyses are available at https://doi.org/10.5281/zenodo.15849246.

Software