Southern Blot Research Articles

Chronic Hepatitis B Genotype C Mouse Model with Persistent Covalently Closed Circular DNA

Hepatitis B virus (HBV) can cause chronic infections, significantly increasing the risk of death from cirrhosis and hepatocellular carcinoma (HCC). A key player in chronic HBV infection is covalently closed circular DNA (cccDNA), a stable episomal form of viral DNA that acts as a persistent reservoir in infected hepatocytes and drives continuous viral replication. Despite the development of several animal models, few adequately replicate cccDNA formation and maintenance, limiting our understanding of its dynamics and the evaluation of potential therapeutic interventions targeting cccDNA. In this study, we aimed to develop a mouse model to investigate cccDNA formation and maintenance. We infected C57BL/6 mice with recombinant adeno-associated virus (rAAV) carrying a 1.3-overlength HBV genome (genotype C) and collected liver tissue at various time points to assess cccDNA levels and viral replication. Our results demonstrated the successful establishment of a chronic hepatitis B mouse model using rAAV-HBV1.3, which supported persistent HBV infection with sustained cccDNA expression in hepatocytes. Serum levels of HBsAg and HBeAg were elevated for up to 12 weeks, while alanine transaminase (ALT) levels remained within the normal range, indicating limited liver damage during this period. We confirmed HBV DNA expression in hepatocytes, and importantly, cccDNA was detected using qPCR after Plasmid-Safe ATP-Dependent DNase treatment, which selectively removes non-cccDNA forms. Additionally, Southern blot analysis confirmed the presence of cccDNA isolated using the Hirt extraction method. This established model provides a valuable platform for studying the long-term maintenance of cccDNA in chronic HBV infection and offers an important tool for testing novel therapeutic strategies aimed at targeting cccDNA.

Genomic and phenotypic characterization of ST2012 clinical Klebsiella quasipneumoniae subsp. similipneumoniae harboring blaNDM−1 in China

BackgroundKlebsiella pneumoniae has emerged as a significant pathogen that causes community and hospital infections due to its high resistance rate and transmissibility. Klebsiella pneumoniae complex is classified into three phylogroups: Klebsiella pneumoniae (KpI), Klebsiella quasipneumoniae (KpII), and Klebsiella variicola (KpIII) in classical taxonomy, but KpII and KpIII are infrequently isolated clinically. Although pathogenic KpII has been reported worldwide, the understanding of this pathogen remains limited.MethodsWhole-genome sequencing (WGS) of K. quasipneumoniae subsp. similipneumoniae ACESH00366hy was performed. Plasmid characterization was demonstrated using S1-PFGE, Southern blotting, and conjugation assays. Antimicrobial susceptibility testing was performed and interpreted according to CLSI, EUCAST, and FDA standards. The virulence of the strain was assessed using the Galleria mellonella infection assay, serum-killing assay, and biofilm formation assay. A phylogenetic tree was constructed to explore its biological evolution.ResultsThe K. quasipneumoniae subsp. similipneumoniae isolate ACESH00366hy, belonging to ST2012 and KL139, contains several resistance genes including blaNDM−1, blaSHV−12, blaOKP−B−2, and oqxAB, as well as various virulence genes including iroE, iutA, mrkABCDFHIJ, entABCDEFS, and fepABCDG. The blaNDM−1 and blaSHV−12 genes were present on the 53,624 bp IncX3 plasmid. Virulence assays showed that the virulence of ACESH00366hy was greater than that of the low-toxicity strain ATCC 700,603. Phylogenetic analysis demonstrated the emergence of ST2012 KpII-B in Asia and revealed the spread of K. quasipneumoniae subsp. similipneumoniae in humans, animals, and the environment.ConclusionThis study highlights the emergence of clinical ST2012 KpII strains harbouring blaNDM−1 via the IncX3 plasmid in China. We evaluated its resistance and virulence characteristics and performed phylogenetic analysis, thereby enhancing our understanding of its resistance and pathogenicity and contributing to the clinical surveillance of K. quasipneumoniae.

CRISPR Diagnostics for Quantification and Rapid Diagnosis of Myotonic Dystrophy Type 1 Repeat Expansion Disorders.

Repeat expansion disorders, exemplified by myotonic dystrophy type 1 (DM1), present challenges in diagnostic quantification because of the variability and complexity of repeat lengths. Traditional diagnostic methods, including PCR and Southern blotting, exhibit limitations in sensitivity and specificity, necessitating the development of innovative approaches for precise and rapid diagnosis. Here, we introduce a CRISPR-based diagnostic method, REPLICA (repeat-primed locating of inherited disease by Cas3), for the quantification and rapid diagnosis of DM1. This method, using in vitro-assembled CRISPR-Cas3, demonstrates superior sensitivity and specificity in quantifying CTG repeat expansion lengths, correlated with disease severity. We also validate the robustness and accuracy of CRISPR diagnostics in quantitatively diagnosing DM1 using patient genomes. Furthermore, we optimize a REPLICA-based assay for point-of-care-testing using lateral flow test strips, facilitating rapid screening and detection. In summary, REPLICA-based CRISPR diagnostics offer precise and rapid detection of repeat expansion disorders, promising personalized treatment strategies.

Whole genome sequencing of CRISPR/Cas9-engineered NF-κB reporter mice for validation and variant discovery

Targeted knockout, mutations, or knock-in of genomic DNA fragments in model organisms have been used widely for functional and cell-tracking studies. The desired genetic perturbation is often accomplished by recombination-based or CRISPR/Cas9-based genome engineering. For validating the intended genetic modification, a local region surrounding the targeted locus is typically examined based on enzymatic cleavage and consequent length patterns, e.g. in a Southern analysis. Despite its wide use, this approach is open to incomplete and ambiguous readouts. With decreasing costs of high-throughput sequencing, it is becoming feasible to consider a large-scale validation of a new strain after a targeted genetic perturbation. Here we describe a dataset of whole-genome sequences and the variant analysis results from four novel reporter mouse strains. This served to validate the strains and identified all the off-target effects on the genome, thereby increasing the genetic diversity of genomic sequences over those represented in the public databases for inbred mice.

Genomic characterization of a bla KPC-2-producing IncM2 plasmid harboring transposon ΔTn6296 in Klebsiella michiganensis.

Klebsiella michiganensis is an emerging hospital-acquired bacterial pathogen, particularly strains harboring plasmid-mediated carbapenemase genes. Here, we recovered and characterized a multidrug-resistant strain, bla KPC-2-producing Klebsiella michiganensis LS81, which was isolated from the abdominal drainage fluid of a clinical patient in China, and further characterized the co-harboring plasmid. K. michiganensis LS81 tested positive for the bla KPC-2 genes by PCR sequencing, with bla KPC-2 located on a plasmid as confirmed by S1 nuclease pulsed-field gel electrophoresis combined with Southern blotting. In the transconjugants, the bla KPC-2 genes were successfully transferred to the recipient strain E. coli EC600. Whole-genome sequencing and bioinformatics analysis confirmed that this strain belongs to sequence type 196 (ST196), with a complete genome comprising a 5,926,662bp circular chromosome and an 81,451bp IncM2 plasmid encoding bla KPC-2 (designated pLS81-KPC). The IncM2 plasmid carried multiple β-lactamase genes such as bla TEM-1B, bla CTX-M-3, and bla KPC-2 inserted in truncated Tn6296 with the distinctive core structure ISKpn27-bla KPC-2-ISKpn6. A comparison with 46 K. michiganensis genomes available in the NCBI database revealed that the closest phylogenetic relative of K. michiganensis LS81 is a clinical isolate from a wound swab in the United Kingdom. Ultimately, the pan-genomic analysis unveiled a substantial accessory genome within the strain, alongside significant genomic plasticity within the K. michiganensis species, emphasizing the necessity for continuous surveillance of this pathogen in clinical environments.

The characterization of an IncN-IncR fusion plasmid co-harboring blaTEM−40, blaKPC−2, and blaIMP−4 derived from ST1393 Klebsiella pneumoniae

Plasmids, as important genetic elements apart from chromosomes, often carry multiple resistance genes and various mobile genetic elements, enabling them to acquire more exogenous genes and confer additional resistance phenotypes to bacteria. Various carbapenem resistance genes are often located on IncN plasmids, and several reports have linked fusion plasmids to IncN plasmids. Therefore, this study aims to explore the emergence, molecular structure characteristics, and resistance features mediated by IncN fusion plasmids carrying multiple carbapenem resistance genes. In this study, species identification was performed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS). Polymerase chain reaction (PCR) was employed to detect the presence of carbapenem resistance genes in the strains. PCR-based replicon typing (PBRT) was used to identify IncN plasmids. Plasmids were analyzed through S1-nuclease pulsed-field gel electrophoresis (S1-PFGE), Southern blotting, conjugation experiments, and stability tests. Whole-genome sequencing (WGS) and antimicrobial susceptibility testing (AST) were conducted to characterize the target strains. Four strains containing IncN plasmids were identified: two Klebsiella pneumoniae, one Escherichia coli, and one Enterobacter cloacae, all harboring carbapenem resistance genes. Among them, two IncN plasmids (pFAHZZU7605-KPC-IMP and pFAHZZU7865-IMP) contained blaIMP−4 and exhibited similar molecular structure characteristics. Notably, the pFAHZZU7605-KPC-IMP plasmid harbored both IncN and IncR replicons. We hypothesize that the pFAHZZU7605-KPC-IMP fusion plasmid resulted from the recombination of a pFAHZZU7865-IMP-like plasmid and an IncR-like plasmid. Further analysis of the plasmid’s genetic elements revealed that insertion sequences ISKpn19 and ISKpn27 played crucial roles in the plasmid recombination and fusion process. In clinical settings, plasmids carrying different resistance genes can undergo fusion, mediated by genetic elements, thereby expanding the resistance spectrum of host bacteria. Hence, it is essential to enhance the monitoring and research of transposable elements to control the spread of multidrug-resistant bacteria.

First documentation of a clinical multidrug-resistant Enterobacter chuandaensis ST2493 isolate co-harboring blaNDM-1 and two blaKPC-2 bearing plasmids.

The increasing prevalence of carbapenem-resistant Enterobacter cloacae complex (CREC) poses great challenges to infection treatment in the clinical setting. In this study, we reported the emergence of carbapenemase in a rare species, Enterobacter chuandaensis, belonging to the Enterobacter cloacae complex (ECC). We elucidated the genetic characteristics of carbapenem-resistant isolate FAHZZU5885, co-harboring blaNDM-1 and blaKPC-2. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and average nucleotide identity (ANI) analysis were used to identify E. chuandaensis. S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and Southern blotting were used to clarify the number and size of the plasmids in FAHZZU5885. Antimicrobial phenotypes were identified by antimicrobial susceptibility testing (AST), and the characteristics of the strain were examined with whole-genome sequencing (WGS). The conjugation experiment and stability assay were conducted to verify the transferability and stability of the plasmid carrying carbapenemase-encoding genes. E. chuandaensis FAHZZU5885 was isolated from a perianal swab of a patient admitted to the ICU. This strain simultaneously carried blaNDM-1 and two blaKPC-2 genes. FAHZZU5885 was resistant to most of the tested antibiotics except for amikacin, tigecycline, and colistin. Two blaKPC-2 were located separately on two different plasmids, the ~ 120kb IncFIA-IncFII plasmid and the ~ 80kb IncR plasmid. Both plasmids shared the conserved sequence klcA-korC-ISkpn6-blaKPC-2-ISkpn27-tnpR-tnpA. The blaNDM-1-bearing plasmid had the potential to transfer and can remain stable after successive passages. In addition, the blaNDM-1 was carried on a ~ 80kb IncFII plasmid with the conserved sequence ISAba125-blaNDM-1-ble-trpF-dsbD-cutA-groS-groL. In summary, this study marks the first report of the multidrug-resistant E. chuandaensis strain FAHZZU5885 harboring two blaKPC-2-bearing plasmids, indicating the potential for the further dissemination of carbapenemase-encoding genes in novel species. The findings contribute to enhancing our understanding of CREC strains, emphasizing the need for continued and comprehensive surveillance of this species.

Asiatic acid inhibits HBV cccDNA transcription by promoting HBx degradation

BackgroundHepatitis B virus (HBV) infection is a persistent global public health problem, and curing for chronic hepatitis B (CHB) through the application of existing antiviral drugs is beset by numerous challenges. The viral protein HBx is a critical regulatory factor in the life cycle of HBV. Targeting HBx is a promising possibility for the development of novel therapeutic strategies.MethodsThe Nano-Glo® HiBiT Lysis Detection System was used to screen the herbal monomer compound library for compounds that inhibit HBx expression. Western blotting was used to examine proteins expression. Southern blotting or Northern blotting were used to detect HBV DNA or HBV RNA. ELISA was performed to detect the HBsAg level. The effect of asiatic acid on HBV in vivo was investigated by using recombinant cccDNA mouse model.ResultsAsiatic acid, an extract of Centella asiatica, significantly reduced the HBx level. Mechanistic studies demonstrated that asiatic acid may promote the degradation of HBx in an autophagy pathway-dependent manner. Subsequently, asiatic acid was found to reduce the amount of HBx bound to covalently closed circular DNA (cccDNA) microchromosomes, and repressive chromatin modifications then occurred, ultimately inhibiting cccDNA transcriptional activity. Moreover, in HBV-infected cells and a mouse model of persistent HBV infection, asiatic acid exhibited potent anti-HBV activity, as evidenced by decreased levels of HBV RNAs, HBV DNA and HBsAg.ConclusionsAsiatic acid was identified as a compound that targets HBx, revealing its potential for application as an anti-HBV agent.

Molecular characterization of the tet (M)-carrying transposon Tn7124 and plasmids in Escherichia coli isolates recovered from swine.

Here, we report the genetic features and evolutionary mechanisms of two tet (M)-bearing plasmids (pTA2 and pTA7) recovered from swine Escherichia coli isolates. The genetic profiles of pTA2 and pTA7 and corresponding transconjugants were accessed by S1 nuclease pulsed-field gel electrophoresis and Southern hybridization, followed by whole genome sequencing and bioinformatics analysis. The biological influences of pTA2 and pTA7 were determined by stability and direct competition assays. Both pTA7 and pTA2 had the IncR backbone sequences but differed in the multidrug resistance region (MDR). The MDR of pTA2 consisted of sul3, tet (M), qnrS1, bleO, oqxAB, floR, aadA1, cmlA1, aadA2, and tet (A)-tetR (A) in addition to 22 insertion sequences. Notably, pTA2 carried the novel complex Tn7124 (IS26-ctp-lp-tet (M)-hp-IS406tnp-IntI4-IS26) harboring tet (M). The fragment carrying tet (M) (IS26-ctp-lp-tet (M)-IS406 tnp-ctp-aadA1-cmlA1-aadA2-dfrA12-IntI1), named Tn6942-like, and the two resistance modules ISVsa3-VirD2-floR-lysR and tet (A)-tetR (A) were located in the MDR of pTA7. Both pTA2 and pTA7 were highly stable in E. coli DH5α cells with no fitness cost to the host or disadvantage in growth competition. These results indicate that transposons carrying tet (M) continuously integrate via mediation with an insertion sequence, which accelerates the transmission of tet (M) in E. coli isolates through integration of other drug-resistant genes, thereby posing a potential serious threat to the efficacy of clinical treatment.

Long-read genome assembly of the insect model organism Tribolium castaneum reveals spread of satellite DNA in gene-rich regions by recurrent burst events.

Eukaryotic genomes are replete with satellite DNAs (satDNAs), large stretches of tandemly repeated sequences that are mostly underrepresented in genome assemblies. Here we combined nanopore long-read sequencing with a reference-guided assembly approach to generate an improved, high-quality genome assembly, TcasONT, of the model beetle Tribolium castaneum Enriched by 45 Mb in repetitive regions, the new assembly comprises almost the entire genome sequence. We use the enhanced assembly to conduct global and in-depth analyses of abundant euchromatic satDNAs. Unexpectedly, we show the extensive spread of satDNAs in gene-rich regions, including long arrays. The sequence similarity relationships between satDNA monomers and arrays indicate a recent exchange of satDNA arrays between different chromosomes. We propose a scenario of their genome dynamics characterized by repeated bursts of satDNAs spreading through euchromatin, followed by a process of elongation and homogenization of arrays. We find that suppressed recombination on the X Chromosome has no significant effect on the spread of satDNAs but the X rather tolerates the amplification of satDNAs into longer arrays. Analyses of arrays' neighboring regions show a tendency of one satDNA to be associated with transposable-like elements. Using 2D electrophoresis followed by Southern blotting, we prove Cast satDNAs' presence in the fraction of extrachromosomal circular DNA (eccDNA). We point to two mechanisms that enable this satDNA spread to occur: transposition by transposable elements and insertion mediated by eccDNA. The presence of such a large proportion of satDNA in gene-rich regions inevitably gives rise to speculation about their possible influence on gene expression.

Transduction of Human Fetal Liver Hematopoietic CD34+ Stem and Progenitor Cells into a Cell Line by Enhancing Telomerase Activity

Background: Human fetal liver hematopoietic stem cells have proven potential as therapeutics but lack extensive research due to their limited supply. Even in vitro expanded fetal liver hematopoietic stem cells enter senescence or lose their self-renewal capacity after a few days in culture. The present study aimed to obtain a homogeneous and persistent supply of hematopoietic stem cells from the fetal liver by establishing a cell line through immortalization of cells by enhancing telomerase activity. Materials and Methods: Human fetal liver hematopoietic CD34+ stem and progenitor cells were transformed and immortalized using retroviruses carrying the human telomerase (hTERT) gene. Following transduction, telomerase activity was assessed using the TRAP assay and telomere length was examined by Southern blotting in transduced cells. Their characterization was conducted using flowcytometry to analyze the CD34+ population of hematopoietic stem cells and their colony forming potential using colony forming unit (CFU) assay. Results: After transduction with hTERT, the life span of human fetal liver hematopoietic CD34+ stem and progenitor cells were extended to 80 population doublings, without any change in cell morphology or population doubling times. Constitutive hTERT expression enhanced the replicative capacity and prevented terminal differentiation of CD34+ fetal liver hematopoietic stem and progenitor cells (FLHSPCs). Moreover, hTERT-transduced stem cells maintained their telomere length and telomerase activity. Conclusion: By introducing telomerase activity into hematopoietic stem and progenitor cells, their lifespan can be extended while maintaining stemness. These modified cells hold promise for in vitro research focused on studying hematopoietic stem cells derived from fetal liver.

Does time matter? Intraspecific diversity of ribosomal RNA genes in lineages of the allopolyploid model grass Brachypodium hybridum with different evolutionary ages

BackgroundPolyploidisation often results in genome rearrangements that may involve changes in both the single-copy sequences and the repetitive genome fraction. In this study, we performed a comprehensive comparative analysis of repetitive DNA, with a particular focus on ribosomal DNA (rDNA), in Brachypodium hybridum (2n = 4x = 30, subgenome composition DDSS), an allotetraploid resulting from a natural cross between two diploid species that resemble the modern B. distachyon (2n = 10; DD) and B. stacei (2n = 20; SS). Taking advantage of the recurrent origin of B. hybridum, we investigated two genotypes, Bhyb26 and ABR113, differing markedly in their evolutionary age (1.4 and 0.14 Mya, respectively) and which resulted from opposite cross directions. To identify the origin of rDNA loci we employed cytogenetic and molecular methods (FISH, gCAPS and Southern hybridisation), phylogenetic and genomic approaches.ResultsUnlike the general maintenance of doubled gene dosage in B. hybridum, the rRNA genes showed a remarkable tendency towards diploidisation at both locus and unit levels. While the partial elimination of 35S rDNA units occurred in the younger ABR113 lineage, unidirectional elimination of the entire locus was observed in the older Bhyb26 lineage. Additionally, a novel 5S rDNA family was amplified in Bhyb26 replacing the parental units. The 35S and 5S rDNA units were preferentially eliminated from the S- and D-subgenome, respectively. Thus, in the more ancient B. hybridum lineage, Bhyb26, 5S and 35S rRNA genes are likely expressed from different subgenomes, highlighting the complexity of polyploid regulatory networks.ConclusionComparative analyses between two B. hybridum lineages of distinct evolutionary ages revealed that although the recent lineage ABR113 exhibited an additive pattern of rDNA loci distribution, the ancient lineage Bhyb26 demonstrated a pronounced tendency toward diploidisation manifested by the reduction in the number of both 35S and 5S loci. In conclusion, the age of the allopolyploid appears to be a decisive factor in rDNA turnover in B. hybridum.

Functional characterization of chalcone reductase gene CHR3 through RNAi

In this experiment, the soybean genome "Jilin 30" was used as a template to clone the target gene CHR3 using specific primers. The sense fragment, antisense fragment, and intron of the target gene were ligated into pCAMBIA3300 through double enzyme digestion to form a stem loop structure. We then transferred the constructed RNAi vector pCAMBIA3301-CHR3 RNAi into the recipient soybean genome via Agrobacterium mediated method, specifically reducing the expression of the target gene CHR3. By genetic transformation, positive plants were obtained, and molecular biology methods such as Southern blotting, real-time quantitative PCR, isoliquiritigenin analysis, and identification of resistance to Phytophthora root rot were used to detect the expression level of the CHR3 gene in the positive plants and study its function.The RNAi expression vector pCAMBIA3300-CHR3-RNAi was successfully constructed using the sense and antisense fragments of 428 bp CHR3 gene and an intron of 110 bp was inserted to form the stem-loop structure of the RNAi vector. PCR was used to detect 6 lines of the T1 generation and 15 lines of the T2 generation. The results of Southern analysis confirmed the integration of CHR3 and marker genes into the soybean genome. The expression CHR3 gene in the T1 genotypes decreased by 13.1 to 58.3%; the expression in the root decreased by 0.9 to 47.4%; the expression in the leaf decreased by 20 to 44.2%; and the expression in the stem decreased by 7.6 to 23%. The content of isoliquiritigenin decreased by 26.7% as transgenic shoots had a lower content of isoliquiritigenin and reduced resistance to Phytophthora sojae. Bangladesh J. Bot. 53(3): 627-633, 2024 (September) Special

Four decades of soil moisture decline: a remote sensing analysis of southern ñeembucú, Paraguay (1983-2023)

Four decades of soil moisture decline: a remote sensing analysis of southern ñeembucú, Paraguay (1983-2023)

Organogenesis in a Broad Spectrum of Grape Genotypes and Agrobacterium-Mediated Transformation of the Podarok Magaracha Grapevine Cultivar.

We present data on the ability for organogenesis in 22 genotypes of grapevine and developed a direct organogenesis protocol for the cultivar Podarok Magaracha and the rootstock Kober 5BB. The protocol does not require replacement of culture media and growth regulators, and the duration is 11 weeks. The cultivation of explants occurs on modified MS medium with the addition of 2.0 mg L-1 benzyladenine and indole-3-butyric acid (0.15 mg L-1 for the rootstock Kober 5BB or 0.05 mg L-1 for the cultivar Podarok Magaracha). The direct organogenesis protocol consists of three time periods: (1) culturing explants for 2 weeks in dark conditions for meristematic bulk tissue, (2) followed by 4 weeks of cultivation in light conditions for regeneration, and (3) 5 weeks of cultivation in dark conditions for shoot elongation. Based on this protocol, conditions for the Agrobacterium-mediated transformation of the Podarok Magaracha cultivar were developed with an efficiency of 2.0% transgenic plants per 100 explants. Two stably transformed lines with integration into the genome of the pBin35SGFP plasmid construction, confirmed by Southern blotting, were obtained.

Review of the technology used for structural characterization of the GMO genome using NGS data

The molecular characterization of genetically modified organisms (GMOs) is essential for ensuring safety and gaining regulatory approval for commercialization. According to CODEX standards, this characterization involves evaluating the presence of introduced genes, insertion sites, copy number, and nucleotide sequence structure. Advances in technology have led to the increased use of next-generation sequencing (NGS) over traditional methods such as Southern blotting. While both methods provide high reproducibility and accuracy, Southern blotting is labor-intensive and time-consuming due to the need for repetitive probe design and analyses for each target, resulting in low throughput. Conversely, NGS facilitates rapid and comprehensive analysis by mapping whole-genome sequencing (WGS) data to plasmid sequences, accurately identifying T-DNA insertion sites and flanking regions. This advantage allows for efficient detection of T-DNA presence, copy number, and unintended gene insertions without additional probe work. This paper reviews the current status of GMO genome characterization using NGS and proposes more efficient strategies for this purpose.

Genome sequence of the hypervirulent ST65 Klebsiella pneumoniae isolate carrying mcr-8 from China

ObjectiveIn this study we report the complete genome sequence of a hypervirulent ST65 Klebsiella pneumoniae isolate harbouring mcr-8 from China. The aim was to investigate its molecular characteristics and resistance mechanisms. MethodsColistin-resistant hypervirulent K. pneumonia was isolated from an in-patient in China. The entire genome was sequenced on the Illumina NovaSeq 6000 System and long-read ONT Platform. De novo assembly was conducted using SPAdes and Unicycler. S1 nuclease pulsed-field gel electrophoresis, Southern blot, and antimicrobial susceptibility testing were performed. Sequence type, antimicrobial resistance, and virulence-related genes were predicted from the sequence. Circular maps of multiple plasmid comparisons were drawn by the BLAST Ring Image. ResultsThe complete genome sequence of K. pneumoniae ACESH00926 consists of one chromosome and two plasmids. ACESH00926 belongs to K2 ST65 according to multilocus sequence typing. ACESH00926 also showed high resistance to colistin (MIC >8 µg/mL). Several ARGs were identified, including the mobile colistin-resistant gene, mcr-8, which was located in an IncFIl(K)/IncFIA(HI1)-type plasmid. The larger plasmid was a pK244-like virulence plasmid that carries a series of virulence genes, such as regulators of the mucoid phenotype (rmpA and rmpA2), salmochelin siderophore biosynthesis (iroB), ABC transporter (iroC), ferric aerobactin receptor (iutA), aerobactin siderophore biosynthesis protein (iucC), and aerobactin synthetase (iucA)-encoded genes, in addition to another plasmid carrying mcr-8 with a conserved genetic context (dgkA-sasA-copR-mcr-8-ccdA-ccdB-xerD-repE-parM-umuC-lexA-klcA). ConclusionsThe necessity of monitoring a combination of colistin-resistant and hypervirulent K. pneumoniae strains in the future is emphasised in this article.

Identification and molecular analysis of watermelon chlorotic stunt virus infecting snake gourd in Saudi Arabia

Snake gourd (Trichosanthes cucumerina) plants exhibiting typical begomovirus-like symptoms of stunted growth, leaf yellowing and mottling were observed at an open field in the Eastern region of Saudi Arabia. Sequencing analysis of the amplified complete DNA molecules revealed that the plants were infected with watermelon chlorotic stunt virus (WmCSV), which is a bipartite begomovirus prevalent mostly in the Old World and a serious threat to cucurbit production in the Arabian Peninsula, Middle East and Africa. The two WmCSV DNA-A isolates (SG31A and SG52A) were 98.9% identical and showed their highest nucleotide (nt) sequence identities (98.7%) with the isolates from Iran and Saudi Arabia. The DNA-B isolates (SG31B and SG52B), on the other hand, were 97.4% identical and exhibited their highest nt sequence identities (99.5 and 97%) with isolates reported from Iran and Oman. In the phylogenetic dendrograms the identified isolates clustered closely with previously reported WmCSV isolates from Iran and Saudi Arabia. Infectivity assays revealed that the DNA-A components alone could not induce infection in Nicotiana benthamiana plants however, together with DNA-B these isolates successfully caused typical begomovirus symptoms and both components were detected successfully using Southern blot hybridization. This study highlights the importance of conducting extensive future begomovirus surveillance to detect spillover events that could threaten native vegetable production in Saudi Arabia. This is crucial as begomoviruses pose a serious threat to vegetable cultivation throughout the Middle East.

Comparative evaluation of gene copy number estimation techniques in genetically modified crops: insights from Southern blotting, qPCR, dPCR and NGS.

Comparative evaluation of gene copy number estimation techniques in genetically modified crops: insights from Southern blotting, qPCR, dPCR and NGS.

Molecular diagnostics of familial hypercholesterolemia in Russia: yesterday, today and tomorrow

Familial hypercholesterolemia is a severe hereditary disease leading to the development of atherosclerosis and its complications in the form of angina pectoris, myocardial infarction, cerebral stroke, or even leading to sudden death. Since the description of the disease, the concept of it has undergone significant evolution. First, it became clear that the prevalence of this disease was significantly higher than originally thought (1:300 for heterozygous familial hypercholesterolemia and not as 1:500 as estimated earlier). Secondly, it has been established that it is not based on the pathology of the low-density lipoprotein receptor gene alone, but includes at least four monogenic forms (defects of the APOB, PCSK9, ARH genes) and may also have a multigenic nature. Thirdly, with the development of DNA analysis methods from the initially available Southern hybridization to next generation DNA sequencing, the exceptional molecular heterogeneity of familial hypercholesterolemia became obvious and, accordingly, the need to establish national spectra of mutations leading to the development of familial hypercholesterolemia was established. Researchers have moved from characterizing individual mutations to creating national registries and databases. Finally, research into the genetics of familial hypercholesterolemia has led to the emergence of new classes of cholesterol-lowering drugs. In Russia, molecular diagnostics of familial hypercholesterolemia has also undergone significant changes since the beginning of the study of familial hypercholesterolemia in 1987 and to the present, consideration of these changes formed the basis of this review.