Pathogenicity Island Research Articles

Proposition of a phagosensor with a unique Teseptimavirus SAL_R1S on a carbon nanotube platform for efficient detection of typhoid pathogen

The detection of the typhoid pathogen, Salmonella enterica serotype Typhi (S. Typhi), holds massive clinical, public health, and epidemiological significance around the globe. Conventional diagnosis relies on bacterial isolation having a set of challenges when it comes to accurate detection, therapeutic intervention and disease management. Substantial reviews and reports exist on the advantages of bacteriophage-based biosensors (phagosensors) concerning Salmonella. However, phagosensor for Salmonella Typhi point of care detection at a lower limit of detection (LOD) has yet to be reported. This study is the earliest endeavor to develop a multi-wall carbon nanotubes (MWCNTs) based electrochemical phagosensor utilizing a unique bacteriophage SAL_R1S as a biomolecular recognition element, selectively binding S. Typhi DMS_A1 at LOD of 1 CFU/ml. S. Typhi DMS_A1, retrieved from patient's blood, consists of 10 pathogenicity islands and a wide range of efflux pump genes in its whole genome, which has not yet been documented for Salmonella. Subsequent screening for its specific bacteriophage from a sewage sample pinpointed the phage SAL_R1S of class Caudoviricetes, family Autographiviridae and genus Teseptimavirus. The whole genome- and tail-fiber protein- based alignment was close to Salmonella phage Vi06 covering 88.8 % and 90 % similarity, respectively. SAL_R1S exclusively binds S. Typhi in a specific manner and also possess excellent genetic feature as a candidate for developing a highly sensitive electrochemical phagosensor. Therefore, it was covalently immobilized onto a modified SPE/MWCNT/PANI-based electrode surface, allowing charge-directed, oriented immobilization which then confirmed through scanning electron microscopy. The electrode surface was featured via field emission scanning electron microscopy, electrochemical impedance spectroscopy, and cyclic voltammetry. The pathogen detection process of the phagosensor is quick (∼ 20 min). It has exceptional selectivity for typhoid pathogens from blood, wastewater or within mixed populations, indicating the application of this proposed phagosensor in clinical settings as a rapid, alternative to available conventional detection techniques, and low-cost surveillance tool.

Roles of the components of the cag-pathogenicity island encoded type IV secretion system in Helicobacter pylori.

The Helicobacter pylori (H. pylori) cytotoxin-associated gene pathogenicity island (cagPAI) encodes 31 genes that assemble the cag type IV secretion system (T4SS) apparatus, which includes structures such as the outer membrane core complex, periplasmic ring, inner membrane complex and bacterial hairs. These proteins interact with each other to inject CagA into the host gastric epithelium. There are also individual unique functions that help H. pylori interfere with host cellular pathways, modulate the immune response and colonize the host for a long time. However, the functions of some of the proteins remain unclear. This review summarizes what is known about the structure and function of these auxiliary components and discusses their role in H. pylori pathogenesis.

H-NS is a bacterial transposon capture protein

The histone-like nucleoid structuring (H-NS) protein is a DNA binding factor, found in gammaproteobacteria, with functional equivalents in diverse microbes. Universally, such proteins are understood to silence transcription of horizontally acquired genes. Here, we identify transposon capture as a major overlooked function of H-NS. Using genome-scale approaches, we show that H-NS bound regions are transposition “hotspots”. Since H-NS often interacts with pathogenicity islands, such targeting creates clinically relevant phenotypic diversity. For example, in Acinetobacter baumannii, we identify altered motility, biofilm formation, and interactions with the human immune system. Transposon capture is mediated by the DNA bridging activity of H-NS and, if absent, more ubiquitous transposition results. Consequently, transcribed and essential genes are disrupted. Hence, H-NS directs transposition to favour evolutionary outcomes useful for the host cell.

Insights into the global genomic features of Salmonella enterica serovar Gallinarum biovars Gallinarum and Pullorum.

Characterize global genomic features of 86 genomes of Salmonella Gallinarum (SG) and Pullorum (SP), which are important pathogens causing systemic infections in poultry. All genomes harbored efflux pump encoding gene mdsA and gold tolerance genes golS and golT. Aminoglycoside (aac(6')-Ib, aadA5, aph(6)-Id, aph(3'')-Ib, ant(2'')-Ia), beta-lactam (blaTEM-1, blaTEM-135), efflux pump (mdsB), fosfomycin (fosA3), sulfonamide (sul1, sul2), tetracycline [tet(A)], trimethoprim (dfrA17), acid (asr), and disinfectant (qacEdelta1) resistance genes, gyrA, gyrB, and parC quinolone resistance point mutations, and mercury tolerance genes (mer) were found in different frequencies. Additionally, 310 virulence genes, pathogenicity islands (including SPI-1, 2, 3, 4, 5, 6, 9, 10, 12, 13, and 14), plasmids [IncFII(S), ColpVC, IncX1, IncN, IncX2, and IncC], and prophages (Fels-2, ST104, 500465-1, pro483, Gifsy-2, 103203_sal5, Fels-1, RE-2010, vB_SenS-Ent2, and L-413C) were detected. MLST showed biovar-specific sequence types, and core genome MLST showed country-specific and global-related clusters. SG and SP global strains carry many virulence factors and important antimicrobial resistance genes. The diverse plasmids and prophages suggest genetic variability. MLST and cgMLST differentiated biovars and showed profiles occurring locally or worldwide.

Transcriptional regulator MarT negatively regulates MarT-regulated motility gene I, a new gene involved in invasion and virulence of Salmonella enterica.

The speciation of Salmonella occurred by acquisition of genomic islands from other bacterial species and continued to diverge into subspecies and serovars with diferent range of host. S. enterica serovar Typhimurium (STM) is a generalist pathogen infecting hosts that include birds, mice, and humans, whilst S. enterica serovar Typhi (STY) is a restricted-host pathogen, infecting only humans. Despite their ranges of hosts, STM and STY possess 97-98% identity. Gain of genes by horizontal transference and loss of genes by mutations, are believed essential for differentiation of Salmonella. Salmonella pathogenicity island 3 (SPI-3) is an example combining these two processes. SPI-3 encodes misL and marT, among other genes. In STM, misL is required for gut colonization. Furthermore, protein MarT, positively regulates expression of misL by binding to misL-promoter. On the other hand, in SPI-3 of STY, marT and misL are pseudogenes. Interestingly, the gene t3766 (gene involved in resistance to H2O2) is present only in STY and is negatively regulated when marT STM is heterologously expressed in STY. Based on the view that MarT might regulate genes implicated in virulence, this work searched for new genes regulated by MarT. In silico searches for possible MarT target genes were performed, and 4 genes were selected for further analysis as they contained at least 2 copies of the consensus MarT-binding sequence in their promoters. Mutating marT in STM or heterologously expressing marT STM in STY confirmed that MarT negatively regulates ORF STY1408 or STM14_2003, its homologue in STM. STY1408 encodes for a putative protein with homology to methyl accepting chemotaxis proteins, which participate in chemotaxis and motility. Therefore, STY1408 was named mrmI (MarT-regulated motility gene I). Motility assays confirmed that the product of mrmI modulates motility. In addition, in vitro infection of cells with STM and STY mutants in mrmI reduces association with cells at 1, 3 and 24 h post-infection. Oral infection of mice showed that a mrmI null mutant was defective in producing systemic disease. Therefore, we conclude that MarT regulated mrmI, is involved in virulence of Salmonella. While pseudogenization of marT might modulate the fitness of narrow host range STY.

Potential Convergence to Accommodate Pathogenicity Determinants and Antibiotic Resistance Revealed in Salmonella Mbandaka.

Salmonella species are causal pathogens instrumental in human food-borne diseases. The pandemic survey related to multidrug resistant (MDR) Salmonella genomics enables the prevention and control of their dissemination. Currently, serotype Mbandaka is notorious as a multiple host-adapted non-typhoid Salmonella. However, its epidemic and MDR properties are still obscure, especially its genetic determinants accounting for virulence and MD resistance. Here, we aim to characterize the genetic features of a strain SMEH pertaining to Salmonella Mbandaka (S. Mbandaka), isolated from the patient's hydropericardium, using cell infections, a mouse model, antibiotic susceptibility test and comparative genomics. The antibiotic susceptibility testing showed that it could tolerate four antibiotics, including chloramphenicol, tetracycline, fisiopen and doxycycline by Kirby-Bauer (K-B) testing interpreted according to the Clinical and Laboratory Standards Institute (CLSI). Both the reproducibility in RAW 264.7 macrophages and invasion ability to infect HeLa cells with strain SMEH were higher than those of S. Typhimurium strain 14028S. In contrast, its attenuated virulence was determined in the survival assay using a mouse model. As a result, the candidate genetic determinants responsible for antimicrobial resistance, colonization/adaptability and their transferability were comparatively investigated, such as bacterial secretion systems and pathogenicity islands (SPI-1, SPI-2 and SPI-6). Moreover, collective efforts were made to reveal a potential role of the plasmid architectures in S. Mbandaka as the genetic reservoir to transfer or accommodate drug-resistance genes. Our findings highlight the essentiality of antibiotic resistance and risk assessment in S. Mbandaka. In addition, genomic surveillance is an efficient method to detect pathogens and monitor drug resistance. The genetic determinants accounting for virulence and antimicrobial resistance underscore the increasing clinical challenge of emerging MDR Mbandaka isolates, and provide insights into their prevention and treatment.

Unusual Case of 20year Male-Resistant Typhoid Fever

A very common infectious disease but still emerging as extensive resistant known as resistant typhoid fever, caused by gram negative Salmonella enterica serovar Typhi(S.Typhi). This bacteria invades human cells by evading host defence system with the help of virulence plasmids and clustered genes called as salmonella pathogenicity islands(SPIs).These factor help bacteria to bind with plasmid mediated antimicrobial resistance gene and enable bacterium to become resistant strain or extensively resistant. After usage of multiple drugs for enteric fever made us to introduce tetracycline as last resort drug.

Vibrio cholerae pathogenicity island 2 encodes two distinct types of restriction systems.

Defense systems are immunity systems that allow bacteria to counter the threat posed by bacteriophages and other mobile genetic elements. Although these systems are numerous and highly diverse, the most common types are restriction enzymes that can specifically recognize and degrade non-self DNA. Here, we show that the Vibrio pathogenicity island 2, present in the pathogen Vibrio cholerae, encodes two types of restriction systems that use distinct mechanisms to sense non-self DNA. The first system is a classical Type I restriction-modification system, and the second is a novel modification-dependent type IV restriction system that recognizes hypermodified cytosines. Interestingly, these systems are embedded within each other, suggesting that they are complementary to each other by targeting both modified and non-modified phages.

Genetic Characteristics of Multidrug-Resistant Salmonella Isolated from Poultry Meat in South Korea.

Given the lack of genetic characterization data for multidrug-resistant (MDR) Salmonella in South Korean poultry, we analyzed 53 MDR Salmonella strains from 1232 poultry meat samples (723 chicken, 509 duck) using whole-genome sequencing. Five serotypes were identified: S. Infantis (30/53, 56.6%), S. Enteritidis (11/53, 20.8%), S. Virchow (9/53, 17.0%), S. Agona (2/53, 3.8%), and S. Indiana (1/53, 1.9%). Sequence types (STs) included ST32, ST11, ST16, ST13, and ST17, with three major clusters, each having two subclusters. Eight core genome sequence types (cgSTs) were identified: 225993, 2268, 58360, 150996, 232041, 96964, 117577, and 267045. Salmonella Infantis and S. Enteritidis had two (117577, 267045) and three (225993, 2268, 58360) cgSTs, respectively, whereas S. Virchow showed allelic differences in identical cgSTs. The S. Enteritidis subcluster was classified as chicken or duck. Twenty-eight antimicrobial resistance genes (ARGs), 10 plasmid replicons, 11 Salmonella pathogenicity islands (SPIs), and 230 virulence genes were identified, showing distinct profiles by cluster and subcluster. Salmonella Infantis, the primary MDR Salmonella, carried the IncFIB (pN55391) plasmid, 10-11 ARGs, nine SPIs, and approximately 163 virulence genes. Three major MDR Salmonella serotypes (S. Infantis, S. Enteritidis, and S. Virchow) had specific genetic profiles that can inform epidemiological surveillance.

Staphylococcal Enterotoxins: Description and Importance in Food.

Staphylococcus aureus stands out as one of the most virulent pathogens in the genus Staphylococcus. This characteristic is due to its ability to produce a wide variety of staphylococcal enterotoxins (SEs) and exotoxins, which in turn can cause staphylococcal food poisoning (SFP), clinical syndromes such as skin infections, inflammation, pneumonia, and sepsis, in addition to being associated with the development of inflammation in the mammary glands of dairy cattle, which results in chronic mastitis and cell necrosis. SEs are small globular proteins that combine superantigenic and emetic activities; they are resistant to heat, low temperatures, and proteolytic enzymes and are tolerant to a wide pH range. More than 24 SE genes have been well described (SEA-SEE, SEG, SEH, SEI, SEJ, SElK, SElL, SElM, SElN, SElO, SElP, SElQ, SElR, SElS, SElT, SElU, SElV, SElW, SElX, SElY, and SElZ), being a part of different SFP outbreaks, clinical cases, and isolated animal strains. In recent years, new genes (sel26, sel27, sel28, sel31, sel32, and sel33) from SEs have been described, as well as two variants (seh-2p and ses-3p) resulting in a total of thirty-three genes from Ses, including the nine variants that are still in the process of genetic and molecular structure evaluation. SEs are encoded by genes that are located in mobile genetic elements, such as plasmids, prophages, pathogenicity islands, and the enterotoxin gene cluster (egc), and housed in the genomic island of S. aureus. Both classical SEs and SE-like toxins (SEls) share phylogenetic relationships, structure, function, and sequence homology, which are characteristics for the production of new SEs through recombination processes. Due to the epidemiological importance of SEs, their rapid assessment and detection have been crucial for food security and public health; for this reason, different methods of identification of SEs have been developed, such as liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS), molecular methods, and whole-genome sequencing; providing the diagnosis of SEs and a better understanding of the occurrence, spread, and eradication of SEs. This review provides scientific information on the enterotoxins produced by S. aureus, such as structural characteristics, genetic organization, regulatory mechanisms, superantigen activity, mechanisms of action used by SEs at the time of interaction with the immune system, methods of detection of SEs, and recent biocontrol techniques used in food.

Unveiling the High Diversity of Clones and Antimicrobial Resistance Genes in Escherichia coli Originating from ST10 across Different Ecological Niches.

In this pioneering in silico study in Peru, we aimed to analyze Escherichia coli (E. coli) genomes for antimicrobial resistance genes (ARGs) diversity and virulence and for its mobilome. For this purpose, 469 assemblies from human, domestic, and wild animal hosts were investigated. Of these genomes, three were E. coli strains (pv05, pv06, and sf25) isolated from chickens in our previous study, characterized for antimicrobial susceptibility profile, and sequenced in this study. Three other genomes were included in our repertoire for having rare cgMLSTs. The phenotypic analysis for antimicrobial resistance revealed that pv05, pv06, and sf25 strains presented multidrug resistance to antibiotics belonging to at least three classes. Our in silico analysis indicated that many Peruvian genomes included resistance genes, mainly to the aminoglycoside class, ESBL-producing E. coli, sulfonamides, and tetracyclines. In addition, through Multi-locus Sequence Typing, we found more than 180 different STs, with ST10 being the most prevalent among the genomes. Pan-genome mapping revealed that, with new lineages, the repertoire of accessory genes in E. coli increased, especially genes related to resistance and persistence, which may be carried by plasmids. The results also demonstrated several genes related to adhesion, virulence, and pathogenesis, especially genes belonging to the high pathogenicity island (HPI) from Yersinia pestis, with a prevalence of 42.2% among the genomes. The complexity of the genetic profiles of resistance and virulence in our study highlights the adaptability of the pathogen to different environments and hosts. Therefore, our in silico analysis through genome sequencing enables tracking the epidemiology of E. coli from Peru and the future development of strategies to mitigate its survival.

Colibactin leads to a bacteria-specific mutation pattern and self-inflicted DNA damage.

Colibactin produced primarily by Escherichia coli strains of the B2 phylogroup cross-links DNA and can promote colon cancer in human hosts. Here, we investigate the toxin's impact on colibactin producers and on bacteria cocultured with producing cells. Using genome-wide genetic screens and mutation accumulation experiments, we uncover the cellular pathways that mitigate colibactin damage and reveal the specific mutations it induces. We discover that although colibactin targets A/T-rich motifs, as observed in human colon cells, it induces a bacteria-unique mutation pattern. Based on this pattern, we predict that long-term colibactin exposure will culminate in a genomic bias in trinucleotide composition. We test this prediction by analyzing thousands of E. coli genomes and find that colibactin-producing strains indeed show the predicted skewness in trinucleotide composition. Our work reveals a bacteria-specific mutation pattern and suggests that the resistance protein encoded on the colibactin pathogenicity island is insufficient in preventing self-inflicted DNA damage.

Vibrio mimicus Lineage Carrying Cholera Toxin and Vibrio Pathogenicity Island, United States and China.

Vibrio mimicus bacteria have caused sporadic cases and outbreaks of cholera-like diarrhea throughout the world, but the association of lineages with such events is unexplored. Genomic analyses revealed V. mimicus lineages carrying the virulence factors cholera toxin and toxin coregulated pilus, one of which has persisted for decades in China and the United States.

Quorum sensing employs a dual regulatory mechanism to repress T3SS gene expression.

Vibrio campbellii utilizes the type III secretion system (T3SS) as a mechanism of pathogenesis, which is a highly studied 'injectisome' complex that delivers exotoxins into host cells during infection. The T3SS pathogenicity island in V. campbellii comprises ∼40 genes that are organized into four structural operons. In this study, we determined that quorum sensing - a method of bacterial communication - regulates T3SS genes both at the transcriptional and post-translational levels to shut down T3SS gene expression at high population densities.

Bacteriophage-driven emergence and expansion of Staphylococcus aureus in rodent populations.

Human activities such as agriculturalization and domestication have led to the emergence of many new pathogens via host-switching events between humans, domesticated and wild animals. Staphylococcus aureus is a multi-host opportunistic pathogen with a global healthcare and economic burden. Recently, it was discovered that laboratory and wild rodents can be colonised and infected with S. aureus, but the origins and zoonotic potential of rodent S. aureus is unknown. In order to trace their evolutionary history, we employed a dataset of 1249 S. aureus genome sequences including 393 of isolates from rodents and other small mammals (including newly determined sequences for 305 isolates from 7 countries). Among laboratory mouse populations, we identified multiple widespread rodent-specific S. aureus clones that likely originated in humans. Phylogeographic analysis of the most common murine lineage CC88 suggests that it emerged in the 1980s in laboratory mouse facilities most likely in North America, from where it spread to institutions around the world, via the distribution of mice for research. In contrast, wild rodents (mice, voles, squirrels) were colonized with a unique complement of S. aureus lineages that are widely disseminated across Europe. In order to investigate the molecular basis for S. aureus adaptation to rodent hosts, genome-wide association analysis was carried out revealing a unique complement of bacteriophages associated with a rodent host ecology. Of note, we identified novel prophages and pathogenicity islands in rodent-derived S. aureus that conferred the potential for coagulation of rodent plasma, a key phenotype of abscess formation and persistence. Our findings highlight the remarkable capacity of S. aureus to expand into new host populations, driven by the acquisition of genes promoting survival in new host-species.

Developing the PIP-eco: An integrated genomic pipeline for identification and characterization of Escherichia coli pathotypes encompassing hybrid forms

Pathogenic Escherichia coli (E. coli) strains are distinguished by their diverse virulence factors, which contribute to a wide spectrum of diseases. These pathogens evolve through the horizontal transfer of virulence factors, resulting in the emergence of hybrid pathotypes with complex and heterogeneous characteristics. Recognizing their profound impact on public health, this study introduces the PIP-eco pipeline, a comprehensive analytical tool designed for the precise identification and characterization of E. coli pathotypes. This PIP-eco pipeline advances beyond traditional molecular techniques by facilitating detailed analysis of both single and hybrid pathotypes. It integrates targeted marker gene analysis, virulence factor-based phylogenetic analysis, and pathogenicity islands (PAIs) profiling to elucidate the genetic diversity of E. coli pathotypes and support their accurate classification. This integrative approach enables PIP-eco to uncover connections among various E. coli pathotypes, highlight shared virulence factors, and provide insights into their evolutionary trajectories. By utilizing experimentally validated marker genes, the pipeline ensures robust identification of pathotypes, particularly those of hybrid pathotypes. Additionally, PAI analysis offers comprehensive genetic investigations, revealing strain-specific variations and potential virulence mechanisms. As a result, the PIP-eco pipeline emerges as a useful tool for dissecting the evolutionary dynamics of E. coli and characterizing complex pathotypes, addressing the critical need for accurate detection and understanding of hybrid pathotypes.

Allelic variations in the chpG effector gene within Clavibacter michiganensis populations determine pathogen host range.

Plant pathogenic bacteria often have a narrow host range, which can vary among different isolates within a population. Here, we investigated the host range of the tomato pathogen Clavibacter michiganensis (Cm). We determined the genome sequences of 40 tomato Cm isolates and screened them for pathogenicity on tomato and eggplant. Our screen revealed that out of the tested isolates, five were unable to cause disease on any of the hosts, 33 were exclusively pathogenic on tomato, and two were capable of infecting both tomato and eggplant. Through comparative genomic analyses, we identified that the five non-pathogenic isolates lacked the chp/tomA pathogenicity island, which has previously been associated with virulence in tomato. In addition, we found that the two eggplant-pathogenic isolates encode a unique allelic variant of the putative serine hydrolase chpG (chpGC), an effector that is recognized in eggplant. Introduction of chpGC into a chpG inactivation mutant in the eggplant-non-pathogenic strain Cm101, failed to complement the mutant, which retained its ability to cause disease in eggplant and failed to elicit hypersensitive response (HR). Conversely, introduction of the chpG variant from Cm101 into an eggplant pathogenic Cm isolate (C48), eliminated its pathogenicity on eggplant, and enabled C48 to elicit HR. Our study demonstrates that allelic variation in the chpG effector gene is a key determinant of host range plasticity within Cm populations.

Modulation of Salmonella virulence by a novel SPI-2 injectisome effector that interacts with the dystrophin-associated protein complex.

In Salmonella enterica, the injectisome machinery encoded by Salmonella pathogenicity island 2 (SPI-2) is conserved among the five subspecies and delivers proteins (effectors) into host cells, which are required for Salmonella virulence. The identification and functional characterization of SPI-2 injectisome effectors advance our understanding of the interplay between Salmonella and its host(s). Using an optimized method for preparing secreted proteins and a clinical isolate of the invasive non-typhoidal Salmonella enterica serovar Enteritidis strain D24359, we identified 22 known SPI-2 injectisome effectors and one new effector-SseM. SseM modulates bacterial growth during murine infection and has a sequence corresponding to a postsynaptic density-95/discs large/zonula occludens-1 (PDZ)-binding motif that is essential for interaction with the PDZ-containing host protein β-2-syntrophin and other components of the dystrophin-associated protein complex (DAPC). To our knowledge, SseM is unique among Salmonella effectors in containing a functional PDZ-binding motif and is the first bacterial protein to target the DAPC.

Genomic characterization and virulence gene profiling of Erysipelothrix rhusiopathiae isolated from widespread muskox mortalities in the Canadian Arctic Archipelago

BackgroundMuskoxen are important ecosystem components and provide food, economic opportunities, and cultural well-being for Indigenous communities in the Canadian Arctic. Between 2010 and 2021, Erysipelothrix rhusiopathiae was isolated from carcasses of muskoxen, caribou, a seal, and an Arctic fox during multiple large scale mortality events in the Canadian Arctic Archipelago. A single strain (‘Arctic clone’) of E. rhusiopathiae was associated with the mortalities on Banks, Victoria and Prince Patrick Islands, Northwest Territories and Nunavut, Canada (2010–2017). The objectives of this study were to (i) characterize the genomes of E. rhusiopathiae isolates obtained from more recent muskox mortalities in the Canadian Arctic in 2019 and 2021; (ii) identify and compare common virulence traits associated with the core genome and mobile genetic elements (i.e. pathogenicity islands and prophages) among Arctic clone versus other E. rhusiopathiae genomes; and iii) use pan-genome wide association studies (GWAS) to determine unique genetic contents of the Arctic clone that may encode virulence traits and that could be used for diagnostic purposes.ResultsPhylogenetic analyses revealed that the newly sequenced E. rhusiopathiae isolates from Ellesmere Island, Nunavut (2021) also belong to the Arctic clone. Of 17 virulence genes analysed among 28 Arctic clone isolates, four genes – adhesin, rhusiopathiae surface protein-A (rspA), choline binding protein-B (cbpB) and CDP-glycerol glycerophosphotransferase (tagF) – had amino acid sequence variants unique to this clone when compared to 31 other E. rhusiopathiae genomes. These genes encode proteins that facilitate E. rhusiopathiae to attach to the host endothelial cells and form biofilms. GWAS analyses using Scoary found several unique genes to be overrepresented in the Arctic clone.ConclusionsThe Arctic clone of E. rhusiopathiae was associated with multiple muskox mortalities spanning over a decade and multiple Arctic islands with distances over 1000 km, highlighting the extent of its spatiotemporal spread. This clone possesses unique gene content, as well as amino acid variants in multiple virulence genes that are distinct from the other closely related E. rhusiopathiae isolates. This study establishes an essential foundation on which to investigate whether these differences are correlated with the apparent virulence of this specific clone through in vitro and in vivo studies.

Molecular mechanism of plasmid elimination by the DdmDE defense system.

Seventh-pandemic Vibrio cholerae strains contain two pathogenicity islands that encode the DNA defense modules DdmABC and DdmDE. In this study, we used cryogenic electron microscopy to determine the mechanistic basis for plasmid defense by DdmDE. The helicase-nuclease DdmD adopts an autoinhibited dimeric architecture. The prokaryotic Argonaute protein DdmE uses a DNA guide to target plasmid DNA. The structure of the DdmDE complex, validated by in vivo mutational studies, shows that DNA binding by DdmE triggers disassembly of the DdmD dimer and loading of monomeric DdmD onto the nontarget DNA strand. In vitro studies indicate that DdmD translocates in the 5'-to-3' direction, while partially degrading the plasmid DNA. These findings provide critical insights into the mechanism of DdmDE systems in plasmid elimination.