Genomic insights into Spiroplasma endosymbionts that induce male-killing and protective phenotypes in the pea aphid

The endosymbiotic bacteria Spiroplasma (Mollicutes) infect diverse plants and arthropods, and some of which induce male killing, where male hosts are killed during development. Male-killing Spiroplasma strains belong to either the phylogenetically distant Citri-Poulsonii or Ixodetis groups. In Drosophila flies, Spiroplasma poulsonii induces male killing via the Spaid toxin. While Spiroplasma ixodetis infects a wide range of insects and arachnids, little is known about the genetic basis of S. ixodetis-induced male killing. Here, we analyzed the genome of S. ixodetis strains in the pea aphid Acyrthosiphon pisum (Aphididae, Hemiptera). Genome sequencing constructed a complete genome of a male-killing strain, sAp269, consisting of a 1.5 Mb circular chromosome and an 80 Kb plasmid. sAp269 encoded putative virulence factors containing either ankyrin repeat, ovarian tumor-like deubiquitinase, or ribosome inactivating protein domains, but lacked the Spaid toxin. Further comparative genomics of Spiroplasma strains in A. pisum biotypes adapted to different host plants revealed their phylogenetic associations and the diversity of putative virulence factors. Although the mechanisms of S. ixodetis-induced male killing in pea aphids remain elusive, this study underlines the dynamic genome evolution of S. ixodetis and proposes independent acquisition events of male-killing mechanisms in insects.

difficile antimicrobial resistance, spore formation, and toxin production

Clostridioides difficile is an anaerobic gastrointestinal pathogen that spreads through the environment as dormant spores. To survive, replicate, and sporulate in the host intestine, C. difficile must adapt to a variety of conditions in its environment, including changes in pH, the availability of metabolites, host immune factors, and a diverse array of other species. Prior studies showed that changes in intestinal conditions, such as pH, can affect C. difficile toxin production, spore formation, and cell survival. However, little is understood about the specific genes and pathways that facilitate environmental adaptation and lead to changes in C. difficile cell outcomes. In this study, we investigated two genes, CD2505 and CD2506, that are differentially regulated by pH to determine if they impact C. difficile growth and sporulation. Using deletion mutants, we examined the effects of both genes (herein smrR and smrT) on sporulation frequency, toxin production, and antimicrobial resistance. We determined that SmrR is a repressor of smrRT that responds to pH and suppresses sporulation and toxin production through regulation of the SmrT transporter. Further, we showed that SmrT confers resistance to erythromycin and lincomycin, establishing a connection between the regulation of sporulation and antimicrobial resistance.IMPORTANCEClostridioides difficile is a mammalian pathogen that colonizes the large intestine and produces toxins that lead to severe diarrheal disease. C. difficile is a major threat to public health due to its intrinsic resistance to antimicrobials and its ability to form dormant spores that are easily spread from host to host. In this study, we examined the contribution of two genes, smrR and smrT, on sporulation, toxin production, and antimicrobial resistance. Our results indicate that SmrR represses smrT expression, while production of SmrT increases spore and toxin production, as well as resistance to antibiotics.

Draft genome sequences of Bacillus licheniformis strains MEZBL63 and MEZBL64 harboring the lichenysin toxin operon isolated from livestock in South Africa

Here, we report the draft genome sequences of two Bacillus licheniformis strains harboring the lichenysin operon that were isolated from healthy goat and horse in South Africa. The genomes were sequenced using Illumina MiSeq and had a length of 4,152,826 and 4,110,075 bp, respectively, with a G + C content of 46%.

Three novel multiplex PCR assays for rapid detection of virulence, antimicrobial resistance, and toxin genes in Acinetobacter calcoaceticus-baumannii complex species

The Acinetobacter calcoaceticus-baumannii (ACB) complex is an often-overlooked group of nosocomial pathogens with a significant environmental presence. Rapid molecular screening methods for virulence, antimicrobial resistance, and toxin (VAT) genes are required to investigate the potential pathogenicity of environmental isolates. This study aimed to develop and apply novel ACB complex-specific multiplex PCR (mPCR) primers and protocols for the rapid detection of eight VAT genes. We optimized three single-tube mPCR assays using reference DNA from ACB complex and other Acinetobacter species. These assays were then applied to detect VAT genes in cultured ACB complex isolates recovered from clinical and environmental sources. Widespread detection of VAT genes in environmental isolates confirmed the validity, functionality, and applicability of these novel assays. Overall, the three newly developed ACB complex species-specific mPCR assays are rapid and simple tools that can be adopted in diagnostic and clinical lab settings. The detection of VAT genes in environmental isolates suggests that environmental niches could serve as a reservoir for potentially pathogenic ACB complex and warrants further investigation. The newly developed mPCR assays are specific, sensitive, and efficient, making them well-suited for high-throughput screening in epidemiological studies and evaluating the potential pathogenicity of ACB complex recovered from various sources.

The role of proteinaceous toxins secreted by Staphylococcus aureus in interbacterial competition

Staphylococcus aureus is highly adapted to colonization of the mammalian host. In humans the primary site of colonization is the epithelium of the nasal cavity. A major barrier to colonization is the resident microbiota, which have mechanisms to exclude S. aureus. As such, S. aureus has evolved mechanisms to compete with other bacteria, one of which is through secretion of proteinaceous toxins. S. aureus strains collectively produce a number of well-characterized Class I, II, and IV bacteriocins as well as several bacteriocin-like substances, about which less is known. These bacteriocins have potent antibacterial activity against several Gram-positive organisms, with some also active against Gram-negative species. S. aureus bacteriocins characterized to date are sporadically produced, and often encoded on plasmids. More recently the type VII secretion system (T7SS) of S. aureus has also been shown to play a role in interbacterial competition. The T7SS is encoded by all S. aureus isolates and so may represent a more widespread mechanism of competition used by this species. T7SS antagonism is mediated by the secretion of large protein toxins, three of which have been characterized to date: a nuclease toxin, EsaD; a membrane depolarizing toxin, TspA; and a phospholipase toxin, TslA. Further study is required to decipher the role that these different types of secreted toxins play in interbacterial competition and colonization of the host.

Evaluation of commercial doses of a feed additive and silymarin on broiler performance with and without CCl4-induced liver damage

Improving productive performance is a daily challenge in the poultry industry. Developing cost-effective additives and strategies that improve performance in antibiotic-free poultry production is critical to maintaining productivity and efficiency. This study evaluates the influence of a commercially available phytogenic feed additive (CA-PFA, that comprises silymarin, betaine and curcumin extracts as main ingredients) and silymarin on commercial broilers' productive performance and liver function with and without carbon tetrachloride (CCl4)-induced liver damage. The experiment was conducted in a completely randomized design, with six treatments, eight replicates, and eight birds per replicate in 18 one-day-old male broilers (Cobb Vantress 500) each; under a 3 × 2 factorial arrangement (3 diets x 2 levels of CCl4, 0 and 1 mL/kg body weight orally). The experimental treatments included 3 diets, commercially recommended doses of CA-PFA (500 mg/kg of feed; this dose provides 70 mg/kg of silymarin, besides the other active ingredients included in the formulation), silymarin (250 mg/kg of feed, containing 28% of active ingredient; this dose provides 70 mg/kg of silymarin as active ingredient) and an additive-free basal diet as a control. A standard commercial silymarin was used as a reference due to its well-known and extensively studied hepatoprotective properties that can mitigate the negative effects of CCl4 in the liver. The data were analyzed as a 2-way ANOVA, and the means showing significant (P ≤ 0.05) differences were then compared using the Post-Hoc Tukey HSD test. No interaction was detected between factors. Exposure to CCl4 had a noticeable detrimental effect on alertness, productive performance, and liver function of broilers without a significant increase in mortality. Including CA-PFA in the diet improved productive performance compared to the basal diet from day 21 to the end of the trial, on day 42. While no influence in feed intake was detected for any treatment, CA-PFA improved body weight gain (BWG) and feed conversion ratio (FCR) significantly (P < 0.05) from day 21 to the end of the trial in healthy and CCl4-exposed birds. The results show that CA-PFA supplementation improves performance parameters in broilers with and without CCl4-induced liver damage, when compared to a basal diet and the addition of a standard commercial silymarin product.

Clinical Outcomes and Management of NAAT-Positive/Toxin-Negative Clostridioides difficile Infection: A Systematic Review and Meta-Analysis

BACKGROUND

Standalone nucleic acid amplification tests (NAATs) are frequently used to diagnose Clostridioides difficile infections (CDI), although they may be unable to distinguish colonization from disease. A 2-stage algorithm pairing NAATs with toxin immunoassays (Toxin) may improve specificity. We evaluated clinical outcomes of patients who were NAAT+/Toxin+ versus NAAT+/Toxin- and treated versus untreated NAAT+/Toxin- cases through systematic review and meta-analysis.

METHODS

We searched EMBASE and MEDLINE from inception to April 1, 2023 for articles comparing CDI outcomes among symptomatic patients tested by NAAT and Toxin tests. The risk differences (RD) of all-cause mortality and CDI recurrence were computed by random effects meta-analysis between patients who were NAAT+/Toxin+ and NAAT+/Toxin-, as well as between patients who were NAAT+/Toxin- and treated or untreated.

RESULTS

Twenty-six observational studies comprising 12 737 patients were included. The 30-day all-cause mortality was not significantly different between those who were NAAT+/Toxin+ (8.4%) and NAAT+/Toxin- (6.7%) (RD = 0.41%, 95% confidence interval [CI] = -.67, 1.49). Recurrence at 60 days was significantly higher among patients who were NAAT+/Toxin+ (19.8%) versus NAAT+/Toxin- (11.0%) (RD = 7.65%, 95% CI = 4.60, 10.71). Among treated compared to untreated NAAT+/Toxin- cases, the all-cause 30-day mortalities were 5.0% and 12.7%, respectively (RD = -7.45%, 95% CI = -12.29, -2.60), but 60-day recurrence was not significantly different (11.6% vs 7.0%, respectively; RD = 5.25%, 95% CI -1.71, 12.22).

CONCLUSIONS

Treatment of patients who were NAAT+/Toxin- was associated with reduced all-cause mortality but not recurrence. Although subject to the inherent limitations of observational studies, these results suggest that some patients who are NAAT+/Toxin- may benefit from treatment.

Diverse genetic contexts of HicA toxin domains propose a role in anti-phage defense

Toxin-antitoxin (TA) modules are prevalent in prokaryotic genomes, often in substantial numbers. For instance, the Mycobacterium tuberculosis genome alone harbors close to 100 TA modules, half of which belong to a singular type. Traditionally ascribed multiple biological roles, recent insights challenge these notions and instead indicate a predominant function in phage defense. TAs are often located within Defense Islands, genomic regions that encode various defense systems. The analysis of genes within Defense Islands has unveiled a wide array of systems, including TAs that serve in anti-phage defense. Prokaryotic cells are equipped with anti-phage Viperins that, analogous to their mammalian counterparts, inhibit viral RNA transcription. Additionally, bacterial Structural Maintenance of Chromosome (SMC) proteins combat plasmid intrusion by recognizing foreign DNA signatures. This study undertakes a comprehensive bioinformatics analysis of genetic elements encoding the HicA double-stranded RNA-binding domain, complemented by protein structure modeling. The HicA toxin domains are found in at least 14 distinct contexts and thus exhibit a remarkable genetic diversity. Traditional bicistronic TA operons represent eight of these contexts, while four are characterized by monocistronic operons encoding fused HicA domains. Two contexts involve hicA adjacent to genes that encode bacterial Viperins. Notably, genes encoding RelE toxins are also adjacent to Viperin genes in some instances. This configuration hints at a synergistic enhancement of Viperin-mediated anti-phage action by HicA and RelE toxins. The discovery of a HicA domain merged with an SMC domain is compelling, prompting further investigation into its potential roles.IMPORTANCEProkaryotic organisms harbor a multitude of toxin-antitoxin (TA) systems, which have long puzzled scientists as "genes in search for a function." Recent scientific advancements have shed light on the primary role of TAs as anti-phage defense mechanisms. To gain an overview of TAs it is important to analyze their genetic contexts that can give hints on function and guide future experimental inquiries. This article describes a thorough bioinformatics examination of genes encoding the HicA toxin domain, revealing its presence in no fewer than 14 unique genetic arrangements. Some configurations notably align with anti-phage activities, underscoring potential roles in microbial immunity. These insights robustly reinforce the hypothesis that HicA toxins are integral components of the prokaryotic anti-phage defense repertoire. The elucidation of these genetic contexts not only advances our understanding of TAs but also contributes to a paradigm shift in how we perceive their functionality within the microbial world.

Identification of the toxin components of Rhizoctonia solani AG1-IA and its destructive effect on plant cell membrane structure

Rice sheath blight is a fungal disease caused mainly by Rhizoctonia solani AG1-IA. Toxins are a major pathogenic factor of R. solani, and some studies have reported their toxin components; however, there is no unified conclusion. In this study, we reported the toxin components and their targets that play a role in R. solani AG1-IA. First, toxins produced by R. solani AG1-IA were examined. Several important phytotoxins, including benzoic acid (BZA), 5-hydroxymethyl-2-furanic aid (HFA), and catechol (CAT), were identified by comparative analysis of secondary metabolites from AG1-IA, AG1-IB, and healthy rice. Follow-up studies have shown that the toxin components of this fungus can rapidly disintegrate the biofilm structure while maintaining the content of host plant membrane components, thereby affecting the organelles, which may also explain the lack of varieties highly resistant to sheath blight.

Computational exploration of the genomic assignments, molecular structure, and dynamics of the ccdABXn2 toxin-antitoxin homolog with its bacterial target, the DNA gyrase, in the entomopathogen Xenorhabdus nematophila

Toxin-antitoxin (TA) modules, initially discovered on bacterial plasmids and subsequently identified within chromosomal contexts, hold a pivotal role in the realm of bacterial physiology. Among these, the pioneering TA system, ccd (Control of Cell Death), primarily localized on the F-plasmid, is known for its orchestration of plasmid replication with cellular division. Nonetheless, the precise functions of such systems within bacterial chromosomal settings remain a compelling subject that demands deeper investigation. To bridge this knowledge gap, our study focuses on exploring ccdABXn2, a chromosomally encoded TA module originating from the entomopathogenic bacterium Xenorhabdus nematophila. We meticulously delved into the system's genomic assignments, structural attributes, and functional interplay. Our findings uncovered intriguing patterns-CcdB toxin homologs exhibited higher conservation levels compared to their CcdA antitoxin counterparts. Moreover, we constructed secondary as well as tertiary models for both the CcdB toxin and CcdA antitoxin using threading techniques and subsequently validated their structural integrity. Our exploration extended to the identification of key interactions, including the peptide interaction with gyrase for the CcdB homolog and CcdB toxin interactions for the CcdA homolog, highlighting the intricate TA interaction network. Through docking and simulation analyses, we unequivocally demonstrated the inhibition of replication via binding the CcdB toxin to its target, DNA gyrase. These insights provide valuable knowledge about the metabolic and physiological roles of the chromosomally encoded ccdABXn2 TA module within the context of X. nematophila, significantly enhancing our comprehension of its functional significance within the intricate ecosystem of the bacterial host.Communicated by Ramaswamy H. Sarma.

Proteotransciptomics of the Most Popular Host Sea Anemone Entacmaea quadricolor Reveals Not All Toxin Genes Expressed by Tentacles Are Recruited into Its Venom Arsenal

While the unique symbiotic relationship between anemonefishes and sea anemones is iconic, it is still not fully understood how anemonefishes can withstand and thrive within the venomous environment of their host sea anemone. In this study, we used a proteotranscriptomics approach to elucidate the proteinaceous toxin repertoire from the most common host sea anemone, Entacmaea quadricolor. Although 1251 different toxin or toxin-like RNA transcripts were expressed in E. quadricolor tentacles (0.05% of gene clusters, 1.8% of expression) and 5375 proteins were detected in milked venom, only 4% of proteins detected in venom were putative toxins (230), and they only represent on average 14% of the normalised protein expression in the milked venom samples. Thus, most proteins in milked venom do not appear to have a toxin function. This work raises the perils of defining a dominant venom phenotype based on transcriptomics data alone in sea anemones, as we found that the dominant venom phenotype differs between the transcriptome and proteome abundance data. E. quadricolor venom contains a mixture of toxin-like proteins of unknown and known function. A newly identified toxin protein family, Z3, rich in conserved cysteines of unknown function, was the most abundant at the RNA transcript and protein levels. The venom was also rich in toxins from the Protease S1, Kunitz-type and PLA2 toxin protein families and contains toxins from eight venom categories. Exploring the intricate venom toxin components in other host sea anemones will be crucial for improving our understanding of how anemonefish adapt to the venomous environment.

Evolutionary Analysis of Cnidaria Small Cysteine-Rich Proteins (SCRiPs), an Enigmatic Neurotoxin Family from Stony Corals and Sea Anemones (Anthozoa: Hexacorallia)

Cnidarians (corals, sea anemones, and jellyfish) produce toxins that play central roles in key ecological processes, including predation, defense, and competition, being the oldest extant venomous animal lineage. Cnidaria small cysteine-rich proteins (SCRiPs) were the first family of neurotoxins detected in stony corals, one of the ocean's most crucial foundation species. Yet, their molecular evolution remains poorly understood. Moreover, the lack of a clear classification system has hindered the establishment of an accurate and phylogenetically informed nomenclature. In this study, we extensively surveyed 117 genomes and 103 transcriptomes of cnidarians to identify orthologous SCRiP gene sequences. We annotated a total of 168 novel putative SCRiPs from over 36 species of stony corals and 12 species of sea anemones. Phylogenetic reconstruction identified four distinct SCRiP subfamilies, according to strict discrimination criteria based on well-supported monophyly with a high percentage of nucleotide and amino acids' identity. Although there is a high prevalence of purifying selection for most SCRiP subfamilies, with few positively selected sites detected, a subset of Acroporidae sequences is influenced by diversifying positive selection, suggesting potential neofunctionalizations related to the fine-tuning of toxin potency. We propose a new nomenclature classification system relying on the phylogenetic distribution and evolution of SCRiPs across Anthozoa, which will further assist future proteomic and functional research efforts.

Effect of animal venom toxins on the main links of the homeostasis of mammals (Review)

The human body is affected by environmental factors. The dynamic balance between the organism and its environment results from the influence of natural, anthropogenic and social aspects. The factors of exogenous origin determine development of adaptive changes. The present article summarises the mechanisms of animal venom toxins and homeostasis disruption in the body of mammals. The mechanisms underlying pathological changes are associated with shifts in biochemical reactions. Components of the immune, nervous and endocrine systems are key in the host defense and adaptation processes in response to venom by triggering signalling pathways (PI3kinase pathway, arachidonic acid cascade). Animal venom toxins initiate the development of inflammatory processes, the synthesis of pro-inflammatory mediators (cytokines), ROS, proteolytic enzymes, activate the migration of leukocytes and macrophages. Keratinocytes and endothelial cells act as protective barriers under the action of animal venom toxins on the body of mammals. In addition, the formation of pores in cell membranes, structural changes in cell ion channels are characteristic of the action of animal venom toxins.

Viper Venom Phospholipase A2 Database: The Structural and Functional Anatomy of a Primary Toxin in Envenomation

Viper venom phospholipase A2 enzymes (vvPLA2s) and phospholipase A2-like (PLA2-like) proteins are two of the principal toxins in viper venom that are responsible for the severe myotoxic and neurotoxic effects caused by snakebite envenoming, among other pathologies. As snakebite envenoming is the deadliest neglected tropical disease, a complete understanding of these proteins' properties and their mechanisms of action is urgently needed. Therefore, we created a database comprising information on the holo-form, cofactor-bound 3D structure of 217 vvPLA2 and PLA2-like proteins in their physiologic environment, as well as 79 membrane-bound viper species from 24 genera, which we have made available to the scientific community to accelerate the development of new anti-snakebite drugs. In addition, the analysis of the sequenced, 3D structure of the database proteins reveals essential aspects of the anatomy of the proteins, their toxicity mechanisms, and the conserved binding site areas that may anchor universal interspecific inhibitors. Moreover, it pinpoints hypotheses for the molecular origin of the myotoxicity of the PLA2-like proteins. Altogether, this study provides an understanding of the diversity of these toxins and how they are conserved, and it indicates how to develop broad, interspecies, efficient small-molecule inhibitors to target the toxin's many mechanisms of action.

Snake Bite-Induced Leukoencephalopathy: A Rare Case

Across the globe, snake envenomation causes significant morbidity and mortality. Although many clinical presentations and complications are observed in different types of snake bites, the incidence of leukoencephalopathy is rare. Although most cases of leukoencephalopathy are seen in viper bites, they are rarely seen in neurotoxic snake bites. In this report, we present a unique case of snake bite-induced leukoencephalopathy following a neurotoxic snake bite. The case highlights the importance of considering this rare complication in cases of snake bites presenting with neurological symptoms, particularly in those affecting higher mental functions.

The Usefulness of Salivary Gland Organoids for Evaluation of the Potency of Botulinum Neurotoxin

BACKGROUND AND OBJECTIVES

Botulinum neurotoxin (BoNT) is a substance used to treat chronic sialorrhea, muscle dystonia, and is used in cosmetic applications. Measuring the potency of BoNT is crucial because it acts even with a small amount. However, the current methods for measuring the potency of BoNT involve using two-dimensional neuroblastoma cell line-based methods. In this study, we aimed to develop a new method to measure the potency of BoNT using a three-dimensional organoid culture system.

MATERIALS AND METHOD

We established the optimal conditions for coculturing N2a neuronal cells with murine salivary gland organoids (SGOs). After determining the appropriate chemical concentrations, we treated the SGOs cocultured with N2a cells with BoNT type A (BoNT/A). We confirmed the expression of salivary gland-related genes and proteins using real-time polymerase chain reaction (PCR) and immunofluorescence staining.

RESULTS

The SGOs cocultured with N2a cells showed that the dendrites or axons of neuronal cells were in contact with the outermost layer of the SGOs. When we applied acetylcholine and neostigmine to the coculture systems, the mRNA expression of Aqp5 and Bhlha15, associated with salivary gland secretory cells, increased. However, this effect was reversed when BoNT/A was applied, as confirmed through real-time PCR.

CONCLUSION

We found that the coculture system of SGOs and N2a neuronal cells can potentially serve as a potency testing platform for BoNT.

LEVEL OF EVIDENCE

NA Laryngoscope, 2024.

Venomics Reveals the Venom Complexity of Sea Anemone Heteractis magnifica

The venoms of various sea anemones are rich in diverse toxins, which usually play a dual role in capturing prey and deterring predators. However, the complex components of such venoms have not been well known yet. Here, venomics of integrating transcriptomic and proteomic technologies was applied for the first time to identify putative protein and peptide toxins from different tissues of the representative sea anemone, Heteractis magnifica. The transcriptomic analysis of H. magnifica identified 728 putative toxin sequences, including 442 and 381 from the tentacles and the column, respectively, and they were assigned to 68 gene superfamilies. The proteomic analysis confirmed 101 protein and peptide toxins in the venom, including 91 in the tentacles and 39 in the column. The integrated venomics also confirmed that some toxins such as the ShK-like peptides and defensins are co-expressed in both the tentacles and the column. Meanwhile, a homology analysis was conducted to predict the three-dimensional structures and potential activity of seven representative toxins. Altogether, this venomics study revealed the venom complexity of H. magnifica, which will help deepen our understanding of cnidarian toxins, thereby supporting the in-depth development of valuable marine drugs.

Panton-Valentine leukocidin-induced neutrophil extracellular traps lack antimicrobial activity and are readily induced in patients with recurrent PVL + -Staphylococcus aureus infections

Staphylococcus aureus strains that produce the toxin Panton-Valentine leukocidin (PVL-SA) frequently cause recurrent skin and soft tissue infections. PVL binds to and kills human neutrophils, resulting in the formation of neutrophil extracellular traps (NETs), but the pathomechanism has not been extensively studied. Furthermore, it is unclear why some individuals colonized with PVL-SA experience recurring infections whereas others are asymptomatic. We thus aimed to (1) investigate how PVL exerts its pathogenicity on neutrophils and (2) identify factors that could help to explain the predisposition of patients with recurring infections. We provide genetic and pharmacological evidence that PVL-induced NET formation is independent of NADPH oxidase and reactive oxygen species production. Moreover, through NET proteome analysis we identified that the protein content of PVL-induced NETs is different from NETs induced by mitogen or the microbial toxin nigericin. The abundance of the proteins cathelicidin (CAMP), elastase (NE), and proteinase 3 (PRTN3) was lower on PVL-induced NETs, and as such they were unable to kill S. aureus. Furthermore, we found that neutrophils from affected patients express higher levels of CD45, one of the PVL receptors, and are more susceptible to be killed at a low PVL concentration than control neutrophils. Neutrophils from patients that experience recurring PVL-positive infections may thus be more sensitive to PVL-induced NET formation, which might impair their ability to combat the infection.

Construction of a Stable Expression System Based on the Endogenous hbpB/hbpC Toxin-Antitoxin System of Halomonas bluephagenesis

Halomonas bluephagenesis is a halophilic bacterium capable of efficiently producing polyhydroxyalkanoates and other valuable chemicals through high salinity open fermentation, offering an appealing platform for next-generation industrial biotechnology. Various techniques have been developed to engineer Halomonas bluephagenesis, each with its inherent shortcomings. Genome editing methods often entail complex and time-consuming processes, while flexible expression systems relying on plasmids necessitate the use of antibiotics. In this study, we developed a stable recombinant plasmid vector, pHbPBC, based on a novel hbpB/hbpC toxin-antitoxin system found within the endogenous plasmid of Halomonas bluephagenesis. Remarkably, pHbPBC exhibited exceptional stability during 7 days of continuous subculture, eliminating the need for antibiotics or other selection pressures. This stability even rivaled genomic integration, all while achieving higher levels of heterologous expression. Our research introduces a novel approach for genetically modifying and harnessing nonmodel halophilic bacteria, contributing to the advancement of next-generation industrial biotechnology.

Snakebite drug discovery: high-throughput screening to identify novel snake venom metalloproteinase toxin inhibitors

Snakebite envenoming results in ∼100,000 deaths per year, with close to four times as many victims left with life-long sequelae. Current antivenom therapies have several limitations including high cost, variable cross-snake species efficacy and a requirement for intravenous administration in a clinical setting. Next-generation snakebite therapies are being widely investigated with the aim to improve cost, efficacy, and safety. In recent years several small molecule drugs have shown considerable promise for snakebite indication, with oral bioavailability particularly promising for community delivery rapidly after a snakebite. However, only two such drugs have entered clinical development for snakebite. To offset the risk of attrition during clinical trials and to better explore the chemical space for small molecule venom toxin inhibitors, here we describe the first high throughput drug screen against snake venom metalloproteinases (SVMPs)-a pathogenic toxin family responsible for causing haemorrhage and coagulopathy. Following validation of a 384-well fluorescent enzymatic assay, we screened a repurposed drug library of 3,547 compounds against five geographically distinct and toxin variable snake venoms. Our drug screen resulted in the identification of 14 compounds with pan-species inhibitory activity. Following secondary potency testing, four SVMP inhibitors were identified with nanomolar EC50s comparable to the previously identified matrix metalloproteinase inhibitor marimastat and superior to the metal chelator dimercaprol, doubling the current global portfolio of SVMP inhibitors. Following analysis of their chemical structure and ADME properties, two hit-to-lead compounds were identified. These clear starting points for the initiation of medicinal chemistry campaigns provide the basis for the first ever designer snakebite specific small molecules.

A Streamlined Method to Obtain Biologically Active TcdA and TcdB Toxins from Clostridioides difficile

The major virulence factors of Clostridioides difficile (C. difficile) are enterotoxins A (TcdA) and B (TcdB). The study of toxins is a crucial step in exploring the virulence of this pathogen. Currently, the toxin purification process is either laborious and time-consuming in C. difficile or performed in heterologous hosts. Therefore, we propose a streamlined method to obtain functional toxins in C. difficile. Two C. difficile strains were generated, each harboring a sequence encoding a His-tag at the 3' end of C. difficile 630∆erm tcdA or tcdB genes. Each toxin gene is expressed using the Ptet promoter, which is inducible by anhydro-tetracycline. The obtained purification yields were 0.28 mg and 0.1 mg per liter for rTcdA and rTcdB, respectively. In this study, we successfully developed a simple routine method that allows the production and purification of biologically active rTcdA and rTcdB toxins with similar activities compared to native toxins.

A Review of Rattlesnake Venoms

Venom components are invaluable in biomedical research owing to their specificity and potency. Many of these components exist in two genera of rattlesnakes, Crotalus and Sistrurus, with high toxicity and proteolytic activity variation. This review focuses on venom components within rattlesnakes, and offers a comparison and itemized list of factors dictating venom composition, as well as presenting their known characteristics, activities, and significant applications in biosciences. There are 64 families and subfamilies of proteins present in Crotalus and Sistrurus venom. Snake venom serine proteases (SVSP), snake venom metalloproteases (SVMP), and phospholipases A2 (PLA2) are the standard components in Crotalus and Sistrurus venom. Through this review, we highlight gaps in the knowledge of rattlesnake venom; there needs to be more information on the venom composition of three Crotalus species and one Sistrurus subspecies. We discuss the activity and importance of both major and minor components in biomedical research and drug development.

Chronic Diarrhea Caused by a Klebsiella oxytoca Toxin Producer Strain Following Antibiotic-Associated Hemorrhagic Colitis: Successful Treatment by Fecal Microbiota Transplant

Klebsiella oxytoca is a gram-negative bacterium found in fecal microbiota and known to cause several infections in humans, including antibiotic-associated hemorrhagic colitis. We present here a case of colitis caused by K. oxytoca toxin-producing strains that evolved in chronic diarrhea successfully treated by fecal microbiota transplant.

SarS and Rot are necessary for the repression of lukED and lukSF-PV in Staphylococcus aureus

IMPORTANCE

The leukocidins play an important role in disarming the host immune system and promoting infection. While both SarS and Rot have been established as repressors of leukocidins, the importance of each repressor in infection is unclear. Here, we demonstrate that repression by SarS and Rot is not additive and show that in addition to upregulating expression of each other, they are also able to bind concurrently to the leukocidin promoters. These findings suggest that both repressors are necessary for maximal repression of lukED and lukSF-PV and illuminate another complex relationship among Staphylococcus aureus virulence regulators.

Comparison of Adjuvant Clindamycin vs Linezolid for Severe Invasive Group A Streptococcus Skin and Soft Tissue Infections

Background

Linezolid may be an option for severe group A Streptococcus (GAS) infections based on its potent in vitro activity and antitoxin effects, but clinical data supporting its use over clindamycin are limited. This study evaluated treatment outcomes in patients with severe GAS skin and soft tissue infections who received either linezolid or clindamycin.

Methods

This retrospective single-center cohort study examined patients with GAS isolated from blood and/or tissue cultures with invasive soft tissue infection or necrotizing fasciitis who underwent surgical debridement and received linezolid or clindamycin for at least 48 hours. The primary outcome was percentage change in Sequential Organ Failure Assessment (SOFA) score from baseline through 72 hours of hospitalization.

Results

After adjustment for time to first surgical intervention among patients with a baseline SOFA score >0 (n = 23 per group), there was no difference in reduction of SOFA score over the first 72 hours in patients receiving clindamycin vs linezolid. In the entire cohort (n = 26, clindamycin; n = 29, linezolid), there was no difference in inpatient mortality (2% vs 1%) or any secondary outcomes, including duration of vasopressor therapy, intensive care unit length of stay, and antibiotic-associated adverse drug events.

Conclusions

There was no difference in reduction of critical illness as measured by SOFA score between baseline and 72 hours among patients treated with clindamycin vs linezolid. Given its more favorable side effect profile, linezolid may be a viable option for the treatment of serious GAS infections and should be further studied.

Ginger blotches on Agaricus bisporus due to monoacetylphloroglucinol production by the pathogen Pseudomonas 'gingeri'

BACKGROUND

Agaricus bisporus is the most widely cultivated and consumed mushroom worldwide. Pseudomonas 'gingeri' is the only pathogenic causative agent of ginger blotch in A. bisporus. Current research on mushroom pathogenic biotoxins is limited to P. tolaasii, which causes brown blotch, while understanding of P. 'gingeri' is lacking, therefore identifying the toxins produced by P. 'gingeri' and evaluating their toxicity on A. bisporus is essential for understanding its pathogenic mechanisms.

RESULTS

A pathogenic bacterium isolated from fruiting bodies of A. bisporus with ginger blotch was identified as P. 'gingeri', and its main toxin identified as 2', 4', 6'-trihydroxyacetophenone monohydrate, also known as monoacetylphloroglucinol (MAPG). Its first known extraction from a mushroom pathogen is reported here. MAPG at 250 μg/mL significantly inhibited the host's mycelial growth, increased branching, caused the structure to become dense and resulted in folds appearing on the surface. An MAPG concentration of 750 μg/mL MAPG led to mycelial death. P. 'gingeri' had high MAPG production in medium containing 0.1 mol/L of either glucose or mannitol (4.30 and 1.85 μg/mL, respectively), and mycelia were inhibited by 69.6% and 41.1%, respectively. The MAPG content was significantly lower in other carbon source media.

CONCLUSION

This work provides a detailed description of the structure and virulence of the P. 'gingeri' biotoxin, which has implications for understanding its pathogenic mechanism and for exploring precise control strategies for A. bisporus ginger blotch disease, such as the development of MAPG inhibitory factors. © 2023 Society of Chemical Industry.

Interbacterial competition mediated by the type VIIb secretion system

Successful occupancy of a given niche requires the colonising bacteria to interact extensively with the biotic and abiotic environment, including other resident microbes. Bacteria have evolved a range of protein secretion machines for this purpose with eleven such systems identified to date. The type VIIb secretion system (T7SSb) is utilised by Bacillota to secrete a range of protein substrates, including antibacterial toxins targeting closely related strains, and the system as a whole has been implicated in a range of activities such as iron acquisition, intercellular signalling, host colonisation and virulence. This review covers the components and secretion mechanism of the T7SSb, the substrates of these systems and their roles in Gram-positive bacteria, with a focus on interbacterial competition.

difficile Toxin-Mediated Cell Death

There is an urgent need for new non-antibiotic based treatment strategies for Clostridioides difficile infection. C. difficile toxin B (TcdB) is a virulent factor that is essential for causing disease. Here, we investigated whether a survival-signaling pathway could protect against TcdB. We found significant increase in caspase-3 apoptotic activity in intestinal epithelial cells of mice exposed to TcdB. Subsequently, activation of the MIF-CD74-Akt pro-survival signaling pathway blocked TcdB-induced caspase-3 activity and intestinal epithelial cell death. This brief report provides proof-of-concept that targeting pro-survival pathways may represent a unique antibiotic-independent strategy for protecting against C. difficile toxin-mediated cell death.

Knowledge about Snake Venoms and Toxins from Colombia: A Systematic Review

Colombia encompasses three mountain ranges that divide the country into five natural regions: Andes, Pacific, Caribbean, Amazon, and Orinoquia. These regions offer an impressive range of climates, altitudes, and landscapes, which lead to a high snake biodiversity. Of the almost 300 snake species reported in Colombia, nearly 50 are categorized as venomous. This high diversity of species contrasts with the small number of studies to characterize their venom compositions and natural history in the different ecoregions. This work reviews the available information about the venom composition, isolated toxins, and potential applications of snake species found in Colombia. Data compilation was conducted according to the PRISMA guidelines, and the systematic literature search was carried out in Pubmed/MEDLINE. Venom proteomes from nine Viperidae and three Elapidae species have been described using quantitative analytical strategies. In addition, venoms of three Colubridae species have been studied. Bioactivities reported for some of the venoms or isolated components-such as antibacterial, cytotoxicity on tumoral cell lines, and antiplasmodial properties-may be of interest to develop potential applications. Overall, this review indicates that, despite recent progress in the characterization of venoms from several Colombian snakes, it is necessary to perform further studies on the many species whose venoms remain essentially unexplored, especially those of the poorly known genus Micrurus.

An Exploration of Novel Bioactives from the Venomous Marine Annelid Glycera alba

The immense biodiversity of marine invertebrates makes them high-value targets for the prospecting of novel bioactives. The present study investigated proteinaceous toxins secreted by the skin and proboscis of Glycera alba (Annelida: Polychaeta), whose congenerics G. tridactyla and G. dibranchiata are known to be venomous. Proteomics and bioinformatics enabled the detection of bioactive proteins that hold potential for biotechnological applications, including toxins like glycerotoxins (GLTx), which can interfere with neuromuscular calcium channels and therefore have value for the development of painkillers, for instance. We also identified proteins involved in the biosynthesis of toxins. Other proteins of interest include venom and toxin-related bioactives like cysteine-rich venom proteins, many of which are known to interfere with the nervous system. Ex vivo toxicity assays with mussel gills exposed to fractionated protein extracts from the skin and proboscis revealed that fractions potentially containing higher-molecular-mass venom proteins can exert negative effects on invertebrate prey. Histopathology, DNA damage and caspase-3 activity suggest significant cytotoxic effects that can be coadjuvated by permeabilizing enzymes such as venom metalloproteinases M12B. Altogether, these encouraging findings show that venomous annelids are important sources of novel bioactives, albeit illustrating the challenges of surveying organisms whose genomes and metabolisms are poorly understood.

Kalium 3.0 is a comprehensive depository of natural, artificial, and labeled polypeptides acting on potassium channels

Here, we introduce the third release of Kalium database (http://kaliumdb.org/), a manually curated comprehensive depository that accumulates data on polypeptide ligands of potassium channels. The major goal of this amplitudinous update is to summarize findings for natural polypeptide ligands of K+ channels, as well as data for the artificial derivatives of these substances obtained over the decades of exploration. We manually analyzed more than 700 original manuscripts and systematized the information on mutagenesis, production of radio- and fluorescently labeled derivatives, and the molecular pharmacology of K+ channel ligands. As a result, data on more than 1200 substances were processed and added enriching the database content fivefold. We also included the electrophysiological data obtained on the understudied and neglected K+ channels including the heteromeric and concatenated channels. We associated target channels in Kalium with corresponding entries in the official database of the International Union of Basic and Clinical Pharmacology. Kalium was supplemented with an adaptive Statistics page, where users are able to obtain actual data output. Several other improvements were introduced, such as a color code to distinguish the range of ligand activity concentrations and advanced tools for filtration and sorting. Kalium is a fully open-access database, crosslinked to other databases of interest. It can be utilized as a convenient resource containing ample up-to-date information about polypeptide ligands of K+ channels.

Typhoid toxin hijacks Wnt5a to establish host senescence and Salmonella infection

Damage to our genome causes acute senescence in mammalian cells, which undergo growth arrest and release a senescence-associated secretory phenotype (SASP) that propagates the stress response to bystander cells. Thus, acute senescence is a powerful tumor suppressor. Salmonella enterica hijacks senescence through its typhoid toxin, which usurps unidentified factors in the stress secretome of senescent cells to mediate intracellular infections. Here, transcriptomics of toxin-induced senescent cells (TxSCs) and proteomics of their secretome identify the factors as Wnt5a, INHBA, and GDF15. Wnt5a establishes a positive feedback loop, driving INHBA and GDF15 expression. In fibroblasts, Wnt5a and INHBA mediate autocrine senescence in TxSCs and paracrine senescence in naive cells. Wnt5a synergizes with GDF15 to increase Salmonella invasion. Intestinal TxSCs undergo apoptosis without Wnt5a, which is required for establishing intestinal TxSCs. The study reveals how an innate defense against cancer is co-opted by a bacterial pathogen to cause widespread damage and mediate infections.

T-cell receptor Vβ8 for detection of biologically active streptococcal pyrogenic exotoxin type C

Streptococcus pyogenes is an important human pathogen, commonly spread by airborne droplets but also by ingestion of contaminated food. Apart from causing infection, this pathogen produces 13 distinct types of streptococcal pyrogenic exotoxins (SPE). The current method for detection cannot distinguish between the biologically active form of SPE that has been reported to cause foodborne outbreaks and the inactivated toxin that poses no health risk. To measure the biological activity of SPE type C (SPE-C), one such toxin that was linked to foodborne outbreaks associated with milk and milk products, we developed a cell-based assay that can discern between biologically active and inactive SPE-C. To the best of our knowledge, this is the first showing that SPE-C activates T-cells expressing Vβ8. With this finding, we used a T-cell line natively expressing Vβ8 that was genetically engineered to also express the luciferase reporter gene under the regulation of nuclear factor of activated T-cells response element in combination with a B-cell line to present the recombinant SPE-C (rSPE-C) toxin via major histocompatibility complex (MHC) class II to the Vβ8 T-cell receptor (TCR) in an assay to detect and to discern between biologically active and inactive rSPE-C. By using this system, we demonstrated that SPE-C induced significant IL-2 secretion after 72 h and visible light emission after only 5 h, doubling by 24 h. We utilize this finding to assess the specificity of the assay and the effect of pasteurization on SPE-C activity. We observed no cross-reactivity with SPE-B and significant loss of SPE-C biological activity in spiked phosphate-buffered saline while SPE-C spiked into milk is heat stable. Once SPE-C has formed, it is infeasible to eliminate it from milk by thermal treatment.

Toxin-Triggered Liposomes for the Controlled Release of Antibiotics to Treat Infections Associated with Gram-Negative Bacteria

Antibiotic resistance has become an urgent threat to health care in recent years. The use of drug delivery systems provides advantages over conventional administration of antibiotics and can slow the development of antibiotic resistance. In the current study, we developed a toxin-triggered liposomal antibiotic delivery system, in which the drug release is enabled by the leukotoxin (LtxA) produced by the Gram-negative pathogen, Aggregatibacter actinomycetemcomitans. LtxA has previously been shown to mediate membrane disruption by promoting a lipid phase change in nonlamellar lipids, such as 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-methyl (N-methyl-DOPE). In addition, LtxA has been observed to bind strongly and nearly irreversibly to membranes containing large amounts of cholesterol. Here, we designed a liposomal delivery system composed of N-methyl-DOPE and cholesterol to take advantage of these interactions. Specifically, we hypothesized that liposomes composed of N-methyl-DOPE and cholesterol, encapsulating antibiotics, would be sensitive to LtxA, enabling controlled antibiotic release. We observed that liposomes composed of N-methyl-DOPE were sensitive to the presence of low concentrations of LtxA, and cholesterol increased the extent and kinetics of content release. The liposomes were stable under various storage conditions for at least 7 days. Finally, we showed that antibiotic release occurs selectively in the presence of an LtxA-producing strain of A. actinomycetemcomitans but not in the presence of a non-LtxA-expressing strain. Together, these results demonstrate that the designed liposomal vehicle enables toxin-triggered delivery of antibiotics to LtxA-producing strains of A. actinomycetemcomitans.

Molecular Biology of Cytoplasmic Incompatibility Caused by Wolbachia Endosymbionts

Among endosymbiotic bacteria living within eukaryotic cells, Wolbachia is exceptionally widespread, particularly in arthropods. Inherited through the female germline, it has evolved ways to increase the fraction of bacterially infected offspring by inducing parthenogenesis, feminization, male killing, or, most commonly, cytoplasmic incompatibility (CI). In CI, Wolbachia infection of males causes embryonic lethality unless they mate with similarly infected females, creating a relative reproductive advantage for infected females. A set of related Wolbachia bicistronic operons encodes the CI-inducing factors. The downstream gene encodes a deubiquitylase or nuclease and is responsible for CI induction by males, while the upstream product when expressed in females binds its sperm-introduced cognate partner and rescues viability. Both toxin-antidote and host-modification mechanisms have been proposed to explain CI. Interestingly, male killing by either Spiroplasma or Wolbachia endosymbionts involves deubiquitylases as well. Interference with the host ubiquitin system may therefore be a common theme among endosymbiont-mediated reproductive alterations.

Recent Developments in Vaccine Design: From Live Vaccines to Recombinant Toxin Vaccines

Vaccines are one of the most effective strategies to prevent pathogen-induced illness in humans. The earliest vaccines were based on live inoculations with low doses of live or related pathogens, which carried a relatively high risk of developing the disease they were meant to prevent. The introduction of attenuated and killed pathogens as vaccines dramatically reduced these risks; however, attenuated live vaccines still carry a risk of reversion to a pathogenic strain capable of causing disease. This risk is completely eliminated with recombinant protein or subunit vaccines, which are atoxic and non-infectious. However, these vaccines require adjuvants and often significant optimization to induce robust T-cell responses and long-lasting immune memory. Some pathogens produce protein toxins that cause or contribute to disease. To protect against the effects of such toxins, chemically inactivated toxoid vaccines have been found to be effective. Toxoid vaccines are successfully used today at a global scale to protect against tetanus and diphtheria. Recent developments for toxoid vaccines are investigating the possibilities of utilizing recombinant protein toxins mutated to eliminate biologic activity instead of chemically inactivated toxins. Finally, one of the most contemporary approaches toward vaccine design utilizes messenger RNA (mRNA) as a vaccine candidate. This approach was used globally to protect against coronavirus disease during the COVID-19 pandemic that began in 2019, due to its advantages of quick production and scale-up, and effectiveness in eliciting a neutralizing antibody response. Nonetheless, mRNA vaccines require specialized storage and transport conditions, posing challenges for low- and middle-income countries. Among multiple available technologies for vaccine design and formulation, which technology is most appropriate? This review focuses on the considerable developments that have been made in utilizing diverse vaccine technologies with a focus on vaccines targeting bacterial toxins. We describe how advancements in vaccine technology, combined with a deeper understanding of pathogen-host interactions, offer exciting and promising avenues for the development of new and improved vaccines.

Genomic assortment and interactive insights of the chromosomal encoded control of cell death (ccd) toxin-antitoxin (TA) module in Xenorhabdus nematophila

In the present circumstances, toxin-antitoxin (TA) modules have a great consideration due to their elusive role in bacterial physiology. TA modules consist of a toxic part and a counteracting antitoxin part and these are abundant genetic loci harbored on bacterial plasmids and chromosomes. The control of cell death (ccd) TA locus was the first identified TA module and its unitary function (such as plasmid maintenance) has been described, however, the function of its chromosomal counterparts is still ambiguous. Here, we are exploring the genomic assortment, structural and functional association of chromosomally encoded ccdAB TA homolog (ccdABXn1) in the genome of an entomopathogenic bacterium Xenorhabdus nematophila. This bacterium is a symbiotic model with the nematode Steinernema carpocapsae that infects and kills the host insect. By genomic assortment analysis, our observations suggested that CcdA antitoxin homologs are not more closely related than CcdB toxin homologs. Further results suggest that the ccdABXn1 TA homolog has sulphonamide (such as 4C6, for CcdA homolog) and peptide (such as gyrase, for CcdB homolog) ligand partners with a typical TA interaction network that may affect essential cellular metabolism of the X. nematophila. Collectively, our results improve the knowledge and conception of the metabolic interactive role of ccdAB TA homologs in X. nematophila physiology.Communicated by Ramaswamy H. Sarma.

The evolutionary ecology of fungal killer phenotypes

Ecological interactions influence evolutionary dynamics by selecting upon fitness variation within species. Antagonistic interactions often promote genetic and species diversity, despite the inherently suppressive effect they can have on the species experiencing them. A central aim of evolutionary ecology is to understand how diversity is maintained in systems experiencing antagonism. In this review, we address how certain single-celled and dimorphic fungi have evolved allelopathic killer phenotypes that engage in antagonistic interactions. We discuss the evolutionary pathways to the production of lethal toxins, the functions of killer phenotypes and the consequences of competition for toxin producers, their competitors and toxin-encoding endosymbionts. Killer phenotypes are powerful models because many appear to have evolved independently, enabling across-phylogeny comparisons of the origins, functions and consequences of allelopathic antagonism. Killer phenotypes can eliminate host competitors and influence evolutionary dynamics, yet the evolutionary ecology of killer phenotypes remains largely unknown. We discuss what is known and what remains to be ascertained about killer phenotype ecology and evolution, while bringing their model system properties to the reader's attention.

Genomic and Phylogenetic Analysis of Bacillus cereus Biovar anthracis Isolated from Archival Bone Samples Reveals Earlier Natural History of the Pathogen

(1) Background: Bacillus cereus biovar anthracis (Bcbva) was the causative agent of an anthrax-like fatal disease among wild chimpanzees in 2001 in Côte d'Ivoire. Before this, there had not been any description of an anthrax-like disease caused by typically avirulent Bacillus cereus. Genetic analysis found that B. cereus had acquired two anthrax-like plasmids, one a pXO1-like toxin producing plasmid and the other a pXO2-like plasmid encoding capsule. Bcbva caused animal fatalities in Cameroon, Democratic Republic of Congo, and the Central African Republic between 2004 and 2012. (2) Methods: The pathogen had acquired plasmids in the wild and that was discovered as the cause of widespread animal fatalities in the early 2000s. Primate bones had been shipped out of the endemic zone for anthropological studies prior to the realized danger of contamination with Bcbva. Spores were isolated from the bone fragments and positively identified as Bcbva. Strains were characterized by classical microbiological methods and qPCR. Four new Bcbva isolates were whole-genome sequenced. Chromosomal and plasmid phylogenomic analysis was performed to provide temporal and spatial context to these new strains and previously sequenced Bcbva. Tau and principal component analyses were utilized to identify genetic and spatial case patterns in the Taï National Park anthrax zone. (3) Results: Preliminary studies positively identified Bcbva presence in several archival bone fragments. The animals in question died between 1994 and 2010. Previously, the earliest archival strains of Bcbva were identified in 1996. Though the pathogen has a homogeneous genome, spatial analyses of a subset of mappable isolates from Taï National Park revealed strains found closer together were generally more similar, with strains from chimpanzees and duikers having the widest distribution. Ancestral strains were located mostly in the west of the park and had lower spatial clustering compared to more recent isolates, indicating a local increase in genetic diversity of Bcbva in the park over space and time. Global clustering analysis indicates patterns of genetic diversity and distance are shared between the ancestral and more recently isolated type strains. (4) Conclusions: Our strains have the potential to unveil historical genomic information not available elsewhere. This information sheds light on the evolution and emergence of a dangerous anthrax-causing pathogen.

The structural basis of hyperpromiscuity in a core combinatorial network of type II toxin-antitoxin and related phage defense systems

Toxin-antitoxin (TA) systems are a large group of small genetic modules found in prokaryotes and their mobile genetic elements. Type II TAs are encoded as bicistronic (two-gene) operons that encode two proteins: a toxin and a neutralizing antitoxin. Using our tool NetFlax (standing for Network-FlaGs for toxins and antitoxins), we have performed a large-scale bioinformatic analysis of proteinaceous TAs, revealing interconnected clusters constituting a core network of TA-like gene pairs. To understand the structural basis of toxin neutralization by antitoxins, we have predicted the structures of 3,419 complexes with AlphaFold2. Together with mutagenesis and functional assays, our structural predictions provide insights into the neutralizing mechanism of the hyperpromiscuous Panacea antitoxin domain. In antitoxins composed of standalone Panacea, the domain mediates direct toxin neutralization, while in multidomain antitoxins the neutralization is mediated by other domains, such as PAD1, Phd-C, and ZFD. We hypothesize that Panacea acts as a sensor that regulates TA activation. We have experimentally validated 16 NetFlax TA systems and used domain annotations and metabolic labeling assays to predict their potential mechanisms of toxicity (such as membrane disruption, and inhibition of cell division or protein synthesis) as well as biological functions (such as antiphage defense). We have validated the antiphage activity of a RosmerTA system encoded by Gordonia phage Kita, and used fluorescence microscopy to confirm its predicted membrane-depolarizing activity. The interactive version of the NetFlax TA network that includes structural predictions can be accessed at http://netflax.webflags.se/.

Investigating A Multi-Domain Polyketide Synthase in Amphidinium carterae

Dinoflagellates are unicellular organisms that are implicated in harmful algal blooms (HABs) caused by potent toxins that are produced through polyketide synthase (PKS) pathways. However, the exact mechanisms of toxin synthesis are unknown due to a lack of genomic segregation of fat, toxins, and other PKS-based pathways. To better understand the underlying mechanisms, the actions and expression of the PKS proteins were investigated using the toxic dinoflagellate Amphidinium carterae as a model. Cerulenin, a known ketosynthase inhibitor, was shown to reduce acetate incorporation into all fat classes with the toxins amphidinol and sulpho-amphidinol. The mass spectrometry analysis of cerulenin-reacted synthetic peptides derived from ketosynthase domains of A. carterae multimodular PKS transcripts demonstrated a strong covalent bond that could be localized using collision-induced dissociation. One multi-modular PKS sequence present in all dinoflagellates surveyed to date was found to lack an AT domain in toxin-producing species, indicating trans-acting domains, and was shown by Western blotting to be post-transcriptionally processed. These results demonstrate how toxin synthesis in dinoflagellates can be differentiated from fat synthesis despite common underlying pathway.

Group B Streptococcus Drives Major Transcriptomic Changes in the Colonic Epithelium

Group B Streptococcus (GBS) is a leading cause of infant sepsis worldwide. Colonization of the gastrointestinal tract is a critical precursor to late-onset disease in exposed newborns. Neonatal susceptibility to GBS intestinal translocation stems from intestinal immaturity; however, the mechanisms by which GBS exploits the immature host remain unclear. β-hemolysin/cytolysin (βH/C) is a highly conserved toxin produced by GBS capable of disrupting epithelial barriers. However, its role in the pathogenesis of late-onset GBS disease is unknown. Our aim was to determine the contribution of βH/C to intestinal colonization and translocation to extraintestinal tissues. Using our established mouse model of late-onset GBS disease, we exposed animals to GBS COH-1 (WT), a βH/C-deficient mutant (KO), or vehicle control (phosphate-buffered saline [PBS]) via gavage. Blood, spleen, brain, and intestines were harvested 4 days post-exposure for determination of bacterial burden and isolation of intestinal epithelial cells. RNA sequencing was used to examine the transcriptomes of host cells followed by gene ontology enrichment and KEGG pathway analysis. A separate cohort of animals was followed longitudinally to compare colonization kinetics and mortality between WT and KO groups. We demonstrate that dissemination to extraintestinal tissues occurred only in the WT exposed animals. We observed major transcriptomic changes in the colons of colonized animals, but not in the small intestines. We noted differential expression of genes that indicated the role of βH/C in altering epithelial barrier structure and immune response signaling. Overall, our results demonstrate an important role of βH/C in the pathogenesis of late-onset GBS disease.

Horizontal gene transfer underlies the painful stings of asp caterpillars (Lepidoptera: Megalopygidae)

Larvae of the genus Megalopyge (Lepidoptera: Zygaenoidea: Megalopygidae), known as asp or puss caterpillars, produce defensive venoms that cause severe pain. Here, we present the anatomy, chemistry, and mode of action of the venom systems of caterpillars of two megalopygid species, the Southern flannel moth Megalopyge opercularis and the black-waved flannel moth Megalopyge crispata. We show that megalopygid venom is produced in secretory cells that lie beneath the cuticle and are connected to the venom spines by canals. Megalopygid venoms consist of large aerolysin-like pore-forming toxins, which we have named megalysins, and a small number of peptides. The venom system differs markedly from those of previously studied venomous zygaenoids of the family Limacodidae, suggestive of an independent origin. Megalopygid venom potently activates mammalian sensory neurons via membrane permeabilization and induces sustained spontaneous pain behavior and paw swelling in mice. These bioactivities are ablated by treatment with heat, organic solvents, or proteases, indicating that they are mediated by larger proteins such as the megalysins. We show that the megalysins were recruited as venom toxins in the Megalopygidae following horizontal transfer of genes from bacteria to the ancestors of ditrysian Lepidoptera. Megalopygids have recruited aerolysin-like proteins as venom toxins convergently with centipedes, cnidarians, and fish. This study highlights the role of horizontal gene transfer in venom evolution.

From Foodborne Disease Outbreak (FBDO) to Investigation: The Plant Toxin Trap, Brittany, France, 2018

On 6 July 2018, the Center for Epidemiology and Public Health of the French Armed Forces was informed of an outbreak of acute gastroenteritis among customers of a dining facility at a military base in Brittany, France. A total of 200 patients were reported out of a population of 1700 (attack rate: 12%). The symptoms were mainly lower digestive tract disorders and occurred rapidly after lunch on 5 July (median incubation period: 3.3 h), suggesting a toxin-like pathogenic process. A case-control survey was carried out (92 cases and 113 controls). Statistical analysis pointed to the chili con carne served at lunch on 5 July as the very likely source of poisoning. Phytohaemagglutinin, a plant lectin, was found in the chili con carne at a concentration above the potentially toxic dose (400 HAU/gram). The raw kidney beans incorporated in the chili con carne presented a high haemagglutination activity (66,667 HAU/gram). They were undercooked, and the phytohaemagglutinin was not completely destroyed. FBDOs due to PHA are poorly documented. This study highlights the need to develop methods for routine testing of plant toxins in food matrices. Improved diagnostic capabilities would likely lead to better documentation, epidemiology, and prevention of food-borne illnesses caused by plant toxins.

Functional Diversity of Novel Lectins with Unique Structural Features in Marine Animals

Due to their remarkable structural diversity, glycans play important roles as recognition molecules on cell surfaces of living organisms. Carbohydrates exist in numerous isomeric forms and can adopt diverse structures through various branching patterns. Despite their relatively small molecular weights, they exhibit extensive structural diversity. On the other hand, lectins, also known as carbohydrate-binding proteins, not only recognize and bind to the diverse structures of glycans but also induce various biological reactions based on structural differences. Initially discovered as hemagglutinins in plant seeds, lectins have been found to play significant roles in cell recognition processes in higher vertebrates. However, our understanding of lectins in marine animals, particularly marine invertebrates, remains limited. Recent studies have revealed that marine animals possess novel lectins with unique structures and glycan recognition mechanisms not observed in known lectins. Of particular interest is their role as pattern recognition molecules in the innate immune system, where they recognize the glycan structures of pathogens. Furthermore, lectins serve as toxins for self-defense against foreign enemies. Recent discoveries have identified various pore-forming proteins containing lectin domains in fish venoms and skins. These proteins utilize lectin domains to bind target cells, triggering oligomerization and pore formation in the cell membrane. These findings have spurred research into the new functions of lectins and lectin domains. In this review, we present recent findings on the diverse structures and functions of lectins in marine animals.

A review of the biological effects of Myrtus communis

The World Health Organization stated that 1.6 million deaths worldwide were caused by contact with chemicals and toxins in 2019. In the same year, the Centers for Disease Control and Prevention stated that natural toxins caused 3960 deaths. Myrtus communis, also known as common Myrtle, is a flowering plant native to the Mediterranean region. Myrtle has been traditionally used to treat diarrhea, inflammation, bleeding, headache, pulmonary and skin diseases. This review was performed to assess Myrtle's protective and therapeutic efficacy against various chemical, natural, and radiational noxious. Multiple databases such as PubMed, Web of Sciences, and Scopus were investigated without publication time limitation. Recent studies have demonstrated its potential as a protective agent against both natural and chemical toxins. One of Myrtle's most significant protective properties is its high antioxidant content. Studies have shown that the antioxidant properties of Myrtle can protect against harmful substances such as heavy metals, pesticides, and other environmental toxins. Additionally, Myrtle has anti-inflammatory properties that can help reduce the damage caused by long-term exposure to toxins. The anti-inflammatory and antimicrobial properties of Myrtle have also proven effective in alleviating gastrointestinal conditions such as gastric ulcers.

Microspatial distribution of trace elements in feline dental hard tissues: early life exposure to essential and toxic elements

Introduction

Trace elements play a key role in dental tissue development, as dental hard tissues accumulate both essential and toxic trace elements during mineralization. Characterization of the spatial accumulation pattern of trace elements may provide insight into exposure to toxic elements over time and to the nature of disease processes affecting the hard dental tissues. Here, we present the first report of the use of laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) to map the microspatial distribution of multiple trace elements, essential and toxic, across feline dental hard tissues.

Methods

Eleven teeth were extracted from 8 cats. Nine teeth were from 7 cats diagnosed with idiopathic tooth resorption on intraoral radiographs prior to extraction. Two teeth were included from a cadaver that had no signs of tooth resorption on intraoral radiographs. The normal dental tissue was analyzed from each sample using LA-ICP-MS to map the microspatial distribution of essential and toxic trace elements across feline enamel, dentin, and cementum.

Results

Results showed a higher accumulation of barium and strontium in coronal dentin as compared to root dentin. The timing of the accumulation mirrors nursing timelines seen in teeth from human and non-human primates, consistent with barium and strontium being sourced from maternal milk. Results also showed a higher uptake of lead in the coronal dentin, suggesting this lead exposure was likely passed from mother to offspring.

Discussion

This work characterizes a baseline for elemental distribution in feline teeth linked to early life exposure to toxic elements such as lead and provides a framework for future studies investigating long-term environmental exposures to trace elements, essential and toxic, and their involvement in feline systemic and dental diseases.

Effect of a Novel Trivalent Vaccine Formulation against Acute Lung Injury Caused by Pseudomonas aeruginosa

An effective vaccine against Pseudomonas aeruginosa would benefit people susceptible to severe infection. Vaccination targeting V antigen (PcrV) of the P. aeruginosa type III secretion system is a potential prophylactic strategy for reducing P. aeruginosa-induced acute lung injury and acute mortality. We created a recombinant protein (designated POmT) comprising three antigens: full-length PcrV (PcrV_#1-#294), the outer membrane domain (#190-342) of OprF (OprF_#190-#342), and a non-catalytic mutant of the carboxyl domain (#406-613) of exotoxin A (mToxA_{#406-#613(E553Δ)}). In the combination of PcrV and OprF, mToxA, the efficacy of POmT was compared with that of single-antigen vaccines, two-antigen mixed vaccines, and a three-antigen mixed vaccine in a murine model of P. aeruginosa pneumonia. As a result, the 24 h-survival rates were 79%, 78%, 21%, 7%, and 36% in the POmT, PcrV, OprF, mTox, and alum-alone groups, respectively. Significant improvement in acute lung injury and reduction in acute mortality within 24 h after infection was observed in the POmT and PcrV groups than in the other groups. Overall, the POmT vaccine exhibited efficacy comparable to that of the PcrV vaccine. The future goal is to prove the efficacy of the POmT vaccine against various P. aeruginosa strains.

Next-Generation Sequencing for Venomics: Application of Multi-Enzymatic Limited Digestion for Inventorying the Snake Venom Arsenal

To improve the characterization of snake venom protein profiles, we report the application of a new generation of proteomic methodology to deeply characterize complex protein mixtures. The new approach, combining a synergic multi-enzymatic and a time-limited digestion (MELD), is a versatile and straightforward protocol previously developed by our group. The higher number of overlapping peptides generated during MELD increases the quality of downstream peptide sequencing and of protein identification. In this context, this work aims at applying the MELD strategy to a venomics purpose for the first time, and especially for the characterization of snake venoms. We used four venoms as the test models for this proof of concept: two Elapidae (Dendroaspis polylepis and Naja naja) and two Viperidae (Bitis arietans and Echis ocellatus). Each venom was reduced and alkylated before being submitted to two different protocols: the classical bottom-up proteomics strategy including a digestion step with trypsin only, or MELD, which combines the activities of trypsin, Glu-C and chymotrypsin with a limited digestion approach. The resulting samples were then injected on an M-Class chromatographic system, and hyphenated to a Q-Exactive Mass Spectrometer. Toxins and protein identification were performed by Peaks Studio X+. The results show that MELD considerably improves the number of sequenced (de novo) peptides and identified peptides from protein databases, leading to the unambiguous identification of a greater number of toxins and proteins. For each venom, MELD was successful, not only in terms of the identification of the major toxins (increasing of sequence coverage), but also concerning the less abundant cellular components (identification of new groups of proteins). In light of these results, MELD represents a credible methodology to be applied as the next generation of proteomics approaches dedicated to venomic analysis. It may open new perspectives for the sequencing and inventorying of the venom arsenal and should expand global knowledge about venom composition.