Members of the genus Streptococcus are major constituents of human skin and the mucosal microbiome, among which Streptococcus pyogenes, Streptococcus agalactiae, and Streptococcus pneumoniae are ...extracellular pathogens that occasionally cause life-threatening infectious diseases. Prior to their successful spread into the blood and deeper organs, pathogenic bacteria must first colonize human epithelial cell surfaces and evade host immunity. Streptococcal extracellular proteins play important roles in this colonization, as they directly interact with the host environment.
This review focuses on recent reports of common and specific virulence factors among these species. Most streptococcal virulence factors show multiple functions. For example, conserved essential glycolytic enzymes localize on the bacterial cell surface and in the cytoplasm and contribute to evasion of host innate immunity, while bacterial glycosidases utilize host glycan via the lectin domain or glycosidase activity for survival in the host environment. Furthermore, various streptococcal species and strains show mutually exclusive interactions between the polysaccharide capsule and glycosidase. In addition, phylogenetic and evolutional analysis methods used for determining the importance of virulence factors of the species are introduced. Synergistic findings obtained by microbiological and evolutional analyses enable investigations of the consequence and correlation between genes and infectious phenotypes.
Bacterial pathogens rapidly adapt to clinical intervention, such as antimicrobial agents and vaccination, via horizontal gene transfer, recombination, and/or natural point mutation. It is vital to continue development of innovative analysis methods to counter the mounting threats from evolving bacteria.
is a major cause of necrotizing fasciitis, a life-threatening subcutaneous soft-tissue infection. At the host infection site, the local environment and interactions between the host and bacteria have ...effects on bacterial gene expression profiles, while the gene expression pattern of
related to this disease remains unknown. In this study, we used a mouse model of necrotizing fasciitis and performed RNA-sequencing (RNA-seq) analysis of
M1T1 strain 5448 by isolating total RNA from infected hind limbs obtained at 24, 48, and 96 h postinfection. RNA-seq analysis results identified 483 bacterial genes whose expression was consistently altered in the infected hindlimbs compared to their expression under
conditions. Genes showing consistent enrichment during infection included 306 encoding molecules involved in virulence, carbohydrate utilization, amino acid metabolism, trace-metal transport, and the vacuolar ATPase transport system. Surprisingly, drastic upregulation of 3 genes, encoding streptolysin S precursor (
), cysteine protease (
), and secreted DNase (
), was noted in the present mouse model (log
fold change, >6.0, >9.4, and >7.1, respectively). Conversely, the number of consistently downregulated genes was 177, including those associated with the oxidative stress response and cell division. These results suggest that in necrotizing fasciitis,
shows an altered metabolism, decreased cell proliferation, and upregulation of expression of major toxins. Our findings are considered to provide critical information for developing novel treatment strategies and vaccines for necrotizing fasciitis.
Necrotizing fasciitis, a life-threatening subcutaneous soft-tissue infection, is principally caused by
The inflammatory environment at the site of infection causes global gene expression changes for survival of the bacterium and pathogenesis. However, no known study regarding transcriptomic profiling of
in cases of necrotizing fasciitis has been presented. We identified 483 bacterial genes whose expression was consistently altered during infection. Our results showed that
infection induces drastic upregulation of the expression of virulence-associated genes and shifts metabolic pathway usage. In particular, high-level expression of toxins, such as cytolysins, proteases, and nucleases, was observed at infection sites. In addition, genes identified as consistently enriched included those related to metabolism of arginine and histidine as well as carbohydrate uptake and utilization. Conversely, genes associated with the oxidative stress response and cell division were consistently downregulated during infection. The present findings provide useful information for establishing novel treatment strategies.
Bacteria in the oral microbiome are poorly identified owing to the lack of established culture methods for them. Thus, this study aimed to use culture-free analysis techniques, including bacterial ...single-cell genome sequencing, to identify bacterial species and investigate gene distribution in saliva. Saliva samples from the same individual were classified as inactivated or viable and then analyzed using 16S rRNA sequencing, metagenomic shotgun sequencing, and bacterial single-cell sequencing. The results of 16S rRNA sequencing revealed similar microbiota structures in both samples, with Streptococcus being the predominant genus. Metagenomic shotgun sequencing showed that approximately 80 % of the DNA in the samples was of non-bacterial origin, whereas single-cell sequencing showed an average contamination rate of 10.4 % per genome. Single-cell sequencing also yielded genome sequences for 43 out of 48 wells for the inactivated samples and 45 out of 48 wells for the viable samples. With respect to resistance genes, four out of 88 isolates carried cfxA, which encodes a β-lactamase, and four isolates carried erythromycin resistance genes. Tetracycline resistance genes were found in nine bacteria. Metagenomic shotgun sequencing provided complete sequences of cfxA, ermF, and ermX, whereas other resistance genes, such as tetQ and tetM, were detected as fragments. In addition, virulence factors from Streptococcus pneumoniae were the most common, with 13 genes detected. Our average nucleotide identity analysis also suggested five single-cell-isolated bacteria as potential novel species. These data would contribute to expanding the oral microbiome data resource.
•Bacterial single-cell seq of saliva suggested five potential novel species.•A healthy oral microbiome contained AMR and virulence factor genes.•Our data contribute to expanding oral microbiome data resource.
Group A Streptococcus (GAS) is a human-specific pathogen responsible for local suppurative and life-threatening invasive systemic diseases. Interaction of GAS with human plasminogen (PLG) is a ...salient characteristic for promoting their systemic dissemination. In the present study, a serotype M28 strain was found predominantly localized in tricellular tight junctions of epithelial cells cultured in the presence of PLG. Several lines of evidence indicated that interaction of PLG with tricellulin, a major component of tricellular tight junctions, is crucial for bacterial localization. A site-directed mutagenesis approach revealed that lysine residues at positions 217 and 252 within the extracellular loop of tricellulin play important roles in PLG-binding activity. Additionally, we demonstrated that PLG functions as a molecular bridge between tricellulin and streptococcal surface enolase (SEN). The wild type strain efficiently translocated across the epithelial monolayer, accompanied by cleavage of transmembrane junctional proteins. In contrast, amino acid substitutions in the PLG-binding motif of SEN markedly compromised those activities. Notably, the interaction of PLG with SEN was dependent on PLG species specificity, which influenced the efficiency of bacterial penetration. Our findings provide insight into the mechanism by which GAS exploits host PLG for acceleration of bacterial invasion into deeper tissues via tricellular tight junctions.
Gut dysbiosis characterized by an imbalanced microbiota is closely involved in the pathogenesis of a widespread gastrointestinal inflammatory disorder, inflammatory bowel disease. However, it is ...unclear how the complex intestinal microbiota affects development or resistant of mucosal inflammation. Our aim was to investigate the impact of the gut microbiota on susceptibility in a mouse model of ulcerative colitis.
We compared the susceptibility to dextran sulfate sodium (DSS)-induced colitis of inbred BALB/c mice obtained from the 3 main distributors of laboratory animals in Japan. Clinical symptoms of the colitis and the faecal microbiota were assessed. Cohousing approach was used to identify whether the gut microbiota is a primary factor determining disease susceptibility.
Here, we showed differences in the susceptibility of BALB/c mice from the vendors to DSS colitis. Analysis of the gut microbiota using 16S ribosomal RNA sequencing revealed clear separation of the gut microbial composition among mice from the vendors. Notably, the abundance of the phylum Actinobacteriota was strongly associated with disease activity. We also observed the expansion of butyrate-producing Roseburia species in mice with decreased susceptibility of the disease. Further cohousing experiments showed that variation in clinical outcomes was more correlated with the gut microbiota than genetic variants among substrains from different suppliers.
A BALB/c substrain that was resistant to DSS-induced colitis was observed, and the severity of DSS-induced colitis was mainly influenced by the gut microbiota. Targeting butyrate-producing bacteria could have therapeutic potential for ulcerative colitis.
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Atg8 is a unique ubiquitin-like protein that is covalently conjugated with a phosphatidylethanolamine through reactions similar to ubiquitination and plays essential roles in autophagy. Atg7 is the ...E1 enzyme for Atg8, and it activates the C-terminal Gly116 of Atg8 using ATP. Here, we report the crystal structure of Atg8 bound to the C-terminal domain of Atg7 in an unprecedented mode. Atg8 neither contacts with the central β-sheet nor binds to the catalytic site of Atg7, both of which were observed in previously reported Atg7–Atg8 structures. Instead, Atg8 binds to the C-terminal α-helix and crossover loop, thereby changing the autoinhibited conformation of the crossover loop observed in the free Atg7 structure into a short helix and a disordered loop. Mutational analyses suggested that this interaction mode is important for the activation reaction. We propose that Atg7 recognizes Atg8 through multiple steps, which would be necessary to induce a conformational change in Atg7 that is optimal for the activation reaction.
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•Activation of Atg8 by Atg7 is essential for autophagy.•Structure of the form II Atg7–Atg8 complex was determined at 2.15-Å resolution.•Atg8 binding to the crossover loop releases the autoinhibited conformation of Atg7.•Atg7 transfers Atg8 from the C-terminal tail to the active site in a cis manner.•Multi-step recognition of Atg8 by Atg7 is required for the activation reaction.
Streptococcus pyogenes is an important pathogen that causes pharyngitis, sepsis, and rheumatic fever. Cell-associated streptococcal C5a peptidase (ScpA) protects S. pyogenes from phagocytosis and has ...been suggested to interrupt host defenses by enzymatically cleaving complement C5a, a major factor in the accumulation of neutrophils at sites of infection. How S. pyogenes recognizes and binds to C5a, however, is unclear. We detected a C5a-binding protein in 8 m urea extracts of S. pyogenes by ligand blotting using biotinylated C5a. Searching of genome databases showed that the C5a-binding protein is identical to the streptococcal plasmin receptor (Plr), also known as streptococcal surface dehydrogenase (SDH) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). In the present study we identified a novel function of this multifunctional protein. Western blotting and immunofluorescence microscopy with anti-Plr/SDH/GAPDH showed that Plr/SDH/GAPDH is located on the bacterial surface and released into the culture supernatant. Next, we examined whether the streptococcal Plr/SDH/GAPDH inhibits the biological effects of C5a on human neutrophils. We found that soluble Plr/SDH/GAPDH inhibits C5a-activated chemotaxis and H2O2 production. Furthermore, our results suggested that soluble Plr/SDH/GAPDH captures C5a, inhibiting its chemotactic function. Also, cell-associated Plr/SDH/GAPDH and ScpA were both necessary for the cleavage of C5a on the bacterial surface. Together, these results indicate that the multifunctional protein Plr/SDH/GAPDH has additional functions that help S. pyogenes escape detection by the host immune system.
The balanced corpus of contemporary written Japanese (BCCWJ) is Japan's first 100 million words balanced corpus. It consists of three subcorpora (publication subcorpus, library subcorpus, and ...special-purpose subcorpus) and covers a wide range of text registers including books in general, magazines, newspapers, governmental white papers, best-selling books, an internet bulletin-board, a blog, school textbooks, minutes of the national diet, publicity newsletters of local governments, laws, and poetry verses. A random sampling technique is utilized whenever possible in order to maximize the representativeness of the corpus. The corpus is annotated in terms of dual POS analysis, document structure, and bibliographical information. The BCCWJ is currently accessible in three different ways including Chunagon a web-based interface to the dual POS analysis data. Lastly, results of some pilot evaluation of the corpus with respect to the textual diversity are reported. The analyses include POS distribution, word-class distribution, entropy of orthography, sentence length, and variation of the adjective predicate. High textual diversity is observed in all these analyses.
Leptospira was isolated from environmental water in central Japan using selective medium comprising five antibiotics, namely sulfamethoxazole, trimethoprim, amphotericin B, fosfomycin, and ...5‐fluorouracil. Of 100 water samples 57 (57%) were culture‐positive and 50 pure cultures were isolated. Of the 50 cultures isolated from water 48 were classified into a saprophytic clade on the basis of 16S ribosomal RNA gene sequences. However, it was previously reported that isolates from soil in Japan belonged to pathogenic, intermediate, and saprophytic clades, the current findings suggest less diversity of Leptospira species in environmental water than that in soil in Japan.
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