Search Results (28)

The by-products that may contain tetrodotoxin (TTX) produced during the processing of farmed pufferfish have caused food safety risks and environmental pollution. Peptidoglycan (PG) of lactic acid bacteria could adsorb TTX; however, its complex structure and poor solubility limited adsorption efficiency. In this study, hydroxyl modifications of three PGs (A3α, A1γ and A4α) were realized via TEMPO-mediated selective oxidation of the primary hydroxyl group. Compared with PGs, it was found that the carboxyl density of hydroxyl-modified PGs (HM-PGs) increased from 1.66 mmol/g to 3.33 mmol/g and the surface electronegativity increased from −36 mV to −59 mV. The adsorption capacity of HM-PGs to TTX reached 1.48 μg/mg, which was comparable to the adsorption of the conventional adsorbent chitosan for aflatoxin B1 (1.39 μg/mg). Moreover, HM-PGs decreased the toxicity of TTX from strong toxic to nearly non-toxic, with the toxicity reduction rate reached 99.85%. After treatment with HM-PGs, the mouse hippocampus and neuronal cell model confirmed that lower neural injury and sodium channel blocking effects were observed in the residual TTX, whose neurotoxicity was lower. Molecular docking simulation and physicochemical analysis revealed that the adsorption of TTX by HM-PGs was a complex adsorption mode driven by the synergy of physicochemical interaction. There were both physical adsorptions based on electrostatic and hydrophobic interactions and chemical binding with strong hydrogen bonding (1.46 Å) and Mayer bond order (0.1229). This study not only developed a new, efficient and safe tool for TTX removal, but also provided a theoretical basis for the development of biological toxin removal material. Full article

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder characterized by cognitive decline and neuronal loss, affecting millions worldwide. Emerging evidence highlights the oral microbiome—a complex ecosystem of bacteria, fungi, viruses, and protozoa as a significant factor in cognitive health. Dysbiosis of the oral microbiome contributes to systemic inflammation, disrupts the blood–brain barrier, and promotes neuroinflammation, processes increasingly implicated in the pathogenesis of AD. This review examines the mechanisms linking oral microbiome dysbiosis to cognitive decline through the oral–brain and oral–gut–brain axis. These interconnected pathways enable bidirectional communication between the oral cavity, gut, and brain via neural, immune, and endocrine signaling. Oral pathogens, such as Porphyromonas gingivalis, along with virulence factors, including lipopolysaccharides (LPS) and gingipains, contribute to neuroinflammation, while metabolic byproducts, such as short-chain fatty acids (SCFAs) and peptidoglycans, further exacerbate systemic immune activation. Additionally, this review explores the influence of external factors, including diet, pH balance, medication use, smoking, alcohol consumption, and oral hygiene, on oral microbial diversity and stability, highlighting their role in shaping cognitive outcomes. The dynamic interplay between the oral and gut microbiomes reinforces the importance of microbial homeostasis in preserving systemic and neurological health. The interventions, including probiotics, prebiotics, and dietary modifications, offer promising strategies to support cognitive function and reduce the risk of neurodegenerative diseases, such as AD, by maintaining a diverse microbiome. Future longitudinal research is needed to identify the long-term impact of oral microbiome dysbiosis on cognition. Full article

Helicobacter pylori is a bacterial pathogen that colonizes the human stomach, where it can cause a variety of diseases. H. pylori uses a cluster of sheathed flagella for motility, which is required for host colonization in animal models. The flagellar sheath is continuous with the outer membrane and is found in most Helicobacter species identified to date. HP0018 is a predicted lipoprotein of unknown function that is conserved in Helicobacter species that have flagellar sheaths but is absent in Helicobacter species that have sheath-less flagella. Deletion of hp0018 in H. pylori B128 resulted in the formation of long chains of outer membrane vesicles, which were most evident in an aflagellated variant of the Δhp0018 mutant that had a frameshift mutation in fliP. Flagellated cells of the Δhp0018 mutant possessed what appeared to be a normal flagellar sheath, suggesting that HP0018 is not required for sheath formation. Cells of the Δhp0018 mutant were also less helical in shape compared to wild-type cells. A HP0018-superfolder green fluorescent fusion protein expressed in the H. pylori Δhp0018 mutant formed fluorescent foci at the cell poles and lateral sites. Co-immunoprecipitation assays with HP0018 identified two enzymes involved in the modification of the cell wall peptidoglycan, AmiA and MltD, as potential HP0018 interaction partners. HP0018 may modulate the activity of AmiA or MltD, and in the absence of HP0018, the unregulated activity of these enzymes may alter the peptidoglycan layer in a manner that results in an altered cell shape and hypervesiculation. Full article

Lysozyme (E.C. 3.2.1.17), an about 14 kDa protein and pI 11, widely spread in nature, is present in humans mainly in milk, saliva, and intestinal mucus as a part of innate defense mechanisms. It is endowed with antimicrobial activity due to its action as an N-acetylmuramidase, cleaving the 1-4β glycosidic linkage in the peptidoglycan layer of Gram-positive bacteria. This antimicrobial activity is exerted only against a limited number of Gram-negative bacteria. Different action mechanisms are proposed to explain its activity against Gram-negative bacteria, viruses, and fungi. The antiviral activity prompted the study of a possible application of lysozyme in the treatment of SARS-CoV-2 infections. Among the different sources of lysozyme, the chicken egg albumen was chosen, being the richest source of this protein (c-type lysozyme, 129 amino acids). Interestingly, the activity of lysozyme hydrochloride against SARS-CoV-2 was related to the heating (to about 100 °C) of this molecule. A chemical–physical characterization was required to investigate the possible modifications of native lysozyme hydrochloride by heat treatment. The FTIR analysis of the two preparations of lysozyme hydrochloride showed appreciable differences in the secondary structure of the two protein chains. HPLC and NMR analyses, as well as the enzymatic activity determination, did not show significant modifications. Full article

We demonstrate that Blautia coccoides JCM1395^T has the potential to be used for tumor-targeted live bacterial therapeutics. Prior to studying its in vivo biodistribution, a sample preparation method for reliable quantitative analysis of bacteria in biological tissues was required. Gram-positive bacteria have a thick outer layer of peptidoglycans, which hindered the extraction of 16S rRNA genes for colony PCR. We developed the following method to solve the issue; the method we developed is as follows. The homogenates of the isolated tissue were seeded on agar medium, and bacteria were isolated as colonies. Each colony was heat-treated, crushed with glass beads, and further treated with restriction enzymes to cleave DNAs for colony PCR. With this method, Blautia coccoides JCM1395^T and Bacteroides vulgatus JCM5826^T were individually detected from tumors in mice intravenously receiving their mixture. Since this method is very simple and reproducible, and does not involve any genetic modification, it can be applied to exploring a wide range of bacterial species. We especially demonstrate that Blautia coccoides JCM1395^T efficiently proliferate in tumors when intravenously injected into tumor-bearing mice. Furthermore, these bacteria showed minimal innate immunological responses, i.e., elevated serum tumor necrosis factor α and interleukin-6, similar to Bifidobacterium sp., which was previously studied as a therapeutic agent with a small immunostimulating effect. Full article

Antibiotic resistant strains of bacteria are a serious threat to human health. With increasing antibiotic resistance in common human pathogens, fewer antibiotics remain effective against infectious diseases. Staphylococcus aureus is a pathogenic bacterium of particular concern to human health as it has developed resistance to many of the currently used antibiotics leaving very few remaining as effective treatment. Alternatives to conventional antibiotics are needed for treating resistant bacterial infections. A deeper understanding of the cellular characteristics of resistant bacteria beyond well characterized resistance mechanisms can allow for increased ability to properly treat them and to potentially identify targetable changes. This review looks at antibiotic resistance in S aureus in relation to its cellular components, the cell wall, cell membrane and virulence factors. Methicillin resistant S aureus bacteria are resistant to most antibiotics and some strains have even developed resistance to the last resort antibiotics vancomycin and daptomycin. Modifications in cell wall peptidoglycan and teichoic acids are noted in antibiotic resistant bacteria. Alterations in cell membrane lipids affect susceptibility to antibiotics through surface charge, permeability, fluidity, and stability of the bacterial membrane. Virulence factors such as adhesins, toxins and immunomodulators serve versatile pathogenic functions in S aureus. New antimicrobial strategies can target cell membrane lipids and virulence factors including anti-virulence treatment as an adjuvant to traditional antibiotic therapy. Full article

Staphylococcus aureus is a major causative agent of bovine mastitis, a disease considered one of the most economically devastating in the dairy sector. Considering the increasing prevalence of antibiotic-resistant strains, novel therapeutic approaches efficiently targeting extra- and intracellular bacteria and featuring high activity in the presence of raw milk components are needed. Here, we have screened a library of eighty peptidoglycan hydrolases (PGHs) for high activity against S. aureus in raw bovine milk, twelve of which were selected for further characterization and comparison in time-kill assays. The bacteriocins lysostaphin and ALE-1, and the chimeric PGH M23LST(L)_SH3b2638 reduced bacterial numbers in raw milk to the detection limit within 10 min. Three CHAP-based PGHs (CHAPGH15_SH3bAle1, CHAPK_SH3bLST_H, CHAPH5_LST_H) showed gradually improving activity with increasing dilution of the raw milk. Furthermore, we demonstrated synergistic activity of CHAPGH15_SH3bAle1 and LST when used in combination. Finally, modification of four PGHs (LST, M23LST(L)_SH3b2638, CHAPK_SH3bLST, CHAPGH15_SH3bAle1) with the cell-penetrating peptide TAT significantly enhanced the eradication of intracellular S. aureus in bovine mammary alveolar cells compared to the unmodified parentals in a concentration-dependent manner. Full article

Lysozymes are hydrolytic enzymes characterized by their ability to cleave the β-(1,4)-glycosidic bonds in peptidoglycan, a major structural component of the bacterial cell wall. This hydrolysis action compromises the integrity of the cell wall, causing the lysis of bacteria. For more than 80 years, its role of antibacterial defense in animals has been renowned, and it is also used as a preservative in foods and pharmaceuticals. In order to improve the antimicrobial efficacy of lysozyme, extensive research has been intended for its modifications. This manuscript reviews the natural antibiotic compound lysozyme with reference to its catalytic and non-catalytic mode of antibacterial action, lysozyme types, susceptibility and resistance of bacteria, modification of lysozyme molecules, and its applications in the food industry. Full article

Muramyl dipeptide (N-acetylmuramyl-L-alanyl-D-isoglutamine, MDP) is the smallest peptidoglycan fragment able to trigger an immune response by activating the NOD2 receptor. Structural modification of MDP can lead to analogues with improved immunostimulating properties. The aim of this work was to prepare mannosylated desmuramyl peptides (ManDMP) containing lipophilic triazole substituents to study their immunomodulating activities in vivo. The adjuvant activity of the prepared compounds was evaluated in the mouse model using ovalbumin as an antigen and compared to the MDP and referent adjuvant ManDMPTAd. The obtained results confirm that the α-position of D-isoGln is the best position for the attachment of lipophilic substituents, especially adamantylethyl triazole. Compound 6c exhibited the strongest adjuvant activity, comparable to the MDP and better than referent ManDMPTAd. Full article

Recent discoveries of reversible N6-methyladenosine (m6A) methylation on messenger RNA (mRNA) and mapping of m6A methylomes in many species have revealed potential regulatory functions of this RNA modification by m6A players—writers, readers, and erasers. Here, we first profile transcriptome-wide m6A in female and male Anopheles sinensis and reveal that m6A is also a highly conserved modification of mRNA in mosquitoes. Distinct from mammals and yeast but similar to Arabidopsis thaliana, m6A in An. sinensis is enriched not only around the stop codon and within 3′-untranslated regions but also around the start codon and 5′-UTR. Gene ontology analysis indicates the unique distribution pattern of m6A in An. sinensis is associated with mosquito sex-specific pathways such as tRNA wobble uridine modification and phospholipid-binding in females, and peptidoglycan catabolic process, exosome and signal recognition particle, endoplasmic reticulum targeting, and RNA helicase activity in males. The positive correlation between m6A deposition and mRNA abundance indicates that m6A can play a role in regulating gene expression in mosquitoes. Furthermore, many spermatogenesis-associated genes, especially those related to mature sperm flagellum formation, are positively modulated by m6A methylation. A transcriptional regulatory network of m6A in An. sinensis is first profiled in the present study, especially in spermatogenesis, which may provide a new clue for the control of this disease-transmitting vector. Full article

Obesity, usually indicated by a body mass index of more than 30 kg/m², is a worsening global health issue. It leads to chronic diseases, including type II diabetes, hypertension, and cardiovascular diseases. Conventional treatments for obesity include physical activity and maintaining a negative energy balance. However, physical activity alone cannot determine body weight as several other factors play a role in the overall energy balance. Alternatively, weight loss may be achieved by medication and surgery. However, these options can be expensive or have side effects. Therefore, dietary factors, including dietary modifications, nutraceutical preparations, and functional foods have been investigated recently. For example, edible mushrooms have beneficial effects on human health. Polysaccharides (essentially β-D-glucans), chitinous substances, heteroglycans, proteoglycans, peptidoglycans, alkaloids, lactones, lectins, alkaloids, flavonoids, steroids, terpenoids, terpenes, phenols, nucleotides, glycoproteins, proteins, amino acids, antimicrobials, and minerals are the major bioactive compounds in these mushrooms. These bioactive compounds have chemo-preventive, anti-obesity, anti-diabetic, cardioprotective, and neuroprotective properties. Consumption of edible mushrooms reduces plasma triglyceride, total cholesterol, low-density lipoprotein, and plasma glucose levels. Polysaccharides from edible mushrooms suppress mRNA expression in 3T3-L1 adipocytes, contributing to their anti-obesity properties. Therefore, edible mushrooms or their active ingredients may help prevent obesity and other chronic ailments. Full article

This study aimed to investigate effects of plasma-activated solution (PAS) on the cell biology of Staphylococcus aureus and qualities of fresh lettuce leaves. PAS was prepared by dielectric barrier discharge plasma and incubated with S. aureus for 10–30 min or with lettuces for 10 min. Effects on cell biology were evaluated with microscopic images, cell integrity, and chemical modification of cellular components. Effects on lettuce quality were estimated with the viable microbial counts, color, contents of vitamin C and chlorophyll, and surface integrity. PAS reduced S. aureus population by 4.95-log and resulted in increased cell membrane leakage. It also resulted in increased contents of reactive oxygen species in cells, C=O bonds in peptidoglycan, and 8-hydroxydeoxyguanosine content in cellular DNA, and reduced ratios of unsaturated/saturated fatty acids in the cell membrane. PAS treatment reduced bacterial load on fresh lettuce and had no negative effects on the quality. Data suggest that PAS can be used for the disinfection of ready-to-eat fresh vegetables. Full article

The gut microbiota is a crucial factor in maintaining homeostasis. The presence of commensal microorganisms leads to the stimulation of the immune system and its maturation. In turn, dysbiosis with an impaired intestinal barrier leads to accelerated contact of microbiota with the host’s immune cells. Microbial structural parts, i.e., pathogen-associated molecular patterns (PAMPs), such as flagellin (FLG), peptidoglycan (PGN), lipoteichoic acid (LTA), and lipopolysaccharide (LPS), induce inflammation via activation of pattern recognition receptors. Microbial metabolites can also develop chronic low-grade inflammation, which is the cause of many metabolic diseases. This article aims to systematize information on the influence of microbiota on chronic inflammation and the benefits of microbiota modification through dietary changes, prebiotics, and probiotic intake. Scientific research indicates that the modification of the microbiota in various disease states can reduce inflammation and improve the metabolic profile. However, since there is no pattern for a healthy microbiota, there is no optimal way to modify it. The methods of influencing microbiota should be adapted to the type of dysbiosis. Although there are studies on the microbiota and its effects on inflammation, this subject is still relatively unknown, and more research is needed in this area. Full article

Muramyl dipeptide (MDP) is the smallest peptidoglycan fragment able to trigger the immune response. Structural modification of MDP can lead to the preparation of analogs with improved immunostimulant properties, including desmuramyl peptides (DMPs). The aim of this work was to prepare the desmuramyl peptide (L-Ala-D-Glu)-containing adamantyl-triazole moiety and its mannosylated derivative in order to study their immunomodulatory activities in vivo. The adjuvant activity of the prepared compounds was evaluated in a murine model using ovalbumin as an antigen, and compared to the reference adjuvant ManAdDMP. The results showed that the introduction of the lipophilic adamantyl-triazole moiety at the C-terminus of L-Ala-D-Glu contributes to the immunostimulant activity of DMP, and that mannosylation of DMP modified with adamantyl-triazole causes the amplification of its immunostimulant activity. Full article

Marine viral sequence space is immense and presents a promising resource for the discovery of new enzymes interesting for research and biotechnology. However, bottlenecks in the functional annotation of viral genes and soluble heterologous production of proteins hinder access to downstream characterization, subsequently impeding the discovery process. While commonly utilized for the heterologous expression of prokaryotic genes, codon adjustment approaches have not been fully explored for viral genes. Herein, the sequence-based identification of a putative prophage is reported from within the genome of Hypnocyclicus thermotrophus, a Gram-negative, moderately thermophilic bacterium isolated from the Seven Sisters hydrothermal vent field. A prophage-associated gene cluster, consisting of 46 protein coding genes, was identified and given the proposed name Hypnocyclicus thermotrophus phage H1 (HTH1). HTH1 was taxonomically assigned to the viral family Siphoviridae, by lowest common ancestor analysis of its genome and phylogeny analyses based on proteins predicted as holin and DNA polymerase. The gene neighbourhood around the HTH1 lytic cassette was found most similar to viruses infecting Gram-positive bacteria. In the HTH1 lytic cassette, an N-acetylmuramoyl-L-alanine amidase (Amidase_2) with a peptidoglycan binding motif (LysM) was identified. A total of nine genes coding for enzymes putatively related to lysis, nucleic acid modification and of unknown function were subjected to heterologous expression in Escherichia coli. Codon optimization and codon harmonization approaches were applied in parallel to compare their effects on produced proteins. Comparison of protein yields and thermostability demonstrated that codon optimization yielded higher levels of soluble protein, but codon harmonization led to proteins with higher thermostability, implying a higher folding quality. Altogether, our study suggests that both codon optimization and codon harmonization are valuable approaches for successful heterologous expression of viral genes in E. coli, but codon harmonization may be preferable in obtaining recombinant viral proteins of higher folding quality. Full article