Growth Of Pathogenic Bacteria Research Articles

Preparation and Analysis of Physicochemical Properties, Antioxidant and Antibacterial Activities of Kombucha Tea Produced from Beijing Bamboo Leaf Tea (Dendrocalamus sp.) and Green Tea

Beijing bamboo (Dendrocalamus sp.), belonging to the Poaceae family, has been largely neglected and underutilized, particularly its leaves. This study aims to investigate the physicochemical properties, antioxidant, and antimicrobial activities of Beijing bamboo leaf and Beijing bamboo leaf kombucha. Hot air drying was conducted at temperatures of 60, 65, and 70ºC, with results indicating that 65ºC is the optimal drying temperature for achieving the highest levels of total phenolic compounds, flavonoids, and antioxidant activities. Beijing bamboo leaf tea underwent a 21-day fermentation process with a kombucha consortium comprising yeasts and acetic acid bacteria. The results showed that the changing trends of pH, total acidity, and total soluble solids were similar between kombucha produced from Beijing bamboo leaf tea and green tea. Fermentation notably enhanced the antioxidant activity of the kombucha, as evidenced by DPPH and FRAP assays, which correlated with increases in phenolics and flavonoids. The antimicrobial efficacy was assessed through the agar diffusion method and minimum inhibitory concentration (MIC), revealing that both Beijing bamboo leaf tea and green tea suppressed the growth of pathogenic bacteria, including Salmonella Typhimurium DMST 562, E. coli DMST 4242, Bacillus cereus DMST 5040, Staphylococcus aureus DMST 8840, and Pseudomonas aeruginosa DMST 4739. Notably, kombucha from green tea exhibited superior antimicrobial effects compared to Beijing bamboo leaf tea kombucha. Additionally, fermentation of Beijing bamboo leaf tea resulted in higher counts of yeast, acetic acid bacteria, and lactic acid bacteria throughout the fermentation process than those observed in green tea kombucha. These findings highlight the potential of Beijing bamboo leaves as a valuable resource for developing functional properties in underutilized plant resources, offering promising applications in the food and health industries.

Chitosan-puerarin composite hydrogel with magnetic enhanced photothermal properties as sustained antimicrobial coatings for beef preservation

The bactericidal properties of traditional food coatings mostly depend on the amount of fungicides present, which reduces the sustainability of food packaging. Herein, we proposed a magnetic field to precisely modulate the near-infrared (NIR) absorption activity to enhance antimicrobial coatings sustainability. Inspired by the typical grinding procedure, the assembly of CP/Fe3O4@TA nanofiber hydrogel was proposed as the coating, applying mechanical force and encouraging the collision of effective molecules of puerarin (PUE), chitosan (CS), and Fe3O4@TA NFs. This hydrogel design offers precise control over the physical and chemical properties, including appearance, viscoelasticity, and rheology. Particularly, significant changes in photothermal performance were observed as a result of magnetic regulation of NIR absorption activity. As a result, the CP/Fe3O4@TA coatings achieve effective bacteria killing performance under NIR irradiation, magnetocaloric effect, boric acid adsorption, and aggregation interference. Finally, the hydrogel coating was applied to the beef surface and serves as an effective barrier against the growth of pathogenic bacteria, thereby preserving the freshness and tenderness of the beef. The finding from this work is expected to open up a new way in active nano hydrogel coating for food preservation.

Structural determinants of Vibrio cholerae FeoB nucleotide promiscuity

Ferrous iron (Fe2+) is required for the growth and virulence of many pathogenic bacteria, including Vibrio cholerae (Vc), the causative agent of the disease cholera. For this bacterium, Feo is the primary system that transports Fe2+ into the cytosol. FeoB, the main component of this system, is regulated by a soluble cytosolic domain termed NFeoB. Recent reanalysis has shown that NFeoBs can be classified as either GTP-specific or NTP-promiscuous, but the structural and mechanistic bases for these differences were not known. To explore this intriguing property of FeoB, we solved the X-ray crystal structures of VcNFeoB in both the apo and GDP-bound forms. Surprisingly, this promiscuous NTPase displayed a canonical NFeoB G-protein fold like GTP-specific NFeoBs. Using structural bioinformatics, we hypothesized that residues surrounding the nucleobase could be important for both nucleotide affinity and specificity. We then solved the X-ray crystal structures of N150T VcNFeoB in the apo and GDP-bound forms to reveal H-bonding differences surround the guanine nucleobase. Interestingly, isothermal titration calorimetry revealed similar binding thermodynamics of the WT and N150T proteins to guanine nucleotides, while the behavior in the presence of adenine nucleotides was dramatically different. AlphaFold models of VcNFeoB in the presence of ADP and ATP showed important conformational changes that contribute to nucleotide specificity among FeoBs. Combined, these results provide a structural framework for understanding FeoB nucleotide promiscuity, which could be an adaptive measure utilized by pathogens to ensure adequate levels of intracellular iron across multiple metabolic landscapes.

Influence of composition changes of Strobilanthes cusia bioactive compounds induced by the hydrolysis and condensation of indican on pathogen biofilm

Strobilanthes cusia is a traditional Chinese medicinal herb containing indole alkaloids, key bioactive components responsible for its pharmacological effects. However, there has been limited research regarding S. cusia compositional impact on antimicrobial properties. This study centered around the hydrolysis and oxidative condensation reactions of indican, aiming to investigate the influence of its intermediate, indoxyl, on pathogenic bacteria growth and biofilm formation. A notable inhibitory effect of indoxyl on Staphylococcus aureus biofilm formation was found. High-performance liquid chromatography and transmission electron microscopy confirmed that indoxyl disrupted the membrane structure of biofilm cells, causing a disturbance in cellular redox balance. These findings suggest that the oxidative reaction of indoxyl within cells could be a prominent factor affecting cell viability. Simultaneously, a portion of indoxyl oxidized externally to form indigo, which did not affect intracellular activities but rather disrupted the biofilm structure. The concept of “compositional changes” enriches the understanding of antimicrobial properties of S. cusia, offering novel approaches for effectively inhibiting pathogenic microorganisms.

Genome assembly, comparative genomics, and identification of genes/pathways underlying plant growth-promoting traits of an actinobacterial strain, Amycolatopsis sp. (BCA-696)

The draft genome sequence of an agriculturally important actinobacterial species Amycolatopsis sp. BCA-696 was developed and characterized in this study. Amycolatopsis BCA-696 is known for its biocontrol properties against charcoal rot and also for plant growth-promotion (PGP) in several crop species. The next-generation sequencing (NGS)-based draft genome of Amycolatopsis sp. BCA-696 comprised of ~ 9.05 Mb linear chromosome with 68.75% GC content. In total, 8716 protein-coding sequences and 61 RNA-coding sequences were predicted in the genome. This newly developed genome sequence has been also characterized for biosynthetic gene clusters (BGCs) and biosynthetic pathways. Furthermore, we have also reported that the Amycolatopsis sp. BCA-696 produces the glycopeptide antibiotic vancomycin that inhibits the growth of pathogenic gram-positive bacteria. A comparative analysis of the BCA-696 genome with publicly available closely related genomes of 14 strains of Amycolatopsis has also been conducted. The comparative analysis has identified a total of 4733 core and 466 unique orthologous genes present in the BCA-696 genome The unique genes present in BCA-696 was enriched with antibiotic biosynthesis and resistance functions. Genome assembly of the BCA-696 has also provided genes involved in key pathways related to PGP and biocontrol traits such as siderophores, chitinase, and cellulase production.

Synthesis of Copper Oxide Nanoparticles Using Leaf Extracts of Dillenia Indica and Mikania Micrantha: Investigation of their Potential as Photocatalysts and Antibacterial Agents

AbstractThe fields of biomedicine and catalysis have both shown a great deal of interest in copper oxide nanoparticles (CuONPs). Green synthesis methods are being frequently employed to develop highly active CuONPs. This research investigates the potential photocatalytic and antibacterial applications of two CuONPs that were synthesized utilizing extracts from Dillenia indica (D‐CuONPs) and Mikania micrantha (M‐CuONPs) leaves. Analysis using electron microscopy revealed that CuONPs are uniformly spherical and average size around 15 nm. The development of single‐phase CuONPs with a monoclinic structure is shown by X‐ray diffraction studies. The FTIR peaks at 695 cm−1 and 860 cm−1 represent a stretching of Cu−O, signifying the formation of CuO nanostructure. The EDX profiles stated that the CuONPs are correlated with compliantly intensified Cu and O signals. Under solar irradiation, around 90 % of congo red (CR) dye was degraded by both CuONPs in 120 min, with the rate constants of 0.0187 and 0.0174 min−1, respectively. Furthermore, CuONPs have excellent antibacterial activity against bacteria belonging to both Gram classes. Overall, CuONPs hold great potential for inhibiting the growth of pathogenic bacteria and for degrading organic dyes in the presence of sunlight. As such, they can be manufactured on a large scale using plant sources.

Calotropis Gigantea Latex-Derived Zinc Oxide Nanoparticles: Biosynthesis, Characterization, and Biofunctional Applications

Latex of C. gigantea was used to synthesize zinc oxide nanoparticles (ZnO NPs) by the green chemistry approach. The crystalline size, shape, and purity of as-synthesized ZnO NPs were characterized through scanning electron microscopy with energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction analysis, and Fourier-transform infrared spectroscopy techniques. Crystalline, spherical ZnO NPs with an average size of 21.8 nm were formed. In addition, the biological properties of the ZnO NPs, such as antioxidant and antibacterial activity, were evaluated by 2,2-diphenyl-1-picrylhydrazyl assay and the agar well-diffusion method. The highest free radical scavenging activities of 83.11 ± 1.89 % were observed at a concentration of 350 μg/mL of C. gigantea latex-mediated ZnO NPs. The latex in the C. gigantea latex-mediated ZnO NPs inhibited the growth of pathogenic bacteria. The maximum zone of inhibition was found in P. aeruginosa and S. aureus. C. gigantea latex-mediated ZnO NPs have significant biocompatibility and broad-spectrum antibacterial properties against wound-causing bacteria and, therefore, can be suggested for use in the formulation of novel creams or gels for healing applications.

Glutamine enhances pneumococcal growth under methionine semi-starvation by elevating intracellular pH.

Bacteria frequently encounter nutrient limitation in nature. The ability of living in this nutrient shortage environment is vital for bacteria to preserve their population and important for some pathogenic bacteria to cause infectious diseases. Usually, we study how bacteria survive after nutrient depletion, a total starvation condition when bacteria almost cease growth and try to survive. However, nutrient limitation may not always lead to total starvation. Bacterial adaptation to nutrient shortage was studied by determining bacterial growth curves, intracellular pH, intracellular amino acid contents, gene transcription, protein expression, enzyme activity, and translation and replication activities. No exogenous supply of methionine results in growth attenuation of Streptococcus pneumoniae, a human pathogen. In this paper, we refer to this inhibited growth state between ceased growth under total starvation and full-speed growth with full nutrients as semi-starvation. Similar to total starvation, methionine semi-starvation also leads to intracellular acidification. Surprisingly, it is intracellular acidification but not insufficient methionine synthesis that causes growth attenuation under methionine semi-starvation. With excessive glutamine supply in the medium, intracellular methionine level was not changed, while bacterial intracellular pH was elevated to ~ 7.6 (the optimal intracellular pH for pneumococcal growth) by glutamine deamination, and bacterial growth under semi-starvation was restored fully. Our data suggest that intracellular acidification decreases translation level and glutamine supply increases intracellular pH to restore translation level, thus restoring bacterial growth. This growth with intracellular pH adjustment by glutamine is a novel strategy we found for bacterial adaptation to nutrient shortage, which may provide new drug targets to inhibit growth of pathogenic bacteria under semi-starvation.

The effect of <i>Streptococcus mutans</i>, <i>Candida albicans</i> and other cariesogenic factors on the concentration of cathelicidin LL-37 in oral fluid in children with early childhood caries

BACKGROUND: Human antimicrobial peptides play a significant role in innate immunity. In the oral cavity salivary glands and mucosal epithelium produce human antimicrobial peptides, including defensins and cathelicidin LL-37. Cathelicidin is the most significant peptide protecting against different types of infections, controls the activity of commensal bacteria and prevents colonization and growth of pathogenic bacteria. AIM: To determine the concentration of cathelicidin LL-37 in the oral fluid of children 2–5 years old and the oral hygiene index depending on some of the parameters and intensity of the carious process in the oral cavity. MATERIALS AND METHODS: The study was conducted in a group of children aged 2-5 years old; the concentration of catelicidine in the oral fluid was determined by enzyme immunoassay. Moreover, the concentration of Streptococcus mutans in saliva, the presence of Candida albicans in dental plaque, oral hygiene index and the concentration of 25-hydroxycalciferol in venous blood were assessed in these children. RESULTS: The stydy revealed the dependence of the concentration of cathelicidin in the oral fluid on the intensity of the carious process in children as well as on the concentration of Streptococcus mutans in saliva, the presence of Candida albicans in plaque and poor oral hygiene. CONCLUSIONS: It was found that in children with high intensity of caries, the concentration of antimicrobial peptide LL-37 is twice lower than in children with low and medium intensity of early childhood caries.

Ethanol extract from Astilbe chinensis inflorescence suppresses inflammation in macrophages and growth of oral pathogenic bacteria.

Chronic oral inflammation and biofilm-mediated infections drive diseases such as dental caries and periodontitis. This study investigated the anti-inflammatory and antibacterial potential of an ethanol extract from Astilbe chinensis inflorescence (GA-13-6) as a prominent candidate for natural complex substances (NCS) with therapeutic potential. In LPS-stimulated RAW 264.7 macrophages, GA-13-6 significantly suppressed proinflammatory mediators, including interleukin-6 (IL-6), tumor necrosis factor (TNF), and nitric oxide (NO), surpassing purified astilbin, a known bioactive compound found in A. chinensis. Furthermore, GA-13-6 downregulated the expression of cyclooxygenase-2 (COX2) and inducible nitric oxide synthase (iNOS), indicating an inhibitory effect on the inflammatory cascade. Remarkably, GA-13-6 exhibited selective antibacterial activity against Streptococcus mutans, Streptococcus sanguinis, and Porphyromonas gingivalis, key players in dental caries and periodontitis, respectively. These findings suggest that complex GA-13-6 holds the potential for the treatment or prevention of periodontal and dental diseases, as well as various other inflammation-related conditions, while averting the induction of antibiotic resistance.

Effect of Zeolite Incorporation on the Ion Release Properties of Silver-Reinforced Glass Ionomer Cement.

Zeolite can release antimicrobial silver ions in a targeted and controlled manner for an extended time, selectively inhibiting the growth of pathogenic oral bacteria when added to dental materials. The objective of this study was to investigate the effect of the addition of zeolite to silver-reinforced glass ionomer cement on the release of silver ions over time. Five concentrations of silver-zeolite (0%, 0.5%, 1%, 2%, 4% wt) were incorporated into silver-reinforced GIC in the form of 10 mm × 2 mm circular disks (n = 5). The disks were incubated in deionized water at 37 °C and ion release from the samples was measured at 1, 2, 7, and 30 days after immersion by inductively coupled atomic emission spectroscopy. Incorporating silver-zeolite increased silver ion release from silver-reinforced GIC disks compared to the control disks (p < 0.05), while incorporating zeolite alone had no effect. Higher concentrations of added silver-zeolite resulted in increased silver ion release. Sustained silver ion release was observed for up to 30 days. Adding silver-zeolite to silver-reinforced GIC may enhance its extended antibacterial effect in the oral cavity.

Transcriptome responses of Lactococcus paracarnosus to different gas compositions and co-culture with Brochothrix thermosphacta

Lactococcus (Lc.) paracarnosus and the phylogenetically closely related Lc. carnosus species are common members of the microbiota in meat stored under modified atmosphere and at low temperature. The effect of these strains on meat spoilage is controversially discussed. While some strains are known to cause spoilage, others are being studied for their potential to suppress the growth of spoilage and pathogenic bacteria. In this study, Lc. paracarnosus DSM 111017T was selected based on a previous study for its ability to suppress the growth of meat spoilers, including Brochothrix thermosphacta. The mechanism by which this bioprotective strain inhibits competing bacteria and how it contributes to spoilage are not yet known. To answer these two questions, we investigated the effect of four different headspace gas mixtures (simulated air (21 % O2/79 % N2); HiOx-MAP (70 % O2/30 % CO2); nonOx-MAP (70 % N2/ 30 % CO2); simulated vacuum (100 % N2) and the presence of Brochothrix (B.) thermosphacta TMW 2.2101 on the growth and transcriptional response of Lc. paracarnosus DSM 111017T when cultured on a meat simulation agar surface at 4 °C. Analysis of genes specifically upregulated by the gas mixtures used revealed metabolic pathways that may lead to different levels of spoilage metabolites production. We propose that under elevated oxygen levels, Lc. paracarnosus preferentially converts pyruvate from glucose and glycerol to uncharged acetoin/diacetyl instead of lactate to counteract acid stress. Due to the potential production of a buttery off-flavour, the strain may not be suitable as a protective culture in meat packaged under high‑oxygen conditions. 70 % N2/ 30 % CO2, simulated vacuum- and the presence of Lc. paracarnosus inhibited the growth of B. thermosphacta TMW 2.2101. However, B. thermosphacta did not affect gene regulation of metabolic pathways in Lc. paracarnosus, and genes previously predicted to be involved in B. thermosphacta growth suppression were not regulated at the transcriptional level. In conclusion, the study indicates that the gas mixture used in packaging significantly affects the metabolism and spoilage potential of Lc. paracarnosus and its ability to inhibit B. thermosphacta growth.

Antibacterial Activity Of Toothpaste Formulation Containing Spirulina platensis Extract Against Streptococcus mutans

Background: The main bacteria involved in the formation of dental caries is Streptococcus mutans (S. mutans). One approach to reduce the growth of S. mutans bacterial colonies is by brushing teeth with toothpaste containing antibacterial agent. The commonly used antibacterial agent is chlorhexidine, which is the gold standard chemical in reducing the colonization of S. mutans bacteria and other oral biofilms. However, over time, it causes various side effects, thus necessitating the search for alternative natural ingredients. One of potential ingredient with antibacterial agent is the Spirulina platensis, which contains secondary metabolites known to inhibit the growth of pathogenic bacteria. Thus, Spirulina platensis can be added to toothpaste as an antibacterial agent. Method: This study employed an experimental laboratory design with a post-test-only control group design. The study consisted of 7 treatments with 5 replications. Antibacterial activity was tested using the agar diffusion method by observing the average diameter of the inhibition zone formed. Data were analyzed using parametric one-way ANOVA. Discussion and Results: In this study, toothpaste with Spirulina platensis extract at concentrations of 0.25%, 0.5%, 1%, 2%, and 3% can inhibited the growth of S. mutans with average inhibition zone diameters of 20.4 mm, 20.8 mm, 21.8 mm, 22.3 mm, and 22.7 mm. The one-way ANOVA parametric test results showed a value of p0.05, indicating a significant difference in the antibacterial activity of S. mutans in all treatment groups. Conclusion: Toothpaste formulations with Spirulina platensis extract have antibacterial activity against S. mutans bacteria.

Chitosan from the base of Flammulina velutipes stipe alleviates oral Candida albicans infection via modulating Th-17 cell differentiation and Streptococcus mutans

The base of Flammulina velutipes (F. velutipes) stipe are agricultural wastes generated during the cultivation of edible fungus F. velutipes with high amount of chitin. Herein, this study firstly prepared chitosan from the base of F. velutipes stipe (FVC) and its structure was identified. It was confirmed that FVC acted as an antigenic substance to activate the immune system in vivo and in vitro, drive T cells to differentiate into Th-17 cells, and establish an effective mucosal immune barrier in the oral cavity, thus inhibited C. albicans infection; On the other hand, FVC maintained the oral flora stability and significantly reduced the abundance of Streptococcus spp., which was closely related to C. albicans infection. On this basis, the inhibitory effects of FVC on oral pathogens Streptococcus mutans and Lactobacillus casei associated with C. albicans infection were further verified, and it was demonstrated that FVC effectively interfered with the growth of pathogenic bacteria by inducing the production of intracellular ROS to damage bacterial cells. Therefore, FVC may be potentially exploited as a novel approach to the prevention and treatment of oral C. albicans infection.

Evaluation of Aloe Vera Gel Combined with Cinnamon Oil with Antibacterial Activity for Wound Healing Application.

Treatment of chronic wounds has been shifted to traditional approaches due to surge in antibiotic resistance. Wounds that fail to heal satisfactorily may result in the amputation of the organ. In this research work, cinnamon oil (CO) and aloe vera (AV) that have been traditionally used as antibacterial agents are combined in a unique gel (COVA) and its antibacterial activity has been evaluated through in vitro and in vivo studies. Antibacterial activity was measured through disk diffusion and agar dilution method against Pseudomonas aeruginosa and Staphylococcus aureus. To check antibacterial and wound healing activity, diabetic excision wound healing rat model was used. Wound closure, wound contraction, tissue hydroxyproline content, antioxidant capacity (TAC), and malondialdehyde (MDA) level were monitored. The minimum inhibitory concentrations of CO + AV for bacterium P. aeruginosa and S. aureus were 100 and 200 µg/ml, respectively. After 14 days, the wounds covered with COVA therapy reached to nearly full wound closure (79% wound contraction) compared to control. The collagen content and level of TAC increased significantly (P < 0.05) in treated groups; therefore, 25% fast healing was observed in wounds treated with CO and AV gel combined. Reduced levels of tissue MDA were observed in all treated groups and specially wound covered with COVA (0.43 mM/mg in control vs 0.25 mM/mg in COVA). Histopathological examination also supported the outcomes. Significantly elevated increase in the level of hydroxyproline was found in rats of COVA treatment group (37.1 ± 0.44). Combination of CO and AV can be potentially used to prevent infection in wound; as these herbal agents not only inhibit the growth of pathogenic bacteria but also accelerate tissue repair.

Papaya extract as a prebiotic strengthens the inhibitory activity of lactobacillus against the growth of pathogenic bacteria

Abstract The flesh leaves, and seeds of papaya contain carbohydrates and dietary fiber that were suggested capable of being metabolized by intestinal microbiota such as L. casei and L. plantarum to produce beneficial secondary metabolites for body health. The effect of papaya flesh, leaf, and seed extracts on L. plantarum and L. casei growth and the synbiotic effect of papaya flesh extract with L. plantarum on the growing of S. aureus, E. coli, and P. aeruginosa in this study, was investigated. Diffusion of paper discs impregnated with various concentrations of the extract was utilized to determine the bacterial growth zone of L. casei, and solid media to calculate the total bacterial population in co-feeding L. plantarum and P. aeruginosa or with S. aureus and E. coli in the presence of papaya flesh extract to determine its synbiotic effect. All extracts increase the growth of L. casei and L. plantarum bacteria. Synbiotic papaya flesh extract suppresses the bacterial growth of P. aeruginosa, S. aureus, and E. coli in a concentration-dependent manner. It is concluded that papaya is a promising prebiotic source, to strengthen the effect of L. plantarum to inhibit the growth of pathogenic bacteria.

Integrating uterine microbiome and metabolome to advance the understanding of the uterine environment in dairy cows with metritis.

Metritis is a prevalent uterine disease that affects the welfare, fertility, and survival of dairy cows. The uterine microbiome from cows that develop metritis and those that remain healthy do not differ from calving until 2 days postpartum, after which there is a dysbiosis of the uterine microbiome characterized by a shift towards opportunistic pathogens such as Fusobacteriota and Bacteroidota. Whether these opportunistic pathogens proliferate and overtake the uterine commensals could be determined by the type of substrates present in the uterus. The objective of this study was to integrate uterine microbiome and metabolome data to advance the understanding of the uterine environment in dairy cows that develop metritis. Holstein cows (n = 104) had uterine fluid collected at calving and at the day of metritis diagnosis. Cows with metritis (n = 52) were paired with cows without metritis (n = 52) based on days after calving. First, the uterine microbiome and metabolome were evaluated individually, and then integrated using network analyses. The uterine microbiome did not differ at calving but differed on the day of metritis diagnosis between cows with and without metritis. The uterine metabolome differed both at calving and on the day of metritis diagnosis between cows that did and did not develop metritis. Omics integration was performed between 6 significant bacteria genera and 153 significant metabolites on the day of metritis diagnosis. Integration was not performed at calving because there were no significant differences in the uterine microbiome. A total of 3 bacteria genera (i.e. Fusobacterium, Porphyromonas, and Bacteroides) were strongly correlated with 49 metabolites on the day of metritis diagnosis. Seven of the significant metabolites at calving were among the 49 metabolites strongly correlated with opportunistic pathogenic bacteria on the day of metritis diagnosis. The main metabolites have been associated with attenuation of biofilm formation by commensal bacteria, opportunistic pathogenic bacteria overgrowth, tissue damage and inflammation, immune evasion, and immune dysregulation. The data integration presented herein helps advance the understanding of the uterine environment in dairy cows with metritis. The identified metabolites may provide a competitive advantage to the main uterine pathogens Fusobacterium, Porphyromonas and Bacteroides, and may be promising targets for future interventions aiming to reduce opportunistic pathogenic bacteria growth in the uterus.

Structural Determinants of Vibrio cholerae FeoB Nucleotide Promiscuity.

Ferrous iron (Fe2+) is required for the growth and virulence of many pathogenic bacteria, including Vibrio cholerae (Vc), the causative agent of the disease cholera. For this bacterium, Feo is the primary system that transports Fe2+ into the cytosol. FeoB, the main component of this system, is regulated by a soluble cytosolic domain termed NFeoB. Recent reanalysis has shown that NFeoBs can be classified as either GTP-specific or NTP-promiscuous, but the structural and mechanistic bases for these differences were not known. To explore this intriguing property of FeoB, we solved the X-ray crystal structures of VcNFeoB in both the apo and GDP-bound forms. Surprisingly, this promiscuous NTPase displayed a canonical NFeoB G-protein fold like GTP-specific NFeoBs. Using structural bioinformatics, we hypothesized that residues surrounding the nucleobase could be important for both nucleotide affinity and specificity. We then solved the X-ray crystal structures of N150T VcNFeoB in the apo and GDP-bound forms to reveal H-bonding differences surround the guanine nucleobase. Interestingly, isothermal titration calorimetry revealed similar binding thermodynamics of the WT and N150T proteins to guanine nucleotides, while the behavior in the presence of adenine nucleotides was dramatically different. AlphaFold models of VcNFeoB in the presence of ADP and ATP showed important conformational changes that contribute to nucleotide specificity among FeoBs. Combined, these results provide a structural framework for understanding FeoB nucleotide promiscuity, which could be an adaptive measure utilized by pathogens to ensure adequate levels of intracellular iron across multiple metabolic landscapes.

Evaluation of living bacterial therapy assisted by pH/reactive oxygen species dual-responsive sodium alginate-based hydrogel for wound infections

The enhancement of antimicrobial wound dressings is of utmost importance in light of the escalating risk of antibiotic resistance caused by excessive antibiotic usage. Conventional antimicrobial materials eradicate pathogenic bacteria while impeding the proliferation of beneficial bacteria during the management of wound infections, thereby disturbing the equilibrium of the skin micro-ecosystem and engendering recurrent cutaneous complications. Lactobacillus rhamnosus (L.rha) is a probiotic that can inhibit the growth of certain pathogenic bacteria by secreting a large number of metabolites. In this paper, we synthesized a cross-linker (SPBA) with a boric acid molecule from succinic acid and 4-(bromomethyl)phenylboronic acid, which formed a boric acid ester bond with a diol on the natural polysaccharide sodium alginate (SA), and obtained a pH/reactive oxygen species (ROS) dual-responsive hydrogel (SA-SPBA) for loading L.rha to treat wound infections. The SA-SPBA@L.rha hydrogel improves the survival of L.rha during storage and has good injectability as well as self-healing properties. The hydrogel showed good biocompatibility, the antimicrobial effect increases in a dose-dependent manner, and it has a certain antioxidant and anti-inflammatory capacity, accelerating wound repair. The use of SA-SPBA@L.rha hydrogel provides a safe and effective strategy for the repair of skin wound infections.

Molecular Basis of Yeasts Antimicrobial Activity-Developing Innovative Strategies for Biomedicine and Biocontrol.

In the context of the growing concern regarding the appearance and spread of emerging pathogens with high resistance to chemically synthetized biocides, the development of new agents for crops and human protection has become an emergency. In this context, the yeasts present a huge potential as eco-friendly agents due to their widespread nature in various habitats and to their wide range of antagonistic mechanisms. The present review focuses on some of the major yeast antimicrobial mechanisms, their molecular basis and practical applications in biocontrol and biomedicine. The synthesis of killer toxins, encoded by dsRNA virus-like particles, dsDNA plasmids or chromosomal genes, is encountered in a wide range of yeast species from nature and industry and can affect the development of phytopathogenic fungi and other yeast strains, as well as human pathogenic bacteria. The group of the "red yeasts" is gaining more interest over the last years, not only as natural producers of carotenoids and rhodotorulic acid with active role in cell protection against the oxidative stress, but also due to their ability to inhibit the growth of pathogenic yeasts, fungi and bacteria using these compounds and the mechanism of competition for nutritive substrate. Finally, the biosurfactants produced by yeasts characterized by high stability, specificity and biodegrability have proven abilities to inhibit phytopathogenic fungi growth and mycelia formation and to act as efficient antibacterial and antibiofilm formation agents for biomedicine. In conclusion, the antimicrobial activity of yeasts represents a direction of research with numerous possibilities of bioeconomic valorization as innovative strategies to combat pathogenic microorganisms.