The Gram-Positive Bacterial Cell Wall

Sucrose laurate and nisin synergistically inhibit Bacillus subtilis by multiple antibacterial targets and play promising application potential in bread preservation

Sucrose laurate, a commonly used emulsifier, was investigated to explore its preservative effect combined with nisin using Bacillus subtilis as indicator. The results suggested that sucrose laurate and nisin exhibited synergistic antibacterial effect with the fractional inhibitory concentration index of 0.5. Moreover, antibacterial mechanism assays revealed that sucrose laurate and nisin compromised the cell wall integrity by retarding peptidoglycan synthesis, dissipated membrane potential, damaged membrane permeability by inactivating the Na+K+-ATPase via hydrogen bonding interaction to trigger K+ leakage, and destroyed cell membrane integrity concurrently with the leakage of protein and nucleic acid; SEM observation revealed their remarkable ability to disrupt cell ultrastructure and induce morphological shrinkage; Gel retardation results demonstrated the alternation in protein expression patterns. Furthermore, the promising effect of sucrose laurate and nisin was evidenced in bread exhibiting extended shelf life. Conclusively, this research could provide scientific basis for expanding the application of sucrose laurate in food industry.

Siderophore-Functionalized Nanodrug for Treating Antibiotic-Resistant Bacteria

The development of nanodrugs targeting multidrug-resistant bacteria, while sparing the beneficial constituents of the microbiome, has emerged as a promising approach to combat disease and curb the rise of antimicrobial resistance. In this investigation, we devised a siderophore-functionalized nanodrug based on a gold nanoparticle construct (AuNP-NSC; Gold nanoparticle_N-heterocyclic_Siderophore_Cyanine7), offering an innovative treatment modality against drug-resistant bacterial pathogens. As a proof of concept, the efficacy of this nanodrug delivery and antimicrobial therapy was evaluated against the notoriously resistant bacterium P. aeruginosa. N-Heterocyclic carbenes (NHCs) exhibit a strong affinity for transition metals, forming highly stable complexes resistant to ligand displacement. The entry of siderophore-conjugated nanodrugs into bacteria is facilitated through specific receptors on the outer membrane. In our study, AuNP-NSC was specifically targeted and imported into resistant Gram-negative P. aeruginosa via binding with ferric iron. Treatment with the developed nanodrug significantly inhibited the proliferation of antibiotic-resistant P. aeruginosa, reducing bacterial counts by more than 95% and mitigating drug resistance. Furthermore, AuNP-NSC markedly diminished P. aeruginosa-induced skin lesions and forestalled systemic organ failure triggered by secondary sepsis in mouse models. These findings underscore the potential of nanodrugs as specialized therapeutic agents for the management of antibiotic-resistant bacterial infections.

Reactions of SleC, Its Structure and Inhibition in Mitigation of Spore Germination in Clostridioides difficile

Spore germination in Clostridioides difficile is initiated by a cascade of activities of several proteins that culminates in the activation of SleC, a cell-wall-processing enzyme. We report herein the details of the enzymatic activities of SleC by the use of synthetic peptidoglycan fragments and of spore sacculi. The reactions include the formation of 1,6-anhydromuramate─a hallmark of lytic transglycosylase activity─as well as a muramate hydrolytic product, both of which proceed through the same transient oxocarbenium species. Furthermore, we report the first X-ray structure of zymogenic prepro-SleC at 2.1 Å resolution. Additionally, the structure provides insights into the YabG and CspB cleavage sites necessary for the activation of the zymogen. The active site of SleC presents relevant differences in contrast to SpoIID, a homologous lytic transglycosylase involved in the sporulation Clostridioides species, explaining the ability of SleC to turn over the spore sacculus, a prerequisite for the germination event. A screening of an in-house library of compounds led to the discovery of an oxadiazole that binds to the mature (activated) form of SleC, whereby it shuts down the ability of spores to germinate in the presence of germinants. This is consistent with the SleC activity as an end-point for the germination cascade. The mechanistic knowledge and the inhibitor hold the promise in addressing an unmet medical need in intervention of recurrent infections by C. difficile.

In Vitro Determination of Antimicrobial, Antioxidant and Antiviral Properties of Greek Plant Extracts

The medicinal potential of plant extracts, especially their antimicrobial, antioxidant, antiviral and cytotoxic properties, has gained significant attention in recent years. This study examined the in vitro bioactivities of several selected Greek medicinal plants, like Eucalyptus globulus L., Thymus vulgaris L., Salvia rosmarinus L. and Ocimum basilicum L., are well-known for their traditional therapeutic use. Minimum inhibitory concentration (MIC) assays were used to evaluate the antimicrobial activity of the extracts against pathogenic bacteria. The antioxidant activity was carried out using the DPPH method, while the cytotoxicity of the plants was determined using the Alamar Blue method. In addition, the antiviral efficacy of the samples was tested against DENV in different cell lines. The majority of medicinal herbs demonstrated significant antimicrobial action (MIC = 30-3000 μg∙mL-1). The extracts showed great antioxidant activity, while the Salvia rosmarinus L. extract turned out to be the most effective (IC50 = 12.89 ± 0.11 μg∙mL-1). In contrast, the extract of Eucalyptus globulus L. had the lowest antioxidant action (IC50 = 71.02 ± 0.42 μg∙mL-1). The results of the Alamar Blue method were presented with CC50 values, and it was shown that Eucalyptus globulus L. extract exhibited the highest cytotoxicity (CC50 = 5.94% v/v ± 0.04). Similarly, the results of the antiviral potential of extracts were expressed as EC50 values, and Eucalyptus globulus L. was characterized as the most effective sample against dengue virus infection, with EC50 values estimated at 2.37% v/v ± 0.6 (HuhD-2 cells infected with DENV-2) and 0.36% v/v ± 0.004 (Huh7.5 cells infected with DVR2A). These findings provide a foundation for further studies in order to combat infectious diseases and promote human health.

A biocompatible β-cyclodextrin inclusion complex containing natural extracts: a promising antibiofilm agent

Biofilms formed by several bacterial strains still pose a significant challenge to healthcare due to their resistance to conventional treatment approaches, including antibiotics. This study explores the potential of loading natural extracts with antimicrobial activities into β-cyclodextrin (βCD) nanoparticles, which are FDA-approved and have superior biocompatibility owing to their cyclic sugar structures, for biofilm eradication. An inclusion complex of βCD carrying Boswellia sacra essential oils (BOS) was prepared and characterized with regard to its physicochemical properties, antimicrobial efficacy, and antibiofilm activities. Encapsulation of BOS into βCD significantly enhanced the antimicrobial activity of BOS by 4-fold against Gram-positive (Staphylococcus aureus and Bacillus subtilis) and by 8-fold against Gram-negative (Escherichia coli and Pseudomonas putida) bacteria, with minimum inhibitory concentrations ranging from 2.5 to 5 mg mL-1. Furthermore, the BOS-βCD complex demonstrated a dual-action against bacterial biofilms where it prevented biofilm formation and disrupted established biofilms. This resulted in a significant reduction in biofilm biomass, with prevention and disruption rates reaching up to 93.78% and 82.17%, respectively. Additionally, the formula revealed an excellent biocompatibility profile with no induction of oxidative stress in human skin fibroblast cells. Our findings suggest that βCD nanoparticles loaded with BOS essential oils hold promise as an effective formula for preventing the formation of bacterial biofilms and combating preformed ones for use in relevant medical applications.

Porphyrin-Polymer as a Photosensitizer Prodrug for Antimicrobial Photodynamic Therapy and Biomolecule Binding Ability

This study presents the development and characterization of a novel porphyrin-Jeffamine polymer conjugate designed to function as a photosensitizer prodrug for antimicrobial photodynamic therapy (aPDT). The conjugate features a photosensitive porphyrin unit covalently attached to a biocompatible polymer backbone, with enhanced solubility, stability, and bioavailability compared to those of the free porphyrin derivatives. The photophysical properties were studied using transient absorption spectroscopy spanning the fs-μs time scales in addition to emission studies. The production of reactive oxygen species upon photoactivation enabled effective bacterial cell killing. Spectroscopic studies confirmed strong binding of the conjugate to DNA through intercalation, likely disrupting DNA replication and transcription. Interaction studies with bovine serum albumin demonstrated substantial serum protein binding, which may positively impact the pharmacokinetics and biodistribution. Overall, this porphyrin-polymer conjugate offers a multifunctional theranostic platform, combining antimicrobial action with DNA and protein binding potential, positioning it as a promising candidate for aPDT and bioimaging applications.

Metal nanoparticles incorporated chitosan-based electrospun nanofibre mats for wound dressing applications: A review

Wound healing is a dynamic physiological process essential for regenerating skin and maintaining coherence in hypodermic tissues. Chitosan-based electrospun nanofibre wound dressings show great promise for expediting the integration of skin and tissues due to their nano-topographic, biodegradable, biocompatible, and antimicrobial properties. However, their moderate bactericidal efficacy and limited mechanical strength hinder their widespread clinical application. The incorporation of specific metal nanoparticles (MNPs) and the functionalization of chitosan have brought attention to their crucial role in wound healing applications, yielding promising results by enhancing antibacterial properties, cell proliferation, cell signaling, and the mechanical robustness of the materials. Chitosan naturally mitigates the cytotoxicity of the incorporated metal nanoparticles within the nanofibers. Chitosan and modified chitosan-based electrospun mats incorporated with metal nanoparticles demonstrate substantial potential for expediting wound healing. This review offers a comprehensive overview of recent advancements in electrospun chitosan-based mats containing MNPs aimed at enhancing wound healing. It covers various aspects, including modification techniques, fabrication methods, wound closure mechanisms, MNP release profiles, histological considerations, addresses existing challenges, and outlines potential future developments.

Evaluation of riboflavin, nanocurcumin, and hydrogen peroxide under light conditions: Reduction of mature dental biofilms and enamel mineral loss

BACKGROUND

Biofilms are a potential harbor for many microorganisms. The aim of this study was to test the efficacy of riboflavin (Rib), nano-micelle curcumin (NC), and hydrogen peroxide (HP), alone and in combination with the respective light (light-emitting diode (LED) or 980 nm diode laser) on the reduction of Streptococcus mutans and Lactobacillus acidophilus dual-species biofilms and their effect on the enamel mineral loss.

MATERIALS AND METHODS

The biofilms were formed on saliva-coated enamel slabs. Then, the biofilms were treated with antimicrobial photodynamic therapy (PDT) based on LED, Rib, and NC photosensitizers and with HP also based on a 980 nm diode laser (n = 8 per group). A crystal violet assay was performed to determine the reduction of the dual-species biofilms. The enamel slabs were analyzed for calcium and phosphorus content by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX).

RESULTS

While HP-PDT showed a reduction of 37% (p < 0.001), PDT with NC resulted in an even greater reduction of dual-species biofilms (40%, p < 0.001) than HP- and Rib-mediated PDT. In the EDX test, no significant difference was found between the control group and the treatment groups.

CONCLUSIONS

The use of natural photosensitizers such as NC in PDT has an effect that may be potentially important in reducing caries-causing bacteria.

Antimicrobial Impact of Wood Vinegar Produced Through Co-Pyrolysis of Eucalyptus Wood and Aromatic Herbs

BACKGROUND

The search for substances that can overcome microorganisms' resistance and enhance the antimicrobial activity of given products has attracted the attention of researchers. Eucalyptus wood vinegar (WV) is a promising product for developing alternative antimicrobials.

OBJECTIVES

This study aimed to evaluate whether the production of WV in the co-pyrolysis of eucalyptus wood with aromatic herbs would incorporate compounds from them into WV and if that would enhance its antimicrobial action.

METHODOLOGY

WV was produced alone and through co-pyrolysis with marjoram (Origanum majorana), Peruvian oregano (Origanum vulgare), rosemary (Salvia rosmarinus), thyme (Thymus vulgaris), and Turkish oregano (Origanum onites) at a proportion of 25% of herbs to the bone-dry wood weight. The antimicrobial effects were assessed against strains of gram-negative and -positive bacteria, and Candida glabrata. Microorganisms' colony growth in agar had their absorbances recorded after inoculation and incubation. Chemical characterization of the new products was performed by gas chromatography and mass spectrometry (GC/MS).

RESULTS

After coproduction, there were relevant chemical changes concerning the original WV. Thymol, for instance, was incorporated into the WV through co-pyrolysis with marjoram, Peruvian and Turkish oregano, and thyme. The coproducts were more efficient than the WV produced only with wood, with thyme-incorporated products having the highest efficiency. This can be attributed to the increase and incorporation of the substances after coproduction, and particularly the role of thymol in enhancing the antimicrobial action.

CONCLUSION

Given the results, the co-production of WV with eucalyptus wood and aromatic herbs has the potential to provide alternative antimicrobial products.

Reducing the degree of crosslinking of peptidoglycan in Listeria monocytogenes promoted the secretion of membrane vesicles

Listeria monocytogenes (LM) is a Gram-positive (G+) bacterium that secretes nanoscale membrane vesicles (MVs). LM MVs comprise various bacterial components and may have potential as an antigen or drug-delivery vehicle; however, the low yield of the LM MVs limits related research. G+-bacterial MVs germinate from the bacterial plasma membrane and must pass through a thick crosslinked peptidoglycan layer for release. Herein, we aimed to increase the release of MVs by reducing the degree of crosslinking of peptidoglycan. We knocked out two genes related to the longitudinal crosslinking of peptidoglycan, dal and dat, and supplemented the knocked-out dal gene through plasmid expression to obtain a stably inherited recombinant strain LMΔdd::pCW633. The structure, particle size, and main protein components of MVs secreted by this recombinant strain were consistent with those secreted from the wild strain, but the yield of MVs was considerably increased (p < 0.05). Furthermore, Listeria ivanovii (LI) was found to secrete MVs that differed in the composition of the main proteins compared with those of LM MVs. The abovementioned method was also feasible for promoting the secretion of MVs from the attenuated LM strain and LI wild-type and attenuated strains. Our study provides a new method to increase the secretion of MVs derived from Listeria that could be extended to other G+ bacteria.

Staphylococcus aureus membrane vesicles: an evolving story

Staphylococcus aureus is an important bacterial pathogen that causes a wide variety of human diseases in community and hospital settings. S. aureus employs a diverse array of virulence factors, both surface-associated and secreted, to promote colonization, infection, and immune evasion. Over the past decade, a growing body of research has shown that S. aureus generates extracellular membrane vesicles (MVs) that package a variety of bacterial components, many of which are virulence factors. In this review, we summarize recent advances in our understanding of S. aureus MVs and highlight their biogenesis, cargo, and potential role in the pathogenesis of staphylococcal infections. Lastly, we present some emerging questions in the field.

An in-depth exploration of the multifaceted roles of EVs in the context of pathogenic single-cell microorganisms

SUMMARYExtracellular vesicles (EVs) have been recognized throughout scientific communities as potential vehicles of intercellular communication in both eukaryotes and prokaryotes, thereby influencing various physiological and pathological functions of both parent and recipient cells. This review provides an in-depth exploration of the multifaceted roles of EVs in the context of bacteria and protozoan parasite EVs, shedding light on their contributions to physiological processes and disease pathogenesis. These studies highlight EVs as a conserved mechanism of cellular communication, which may lead us to important breakthroughs in our understanding of infection, mechanisms of pathogenesis, and as indicators of disease. Furthermore, EVs are involved in host-microbe interactions, offering insights into the strategies employed by bacteria and protozoan parasites to modulate host responses, evade the immune system, and establish infections.

Bacteria and Allergic Diseases

Microorganisms colonize all barrier tissues and are present on the skin and all mucous membranes from birth. Bacteria have many ways of influencing the host organism, including activation of innate immunity receptors by pathogen-associated molecular patterns and synthesis of various chemical compounds, such as vitamins, short-chain fatty acids, bacteriocins, toxins. Bacteria, using extracellular vesicles, can also introduce high-molecular compounds, such as proteins and nucleic acids, into the cell, regulating the metabolic pathways of the host cells. Epithelial cells and immune cells recognize bacterial bioregulators and, depending on the microenvironment and context, determine the direction and intensity of the immune response. A large number of factors influence the maintenance of symbiotic microflora, the diversity of which protects hosts against pathogen colonization. Reduced bacterial diversity is associated with pathogen dominance and allergic diseases of the skin, gastrointestinal tract, and upper and lower respiratory tract, as seen in atopic dermatitis, allergic rhinitis, chronic rhinosinusitis, food allergies, and asthma. Understanding the multifactorial influence of microflora on maintaining health and disease determines the effectiveness of therapy and disease prevention and changes our food preferences and lifestyle to maintain health and active longevity.

Double-Wing Motif Protein is a Novel Biofilm Regulatory Factor of the Plant Disease Biocontrol Agent, Bacillus subtilis

Transposon mutagenesis screening of Bacillus subtilis YB-1471, a novel rhizosphere biocontrol agent of Fusarium crown rot (FCR) of wheat, resulted in the identification of orf04391, linked to reduced biofilm formation. The gene encodes a protein possessing a putative tertiary structure of a "double-wing" DNA-binding domain. Expression of orf04391 increased during biofilm development in stationary cultures and during rapid growth in shaking cultures. An orf04391 deletion strain showed reduced biofilm production related to lower levels of the extracellular matrix, and the mutant also had reduced sporulation, adhesion, root colonization, and FCR biocontrol efficiency. Transcriptome analysis of YB-1471 and Δorf04391 in stationary culture showed that the loss of orf04391 resulted in altered expression of numerous genes, including sinI, an initiator of biofilm formation. DNA binding was shown with his-tagged Orf04391 binding to the sinIR operon in vivo and in vitro. Orf04391 appears to be a transcriptional regulator of biofilm formation in B. subtilis through the Spo0A-SinI/SinR pathway.

Chitosan and its derivatives regulate lactic acid synthesis during milk fermentation

Introduction

The influence of chitosan's physicochemical characteristics on the functionality of lactic acid bacteria and the production of lactic acid remains very obscure and contradictory to date. While some studies have shown a stimulatory effect of oligochitosans on the growth of Lactobacillus spp, other studies declare a bactericidal effect of chitosan. The lack and contradiction of knowledge prompted us to study the effect of chitosan on the growth and productivity of L. bulgaricus in the presence of chitosan and its derivatives.

Methods

We used high molecular weight chitosan (350 kDa) and oligochitosans (25.4 and 45.3 kDa). The experiment was carried out with commercial strain of L. bulgaricus and the low fat skim cow milk powder reconstituted with sterile distilled water. After fermentation, dynamic viscosity, titratable acidity, pH, content of lactic acid, colony forming units, chitosan and oligochitosans radii were measured in the samples. Fermented dairy products were also examined using sodium dodecyl sulfate electrophoretic analysis, gas chromatography-mass spectrometry and light microscopy.

Results and discussion

The results of the study showed that when L. bulgaricus was cultured in the presence of 25.4 kDa oligochitosans at concentrations of 0.0025%, 0.005%, 0.0075% and 0.01%, the average rate of LA synthesis over 24 hours was 11.0 × 10-3 mol/L/h, 8.7 × 10-3 mol/L/h, 6.8 × 10-3 mol/L/h, 5.8 × 10-3 mol/L/h, respectively. The 45.3 kDa oligochitosans had a similar effect, while the average rate of lactic acid synthesis in the control sample was only 3.5 × 10-3 mol/L/h. Notably, 350 kDa chitosan did not affect the rate of lactic acid synthesis compared with the control sample. Interestingly, interaction of chitosan with L. bulgaricus led to a slowdown in the synthesis of propanol, an increase in the content of unsaturated and saturated fatty acids, and a change in the composition and content of other secondary metabolites. The quantity of L. bulgaricus in a sample with 0.01% chitosan exceeded their content in the control sample by more than 1,700 times. At the same chitosan concentration, the fermentation process was slowed down, increasing the shelf life of the fermented milk product from 5 to 17 days while maintaining a high content of L. bulgaricus (6.34 × 106 CFU/g).

Streptococcus dysgalactiae subsp. equisimilis infection and its intersection with Streptococcus pyogenes

SUMMARYStreptococcus dysgalactiae subsp. equisimilis (SDSE) is an increasingly recognized cause of disease in humans. Disease manifestations range from non-invasive superficial skin and soft tissue infections to life-threatening streptococcal toxic shock syndrome and necrotizing fasciitis. Invasive disease is usually associated with co-morbidities, immunosuppression, and advancing age. The crude incidence of invasive disease approaches that of the closely related pathogen, Streptococcus pyogenes. Genomic epidemiology using whole-genome sequencing has revealed important insights into global SDSE population dynamics including emerging lineages and spread of anti-microbial resistance. It has also complemented observations of overlapping pathobiology between SDSE and S. pyogenes, including shared virulence factors and mobile gene content, potentially underlying shared pathogen phenotypes. This review provides an overview of the clinical and genomic epidemiology, disease manifestations, treatment, and virulence determinants of human infections with SDSE with a particular focus on its overlap with S. pyogenes. In doing so, we highlight the importance of understanding the overlap of SDSE and S. pyogenes to inform surveillance and disease control strategies.

Ultra-Photostable Bacterial-Seeking Near-Infrared CPDs for Simultaneous NIR-II Bioimaging and Antibacterial Therapy

Bacterial infections can pose significant health risks as they have the potential to cause a range of illnesses. These infections can spread rapidly and lead to complications if not promptly diagnosed and treated. Therefore, it is of great significance to develop a probe to selectively target and image pathogenic bacteria while simultaneously killing them, as there are currently no effective clinical solutions available. This study presents a novel approach using near-infrared carbonized polymer dots (NIR-CPDs) for simultaneous in vivo imaging and treatment of bacterial infections. The core-shell structure of the NIR-CPDs facilitates their incorporation into bacterial cell membranes, leading to an increase in fluorescence brightness and photostability. Significantly, the NIR-CPDs exhibit selective bacterial-targeting properties, specifically identifying Staphylococcus aureus (S. aureus) while sparing Escherichia coli (E. coli). Moreover, under 808 nm laser irradiation, the NIR-CPDs exhibit potent photodynamic effects by generating reactive oxygen species that target and damage bacterial membranes. In vivo experiments on infected mouse models demonstrate not only precise imaging capabilities but also significant therapeutic efficacy, with marked improvements in wound healing. The study provides the dual-functional potential of NIR-CPDs as a highly effective tool for the advancement of medical diagnostics and therapeutics in the fight against bacterial infections.

Tagetes erecta-Mediated Biosynthesis of Mn3O4 Nanoparticles: Structural, Electrochemical, and Biological Investigations

Mn3O4 nanoparticles (NPs) find diverse applications in the fields of medicine, biomedicine, biosensors, water treatment and purification, electronics, electrochemistry, and photoelectronics. The production of Mn3O4 NPs was reported earlier through various physical, chemical, and green routes, but no studies have still been performed on their biosynthesis from Tagetes erecta. We synthesized manganese oxide NPs, i.e., (Mn3O4)L and (Mn3O4)P NPs, by utilizing leaves and petals, respectively, of T. erecta as reducing and stabilizing agents. The investigated green path is eco-friendly and does not involve any hazardous raw materials. The structural properties of NPs were determined by X-ray diffraction (XRD) analysis, spectroscopies (Fourier transform infrared (FTIR), Raman, and UV-visible), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The NPs were also evaluated for their electrochemical properties by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD). XRD analysis was performed to verify their tetragonal geometry, and the crystallite size (19.24 nm) of (Mn3O4)P was smaller than that (20.84 nm) of (Mn3O4)L NPs. SEM images displayed a porous and spherical morphology with a diameter of 14-35 nm. FTIR spectra of (Mn3O4)L and (Mn3O4)P displayed Mn-O vibrations at 605.69 and 616.87 cm-1, respectively, and the hydrous nature of the material. Raman spectroscopy revealed the existence of tetrahedral and octahedral units along with A1g, T2g, and Eg active modes of Mn3O4 and 2TO mode. UV-visible analyses of (Mn3O4)L and (Mn3O4)P NPs showed absorption peaks at 272.3 and 268.8 nm, along with band gaps of 4.83 and 5.49 eV, respectively. TGA curves displayed good thermal stabilities up to 600 °C and a loss of moisture content. DSC curves exhibited exothermic/endothermic peaks with glass transition temperatures of 258.9 and 308.7 °C for (Mn3O4)P and (Mn3O4)L, respectively. The CV curves showed redox peaks and confirmed that the electrochemical reaction takes place in the Mn3O4 material. GCD scans revealed the capacitive behavior of NPs and their suitability as electrodes in energy storage devices. However, (Mn3O4)L will act as a good material for energy storage applications as compared to (Mn3O4)P NPs. The synthesized NPs were also tested for their antibacterial efficacy by biofilm inhibition and agar well diffusion methods. The NPs showed higher activities against Staphylococcus aureus (Gram-positive) than against Escherichia coli (Gram-negative), and (Mn3O4)P was more bioactive than (Mn3O4)L.

The Potential Health Benefits of Gallic Acid: Therapeutic and Food Applications

Gallic acid (GA), a phenolic acid found in fruits and vegetables, has been consumed by humans for centuries. Its extensive health benefits, such as antimicrobial, antioxidant, anticancer, anti-inflammatory, and antiviral properties, have been well-documented. GA's potent antioxidant capabilities enable it to neutralize free radicals, reduce oxidative stress, and protect cells from damage. Additionally, GA exerts anti-inflammatory effects by inhibiting inflammatory cytokines and enzymes, making it a potential therapeutic agent for inflammatory diseases. It also demonstrates anticancer properties by inhibiting cancer cell growth and promoting apoptosis. Furthermore, GA offers cardiovascular benefits, such as lowering blood pressure, decreasing cholesterol, and enhancing endothelial function, which may aid in the prevention and management of cardiovascular diseases. This review covers the chemical structure, sources, identification and quantification methods, and biological and therapeutic properties of GA, along with its applications in food. As research progresses, the future for GA appears promising, with potential uses in functional foods, pharmaceuticals, and nutraceuticals aimed at improving overall health and preventing disease. However, ongoing research and innovation are necessary to fully understand its functional benefits, address current challenges, and establish GA as a mainstay in therapeutic and nutritional interventions.

Comprehensive double-mutant analysis of the Bacillus subtilis envelope using double-CRISPRi

Understanding bacterial gene function remains a major biological challenge. Double-mutant genetic interaction (GI) analysis addresses this challenge by uncovering the functional partners of targeted genes, allowing us to associate genes of unknown function with novel pathways and unravel connections between well-studied pathways, but is difficult to implement at the genome-scale. Here, we develop and use double-CRISPRi to systematically quantify genetic interactions at scale in the Bacillus subtilis envelope, including essential genes. We discover > 1000 known and novel genetic interactions. Our analysis pipeline and experimental follow-ups reveal the distinct roles of paralogous genes such as the mreB and mbl actin homologs, and identify new genes involved in the well-studied process of cell division. Overall, our study provides valuable insights into gene function and demonstrates the utility of double-CRISPRi for high-throughput dissection of bacterial gene networks, providing a blueprint for future studies in diverse bacterial species.

Morphological and pathogenic investigation of the emerging fungal threat Emergomyces africanus

Emergomyces africanus is a highly fatal fungal pathogen affecting individuals with advanced HIV disease. Molecular patterns and ultrastructural aspects of E. africanus are unknown, and pathogenic models have not been investigated in detail. Since the cell wall of fungi is a determinant for interaction with the host and antifungal development, we characterized the ultrastructural aspects of E. africanus and the general properties of cell wall components under different conditions of growth in vitro and in vivo. We also tested the pathogenic potential of E. africanus in a Galleria mellonella model of infection. Transmission electron microscopy revealed the common intracellular, ultrastructural features of fungi in association with a thick cell wall. Scanning electron microscopy revealed a smooth cell surface, with no apparent decorative structures. Yeast cultures of E. africanus showed the distribution of chitin, chitooligomers, and mannoproteins commonly observed in fungi. However, in mixed microenvironments containing yeast and filamenting forms of E. africanus, the detection of chitooligomers was increased in comparison with isolated yeast cells, while the detection of these components in filamenting forms was markedly reduced. These observations were suggestive of the ability of E. africanus to change its cell wall composition in response to different microenvironments. Although E. africanus was unable to kill G. mellonella, this infection model allowed us to isolate infected hemocytes for further analysis of mannoproteins, chitin, and chitooligomers. Once again, the detection of E. africanus chitooligomers was markedly increased. These results reveal previously unknown ultrastructural features of E. africanus and suggest a high plasticity in the cell wall of this lethal pathogen.

IMPORTANCE

The epidemiology of fungal infections is very dynamic, and novel health emergencies are hard to predict. New fungal pathogens have been continuously emerging for the last few decades, and Emergomyces africanus is one of these threats to human health. This complex scenario points to the need for generating knowledge about emerging pathogens so that new therapeutic strategies can be designed. In this study, we characterized the general cellular and pathogenic properties of the emerging fungal pathogen E. africanus. Our results reveal that E. africanus manifests some of the typical properties of fungal cells but also exhibits some unique characteristics that might be helpful for the future development of therapeutic strategies.

Engineered bacteriophages: A panacea against pathogenic and drug resistant bacteria

Antimicrobial resistance (AMR) is a major global concern; antibiotics and other regular treatment methods have failed to overcome the increasing number of infectious diseases. Bacteriophages (phages) are viruses that specifically target/kill bacterial hosts without affecting other human microbiome. Phage therapy provides optimism in the current global healthcare scenario with a long history of its applications in humans that has now reached various clinical trials. Phages in clinical trials have specific requirements of being exclusively lytic, free from toxic genes with an enhanced host range that adds an advantage to this requisite. This review explains in detail the various phage engineering methods and their potential applications in therapy. To make phages more efficient, engineering has been attempted using techniques like conventional homologous recombination, Bacteriophage Recombineering of Electroporated DNA (BRED), clustered regularly interspaced short palindromic repeats (CRISPR)-Cas, CRISPY-BRED/Bacteriophage Recombineering with Infectious Particles (BRIP), chemically accelerated viral evolution (CAVE), and phage genome rebooting. Phages are administered in cocktail form in combination with antibiotics, vaccines, and purified proteins, such as endolysins. Thus, phage therapy is proving to be a better alternative for treating life-threatening infections, with more specificity and fewer detrimental consequences.

Exploring bacterial extracellular vesicles: Focus on WHO critical priority pathogens

Bacterial extracellular vesicles (EVs) are cell-derived particles with a phospholipidic bilayer structure and diameter ranging from 20 to 250 nm, comprising a varied of components, including bioactive proteins, lipids, DNA, RNA, and other metabolites. These EVs play an essential role in bacterial and host function and are recognized as essential keys in cell-to-cell communication and pathogenesis. Due to these characteristics and functions, EVs exhibit great potential for biomedical applications and are promising tools for the development of drug delivery systems and vaccines, as well as for use in disease diagnostics. An interesting focus of this review is on the clinical relevance of EVs, with a particular emphasis on two critical pathogens, Acinetobacter baumannii and Klebsiella pneumoniae. Insights into the outer membrane vesicles (OMVs) derived from these bacteria underscore their roles in antimicrobial resistance and pathogenicity. Additionally, the review explores OMV-based vaccine strategies as a promising means to mitigating these pathogens.

Antibiotic-Loaded Nano-Sized Delivery Systems: An Insight into Gentamicin and Vancomycin

The fight against infectious disease has remained an ever-evolving challenge in the landscape of healthcare. The ability of pathogens to develop resistance against conventional drug treatments has decreased the effectiveness of therapeutic interventions, and antibiotic resistance is recognized as one of the main challenges of our time. The goal of this systematic review paper is to provide insight into the research papers published on innovative nanosized drug delivery systems (DDSs) based on gentamycin and vancomycin and to discuss the opportunity of their repurposing through nano DDS formulations. These two antibiotics are selected because (i) gentamicin is the first-line drug used to treat suspected or confirmed infections caused by Gram-negative bacterial infections and (ii) vancomycin is used to treat serious Gram-positive bacterial infections. Moreover, both antibiotics have severe adverse effects, and one of the purposes of their formulation as nanosized DDSs is to overcome them. The review paper includes an introduction focusing on the challenges of infectious diseases and traditional therapeutic treatments, a brief description of the chemical and pharmacological properties of gentamicin and vancomycin, case studies from the literature on innovative nanosized DDSs as carriers of the two antibiotic drugs, and a discussion of the results found in the literature.

Survival of Salmonella enterica and Enterococcus faecium on Abiotic Surfaces During Storage at Low Relative Humidity

Currently, there is limited knowledge on the survival of bacteria on surfaces during postharvest handling of dry products such as onions. Extended survival of microorganisms, coupled with a lack of established and regular, validated cleaning or sanitation methods could enable cross-contamination of these products. The aim of the study was to evaluate the survival of a potential surrogate, Enterococcus faecium, and Salmonella enterica on typical onion handling surfaces, polyurethane (PU), and stainless steel (SS), under low relative humidity. The influence of onion extract on the survival of E. faecium and Salmonella on PU and SS was also investigated. Rifampin-resistant E. faecium NRRL B-2354 and a five-strain cocktail of Salmonella suspended in 0.1% peptone or onion extract were separately inoculated onto PU and SS coupons (2 × 2 cm), at high, moderate, or low (7, 5, or 3 log CFU/cm2) levels. The inoculated surfaces were stored at ∼34% relative humidity and 21°C for up to 84 days. Triplicate samples were enumerated at regular intervals in replicate trials. Samples were enriched when populations fell below the limit of detection by plating (0.48 log CFU/cm2). Scanning electron microscopy was used to observe the cell distribution on the coupons. Reductions of E. faecium of less than ∼2 log were observed on PU and SS over 12 weeks at all inoculum levels and with both inoculum carriers. In 0.1% peptone, Salmonella populations declined by 2 to 3 log over 12 weeks at the high and moderate inoculum levels; at the low inoculum level, Salmonella could not be recovered by enrichment at 84 days. Survival of E. faecium and Salmonella was significantly (P < 0.05) enhanced over 84 days of storage when suspended in onion extract, where cells were covered by a layer of onion extract. E. faecium might have utility as a conservative surrogate for Salmonella when evaluating microbial survival on dry food-contact surfaces.

Antibacterial efficacy ofRumex dentatusleaf extract-enriched zinc oxide and iron doped zinc nanoparticles: a comparative study

In the current investigation, zinc oxide (ZnO) nanoparticles and Fe-doped ZnO nanoparticles were sustainably synthesized utilizing an extract derived from theRumex dentatusplant through a green synthesis approach. The Scanning electron microscope (SEM), X-ray diffraction (XRD), Energy-dispersive x-ray spectroscopy (EDX), Ultra-violet visible spectroscopy (UV-vis) spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and Thermogravimetric analysis (TGA) techniques were used to examine the compositional, morphological, optical, and thermal properties of both samples. The doping of iron into ZnO NPs has significantly influenced their properties. The analysis firmly established that both ZnO NPs and Fe-doped ZnO NPs have hexagonal wurtzite structures and spherical shapes by XRD and SEM. The EDX analysis suggests that iron atoms have been successfully integrated into the ZnO lattice. The change in color observed during the reaction indicated the formation of nanoparticles. The UV-vis peaks at 364 nm and 314 nm confirmed the presence of ZnO NPs and Fe-doped ZnO NPs, respectively. The band gap of ZnO NPs by Fe dopant displayed a narrowing effect. This indicates that adding iron ions to ZnO NPs offers a control band gap. The thermal study TGA revealed that Fe-doped ZnO NPs remain stable when heated up to 600 °C. The antibacterial efficacy of ZnO NPs and Fe-doped ZnO NPs was evaluated against several bacterial strains. The evaluation is based on the zone of inhibition (ZOI). Both samples exhibited excellent antibacterial properties as compared to conventional pharmaceutical agents. These results suggest that synthesizing nanoparticles through plant-based methods is a promising approach to creating versatile and environmentally friendly biomedical products.

Lactobacillus Persisters Formation and Resuscitation

Lactobacillus is a commonly used probiotic, and many researchers have focused on its stress response to improve its functionality and survival. However, studies on persister cells, dormant cells that aid bacteria in surviving general stress, have focused on pathogenic bacteria that cause infection, not Lactobacillus. Thus, understanding Lactobacillus persister cells will provide essential clues for understanding how Lactobacillus survives and maintains its function under various environmental conditions. We treated Lactobacillus strains with various antibiotics to determine the conditions required for persister formation using kill curves and transmission electron microscopy. In addition, we observed the resuscitation patterns of persister cells using single-cell analysis. Our results show that Lactobacillus creates a small population of persister cells (0.0001-1% of the bacterial population) in response to beta-lactam antibiotics such as ampicillin and amoxicillin. Moreover, only around 0.5-1% of persister cells are heterogeneously resuscitated by adding fresh media; the characteristics are typical of persister cells. This study provides a method for forming and verifying the persistence of Lactobacillus and demonstrates that antibiotic-induced Lactobacillus persister cells show characteristics of dormancy, sensitivity of antibiotics, same as exponential cells, multi-drug tolerance, and resuscitation, which are characteristics of general persister cells. This study suggests that the mechanisms of formation and resuscitation may vary depending on the characteristics, such as the membrane structure of the bacterial species.

Bacterial nucleoid is a riddle wrapped in a mystery inside an enigma

Bacterial chromosome, the nucleoid, is traditionally modeled as a rosette of DNA mega-loops, organized around proteinaceous central scaffold by nucleoid-associated proteins (NAPs), and mixed with the cytoplasm by transcription and translation. Electron microscopy of fixed cells confirms dispersal of the cloud-like nucleoid within the ribosome-filled cytoplasm. Here, I discuss evidence that the nucleoid in live cells forms DNA phase separate from riboprotein phase, the "riboid." I argue that the nucleoid-riboid interphase, where DNA interacts with NAPs, transcribing RNA polymerases, nascent transcripts, and ssRNA chaperones, forms the transcription zone. An active part of phase separation, transcription zone enforces segregation of the centrally positioned information phase (the nucleoid) from the surrounding action phase (the riboid), where translation happens, protein accumulates, and metabolism occurs. I speculate that HU NAP mostly tiles up the nucleoid periphery-facilitating DNA mobility but also supporting transcription in the interphase. Besides extruding plectonemically supercoiled DNA mega-loops, condensins could compact them into solenoids of uniform rings, while HU could support rigidity and rotation of these DNA rings. The two-phase cytoplasm arrangement allows the bacterial cell to organize the central dogma activities, where (from the cell center to its periphery) DNA replicates and segregates, DNA is transcribed, nascent mRNA is handed over to ribosomes, mRNA is translated into proteins, and finally, the used mRNA is recycled into nucleotides at the inner membrane. The resulting information-action conveyor, with one activity naturally leading to the next one, explains the efficiency of prokaryotic cell design-even though its main intracellular transportation mode is free diffusion.

Strategies to Promote the Journey of Nanoparticles Against Biofilm-Associated Infections

Biofilm-associated infections are one of the most challenging healthcare threats for humans, accounting for 80% of bacterial infections, leading to persistent and chronic infections. The conventional antibiotics still face their dilemma of poor therapeutic effects due to the high tolerance and resistance led by bacterial biofilm barriers. Nanotechnology-based antimicrobials, nanoparticles (NPs), are paid attention extensively and considered as promising alternative. This review focuses on the whole journey of NPs against biofilm-associated infections, and to clarify it clearly, the journey is divided into four processes in sequence as 1) Targeting biofilms, 2) Penetrating biofilm barrier, 3) Attaching to bacterial cells, and 4) Translocating through bacterial cell envelope. Through outlining the compositions and properties of biofilms and bacteria cells, recent advances and present the strategies of each process are comprehensively discussed to combat biofilm-associated infections, as well as the combined strategies against these infections with drug resistance, aiming to guide the rational design and facilitate wide application of NPs in biofilm-associated infections.

Synthesis and biological evaluation of titanium dioxide/thiopolyurethane composite: anticancer and antibacterial effects

Nanocomposites incorporating titanium dioxide (TiO2) have a significant potential for various industrial and medical applications. These nanocomposites exhibit selectivity as antimicrobial and anticancer agents. Antimicrobial activity is crucial for medical uses, including applications in food processing, packaging, and surgical instruments. Additionally, these nanocomposites exhibit selectivity as anticancer agents. A stable nanocomposite as a new anticancer and antibacterial chemical was prepared by coupling titanium dioxide nanoparticles with a polyurethane foam matrix through the thiourea group. The titanium dioxide/thiopolyurethane nanocomposite (TPU/TiO2) was synthesized from low-cost Ilmenite ore and commercial polyurethane foam. EDX analysis was used to determine the elemental composition of the titanium dioxide (TiO2) matrix. TiO2NPs were synthesized and were characterized using TEM, XRD, IR, and UV-Vis spectra. TiO2NPs and TPU foam formed a novel composite. The MTT assay assessed Cisplatin and HepG-2 and MCF-7 cytotoxicity in vitro. Its IC50 values for HepG-2 and MCF-7 were 122.99 ± 4.07 and 201.86 ± 6.82 µg/mL, respectively. The TPU/TiO2 exhibits concentration-dependent cytotoxicity against MCF-7 and HepG-2 cells in vitro. The selective index was measured against both cell lines; it showed its safety against healthy cells. Agar well-diffusion exhibited good inhibition zones against Escherichia coli (12 mm), Bacillus cereus (10 mm), and Aspergillus niger (19 mm). TEM of TPU/TiO2-treated bacteria showed ultrastructure changes, including plasma membrane detachment from the cell wall, which caused lysis and bacterial death. TPU/TiO2 can treat cancer and inhibit microbes in dentures and other items. Also, TPU/TiO2 inhibits E. coli, B. cereus, and A. niger microbial strains.

A rationally engineered small antimicrobial peptide with potent antibacterial activity

Antimicrobial resistance (AMR) is a silent pandemic declared by the WHO that requires urgent attention in the post-COVID world. AMR is a critical public health concern worldwide, potentially affecting people at different stages of life, including the veterinary and agriculture industries. Notably, very few new-age antimicrobial agents are in the current developmental pipeline. Thus, the design, discovery, and development of new antimicrobial agents are required to address the menace of AMR. Antimicrobial peptides (AMPs) are an important class of antimicrobial agents for combating AMR due to their broad-spectrum activity and ability to evade AMR through a multimodal mechanism of action. However, molecular size, aggregability, proteolytic degradation, cytotoxicity, and hemolysis activity significantly limit the clinical application of natural AMPs. The de novo design and engineering of a short synthetic amphipathic AMP (≤16 aa, Mol. Wt. ≤ 2 kDa) with an unusual architecture comprised of coded and noncoded amino acids (NCAAs) is presented here, which demonstrates potent antibacterial activity against a few selected bacterial strains mentioned in the WHO priority list. The designer AMP is conformationally ordered in solution and effectively permeabilizes the outer and inner membranes, leading to bacterial growth inhibition and death. Additionally, the peptide is resistant to proteolysis and has negligible cytotoxicity and hemolysis activity up to 150 μM toward cultured human cell lines and erythrocytes. The designer AMP is unique and appears to be a potent therapeutic candidate, which can be subsequently subjected to preclinical studies to explicitly understand and address the menace of AMR.

Prokaryotic microvesicles Ortholog of eukaryotic extracellular vesicles in biomedical fields

Every single cell can communicate with other cells in a paracrine manner via the production of nano-sized extracellular vesicles. This phenomenon is conserved between prokaryotic and eukaryotic cells. In eukaryotic cells, exosomes (Exos) are the main inter-cellular bioshuttles with the potential to carry different signaling molecules. Likewise, bacteria can produce and release Exo-like particles, namely microvesicles (MVs) into the extracellular matrix. Bacterial MVs function with diverse biological properties and are at the center of attention due to their inherent therapeutic properties. Here, in this review article, the comparable biological properties between the eukaryotic Exos and bacterial MVs were highlighted in terms of biomedical application. Video Abstract.

Characterization and in-vitro plant-based control of hindgut bacteria isolated from Odontotermes obesus Rambur (Termitidae) and Heterotermes indicola Wasmann (Rhinotermitidae)

Termites cause a serious menace to wooden structures all over the world. They rely mostly on entozoic fauna residing in their hindgut for the digestion of cellulosic and hemicellulosic materials. One of the ways to control termites is through their gut symbionts. The present study was designed to characterize the hindgut bacteria isolated from Odontotermes obesus and Heterotermes indicola. Furthermore, the growth inhibitory effect of eight tropical plant extracts was investigated to find out potential control agents for these bacterial isolates. The characterization of bacteria was carried out based on their morphology, Gram staining, biochemical and amplification of 16SrRNA gene. Amplified products were sequenced to confirm their relationship with bacterial isolates from termites of other regions. The growth inhibitory effect of ethanolic leaf extracts of eight plants was evaluated in an invitro agar well diffusion method. Qualitative and quantitative phytochemical analysis of the most effective plant was carried out to learn about bioactive agents. The results confirmed the presence of five bacteria from each termite species. The Bacillus cereus, Escherichia coli, and Lysinibacillus fusiformis were common to both termites whereas Lysinibacillus xylanilyticus and Lysinibacillus macrolides were found in O. obesus only and H. indicola harbor Bacillus subtilis and Shigella sonnei in addition to common three ones. Among the plant extracts of Carica papaya, Eucalyptus camaldulensis, Osmium basilicum, Grevillea robusta, Eucalyptus globulus, Pongamia pinnata, Mentha longifolia, and Melia azedarach, the G. robusta > E. camaldulensis > O. basilicum were found to have growth inhibitory effects with increasing concentrations from 100 to 2000 µg/mL. The biodiversity of the bacterial fauna is important for the biological control of termites. Leaf extracts of these medicinal plants can be used to control termite infestation in an environment-friendly manner to save huge economic loss.

Nonelectroactive clostridium obtains extracellular electron transfer-capability after forming chimera with Geobacter

Extracellular electron transfer (EET) of microorganisms is a major driver of the microbial growth and metabolism, including reactions involved in the cycling of C, N, and Fe in anaerobic environments such as soils and sediments. Understanding the mechanisms of EET, as well as knowing which organisms are EET-capable (or can become so) is fundamental to electromicrobiology and geomicrobiology. In general, Gram-positive bacteria very seldomly perform EET due to their thick non-conductive cell wall. Here, we report that a Gram-positive Clostridium intestinale (C.i) attained EET-capability for ethanol metabolism only after forming chimera with electroactive Geobacter sulfurreducens (G.s). Mechanism analyses demonstrated that the EET was possible after the cell fusion of the two species was achieved. Under these conditions, the ethanol metabolism pathway of C.i was integrated by the EET pathway of G.s, by which achieved the oxidation of ethanol for the subsequent reduction of extracellular electron acceptors in the coculture. Our study displays a new approach to perform EET for Gram-positive bacteria via recruiting the EET pathway of an electroactive bacterium, which suggests a previously unanticipated prevalence of EET in the microbial world. These findings also provide new perspectives to understand the energetic coupling between bacterial species and the ecology of interspecies mutualisms.

Photodynamic inactivation of bacteria: Why it is not enough to excite a photosensitizer

BACKGROUND

The development of multidrug resistance (MDR) in infectious agents is one of the most serious global problems facing humanity. Antimicrobial photodynamic therapy (APDT) shows encouraging results in the fight against MDR pathogens, including those in biofilms.

METHODS

Photosensitizers (PS), monocationic methylene blue, polycationic and polyanionic derivatives of phthalocyanines, electroneutral and polycationic derivatives of bacteriochlorin were used to study photodynamic inactivation of Gram-positive and Gram-negative planktonic bacteria and biofilms under LED irradiation. Zeta potential measurements, confocal fluorescence imaging, and coarse-grained modeling were used to evaluate the interactions of PS with bacteria. PS aggregation and photobleaching were studied using absorption and fluorescence spectroscopy.

RESULTS

The main approaches to ensure high efficiency of bacteria photosensitization are analyzed.

CONCLUSIONS

PS must maintain a delicate balance between binding to exocellular and external structures of bacterial cells and penetration through the cell wall so as not to get stuck on the way to photooxidation-sensitive structures of the bacterial cell.

Surface-modified bacteria: synthesis, functionalization and biomedical applications

The past decade has witnessed a great leap forward in bacteria-based living agents, including imageable probes, diagnostic reagents, and therapeutics, by virtue of their unique characteristics, such as genetic manipulation, rapid proliferation, colonization capability, and disease site targeting specificity. However, successful translation of bacterial bioagents to clinical applications remains challenging, due largely to their inherent susceptibility to environmental insults, unavoidable toxic side effects, and limited accumulation at the sites of interest. Cell surface components, which play critical roles in shaping bacterial behaviors, provide an opportunity to chemically modify bacteria and introduce different exogenous functions that are naturally unachievable. With the help of surface modification, a wide range of functionalized bacteria have been prepared over the past years and exhibit great potential in various biomedical applications. In this article, we mainly review the synthesis, functionalization, and biomedical applications of surface-modified bacteria. We first introduce the approaches of chemical modification based on the bacterial surface structure and then highlight several advanced functions achieved by modifying specific components on the surface. We also summarize the advantages as well as limitations of surface chemically modified bacteria in the applications of bioimaging, diagnosis, and therapy and further discuss the current challenges and possible solutions in the future. This work will inspire innovative design thinking for the development of chemical strategies for preparing next-generation biomedical bacterial agents.

Controlling biofilm and virulence properties of Gram-positive bacteria by targeting wall teichoic acid and lipoteichoic acid

Wall teichoic acid (WTA) and lipoteichoic acid (LTA) are structural components of Gram-positive bacteria's peptidoglycan and cell membrane, which are mostly anionic glycopolymers. WTA confers numerous physiological, virulence, and pathogenic features to bacterial pathogens. It controls cell shape, cell division, and the localisation of autolytic enzymes and ion homeostasis. In the context of virulence and pathogenicity, it aids bacterial cell attachment and colonisation and protects against the host defence system and antibiotics. Having such a broad function in pathogenic bacteria's lifecycle, WTA/LTA become one of the potential targets for antibacterial agents to reduce bacterial infection in the host. The number of reports for targeting the WTA/LTA pathway has risen, mostly by focusing on three distinct targets: antivirulence targets, β-lactam potentiator targets, and essential targets. The current review looked at the role of WTA/LTA in biofilm development and virulence in a range of Gram-positive pathogenic bacteria. Furthermore, alternate strategies, such as the application of natural and synthetic compounds that target the WTA/LTA pathway, have been thoroughly discussed. Moreover, the application of nanomaterials and a combination of drugs have also been discussed as a viable method for targeting the WTA/LTA in numerous Gram-positive bacteria. In addition, a future perspective for controlling bacterial infection by targeting the WTA/LTA is proposed.

Powering mesoporous silica nanoparticles into bioactive nanoplatforms for antibacterial therapies: strategies and challenges

Bacterial infection has been a major threat to worldwide human health, in particular with the ever-increasing level of antimicrobial resistance. Given the complex microenvironment of bacterial infections, conventional use of antibiotics typically renders a low efficacy in infection control, thus calling for novel strategies for effective antibacterial therapies. As an excellent candidate for antibiotics delivery, mesoporous silica nanoparticles (MSNs) demonstrate unique physicochemical advantages in antibacterial therapies. Beyond the delivery capability, extensive efforts have been devoted in engineering MSNs to be bioactive to further synergize the therapeutic effect in infection control. In this review, we critically reviewed the essential properties of MSNs that benefit their antibacterial application, followed by a themed summary of strategies in manipulating MSNs into bioactive nanoplatforms for enhanced antibacterial therapies. The chemically functionalized platform, photo-synergized platform, physical antibacterial platform and targeting-directed platform are introduced in details, where the clinical translation challenges of these MSNs-based antibacterial nanoplatforms are briefly discussed afterwards. This review provides critical information of the emerging trend in turning bioinert MSNs into bioactive antibacterial agents, paving the way to inspire and translate novel MSNs-based nanotherapies in combating bacterial infection diseases.

Fluorescent optotracers for bacterial and biofilm detection and diagnostics

Effective treatment of bacterial infections requires methods that accurately and quickly identify which antibiotic should be prescribed. This review describes recent research on the development of optotracing methodologies for bacterial and biofilm detection and diagnostics. Optotracers are small, chemically well-defined, anionic fluorescent tracer molecules that detect peptide- and carbohydrate-based biopolymers. This class of organic molecules (luminescent conjugated oligothiophenes) show unique electronic, electrochemical and optical properties originating from the conjugated structure of the compounds. The photophysical properties are further improved as donor-acceptor-donor (D-A-D)-type motifs are incorporated in the conjugated backbone. Optotracers bind their biopolymeric target molecules via electrostatic interactions. Binding alters the optical properties of these tracer molecules, shown as altered absorption and emission spectra, as well as ON-like switch of fluorescence. As the optotracer provides a defined spectral signature for each binding partner, a fingerprint is generated that can be used for identification of the target biopolymer. Alongside their use for in situ experimentation, optotracers have demonstrated excellent use in studies of a number of clinically relevant microbial pathogens. These methods will find widespread use across a variety of communities engaged in reducing the effect of antibiotic resistance. This includes basic researchers studying molecular resistance mechanisms, academia and pharma developing new antimicrobials targeting biofilm infections and tests to diagnose biofilm infections, as well as those developing antibiotic susceptibility tests for biofilm infections (biofilm-AST). By iterating between the microbial world and that of plants, development of the optotracing technology has become a prime example of successful cross-feeding across the boundaries of disciplines. As optotracers offers a capacity to redefine the way we work with polysaccharides in the microbial world as well as with plant biomass, the technology is providing novel outputs desperately needed for global impact of the threat of antimicrobial resistance as well as our strive for a circular bioeconomy.

Photoacoustic based evaluation of viscoelastic properties of Gram-negative and Gram-positive bacterial colonies

Mechanical properties of bacterial colonies are crucial considering both addressing their pathogenic effects and exploring their potential applications. Viscoelasticity is a key mechanical property with major impacts on the cell shapes and functions, which reflects the information about the cell envelope constituents. Hereby, we have proposed the application of photoacoustic viscoelasticity (PAVE) for studying the rheological properties of bacterial colonies. In this regard, we employed an intensity-modulated laser beam as the excitation source followed by the phase delay measurement between the generated PA signal and the reference for the characterization of colonies of two different types of Gram-positive and Gram-negative bacteria. The results of our study show that the colony of Staphylococcus aureus as Gram-positive bacteria has a significantly higher viscoelasticity ratio compared to that value for Acinetobacter baumannii as Gram-negative bacteria (77% difference). This may be due to the differing cell envelope structure between the two species, but we cannot rule out effects of biofilm formation in the colonies. Furthermore, a lumped model has been provided for the mechanical properties of bacterial colonies.

The Effect of Cryopreservation on the Survival of Nocardia farcinica and Yersinia pestis vaccine strains

Pathogenic microorganisms are valuable biological resources, closely related to biosecurity, human health, environmental protection, and renewable energy. It is very important to properly preserve the microbial resources by methods to maintain the purity, viability, and integrity, and to avoid prolonged degradation. The present work aims to explore the cryopreservation technology of Nocardia farcinica (Gram-positive bacteria) and Yersinia pestis vaccine strains (Gram-negative bacteria). The effects of cryoprotectants (CPAs), freezing temperature, and freeze-thaw cycles on the two bacteria in the cryopreservation process were studied. The results showed that the addition of CPAs (glycerol, propylene glycol, sucrose, glucose, l-carnitine, l-proline, and skim milk) significantly enhanced the survival rates of the N. farcinica and Y. pestis vaccine strains. However, high concentrations of CPAs can produce biochemical toxicity in the two pathogens. The utilization of composite CPAs not only reduced the toxicity but also improved the survival rates of samples during cryopreservation. The optimal composite CPA for N. farcinica is 0.292 M sucrose, 0.62 M l-carnitine, and 2.82 M glycerol. The optimal composite CPA for Y. pestis is 0.62 M l-carnitine, 8.46 M glycerin, and 0.292 M sucrose. The results showed that the quality of the strains stored at -80°C and -196°C was better. For the case of freeze-thaw cycles, the two pathogens have different degrees of reduction, and the survival rate of Y. pestis decreased more than that of N. farcinica. The uniform distribution of bacteria in CPAs can form uniform nucleation sites in the solution system, which is beneficial to the cryopreservation of strains, as can be seen from the experimental results from a differential scanning calorimeter. This study may provide a reference for better preservation of precious natural biological resources of pathogenic microorganisms.

von Willebrand factor-binding protein (vWbp)-activated factor XIII and transglutaminase 2 (TG2) promote cross-linking between FnBPA from Staphylococcus aureus and fibrinogen

The secreted von Willebrand factor-binding protein (vWbp) from Staphylococcus aureus interacts with the coagulation factors prothrombin and fibrinogen (Fbg), leading to the non-proteolytic transglutaminase activation of Factor XIII (FXIII). In this study we found that vWbp-activated FXIII catalyses the incorporation of amino-donor dansylcadaverine into region A of fibronectin-binding protein A (FnBPA). Incubation of Fbg with recombinant region A of S. aureus Fbg-binding proteins FnBPA, FnBPB, ClfA or ClfB in presence of vWbp-activated FXIII resulted in the formation of high molecular heteropolymers with FnBPA only, suggesting a specificity of the cross-linking reaction between fibrin(ogen) and the staphylococcal surface. As previously observed, cross-linking sites were mapped to the α-chain and the N1 subdomain of fibrin(ogen) and region A of FnBPA, respectively. Comparable results were obtained when tissue tranglutaminase-2 (TG2) was tested for cross-linking of FnBPA and Fbg. Of note, FnBPA-mediated covalent cross-linking promoted by vWbp-activated FXIII was also observed when bacteria were allowed to attach to fibrin(ogen). Together these findings suggest a novel pathogenetic mechanism by which the transglutaminase action of FXIII and/or TG2 contributes to entrapment and persistence of S. aureus in blood and host tissues.

Impact of disposable mask microplastics pollution on the aquatic environment and microalgae growth

The COVID-19 pandemic has mandated people to use medical masks to protect the public. However the improper management of disposable mask waste has led to the increase of marine pollution, in terms of water quality, and the decline in aquatic microorganisms. The aim of this research was to investigate the impact of disposable mask waste on fresh water and microalgae biomass quality. Disposable masks (untreated or treated with Enterococcus faecalis) were placed in 10-L glass reactors containing fresh water or water containing algal Chlorella sp. and its growth supplements (Chlorella medium) (four 10-L reactors in total) and kept in controlled conditions for 3 months. Water and biomass yield quality were evaluated using water quality analysis, spectroscopy, scanning electron microscopy (SEM), and proximate lipid and protein analysis. Disposable masks, incubated in either fresh water or Chlorella medium, affected several water quality parameters such as chemical oxygen demand (COD), biological oxygen demand (BOD), dissolved oxygen (DO), and pH. Microplastic identification revealed that some fibers were present in the water following a 100-day treatment process. Fourier transform-infrared spectroscopy (FTIR) analysis was used to determine the change in important, organic functional groups and highlighted the disappearance of a peak at 1530 cm-1 corresponding to the primary protein (C-N) and the appearance of new peaks at 1651 cm-1 and 1270 cm-1 corresponding to methyl alcohol (CH2OH) and ketone (C = O), respectively. This indicated the detrimental effect of disposable mask fragmentation on the biomass quality. The SEM investigation has shown a damage to the surface membrane of Chlorella sp. cells. Altogether, disposable masks decreased the water quality and damaged microalgae by inhibiting their growth. Therefore, the disposable mask contaminated by various microbes, after being used by a human, may be one of the most dangerous hazards to the environment.

Capsular Polysaccharide Is Essential for the Virulence of the Antimicrobial-Resistant Pathogen Enterobacter hormaechei

Nosocomial infections caused by multidrug-resistant (MDR) Enterobacter cloacae complex (ECC) pathogens are on the rise. However, the virulence strategies employed by these pathogens remain elusive. Here, we study the interaction of ECC clinical isolates with human serum to define how this pathogen evades the antimicrobial action of complement, one of the first lines of host-mediated immune defense. We identified a small number of serum-sensitive strains, including Enterobacter hormaechei strain NR3055, which we exploited for the in vitro selection of serum-resistant clones. Comparative genomics between the serum-sensitive NR3055 strain and the isolated serum-resistant clones revealed a premature stop codon in the wzy gene of the capsular polysaccharide biosynthesis locus of NR3055. The complementation of wzy conferred serum resistance to NR3055, prevented the deposition of complement proteins on the bacterial surface, inhibited phagocytosis by human neutrophils, and rendered the bacteria virulent in a mouse model of peritonitis. Mice exposed to a nonlethal dose of encapsulated NR3055 were protected from subsequent lethal infections by encapsulated NR3055, whereas mice that were previously exposed to unencapsulated NR3055 succumbed to infection. Thus, capsule is a key immune evasion determinant for E. hormaechei, and it is a potential target for prophylactics and therapeutics to combat these increasingly MDR human pathogens. IMPORTANCE Infections caused by antimicrobial resistant bacteria are of increasing concern, especially those due to carbapenem-resistant Enterobacteriaceae pathogens. Included in this group are species of the Enterobacter cloacae complex, regarding which there is a paucity of knowledge on the infection biology of the pathogens, despite their clinical relevance. In this study, we combine techniques in comparative genomics, bacterial genetics, and diverse models of infection to establish capsule as an important mechanism of Enterobacter pathogens to resist the antibacterial activity of serum, a first line of host defense against bacterial infections. We also show that immune memory targeting the Enterobacter capsule protects against lethal infection. The further characterization of Enterobacter infection biology and the immune response to infection are needed for the development of therapies and preventative interventions targeting these highly antibiotic resistant pathogens.

Hybrid biomaterials to preconcentrate and determine toxic metals and metalloids: a review

Toxic elements represent a serious threat to the environment and cause harmful effects on different environmental components, even at trace levels. These toxic elements are often difficult to detect through the typical instrumentation of an analytical laboratory because they are found at very low concentrations in matrices such as food and water. Therefore, preconcentration plays a fundamental role since it allows the effects of the matrix to be minimized, thus reaching lower detection limits and greater sensitivity of detection techniques. In recent years, solid-phase extraction has been successfully used for the preconcentration of metals as an environmentally friendly technique due to the fact that it eliminates or minimizes the use of reagents and solvents and offers reduced analysis times and low generation of waste in the laboratory. Hybrid biomaterials are low-cost, eco-friendly, and useful as efficient solid phases for the preconcentration of elements. In this review, recent investigations based on the use of hybrid biomaterials for the preconcentration and determination of toxic metals are presented and discussed, given special attention to bionanomaterials. A brief description of hybrid biomaterials often used for analytical purposes, as well as analytical techniques mostly used to characterize the hybrid biomaterials, is explained. Finally, the future prospects that encourage the search for new hybrid biomaterials are commented upon.

Structure-function analysis of Lactiplantibacillus plantarum DltE reveals D-alanylated lipoteichoic acids as direct cues supporting Drosophila juvenile growth

Metazoans establish mutually beneficial interactions with their resident microorganisms. However, our understanding of the microbial cues contributing to host physiology remains elusive. Previously, we identified a bacterial machinery encoded by the dlt operon involved in Drosophila melanogaster's juvenile growth promotion by Lactiplantibacillus plantarum. Here, using crystallography combined with biochemical and cellular approaches, we investigate the physiological role of an uncharacterized protein (DltE) encoded by this operon. We show that lipoteichoic acids (LTAs) but not wall teichoic acids are D-alanylated in Lactiplantibacillus plantarumNC8 cell envelope and demonstrate that DltE is a D-Ala carboxyesterase removing D-Ala from LTA. Using the mutualistic association of L. plantarumNC8 and Drosophila melanogaster as a symbiosis model, we establish that D-alanylated LTAs (D-Ala-LTAs) are direct cues supporting intestinal peptidase expression and juvenile growth in Drosophila. Our results pave the way to probing the contribution of D-Ala-LTAs to host physiology in other symbiotic models.

Construction and application of a heterogeneous quality control library for the Xpert MTB/RIF assay in tuberculosis diagnosis

Proficiency testing based on quality control materials is an important component of the quality assurance system for detection methods. However, in the detection of infectious diseases, it is a challenge to use quality control materials derived from clinical samples or pathogens owing to their infectious nature. The Xpert MTB/RIF assay, endorsed by the World Health Organization, is one of the most widely implemented assays in the detection of Mycobacterium tuberculosis along with rifampicin resistance and its heterogeneity. Clinical isolates are typically used as quality controls for this assay, leading to concerns about biosafety, constrained target sequence polymorphisms, and time-consuming preparation. In this study, a heterogeneous quality control library for the Xpert MTB/RIF assay was constructed based on DNA synthesis and site-directed mutation, which provides sufficient rifampicin resistance polymorphisms, enabling monitoring all five probes of Xpert MTB/RIF and its combinations. Escherichia coli and Bacillus subtilis were used as heterogeneous hosts rather than the pathogen itself to eliminate biosafety risks; thus, preparation does not require a biosafety level III laboratory and the production time is reduced from a few months to a few days. The panel was stable for more than 15 months stored at 4°C and could be distributed at room temperature. All 11 laboratories in Shanghai participating in a pilot survey identified the specimens with corresponding probe patterns, and discordant results highlighted inappropriate operations in the process. Collectively, we show, for the first time, that this library, based on heterogeneous hosts, is an appropriate alternative for M. tuberculosis detection.

New Insights into the Physiology of the Propionate Producers Anaerotignum propionicum and Anaerotignum neopropionicum (Formerly Clostridium propionicum and Clostridium neopropionicum)

Propionate is an important platform chemical that is available through petrochemical synthesis. Bacterial propionate formation is considered an alternative, as bacteria can convert waste substrates into valuable products. In this regard, research primarily focused on propionibacteria due to high propionate titers achieved from different substrates. Whether other bacteria could also be attractive producers is unclear, mostly because little is known about these strains. Therefore, two thus far less researched strains, Anaerotignum propionicum and Anaerotignum neopropionicum, were investigated with regard to their morphologic and metabolic features. Microscopic analyses revealed a negative Gram reaction despite a Gram-positive cell wall as well as surface layers for both strains. Furthermore, growth, product profiles, and the potential for propionate formation from sustainable substrates, i.e., ethanol or lignocellulosic sugars, were assessed. Results showed that both strains can oxidize ethanol to different extents. While A. propionicum only partially used ethanol, A. neopropionicum converted 28.3 mM ethanol to 16.4 mM propionate. Additionally, the ability of A. neopropionicum to produce propionate from lignocellulose-derived substrates was analyzed, leading to propionate concentrations of up to 14.5 mM. Overall, this work provides new insights into the physiology of the Anaerotignum strains, which can be used to develop effective propionate producer strains.

Application of depolymerized chitosan in crop production: A review

Currently, chitosan (CHT) is well known for its uses, particularly in veterinary and agricultural fields. However, chitosan's uses suffer greatly due to its extremely solid crystalline structure, it is insoluble at pH levels above or equal to 7. This has sped up the process of derivatizing and depolymerizing it into low molecular weight chitosan (LMWCHT). As a result of its diverse physicochemical as well as biological features which include antibacterial activity, non-toxicity, and biodegradability, LMWCHT has evolved into new biomaterials with extremely complex functions. The most important physicochemical and biological property is antibacterial, which has some degree of industrialization today. CHT and LMWCHT have potential due to the antibacterial and plant resistance-inducing properties when applied in crop production. This study has highlighted the many advantages of chitosan derivatives as well as the most recent studies on low molecular weight chitosan applications in crop development.