Bacterial Release Research Articles

Cloning and expression of the bacteriophage-derived endolysin against Aeromonas hydrophila

Hemorrhagic septicemia disease in striped catfish is caused by Aeromonas hydrophila bacterium. Antibiotics are commonly used to treat this disease, however, due to antibiotic resistance in A. hydrophila, it is necessary to have an alternative antibacterial agent to antibiotics. Endolysins are bacteriophage-encoded peptidoglycan hydrolases that are synthesized at the end of the lytic phage replication cycle, they lyse the host bacterial cell wall and release new bacteriophage virions. In this study, an endolysin (cell wall hydrolase) derived from A. hydrophila phage PVN02 was artificially synthesized, cloned into pET28a(+) and successfully expressed in E. coli BL21 (DE3). The recombinant endolysin, cell wall hydrolase strongly exhibited antimicrobial activity against A. hydrophila with a reduction of 3-log CFU/ml of A. hydrophila after 30 minutes of mixing and further 30 minutes of incubation, the bacterial cells were lysed completely. It should be emphasized that the lytic activity by the recombinant endolysin to A. hydrophila bacteria did not require a pretreatment with an outer-membrane permeabilizer. The results of our study showed a potential of use this recombinant endolysin as a novel antibacterial agent to replace antibiotics in the treatment of hemorrhagic septicemia diseases in striped catfish.

Epidermis as a Platform for Bacterial Transmission.

The epidermis constitutes a continuous external layer covering the body, offering protection against bacteria, the most abundant living organisms that come into contact with this barrier. The epidermis is heavily colonized by commensal bacterial organisms that help protect against pathogenic bacteria. The highly regulated and dynamic interaction between the epidermis and commensals involves the host’s production of nutritional factors promoting bacterial growth together to chemical and immunological bacterial inhibitors. Signal trafficking ensures the system’s homeostasis; conditions that favor colonization by pathogens frequently foster commensal growth, thereby increasing the bacterial population size and inducing the skin’s antibacterial response, eliminating the pathogens and re-establishing the normal density of commensals. The microecological conditions of the epidermis favors Gram-positive organisms and are unsuitable for long-term Gram-negative colonization. However, the epidermis acts as the most important host-to-host transmission platform for bacteria, including those that colonize human mucous membranes. Bacteria are frequently shared by relatives, partners, and coworkers. The epidermal bacterial transmission platform of healthcare workers and visitors can contaminate hospitalized patients, eventually contributing to cross-infections. Epidermal transmission occurs mostly via the hands and particularly through fingers. The three-dimensional physical structure of the epidermis, particularly the fingertips, which have frictional ridges, multiplies the possibilities for bacterial adhesion and release. Research into the biology of bacterial transmission via the hands is still in its infancy; however, tribology, the science of interacting surfaces in relative motion, including friction, wear and lubrication, will certainly be an important part of it. Experiments on finger-to-finger transmission of microorganisms have shown significant interindividual differences in the ability to transmit microorganisms, presumably due to genetics, age, sex, and the gland density, which determines the physical, chemical, adhesive, nutritional, and immunological status of the epidermal surface. These studies are needed to optimize interventions and strategies for preventing the hand transmission of microorganisms.

Evaluation of Bacillus velezensis for Biological Control of Rhizoctonia solani in Bean by Alginate/Gelatin Encapsulation Supplemented with Nanoparticles.

Plant growth promoting rhizobacteria (PGPR) are a group of bacteria that can increase plant growth; but due to unfavorable environmental conditions, PGPR are biologically unstable and their survival rates in soil are limited. Therefore, the suitable application of PGPR as a plant growth stimulation is one of the significant challenges in agriculture. This study presents an intelligent formulation based on Bacillus velezensis VRU1 encapsulation enriched with nanoparticles that was able to control Rhizoctonia solani on the bean. The spherical structure of the capsule was observed based on the Scanning Electron Microscope image. Results indicated that with increasing gelatin concentration, the swelling ratio and moisture content were increased; and since the highest encapsulation efficiency and bacterial release were observed at a gelatin concentration of 1.5%, this concentration was considered in mixture with alginate for encapsulation. The application of this formulation which is based on encapsulation and nanotechnology appears to be a promising technique to deliver PGPR in soil and is more effective for plants.

Hybrid "Kill and Release" Antibacterial Cellulose Papers Obtained via Surface-Initiated Atom Transfer Radical Polymerization.

Infectious diseases triggered by bacteria cause a severe risk to human health. To counter this issue, surfaces coated with antibacterial materials have been widely used in daily life to kill these bacteria. The substrates enabled with a hybrid kill and release strategy can be employed not only to kill the bacteria but also to wash them using external stimuli (temperature, pH, etc.). Utilizing this concept, we develop thermoresponsive antibacterial-cellulose papers to exhibit hybrid kill and release properties. Thermoresponsive copolymers [p(NIPAAm-co-AEMA)] are grafted on cellulose papers using a surface-initiated atom transfer radical polymerization approach for bacterial debris release. Later for antibacterial properties, silver nanoparticles (AgNPs) are immobilized on thermoresponsive copolymer-grafted cellulose papers using electrostatic interactions. We confirm the thermoresponsive copolymer grafting and AgNP coating by attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy. Thermoresponsiveness and reusability of the modified cellulose papers are confirmed through water contact angle measurements. The interaction potency between AgNPs and modified cellulose is validated by inductively coupled plasma atomic emission spectroscopy analysis. Gram-negative bacteria Escherichia coli (E. coli DH5-α) is used to demonstrate antibacterial hybrid kill and release performance. Agar-diffusion testing demonstrates the antibacterial nature of the modified cellulose papers. The fluorescence micrograph reveals that modified cellulose papers can effectively release almost all the dead bacterial debris from their surfaces after thermal stimulus wash. The modified cellulose paper surfaces are expected to have wide applications in the field of exploring more antibacterial and smart surfaces.

PH-Responsive Smart Wettability Surface with Dual Bactericidal and Releasing Properties.

Biomaterial-associated infections caused by pathogenic bacteria have important implications on human health. This study presents the design and preparation of a smart surface with pH-responsive wettability. The smart surface exhibited synergistic antibacterial function, with high liquid repellency against bacterial adhesion and highly effective bactericidal activity. The wettability of the surface can switch reversibly between superhydrophobicity and hydrophobicity in response to pH; this controls bacterial adhesion and release. Besides, the deposited silver nanoparticles of the surface were also responsible for bacterial inhibition. Benefiting from the excellent liquid repellency, the surface could highly resist bacterial adhesion after immersing in a bacterial suspension for 10 s (85%) and 1 h (71%). Adhered bacteria can be easily eliminated using deposited silver nanoparticles during the subsequent treatment of alkaline bacterial suspension, and the ratio of deactivated bacteria was above 75%. After the pH returned to neutral, the deactivated bacteria can be easily released from the surface. This antibacterial surface showed an improved bacterial removal efficiency of about 99%. The results shed light on future antibacterial applications of the smart surface combining both bactericidal and adhesion-resistant functionalities.

Cationic peptide-based salt-responsive antibacterial hydrogel dressings for wound healing

Development of biological dressings has received widespread attentions due to their good breathability, biocompatibility, wettability, and the ability to absorb wound exudate without sticking to the wound. However, current proposed antibacterial hydrogels are limited antibacterial ability, short service life and insufficient biocompatibility, which are still challenging to address intricate practical applications. Here we develop a cationic peptide-based, salt-responsive hydrogel dressing with triple functions of antifouling, bactericidal, and bacterial release by combining ε-poly-l-lysine, poly(ethylene glycol) diglycidyl ether, and poly(DVBAPS-co-GMA) via a one-pot method. These designed hydrogels enabled to further quaternize to enhance antibacterial property due to the presence of amine residues. The resultant hydrogels present good antibacterial activity (>90%), biocompatibility, cell proliferation efficacy (~400%) and adhesiveness. Through in vivo and in vitro antibacterial capability tests, it is also found that hydrogels have good antifouling and sterilization capabilities, and the sterilization rate could reach up to ~96%. In addition, ~94% of the attached bacterial can be released after saline/water switching for several cycles. Taken together, the designed multiple antibacterial dressing prolongs the lifespan relying on reversible salt-responsive release and meet special requirements for wound healing. This work not only provides a platform to highlight its promising potentials in wound management but also gives a custom strategy to biomedical applications.

Intracellular niche-specific profiling reveals transcriptional adaptations required for the cytosolic lifestyle of Salmonella enterica.

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a zoonotic pathogen that causes diarrheal disease in humans and animals. During salmonellosis, S. Typhimurium colonizes epithelial cells lining the gastrointestinal tract. S. Typhimurium has an unusual lifestyle in epithelial cells that begins within an endocytic-derived Salmonella-containing vacuole (SCV), followed by escape into the cytosol, epithelial cell lysis and bacterial release. The cytosol is a more permissive environment than the SCV and supports rapid bacterial growth. The physicochemical conditions encountered by S. Typhimurium within the epithelial cytosol, and the bacterial genes required for cytosolic colonization, remain largely unknown. Here we have exploited the parallel colonization strategies of S. Typhimurium in epithelial cells to decipher the two niche-specific bacterial virulence programs. By combining a population-based RNA-seq approach with single-cell microscopic analysis, we identified bacterial genes with cytosol-induced or vacuole-induced expression signatures. Using these genes as environmental biosensors, we defined that Salmonella is exposed to oxidative stress and iron and manganese deprivation in the cytosol and zinc and magnesium deprivation in the SCV. Furthermore, iron availability was critical for optimal S. Typhimurium replication in the cytosol, as well as entC, fepB, soxS, mntH and sitA. Virulence genes that are typically associated with extracellular bacteria, namely Salmonella pathogenicity island 1 (SPI1) and SPI4, showed increased expression in the cytosol compared to vacuole. Our study reveals that the cytosolic and vacuolar S. Typhimurium virulence gene programs are unique to, and tailored for, residence within distinct intracellular compartments. This archetypical vacuole-adapted pathogen therefore requires extensive transcriptional reprogramming to successfully colonize the mammalian cytosol.

Antimicrobial, Antibiofilm, and Anti-persister Activities of Penfluridol Against Staphylococcus aureus.

Staphylococcus aureus has increasingly attracted global attention as a major opportunistic human pathogen owing to the emergence of biofilms (BFs) and persisters that are known to increase its antibiotic resistance. However, there are still no effective antimicrobial agents in clinical settings. This study investigated the antimicrobial activity of penfluridol (PF), a long-acting antipsychotic drug, against S. aureus and its clinical isolates via drug repurposing. PF exhibited strong bactericidal activity against S. aureus, with a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 4–8 and 16–32 μg/ml, respectively. PF could significantly inhibit biofilm formation and eradicate 24 h preformed biofilms of S. aureus in a dose-dependent manner. Furthermore, PF could effectively kill methicillin-resistant S. aureus (MRSA) persister cells and demonstrated considerable efficacy in a mouse model of subcutaneous abscess, skin wound infection, and acute peritonitis caused by MRSA. Notably, PF exerted almost no hemolysis activity on human erythrocytes, with limited cytotoxicity and low tendency to cause resistance. Additionally, PF induced bacterial membrane permeability and ATP release and further caused membrane disruption, which may be the underlying antibacterial mechanism of PF. In summary, our findings suggest that PF has the potential to serve as a novel antimicrobial agent against S. aureus biofilm- or persister-related infections.

Quinic acid: a potential antibiofilm agent against clinical resistant Pseudomonas aeruginosa

BackgroundThe biofilm state of pathogens facilitates antimicrobial resistance which makes difficult-to-treat infections. In this regard, it has been found that the compounds screened from plant extracts represent one category of the most promising antibiofilm agents. However, the antibiofilm activities and the active ingredients of plant extracts remain largely unexplored. In this background, the study is (1) to screen out the plant extracts with antibiofilm ability against Pseudomonas aeruginosa, and (2) to identify the active ingredients in the plant extracts and elucidate the underlying mechanism of the antibiofilm activities.MethodsMicro-broth dilution method, in vitro biofilm model, LC–MS/MS analysis and P. aeruginosa-mouse infection model were adopted to assess the antibiofilm activity. GC–MS analysis was performed to detect the active ingredients in plasma. RNA-Seq, GO analysis, KEGG analysis and RT-qPCR were adopted to elucidate the underlying mechanism of antibiofilm activities against P. aeruginosa.ResultsLonicerae Japonicae Flos (LJF) among 13 plants could exert significant inhibitory effects on bacterial biofilm formation, mobility and toxin release in vitro, and it could exert antibiofilm effect in vivo too. Moreover, quinic acid, as one metabolite of chlorogenic acid, was found as an active ingredient in LJF against the biofilm of P. aeruginosa. The active ingredient significantly inhibited EPS secretion in biofilm formation and maturity and could achieve synergistic antibiofilm effect with levofloxacin. It reduced the biofilm formation by regulating core targets in quorum sensing system. In GO process, it was found that the core targets were significantly enriched in multiple biological processes involving locomotion, chemotaxis and motility mediated by flagellum/cilium, which was related to KEGG pathways such as bacterial chemotaxis, oxidative phosphorylation, ribosome, biofilm formation, cyanoamino acid metabolism and quorum sensing. Finally, the binding of quinic acid with core targets rhlA, rhlR and rhlB were validated by molecular docking and RT-qPCR.ConclusionsIn summary, the study verified the in vitro and in vivo antibiofilm effects of LJF against P. aeruginosa and elucidated the active ingredients in LJF and its conceivable pharmacological mechanism, indicating that quinic acid could have the potential of an antibiofilm agent against P. aeruginosa and related infections.Graphic abstract

A novel encapsulation of Streptomyces fulvissimus Uts22 by spray drying and its biocontrol efficiency against Gaeumannomyces graminis, the causal agent of take-all disease in wheat.

Wheat is a valuable food source that is exposed to many diseases that reduce its quantity and quality. One of the most important diseases affecting wheat is take-all, caused by Gaeumannomyces graminis var. tritici. The application of bacterial inoculants into the soil can increase plant nutrient absorption and enhance the efficiency of probiotic bacteria. For increased beneficial bacteria efficiency, the encapsulation technique has been used in agriculture. The results of Fourier transform infrared (FTIR) and X-ray diffraction analysis (XRD) indicated that the prepared formulation is a mixture of gellan and chitosan. Using SEM, the spherical structure of the microcapsules was confirmed. It was observed that the increase in bacterial release was gradual, and the highest amount of bacteria was released (109 CFU mL-1 ) on the 50th day. Greenhouse experiments showed that plants treated with S. fulvissimus Uts22 microcapsules had the highest efficiency with 90% disease control. Moreover, the highest fresh and dry weights of roots and shoots were observed in this treatment. In this study, a new type of formulation aiming at controlling wheat take-all disease was developed through bacterial and nanoparticles loaded chitosan- gellan gum microcapsules with spray drying method. This formulation has many advantages, such as a large surface area and high internal porosity and increased water-holding capacity, while it also provides a proper habitat for bacteria to increase colonization rates and offers protection of the soil. © 2021 Society of Chemical Industry.

Bacteriophage therapy for challenging bacterial infections: achievements, limitations and prospects for future clinical use by veterinary dermatologists.

Bacteriophages were discovered just over 100 years ago and have been used to treat bacterial infections in animals since the 1920s. The antimicrobial resistance crisis has led to a new surge of interest in the use of bacteriophage therapy as an alternative or supplement to antimicrobial therapy in humans and other animals. To describe the nature of bacteriophages and provide a critical review and update on the clinical use of bacteriophages in the treatment of challenging bacterial infections, with an emphasis on companion animal veterinary applications. The scientific literature on the subject was critically evaluated. Findings from the most pertinent papers have been presented in summary form and critiqued. Over the last 20 years there has been a considerable increase in the volume and quality of publications dealing with bacteriophage therapy. Some recent papers build on excellent work published in the 1980s and describe promising veterinary applications. Challenges related particularly to the registration and approval of phage remedies will need to be overcome before phage therapy can become a mainstream tool for use in veterinary settings. Considerably more research, particularly controlled clinical trials, needs to be done. Bacteriophage therapy is one of the most promising approaches to tackling the looming antimicrobial resistance crisis, yet substantial regulatory challenges will need to be overcome before it enters widespread use. Phage therapy also may, in the future, improve the management of challenging bacterial infections that are not necessarily multidrug-resistant.

Decitabine Promotes Modulation in Phenotype and Function of Monocytes and Macrophages That Drive Immune Response Regulation

Decitabine is an approved hypomethylating agent used for treating hematological malignancies. Although decitabine targets altered cells, epidrugs can trigger immunomodulatory effects, reinforcing the hypothesis of immunoregulation in treated patients. We therefore aimed to evaluate the impact of decitabine treatment on the phenotype and functions of monocytes and macrophages, which are pivotal cells of the innate immunity system. In vitro decitabine administration increased bacterial phagocytosis and IL-8 release, but impaired microbicidal activity of monocytes. In addition, during monocyte-to-macrophage differentiation, treatment promoted the M2-like profile, with increased expression of CD206 and ALOX15. Macrophages also demonstrated reduced infection control when exposed to Mycobacterium tuberculosis in vitro. However, cytokine production remained unchanged, indicating an atypical M2 macrophage. Furthermore, when macrophages were cocultured with lymphocytes, decitabine induced a reduction in the release of inflammatory cytokines such as IL-1β, TNF-α, and IFN-γ, maintaining IL-10 production, suggesting that decitabine could potentialize M2 polarization and might be considered as a therapeutic against the exacerbated immune response.

In silico analysis of bacterial translation factors reveal distinct translation event specific pI values

BackgroundProtein synthesis is a cellular process that takes place through the successive translation events within the ribosome by the event-specific protein factors, namely, initiation, elongation, release, and recycling factors. In this regard, we asked the question about how similar are those translation factors to each other from a wide variety of bacteria? Hence, we did a thorough in silico study of the translation factors from 495 bacterial sp., and 4262 amino acid sequences by theoretically measuring their pI and MW values that are two determining factors for distinguishing individual proteins in 2D gel electrophoresis in experimental procedures. Then we analyzed the output from various angles.ResultsOur study revealed the fact that it’s not all same, or all random, but there are distinct orders and the pI values of translation factors are translation event specific. We found that the translation initiation factors are mainly basic, whereas, elongation and release factors that interact with the inter-subunit space of the intact 70S ribosome during translation are strictly acidic across bacterial sp. These acidic elongation factors and release factors contain higher frequencies of glutamic acids. However, among all the translation factors, the translation initiation factor 2 (IF2) and ribosome recycling factor (RRF) showed variable pI values that are linked to the order of phylogeny.ConclusionsFrom the results of our study, we conclude that among all the bacterial translation factors, elongation and release factors are more conserved in terms of their pI values in comparison to initiation and recycling factors. Acidic properties of these factors are independent of habitat, nature, and phylogeny of the bacterial species. Furthermore, irrespective of the different shapes, sizes, and functions of the elongation and release factors, possession of the strictly acidic pI values of these translation factors all over the domain Bacteria indicates that the acidic nature of these factors is a necessary criterion, perhaps to interact into the partially enclosed rRNA rich inter-subunit space of the translating 70S ribosome.

Host-Guest Interaction-Mediated Photo/Temperature Dual-Controlled Antibacterial Surfaces.

Development of smart switchable surfaces to solve the inevitable bacteria attachment and colonization has attracted much attention; however, it proves very challenging to achieve on-demand regeneration for noncontaminated surfaces. We herein report a smart, host-guest interaction-mediated photo/temperature dual-controlled antibacterial surface, topologically combining stimuli-responsive polymers with nanobactericide. From the point of view of long-chain polymer design, the peculiar hydration layer generated by hydrophilic poly(2-hydroxyethyl methacrylate) (polyHEMA) segments severs the route of initial bacterial attachment and subsequent proliferation, while the synergistic effect on chain conformation transformation poly(N-isopropylacrylamide) (polyNIPAM) and guest complex dissociation azobenzene/cyclodextrin (Azo/CD) complex greatly promotes the on-demand bacterial release in response to the switch of temperature and UV light. Therefore, the resulting surface exhibits triple successive antimicrobial functions simultaneously: (i) resists ∼84.9% of initial bacterial attachment, (ii) kills ∼93.2% of inevitable bacteria attack, and (iii) releases over 94.9% of killed bacteria even after three cycles. The detailed results not only present a potential and promising strategy to develop renewable antibacterial surfaces with successive antimicrobial functions but also contribute a new antimicrobial platform to biomedical or surgical applications.

Bacterial Meningitis in Children: Neurological Complications, Associated Risk Factors, and Prevention.

Bacterial meningitis is a devastating infection, with a case fatality rate of up to 30% and 50% of survivors developing neurological complications. These include short-term complications such as focal neurological deficit and subdural effusion, and long-term complications such as hearing loss, seizures, cognitive impairment and hydrocephalus. Complications develop due to bacterial toxin release and the host immune response, which lead to neuronal damage. Factors associated with increased risk of developing neurological complications include young age, delayed presentation and Streptococcus pneumoniae as an etiologic agent. Vaccination is the primary method of preventing bacterial meningitis and therefore its complications. There are three vaccine preventable causes: Haemophilus influenzae type b (Hib), S. pneumoniae, and Neisseria meningitidis. Starting antibiotics without delay is also critical to reduce the risk of neurological complications. Additionally, early adjuvant corticosteroid use in Hib meningitis reduces the risk of hearing loss and severe neurological complications.

Bi-continuous positively-charged PVDF membranes formed by a dual-bath procedure with bacteria killing/release ability

• Original positively-charged copolymers are synthesized. • Positively charged membranes are formed by dual-bath procedure. • Bacteria killing occurs upon contact with the membrane’s surface. • Membranes can be regenerated by washing with saline solution. • Membranes can kill while rejecting bacteria. This work reports the synthesis of a unique positively-charged copolymer obtained from the reaction between iodomethane and a random copolymer of styrene and 4-vinylpyridine. This copolymer, referred to as qP(S- r -4-VP), was fully characterized by 1 H NMR, FT-IR, XPS and GPC, and then mixed with poly(vinylidene fluoride) (PVDF) to form porous membranes able to kill bacteria upon contact. Membranes were prepared by a dual-bath procedure using methanol (10 min) and water (24 h). They exhibited typical bi-continuous structure with large pores (mean pore flow diameter: 0.2–0.45 µm) that decreased with the copolymer content, and large porosity (77%-80%). The presence of the copolymer on the membrane surface was ascertained by FT-IR. All membranes exhibited a high water contact angle in air (>140°), but hydration capacity was enhanced with the copolymer content in the membrane (from 10 mg/cm 3 for the virgin membrane up to 225 mg/cm 3 for modified membranes). The surface charge of the membrane increased with the copolymer content. Q3 membrane (containing 3 wt% copolymer) was selected as the best membrane able to kill various bacteria including Escherichia coli , Stenotrophomonas maltophilia and Staphylococcus epidermidis . Besides, washing with a saline solution of sodium citrate or sodium hexametaphosphate disturbed electrostatic and hydrophobic interactions between dead bacteria and membrane surface, making bacterial release possible. Membrane regeneration properties were also demonstrated from multiple killing/release cycles. Finally, it was shown that membranes were able to kill bacteria during a dead-end filtration process, while achieving 100% rejection. The material and membrane presented in the frame of this work could be of interest to decrease the pathogenicity of a feed during separation

PspC domain-containing protein (PCP) determines Streptococcus mutans biofilm formation through bacterial extracellular DNA release and platelet adhesion in experimental endocarditis.

Bacterial extracellular DNA (eDNA) and activated platelets have been found to contribute to biofilm formation by Streptococcus mutans on injured heart valves to induce infective endocarditis (IE), yet the bacterial component directly responsible for biofilm formation or platelet adhesion remains unclear. Using in vivo survival assays coupled with microarray analysis, the present study identified a LiaR-regulated PspC domain-containing protein (PCP) in S. mutans that mediates bacterial biofilm formation in vivo. Reverse transcriptase- and chromatin immunoprecipitation-polymerase chain reaction assays confirmed the regulation of pcp by LiaR, while PCP is well-preserved among streptococcal pathogens. Deficiency of pcp reduced in vitro and in vivo biofilm formation and released the eDNA inside bacteria floe along with reduced bacterial platelet adhesion capacity in a fibrinogen-dependent manner. Therefore, LiaR-regulated PCP alone could determine release of bacterial eDNA and binding to platelets, thus contributing to biofilm formation in S. mutans-induced IE.

Exosome-Like Nanoparticles From Lactobacillus rhamnosusGG Protect Against Alcohol-Associated Liver Disease Through Intestinal Aryl Hydrocarbon Receptor in Mice.

Alcohol‐associated liver disease (ALD) is a major cause of mortality. Gut barrier dysfunction–induced bacterial translocation and endotoxin release contribute to the pathogenesis of ALD. Probiotic Lactobacillus rhamnosus GG (LGG) is known to be beneficial on experimental ALD by reinforcing the intestinal barrier function. In this study, we aim to investigate whether the protective effects of LGG on intestinal barrier function is mediated by exosome‐like nanoparticles (ELNPs) released by LGG. Intestinal epithelial cells and macrophages were treated with LGG‐derived ELNPs (LDNPs) isolated from LGG culture. LDNPs increased tight junction protein expression in epithelial cells and protected from the lipopolysaccharide‐induced inflammatory response in macrophages. Three‐day oral application of LDNPs protected the intestine from alcohol‐induced barrier dysfunction and the liver from steatosis and injury in an animal model of ALD. Co‐administration of an aryl hydrocarbon receptor (AhR) inhibitor abolished the protective effects of LDNPs, indicating that the effects are mediated, at least in part, by intestinal AhR signaling. We further demonstrated that LDNP administration increased intestinal interleukin‐22‐Reg3 and nuclear factor erythroid 2‐related factor 2 (Nrf2)–tight junction signaling pathways, leading to the inhibition of bacterial translocation and endotoxin release in ALD mice. This protective effect was associated with LDNP enrichment of bacterial tryptophan metabolites that are AhR agonists. Conclusions: Our results suggest that the beneficial effects of LGG and their supernatant in ALD are likely mediated by bacterial AhR ligand–enriched LDNPs that increase Reg3 and Nrf2 expression, leading to the improved barrier function. These findings provide a strategy for the treatment of ALD and other gut barrier dysfunction–associated diseases.

Development of a microencapsulated probiotic delivery system for New Zealand black-footed abalone (Haliotis iris)

Conventional methods of probiotics delivery to farmed aquatic animals are not efficient due to loss of probiotic’s viability before the probiotics can reach their site of action. This study aims to develop a microencapsulated probiotic delivery system for black-footed abalone (Haliotis iris). An emulsion technique was used to encapsulate probiotic bacteria within chitosan-coated alginate microparticles (CALG). The efficacy of CALG microparticles in delivering probiotics to abalone was assessed using ex vivo and in vivo experiments. Microparticles (113 ± 4 µm) with encapsulation efficiency of more than 75% were developed using an internal gelation formulation approach. The ex vivo release experiments revealed the lack of probiotic discharge in the first 6 h of incubating CALG in seawater followed by a slight bacterial release within the next 20 h. The exposure of CALG microparticles to simulated gastric and intestinal media showed a significantly higher release of encapsulated bacteria in the simulated intestinal medium. The results of feeding trial revealed that the number of probiotic bacteria in probiotic-fed abalone was significantly higher than the one in the control animals. The results suggest that CALG microparticles can be used as a controlled release system for delivering viable probiotic bacteria to the gastrointestinal tract of abalone.

GGQ methylation enhances both speed and accuracy of stop codon recognition by bacterial class-I release factors

Accurate translation termination in bacteria requires correct recognition of the stop codons by the class-I release factors (RFs) RF1 and RF2, which release the nascent peptide from the peptidyl tRNA after undergoing a “compact to open” conformational transition. These RFs possess a conserved Gly-Gly-Gln (GGQ) peptide release motif, of which the Q residue is posttranslationally methylated. GGQ-methylated RFs have been shown to be faster in peptide release than the unmethylated ones, but it was unknown whether this modification had additional roles. Using a fluorescence-based real-time in vitro translation termination assay in a stopped-flow instrument, we demonstrate that methylated RF1 and RF2 are two- to four-fold more accurate in the cognate stop codon recognition than their unmethylated variants. Using pH titration, we show that the lack of GGQ methylation facilitates the “compact to open” transition, which results in compromised accuracy of the unmethylated RFs. Furthermore, thermal melting studies using circular dichroism and SYPRO-orange fluorescence demonstrate that GGQ methylation increases overall stability of the RF proteins. This increased stability, we suspect, is the basis for the more controlled conformational change of the methylated RFs upon codon recognition, which enhances both their speed and accuracy. This GGQ methylation-based modulation of the accuracy of RFs can be a tool for regulating translational termination in vivo.