Survival Of Bacteria Research Articles

A new Eosin Y-based ‘turn[sbnd]on’ fluorescent sensor for ratiometric sensing of toxic mercury ion (Hg2+) offering unaided eye detection and its antibacterial activity

A unique fluorescent molecule (ND-S) was obtained from Eosin Y in two simple yet high yielding steps (1). ND-S has special metal ion sensing ability, such that it can selectively detect toxic Hg2+ present in very low concentration in aqueous solutions in the presence of other competing metal ions. The host-guest complexation is ratiometric and is associated with significant increase in fluorescence during the process. Isothermal titration calorimetry (ITC) experiments provided thermodynamic parameters related to interaction between ND-S and Hg2+. Using inductively coupled plasma mass spectrometry (ICP-MS), the Hg2+(aq) removal efficiency of ND-S was estimated to be 99.88%. Appreciable limit of detection (LOD = 7.4 nM) was observed. Other competing ions did not interfere with the sensing of Hg2+ by ND-S. The effects of external stimuli (temperature and pH) were studied. Besides, the complex (ND-M), formed by 1:1 coordination of ND-S and Hg2+ was found to be effective against the survival of Gram-positive bacteria (S. aureus and B. subtilis) with a high selectivity index. Moreover, bacterial cell death mechanism was studied systematically. Overall, we have shown the transformation of a toxic species (Hg2+), extracted from polluted water by a biocompatible sensor (ND-S), into an effective and potent antibacterial agent (ND-M).

A Lignin Silver Nanoparticles/Polyvinyl Alcohol/Sodium Alginate Hybrid Hydrogel with Potent Mechanical Properties and Antibacterial Activity.

Antibacterial hydrogels have attracted significant attention due to their diverse applications, efficient antimicrobial properties, and adaptability to various environments and requirements. However, their relatively fragile structure, coupled with the potential for environmental toxicity when exposed to their surroundings for extended periods, may significantly limit their practical application potential. In this work, a composite hydrogel was synthesized with outstanding mechanical features and antibacterial capability. The hydrogel was developed through the combination of the eco-friendly and enduring antibacterial agent, lignin silver nanoparticles (Lig-Ag NPs), with polyvinyl alcohol (PVA) and sodium alginate (SA), in varying proportions. The successful synthesis of the hydrogel and the dispersed distribution of Lig-Ag NPs within the hydrogel were confirmed by various analytical techniques, including field emission scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), mercury intrusion porosimetry (MIP), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The formation of multiple hydrogen bonds between Lig-Ag NPs and the composites contributed to a more stable and dense network structure of the hydrogel, consequently enhancing its mechanical properties. Rheological tests revealed that the hydrogel exhibited an elastic response and demonstrated outstanding self-recovery properties. Significantly, the antibacterial hydrogel demonstrated effectiveness against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), achieving a <5% survival of bacteria within 12 h. This study presented a green and straightforward synthetic strategy for the application of antibacterial composite hydrogels in various fields.

The role of autophagy in odontogenesis, dental implant surgery, periapical and periodontal diseases.

Autophagy is a cellular process that is evolutionarily conserved, involving the sequestration of damaged organelles and proteins into autophagic vesicles, which subsequently fuse with lysosomes for degradation. Autophagy controls the development of many diseases by influencing apoptosis, inflammation, the immune response and different cellular processes. Autophagy plays a significant role in the aetiology of disorders associated with dentistry. Autophagy controls odontogenesis. Furthermore, it is implicated in the pathophysiology of pulpitis and periapical disorders. It enhances the survival, penetration and colonization of periodontal pathogenic bacteria into the host periodontal tissues and facilitates their escape from host defences. Autophagy plays a crucial role in mitigating exaggerated inflammatory reactions within the host's system during instances of infection and inflammation. Autophagy also plays a role in the relationship between periodontal disease and systemic diseases. Autophagy promotes wound healing and may enhance implant osseointegration. This study reviews autophagy's dento-alveolar effects, focusing on its role in odontogenesis, periapical diseases, periodontal diseases and dental implant surgery, providing valuable insights for dentists on tooth development and dental applications. A thorough examination of autophagy has the potential to discover novel and efficacious treatment targets within the field of dentistry.

Los fructanos de agave promueven la formación de biopelícula in vitro en el consorcio probiótico Lactobacillus delbrueckii ssp. lactis, L. delbrueckii ssp. bulgaricus y Streptococcus thermophilus

In recent years the relationship between the intestinal microbiota, the host and chronic non-communicable diseases has brought interest into the study of its formation and maintenance in the host. Lactic acid bacteria (BAL) are Gram-positive bacteria with probiotic activity, which have been associated with many health benefits, such as decreased body fat mass and lower risk of type II diabetes mellitus. One of the main colonization mechanisms and bacteria survival strategies is the production of biofilms and the use of prebiotics as substrates to achieve a balance within intestinal microbiota. However, there is not enough evidence to demonstrate the biofilm formation in the presence of agave fructans (AF). This study aimed to evaluate in vitro the biofilm formation in a consortium of lactic acid bacteria: Lactobacillus delbrueckii ssp. lactis, Lactobacillus delbrueckii ssp. bulgaricus y Streptococcus thermophilus in the presence of AF at different concentrations: 0%, 0,1%, 4%, 8% y 16%. The addition of 0,1% of AF correlates with the best capacity for biofilm formation. The findings imply the possibility of modulating the biofilm formation of lactic acid bacteria with AF. These results can contribute positively to the host, by generating intestinal homeostasis, colonization resistance, stability to food digestion and chemical modifications of drugs and carry out beneficial functions to the health.

Comparative transcriptome analysis explored the molecular mechanisms of a luxR-type regulator regulating intracellular survival of Aeromonas hydrophila.

Aeromonas hydrophila is not a traditional intracellular bacterium. However, previous studies revealed that pathogenic A. hydrophila B11 could temporarily survive for at least 24 h in fish phagocytes, and the regulation of intracellular survival in bacteria was associated with regulators of the LuxR-type. The mechanisms of luxR08110 on the A. hydrophila's survival in macrophages were investigated using comprehensive transcriptome analysis and biological phenotype analysis in this study. The results showed that after luxR08110 was silenced, the intracellular survival ability of bacteria was significantly diminished. Comparative transcriptome analysis revealed that luxR08110 was a critical regulator of A. hydrophila, which regulated the expression of over 1200 genes, involving in bacterial flagellar assembly and chemotaxis, ribosome, sulphur metabolism, glycerolipid metabolism, and other mechanisms. Further studies confirmed that after the inhibition of expression of luxR08110, the motility, chemotaxis and adhesion of A. hydrophila significantly decreased. Moreover, compared with the wild-type strain, the survival rates of silencing strain were all considerably reduced under both H2O2 and low pH stress conditions. According to both transcriptome analysis and phenotypic tests, the luxR08110 of A. hydrophila could act as global regulator in bacteria intracellular survival. This regulator regulated intracellular survival of A. hydrophila mainly through two ways. One way is to regulate bacterial flagellar synthesis and further affects the motility, chemotaxis and adhesion of bacteria. The other way is to regulate sulphur and glycerolipid metabolisms, thus affecting bacterial energy production and the ability to resist environmental stress.

Impact of microwave heating on product safety and quality in meatballs

The effects of microwave heating at different processing time and power levels (360 W, 600 W and 900 W) on Salmonella Typhimurium, Escherichia coli O157:H7, Listeria monocytogenes and Staphylococcus aureus in Turkish type meatballs were evaluated. Besides, the changes in the textural and sensorial properties of meatballs were determined to reveal the cooking time and temperatures that would make the product safety without affecting the consumer preferences. In this direction, the experimentally contaminated meatballs were subjected to microwave heating at low, medium and high power levels for different processing times and analysed for the survival of the relevant pathogenic bacteria. The total aerobic bacteria count in meatballs could be reduced approximately 3–4 log CFU/g by medium and high microwave powers, whereas 5–7 log CFU/g inhibition was obtained in meatballs inoculated with pathogens. The increase in power level together with the increasing process time resulted in a decrease in the counts of bacteria and an undesirable effect on the textural and sensorial qualities of meatballs. Microwave heating at medium and high power levels as from 3 min, caused excessive drying and blackening of the product, making it difficult to consume due to crust formation. Consequently, to achieve optimal acceptability of the product by consumers, meatballs should be heated with a microwave power of 600 W and 900 W for 3 min.

Synthesis, Crystal Structures and Antibacterial Activity of Nickel(II) and Copper(II) Complexes Derived from (E)-2-((2,3-dihydrobenzo[b][1,4]dioxin-6-yl)methylene)- N-phenylhydrazinecarbothioamide

The biosynthesis of fatty acids is essential for the survival of bacteria, and β-ketoacyl-acyl carrier protein synthase III (FabH) is a promising target for antibacterial drug development. Nickel(II) complex [NiL2] (1) and copper(II) complex [CuL2] (2), where L is (E)-2-((2,3-dihydrobenzo[b][1,4]dioxin-6-yl)methylene)-N-phenylhydrazinecarbothioamide, were synthesized and characterized by elemental analysis, IR and 1H NMR spectroscopy and HRMS. Structures of the complexes were further studied by single crystal X-ray determination, which reveals that the nickel and copper atoms in the complexes are in tetrahedral geometry. These compounds were evaluated for their antibacterial and E. coli FabH inhibitory activities.

Nanofiltration membrane with surface nanostructure induced by interfacial modification for heavy metal ions removal, salt selection and antibacterial

Positively charged nanofiltration membranes offer promising options for the removal of heavy metal ions. However, their electrical properties often lead to serious drawbacks such as impaired filtration performance and poor fouling resistance, thus further modification of these positively charged membranes are imperative. Herein, we report the interfacial manipulation of nanofiltration membranes using a hydroxyl monomer (β-cyclodextrin) in concert with the typical positively charged ammonia monomer (polyethyleneimine) to achieve efficient removal of heavy metals, improved perm-selectivity and fouling resistance. The results indicated that water flux of the modified membrane was increased by over 2-folds owing to structural modification compared with pristine membrane. The charge effects and enhanced cross-linking improve the rejection of salts ions, especially divalent ions. The topological and Turing-structured membranes reached 99.9% removal of heavy metal ions due to the combination of adsorption, complexation, Donnan and site resistance effects, and has excellent stability. Additionally, the functionalized membranes exhibited reduced adhesion and survival of bacteria on the surface based on the excellent bacteriostatic and hydrophilicity properties. These findings revealed the mechanism of interfacial modification induction on the nanostructure and properties of membranes and provided an efficient solution for the synthesis of multifunctional membranes.

Assessment of lactic acid bacteria survivability in Amla, beetroot, date jam by physicochemical, textural, and sensorial means of storage

Assessment of lactic acid bacteria survivability in Amla, beetroot, date jam by physicochemical, textural, and sensorial means of storage

Assessment of antibiotic-resistant infection risks associated with reclaimed wastewater irrigation in intensive tomato cultivation

Agricultural irrigation using reclaimed urban wastewater (RWW) represents a sustainable practice to meet the ever-increasing water stress in modern societies. However, the occurrence of residual antibiotics and antibiotic resistant bacteria (ARB) in RWW is an important human health concern. This study applied for the first time a novel Simple-Death dose-response model to the field data of Escherichia coli and Pseudomonas spp. collected from three greenhouses for cultivation of tomatoes irrigated with RWW. The model estimates the risk of infection by enteropathogenic E. coli associated with consumption of tomatoes and the risk of eye-infection caused by Pseudomonas aeruginosa in cultivation soil through hand-to-eye contacts. The fraction of antibiotic resistant (AR)-E. coli measured in irrigation water and AR-Pseudomonas spp. in soil was incorporated in the model to estimate the survival of ARB and antibiotic susceptible bacteria in the presence of trace level of antibiotics in human body. The results showed that the risk of E. coli infection through consumption of tomatoes irrigated with RWW is within the WHO and USEPA recommended risk threshold (<10−4); Pseudomonas aeruginosa eye-infection risk is at or below the acceptable risk level. The presence of residual antibiotic in human body reduced the overall risk probabilities of infections but selectively enhanced the survival of ARB in comparison to their susceptible counterparts, which resulted in antibiotic untreatable infection. Therefore, the outcomes of this study call for a new risk threshold for antibiotic untreatable infections and highlight the key importance of adopting work safety measures for better human health protection.

Rare Earth-Carbon Dots Nanocomposite-Modified Glass Nanopipettes: Electro-Optical Detection of Bacterial ppGpp.

As an important alarmone nucleotide, guanosine 3'-diphosphate-5'-diphosphate (ppGpp) can regulate the survival of bacteria under strict environmental conditions. Direct detection of ppGpp in bacteria with high sensitivity and selectivity is crucial for elucidating the role of ppGpp in bacterial stringent response. Herein, the terbium-carbon dots nanocomposite (CDs-Tb) modified glass nanopipet was developed for the recognition of ppGpp. The CDs-Tb in glass nanopipette preserved their fluorescence properties as well as the coordination capacity of Tb3+ toward ppGpp. The addition of ppGpp not only led to the fluorescence response of CDs-Tb but also triggered variations of surface charge inside the glass nanopipet, resulting in the ionic current response. Compared with nucleotides with similar structures, this method displayed good selectivity toward ppGpp. Moreover, the dual signals (fluorescence and ionic current) offered a built-in correction for potential interference. Apart from the high selectivity, the proposed method can determine the concentration of ppGpp from 10-13 to 10-7 M. Taking advantage of the significant analytical performance, we monitored ppGpp in Escherichia coli under different nutritional conditions and studied the relationship between ppGpp and DNA repair, which is helpful for overcoming antibiotic resistance and promoting the development of potential drugs for antibacterial treatment.

α-Methylacyl-CoA Racemase from Mycobacterium tuberculosis-Detailed Kinetic and Structural Characterization of the Active Site.

α-Methylacyl-CoA racemase in M. tuberculosis (MCR) has an essential role in fatty acid metabolism and cholesterol utilization, contributing to the bacterium's survival and persistence. Understanding the enzymatic activity and structural features of MCR provides insights into its physiological and pathological significance and potential as a therapeutic target. Here, we report high-resolution crystal structures for wild-type MCR in a new crystal form (at 1.65 Å resolution) and for three active-site mutants, H126A, D156A and E241A, at 2.45, 1.64 and 1.85 Å resolutions, respectively. Our analysis of the new wild-type structure revealed a similar dimeric arrangement of MCR molecules to that previously reported and details of the catalytic site. The determination of the structures of these H126A, D156A and E241A mutants, along with their detailed kinetic analysis, has now allowed for a rigorous assessment of their catalytic properties. No significant change outside the enzymatic active site was observed in the three mutants, establishing that the diminution of catalytic activity is mainly attributable to disruption of the catalytic apparatus involving key hydrogen bonding and water-mediated interactions. The wild-type structure, together with detailed mutational and biochemical data, provide a basis for understanding the catalytic properties of this enzyme, which is important for the design of future anti-tuberculosis drug molecules.

D-Glucosamine is a Potential Urease Inhibitor from Middle Eastern Medicinal Plants for Combatting Helicobacter Pylori Infections; a Molecular Docking and Simulation Approach.

Helicobacter pylori stands as a significant risk factor for both peptic and stomach ulcers. Their resistance to the highly acidic host environment primarily stems from their capability to produce urease, an enzyme that rapidly converts urea into NH3 and CO2. These byproducts are crucial for the bacterium's survival under such harsh conditions. Given the pivotal role of medicinal plants in treating various ailments with minimal side effects, there is an urgent need for a natural drug that can effectively eliminate H. pylori by inhibiting urease. Hence, the current study aims to identify the most potent urease inhibitor among the natural compounds found in Middle Eastern medicinal plants, taking into consideration factors such as optimal affinity, drug-like properties, pharmacokinetic characteristics, and thermodynamic attributes. In total, 5599 ligand conformers from 151 medicinal plants were subjected to docking against the urease's active site. The top-ranking natural compounds, as determined by their high docking scores, were selected for further analysis. Among these compounds, D-glucosamine (PubChem code 439,213) exhibited the most interactions with the crucial amino acid residues in the urease's active site. Furthermore, D-glucosamine demonstrated superior absorption, distribution, metabolism, excretion, and toxicity properties compared to other top-ranked candidates. Molecular dynamics simulations conducted over 100 nanoseconds revealed stable root mean square deviations and fluctuations of the protein upon complexation with D-glucosamine. Additionally, the radius of gyration and solvent-accessible surface area values for the D-glucosamine-urease complex were notably lower than those observed in other typical urease-inhibitor complexes. In conclusion, this study provides valuable insights into the potential development of D-glucosamine as a novel urease inhibitor. This promising compound holds the potential to serve as an effective drug for combating H. pylori infections in the near future.

Comparative survival study of Bacillus coagulans and Enterococcus faecium microencapsulated in chitosan-alginate nanoparticles in simulated gastrointestinal condition

Probiotics have poor gastrointestinal delivery because they lose their viability during intestinal passage. Microencapsulation has a significant effect on the survival of probiotic bacteria. This study aimed to synthesize chitosan-alginate nanoparticles and encapsulate Bacillus coagulans NBRC-12583 and Enterococcus faecium MGFR1 in alginate (Alg), chitosan (Cht) and inulin (Inu) by micro- and nano-encapsulation to investigate the viability of encapsulated strains in simulated gastrointestinal condition. The survival of free and encapsulated bacteria was studied for 120 min. The population of B. coagulans encapsulated in Cht-Alg only decreased by 0.86 log CFU, while that of E. faecium encapsulated in Cht-Alg nanoparticles only decreased by 0.27 log CFU. Treated with simulated intestinal fluid, B. coagulans and E. faecium populations decreased by 1.03 and 0.17 log CFU, respectively. E. faecium microencapsulated in Cht-Alg and Inu had a maximum encapsulation efficiency of 96.78%. E. faecium encapsulated in Cht-Alg nanoparticles and Inu was more viable than other encapsulated bacteria. Scanning electron microscopy was done to investigate the microcapsules' surface morphology, structure, internal cross-sectional view, and the zeta potential for the surface charge of Cht-Alg nanoparticles. The viability of the probiotic bacteria was enhanced significantly by microencapsulation and nanomaterial-based encapsulation within the chitosan-alginate and inulin matrix.

Evaluation of the Antimicrobial, Cytotoxic, and Physical Properties of Selected Nano-Complexes in Bovine Udder Inflammatory Pathogen Control.

Mastitis in dairy cows is a worldwide problem faced by dairy producers. Treatment mainly involves antibiotic therapy, however, due to widespread antibiotic resistance among bacteria, such treatments are no longer effective. For this reason, scientists are searching for new solutions to combat mastitis, which is caused by bacteria, fungi, and algae. One of the most promising solutions, nanotechnology, is attracting research due to its biocidal properties. The purpose of this research was to determine the biocidal properties of nanocomposites as a potential alternative to antibiotics in the control of mastitis, as well as to determine whether the use of nanoparticles and what concentration is safe for the breeder and the animal. In this study, the effects of Ag, Au, Cu, Fe, and Pt nanoparticles and their complexes were evaluated in relation to the survival of bacteria and fungi isolated from cattle diagnosed with mastitis, their physicochemical properties, and their toxicity to bovine and human mammary epithelial cells BME-UV1 and HMEC (human microvascular endothelial cells). Moreover, E. coli, S. aureus, C. albicans, and Prototheca sp. invasion was assessed using the alginate bead (bioprinted) model. The NPs were tested at concentrations of 25, 12.5, 6.25, 3.125, 1.56 mg/l for Au, Ag, Cu and Fe NPs, and 10, 5, 2.5, 1.25, 0.625 mg/l for Pt. With the exception of Fe and Pt, all exhibited biocidal properties against isolates, while the AgCu complex had the best effect. In addition, nanoparticles showed synergistic effects, while the low concentrations had no toxic effect on BME-UV1 and HMEC cells. Synergistic effects of nanoparticles and no toxicity to bovine and human cells might, in the future, be an effective alternative in the fight against microorganisms responsible for mastitis, and the implementation of research results in practice would reduce the percentage of dairy cows suffering from mastitis. The problem of increasing antibiotic resistance is posing a global threat to human's and animal's health, and requires comprehensive research to evaluate the potential use of nanoparticles - especially their complexes - as well as to determine whether nanoparticles are safe for the breeders and the animals. The conducted series of studies allows further consideration of the use of the obtained results in practice, creating a potentially new alternative to antibiotics in the treatment and prevention of mastitis in dairy cattle.

The effects of fortification of yogurt with various functional flours on survival and growth of probiotic bacteria and sensory properties of the yogurt

PurposeThe purpose of this study is to determine the viability of Lacticaseibacillus rhamnosus GR-1 (L. rhamnosus GR-1) in five yogurt samples with or without quinoa, chickpea, soybean and rice flour over various fermentation periods and refrigerated storage durations, with a focus on exploring the potential of functional foods, which provide health benefits beyond nutritional value. Additionally, the study aimed to evaluate consumer acceptance of yogurt fortified with functional flour. Using a nine-point hedonic scale, from 1 (dislike extremely) to 9 (like extremely), participants rated appearance, flavour, texture and overall acceptability.Design/methodology/approachThe samples were inoculated with the probiotic strain L. rhamnosus GR-1 and fermented for 0, 2, 4 and 6 h at 38°C, followed by refrigerated storage at 4°C for 1, 15 and 30 days, respectively. Microbial enumeration was performed throughout fermentation and storage to assess the viability of L. rhamnosus GR-1. A sensory evaluation involving 86 participants was conducted to assess the consumer acceptability of the yogurt samples.FindingsNotably, L. rhamnosus GR-1 achieved viable counts of 108 colony-forming units per mL in all treatments at all fermentation time points. Over the 30-day storage period, no statistically significant differences (p < 0.05) in average pH values were observed among the five treatments, and within each treatment, pH levels remained stable, with an overall mean of 4.2 ± 0.64. Treatment 4, which featured rice flour fortification, received higher hedonic scores from sensory panellists in terms of appearance, flavour, texture and overall acceptability. These findings indicate that incorporating functional flours in conjunction with cow’s milk effectively promotes and preserves the viability of L. rhamnosus GR-1 in yogurt.Originality/valueExploring the potential of probiotic yogurt enriched with diverse functional flours to enhance nutritional content and health benefits as well as attract new consumers, this study addressed a critical gap in understanding consumer perceptions and generated insights for creating innovative and health-promoting dairy products.

Bactericidal Efficacy of the Combination of Maresin-like Proresolving Mediators and Carbenicillin Action on Biofilm-Forming Burn Trauma Infection-Related Bacteria.

Biofilm-associated bacterial infections are the major reason for treatment failure in many diseases including burn trauma infections. Uncontrolled inflammation induced by bacteria leads to materiality, tissue damage, and chronic diseases. Specialized proresolving mediators (SPMs), including maresin-like lipid mediators (MarLs), are enzymatically biosynthesized from omega-3 essential long-chain polyunsaturated fatty acids, especially docosahexaenoic acid (DHA), by macrophages and other leukocytes. SPMs exhibit strong inflammation-resolving activities, especially inflammation provoked by bacterial infection. In this study, we explored the potential direct inhibitory activities of three MarLs on Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa and Escherichia coli) bacteria in their biofilms that are leading bacteria in burn trauma-related infections. We also examined the effects of MarLs on the bactericidal activities of a typical broad-spectrum antibiotic, carbenicillin (carb), on these bacteria in their preformed biofilms. The results revealed that MarLs combined with carbenicillin can inhibit the survival of Gram-positive and Gram-negative bacteria in their biofilms although MarLs alone did not exhibit bactericidal activity. Thus, our findings suggest that the combination of MarLs and carbenicillin can lower the antibiotic requirements to kill the bacteria in preformed biofilms.

Prokaryotic DNA Crossroads: Holliday Junction Formation and Resolution.

Cells are continually exposed to a multitude of internal and external stressors, which give rise to various types of DNA damage. To protect the integrity of their genetic material, cells are equipped with a repertoire of repair proteins that engage in various repair mechanisms, facilitated by intricate networks of protein-protein and protein-DNA interactions. Among these networks is the homologous recombination (HR) system, a molecular repair mechanism conserved in all three domains of life. On one hand, HR ensures high-fidelity, template-dependent DNA repair, while on the other hand, it results in the generation of combinatorial genetic variations through allelic exchange. Despite substantial progress in understanding this pathway in bacteria, yeast, and humans, several critical questions remain unanswered, including the molecular processes leading to the exchange of DNA segments, the coordination of protein binding, conformational switching during branch migration, and the resolution of Holliday Junctions (HJs). This Review delves into our current understanding of the HR pathway in bacteria, shedding light on the roles played by various proteins or their complexes at different stages of HR. In the first part of this Review, we provide a brief overview of the end resection processes and the strand-exchange reaction, offering a concise depiction of the mechanisms that culminate in the formation of HJs. In the latter half, we expound upon the alternative methods of branch migration and HJ resolution more comprehensively and holistically, considering the historical research timelines. Finally, when we consolidate our knowledge about HR within the broader context of genome replication and the emergence of resistant species, it becomes evident that the HR pathway is indispensable for the survival of bacteria in diverse ecological niches.

Removed: Development of synbiotic juice by spray drying of Lactobacillus paracaesii sub sp. tolerans N2-45 along with galacto-oligosaccharides using different carrier materials

Synbiotics have been intensively studied for the numerous health benefits they provide to the host, as well as prospective alternative therapy techniques for a variety of disorders. In this investigation, wild strain and thermally adapted strain of Lactobacillus sp. (probiotics) were combined with GOS – Galacto-oligosaccharides (prebiotic). The combination of probiotics + prebiotics - along with carrier materials (Maltodextrin, Corn starch, Acacia Gum) were spray-dried and their characteristics were assessed. Spray-dried powders were tested for 8 weeks at three different storage temperatures (4 °C, 30 °C, and 37 °C) (56 days). At different temperatures (4 °C, 30 °C, 37 °C), N2-45+corn starch + GOS has a greater survival. As a result, corn starch appears to be the best carrier material for microencapsulation. The encapsulated powder was subjected to gastric juice studies and sub-lethal stress analysis. N2-45+corn starch + GOS exhibited the best survival % in both simulated gastric and intestinal juice of all the Lactobacilli spray-dried powders. The Synbiotic squash juice was prepared and sensory analysis was done using the statistical method - PCA model. Sensory qualities did not differ significantly between the control and synbiotic fruit drink. As a result, 75 mg of synbiotic per serving can be regarded healthful and cost-effective when making any flavoured synbiotic fruit drinks. Thus this improves the probiotic bacteria's survivability throughout passage through the upper digestive system.

Functional characterization of RhuB as a second TonB2-dependent hemin receptor in Riemerella anatipestifer CH-1.

In the previous study, it was shown that Riemerella anatipestifer (R. anatipestifer, RA), a pathogen in ducks and some other birds, encodes a hemin uptake system. The R. anatipestifer hemin uptake receptor RhuR is a TonB2-dependent hemin transporter. However, it remains unclear whether R. anatipestifer encodes additional TonB-dependent hemin transporters. Herein, we demonstrated that R. anatipestifer hemin uptake receptor B (RhuB) of R. anatipestifer CH-1 (RA CH-1) was negatively regulated by iron and mediated by the Fur protein, and knocking out rhuB damaged the ability of RA CH-1 to utilize iron from duck hemoglobin (Hb) but not that from duck serum. Moreover, the ability to use iron from Hb was restored by the expression rhuB in trans. Furthermore, the RhuB of RA CH-1 is a membrane protein, and recombinant RhuB could bind hemin at a 1:1 molar ratio in vitro. Compared to that of ΔtonB1ΔrhuR, the ability of ΔtonB1ΔrhuRΔrhuB to utilize hemin was impaired; meanwhile, compared to that of ΔtonB2ΔrhuR, the hemin utilization ability of ΔtonB2ΔrhuRΔrhuB was not affected, indicating that RhuB is a TonB2-dependent receptor. Compared to ΔrhuB, ΔrhuBΔrhuA did not affect hemin utilization. However, compared to ΔrhuA, ΔrhuBΔrhuA had reduced ability to utilize hemin, suggesting that RhuA relies on RhuB for its activity. Finally, the deletion of rhuB did not affect the virulence of RA CH-1. These results suggested that RhuB encodes a TonB2-dependent hemin receptor. The characterization of the second TonB-dependent receptor in R. anatipestifer enriches our understanding of the hemin uptake system of this bacterium.IMPORTANCEIron is essential for the survival of most bacteria, and hemin of hemoglobin can serve as an important iron source. In our previous studies, we showed that R. anatipestifer CH-1 encodes a TonB2-dependent hemin receptor RhuR, which is involved in hemin uptake. The deletion of rhuR did not abolish hemin utilization by RA CH-1. We hypothesized that additional hemin uptake systems exist in this bacterium. In this study, we identified the second TonB2-dependent hemin receptor RhuB in RA CH-1 through hemin utilization, protein localization, and hemin-binding experiments. The duck infection model showed that the deletion of rhuB did not affect the virulence of RA CH-1. This study is not only important for further understanding the hemin utilization mechanism of R. anatipestifer, but also for enriching the hemin uptake transporters of gram-negative bacteria.