Bacterial Cells Research Articles

Synergistic antimicrobial action of chlorogenic acid and ultraviolet-A (365 nm) irradiation; mechanisms and effects on DNA integrity

Chlorogenic acid (CGA) is abundant in various plants and notably in coffee beans. This study investigated the bactericidal activity of CGA combined with ultraviolet-A light (UVA, 365 nm) (CGA + UVA) against Escherichia coli DH5α, with the aim of developing novel strategies for food preservation and healthcare. CGA + UVA treatment was superiorin reducing bacterial survival than either treatment alone. At 20 J/cm2 and pH 7, CGA (0.3%) + UVA treatment resulted in only about a 3-log reduction in bacterial survival, whereas at 15 J/cm2 and pH 3, no surviving bacteria could be detected, demostrating that the treatment was more effective at acidic pH. CGA + UVA treatment was also bactericidal in green plum juice, confirming that its low pH-dependent property could be effective in acidic food products. To elucidate the bactericidal mechanism of CGA + UVA treatment, its effects on reactive oxygen species (ROS) generation, membrane integrity, and enzyme activity were measured. ROS generated via the type-1 reaction, such as hydrogen peroxide (H2O2) and hydroxyl radicals (·OH), were mainly detected. CGA + UVA disrupted the bacterial cell membrane, causing the leakage of cellular components, particularly proteins. CGA + UVA treatment also led to deoxyribonucleic acid (DNA) degradation and reduced succinate-coenzyme Q reductase activity by approximately 72 %. Furthermore, CGA + UVA treatment decreased β-lactamase activity and plasmid transforming efficacy with maximal reductions of 68 % and 98 %, respectively, highlighting its potential for increasing antibiotic susceptibility and preventing the spread of antimicrobial resistance. The results demonstrate that CGA + UVA treatment could be used to effectively combat antibiotic-resistant bacteria and prevent the spoilage of preserved foods or food poisoning.

Hunting the Cell Cycle Snark.

In this very personal hunt for the meaning of the bacterial cell cycle, the snark, I briefly revisit and update some of the mechanisms we and many others have proposed to regulate the bacterial cell cycle. These mechanisms, which include the dynamics of calcium, membranes, hyperstructures, and networks, are based on physical and physico-chemical concepts such as ion condensation, phase transition, crowding, liquid crystal immiscibility, collective vibrational modes, reptation, and water availability. I draw on ideas from subjects such as the 'prebiotic ecology' and phenotypic diversity to help with the hunt. Given the fundamental nature of the snark, I would expect that its capture would make sense of other parts of biology. The route, therefore, followed by the hunt has involved trying to answer questions like "why do cells replicate their DNA?", "why is DNA replication semi-conservative?", "why is DNA a double helix?", "why do cells divide?", "is cell division a spandrel?", and "how are catabolism and anabolism balanced?". Here, I propose some relatively unexplored, experimental approaches to testing snark-related hypotheses and, finally, I propose some possibly original ideas about DNA packing, about phase separations, and about computing with populations of virtual bacteria.

ANTIOXIDANT AND ANTIBACTERIAL PROPERTIES OF BRASSICA JUNCEA EXTRACTS AND SILVER NANOPARTICLES: A SYNERGISTIC APPROACH AGAINST ESCHERICHIA COLI

Brassica juncea, a plant known for its anticancer and antioxidant characteristics, is rich in glucosinolates, flavonoids, carotenoids, and phenolic acids. AEBJ exhibited a high concentration of total flavonoids, measuring 201.09 ± 0.232 mg/g in terms of quercetin equivalents. However, it had a relatively lower total phenolic content, measuring 49.43 ± 1.114 mg/g in terms of tannic acid equivalents. The structural characterisation of silver nanoparticles was performed using UV-Visible spectroscopy, followed by the study of these nanoparticles utilising surface plasmon resonance (SPR) measurements. The interaction between silver ions and extracts of Brassica juncea was seen, and the presence of AgNPs was verified through the detection of a visible peak at 425 nm. The Silver Nanoparticle (BJ 1) effectively suppressed the generation of DPPH radicals within the concentration range of 10-100 µg/ml. The linear regression coefficients for this inhibition were calculated to be 0.9869 and 0.9488, respectively. The IC50 values for Silver Nanoparticle (BJ 1) and BHT were 45.413 and 50.173, respectively. Silver Nanoparticle (BJ 1) exhibited a decrease in the conversion of ferricyanide to ferrocyanide as the concentration increased from 50-250 µg/ml. This was accompanied by an increase in the absorption of green light at a wavelength of 700 nm. The investigation into the antibacterial activity of silver nanoparticles (BJ 1) and Brassica juncea extracts against Escherichia coli has demonstrated substantial potential as antimicrobial agents. The findings indicate that both drugs demonstrate inhibitory effects on the growth of E. coli, with the concentration levels playing a substantial influence. This implies a mutually beneficial interaction between the two drugs, which could potentially amplify their efficacy in fighting bacterial infections. Greater doses of Brassica juncea extract exhibited bigger areas of inhibition, so validating its bioactive activities against pathogenic microorganisms. Furthermore, the Silver nanoparticle (BJ 1) had a potent antibacterial impact as a result of their capability to disturb bacterial cell membranes and impede metabolic activities. The combination of these two medicines has the potential to enhance therapy efficacy in clinical settings. Subsequent investigations should delve into the mechanisms underlying their antibacterial properties and evaluate their safety profiles for future medicinal uses. KEYWORDS: Brassica juncea; Silver Nanoparticles; Antioxidant Activity; DPPH; Reducing Power Assay; Antimicrobial Activity; Escherichia coli

The affinity towards the hydrophobic region of biomimicking bacterial membranes drives the antimicrobial activity of EFV12 peptide from Lactobacillus gasseri gut microbiota

The gut microbiota consists of a large variety of microorganisms, which interact with the immune system and exert essential roles for the human body health. Many of these microorganisms are also capable of producing various bioactive molecules, such as selective antimicrobial peptides, thus promoting the proliferation of only certain bacterial strains. These result in the shaping of the composition of the local microbiome and the co-evolution with a complex microbiome. Recently, a small peptide, named EFV12 and deriving from the bacterium Lactobacillus gasseri SF1109 regularly placed in the human intestine, showed a significant antimicrobial activity. Here we discuss a biophysical study on the structural changes induced by the peptide on lipid bilayers mimicking bacterial membranes with the aim of shedding light on the molecular features driving the biocidal activity against Gram(+) and Gram(−) strains. Supported Lipid Bilayers and liposomes composed of 1,2-oleoyl-sn-glycero-3-phosphocholine and 1,2-oleoyl-sn-glycero-3-rac-phosphoglycerol, both in the absence and presence of cardiolipin and lipopolysaccharides (LPSs), were selected to investigate the peptide-lipid interactions through a combination of specular Neutron Reflectometry, Dynamic Light Scattering, Small-Angle X-ray Scattering and Circular Dichroism measurements. The obtained results indicated association of EFV12 peptide with the hydrophobic region of lipid bilayers, which caused their destabilization, and is thus driving the antimicrobial activity against bacterial cells.

Single Atom Engineered Antibiotics Overcome Bacterial Resistance

AbstractThe outbreak of antibiotic‐resistant bacteria, or “superbugs”, poses a global public health hazard due to their resilience against the most effective last‐line antibiotics. Identifying potent antibacterial agents capable of evading bacterial resistance mechanisms represents the ultimate defense strategy. This study shows that –the otherwise essential micronutrient– manganese turns into a broad‐spectrum potent antibiotic when coordinated with a carboxylated nitrogen‐doped graphene. This antibiotic material (termed NGA‐Mn) not only inhibits the growth of a wide spectrum of multidrug‐resistant bacteria but also heals wounds infected by bacteria in vivo and, most importantly, effectively evades bacterial resistance development. NGA‐Mn exhibits up to 25‐fold higher cytocompatibility to human cells than its minimum bacterial inhibitory concentration, demonstrating its potential as a next‐generation antibacterial agent. Experimental findings suggest that NGA‐Mn acts on the outer side of the bacterial cell membrane via a multimolecular collective binding, blocking vital functions in both Gram‐positive and Gram‐negative bacteria. The results underscore the potential of single‐atom engineering toward potent antibiotics, offering simultaneously a long‐sought solution for evading drug resistance development while being cytocompatible to human cells.

Effect of silver nanoparticles and REP-PCR typing of Staphylococcus aureus isolated from various sources

This is the primary study at Matrouh Governorate to unveil antibiotic resistance, biofilm formation, silver nanoparticles (Ag-NPs) effect using electron microscopy, and REP-PCR analysis of Staphylococcus aureus strains isolated from COVID-19 patients, contaminated food, and Morel’s diseased sheep and goats. A total of 15 S. aureus strains were isolated; five from each of the COVID-19 patients, Morel's diseased sheep and goats, and contaminated food. All strains were considered multidrug-resistant (MDR). All strains showed the presence of biofilm. Morphological changes in the cell surface of the bacterium were evidenced, and penetration with the rupture of some bacterial cells. Based on REP-PCR analysis, 4 clusters (C1-C4) with dissimilarity between clusters C1 and C2 8% and between C3 and C4 15%. Cluster I included 3 strains from contaminated food with a similarity of 97%, and Cluster II included 2 strains from contaminated food and 2 from COVID-19-infected patients with a similarity of 96% (confirming the zoonotic nature of this pathogen). Cluster III contained 4 strains isolated from Morel's diseased sheep & goats with a similarity ratio of 99% in comparison the 4th cluster contained 3 strains isolated from COVID-patients and one from Morel's diseased sheep & goats with a similarity ratio of 92%.

Quorum sensing orchestrates parallel cell death pathways in Vibrio cholerae via Type 6 secretion dependent and independent mechanisms.

Cell death is a fundamental biological process. In mammals, cell death sculpts tissues during development, enables injury recovery, and regulates immunity. In bacteria, cell death mechanisms remain little explored. Recently, colonies formed by the pathogen Vibrio cholerae were demonstrated to undergo a spatio-temporal program of cell death. The program is controlled by quorum sensing (QS) and driven by the Type VI secretion system. Here, we discover QS-controlled genes, called vca0646-0649 , that cause cell death in V. cholerae colonies independently of the Type VI secretion system. These findings indicate that a second cell death pathway exists in V. cholerae . The results expand our understanding of bacterial cell death mechanisms and provide insight into how cell death shapes bacterial community structure.

Development of a Bio-Selecting Agent Based on Immobilized Bacterial Cells with Amidase Activity for Bio-Detection of Acrylamide

Actinobacteria cells Rhodococcus erythropolis 4-1 and Rhodococcus erythropolis 11-2 and Proteobacteria Alcaligenes faecalis 2, which have amidase activity, were immobilized by entrapping barium alginate and agarose into the gel structure, as well as by obtaining biofilms on thermally expanded graphite (TEG). The operational stability of such immobilized biocatalysts after storage in frozen and dehydrated form was determined, and a prototype of a conductometric acrylamide biosensor based on such a bioselective agent was developed. The most preferred method for storing immobilized cells was freezing at temperatures from –20 to –80°C; long-term storage is also possible wet at 4–25°C. It was shown that these cells were most preferable for the biodetection of acrylamide A. faecalis 2, immobilized in an agarose gel structure. An agarose gel with bacterial cells immobilized in its structure had greater mechanical strength and stability during successive cycles of conversion of acrylamide into acrylic acid compared to barium alginate gel. The mechanical strength of barium alginate gel can be enhanced by the addition of carbon nanomaterials during cell immobilization. Growing biofilms on carbon materials used for manufacturing electrodes is also promising. Biofilms of R. erythropolis 11-2 on TEG are capable of converting acrylamide into acrylic acid in more than 20 reaction cycles while maintaining at least 50% amidase activity.

Experimental and theoretical exploration of bactericidal and photo-catalytical activities of hierarchically porous AuNRs@CuO nanocomposite

In this study, a novel binary nanocomposite consisting of CuO nanosheets functionalized with gold nanorods (AuNRs@CuO), was successfully prepared using a two-step synthetic procedure and further investigated via Density Functional Theory. The physicochemical properties of prepared nanomaterials were analysed using Fourier transform infrared spectroscopy, X-ray diffraction, Field emission scanning electron microscopy, High-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy confirming successful fabrication with improved surface properties. Experimental analyses, including antibacterial assays and morphological studies of bacterial cells demonstrates superior bactericidal properties of AuNRs@CuO nanocomposite compared to pristine CuO nanosheets. Furthermore, molecular docking score provide theoretical insights into the underlying mechanism governing the enhanced antibacterial activity, highlighting the favorable interaction with the bacterial cells. The synergistic effect of CuO nanosheets and AuNRs further improves the photocatalytic efficacy, culminating in a high-yield photocatalyst that achieves 98.7% degradation for Indigo carmine under Xenon lamp irradiation compared to 40.8% and 62.4% for AuNRs and CuO nanosheets alone. Improved charge separation and generation of H+ as major reactive oxygen species from the nanocomposite to Indigo carmine was revealed by radical scavenger activity and photoluminescence studies. After cycles of operation, the morphology and surface state of the photocatalyst remained unchanged, as investigated by FESEM and HRTEM analysis. The novelty of this study lies in the integration of AuNRs and CuO nanosheets as an efficient photocatalytic material for the remediation of toxic organic dyes in wastewater, presenting a promising advancement in sustainable water treatment technologies.

Quorum quenching as a mechanism for Cu-bearing stainless steel to conduct nonbiocidal retardation of biofilm development

Bacterial contamination induced by stubborn biofilms has threatened many industries. Significant efforts have concentrated on mitigating surface-associated biofilms with focus on killing or removing bacterial cells, which are always short duration and suboptimal inhibition on biofilms. Here, we reported a sustainable and nonbiocidal strategy of control biofilms by applying a Cu-bearing stainless steel (SS) to interrupt quorum sensing (QS), mentioned as quorum quenching (QQ). It was found that Cu-bearing SS with the micro-galvanic couples structure consisting of the precipitated Cu-rich phases and the matrix triggers charge transfer reactions with bacteria/media, resulting in an overexpression of reactive oxygen species (ROS), which is responsible for QQ. Studies with luxS-delated mutant which cannot mediate the QS mechanism confirmed that QS could be the target for antibacterial metals to produce a sub-/non-lethal biofilm structural inhibition. And inducing ROS production has been a strategy to endow metals with QQ ability. Thereby, defective biofilms with the QS deletion phenotype would be gratifying to provide a sufficient window period for effective decontamination, curbing the solid surface as for contamination spreader. This research introduces a promising and practical QQ strategy for combating bacterial contamination from the root in active microbial environments, providing insights into the material modifications.

Discovery of a Small-Molecule Inhibitor Targeting the Biofilm Regulator BrpT in Vibrio vulnificus.

Vibrio vulnificus, an opportunistic human pathogen, employs biofilm formation as a key survival and virulence mechanism. BrpT, a transcriptional regulator, is essential for V. vulnificus biofilm development by regulating the expression of biofilm-related genes. In this study, we aimed to identify a small molecule inhibitor of BrpT to combat V. vulnificus biofilm formation. High-throughput screening of 7,251 compounds using an Escherichia coli reporter strain carrying the arabinose-inducible brpT gene and a BrpT-activated promoter fused to the luxCDABE operon identified a hit compound, BTI (BrpT Inhibitor). BTI potently inhibited BrpT activity in V. vulnificus (EC50 of 6.48 μM) without affecting bacterial growth or host cell viability. Treatment with BTI significantly reduced the expression of the BrpT regulon and impaired biofilm formation and colony rugosity in V. vulnificus, thus increasing its susceptibility to antibiotics. In vitro biochemical analyses revealed that BTI directly binds to BrpT and inhibits its transcriptional regulatory activity. The identification of BTI as a specific inhibitor of BrpT that effectively diminishes V. vulnificus biofilm formation provides a promising foundation for the development of novel anti-biofilm strategies, with the potential to address the growing challenge of antibiotic resistance and improve the treatment of biofilm-associated infections.

Competition between transient oscillations and early stochasticity in exponentially growing populations

It has been recently shown that the exponential growth rate of a population of bacterial cells starting from a single cell shows transient oscillations due to early synchronized bursts of division. These oscillations are enhanced by cell size regulation and contain information about single-cell growth statistics. Here, we report a phase transition in these oscillations as a function of growth rate variability. Below the transition point, these oscillations become asymptotically deterministic and can be measured experimentally, while above the transition point, the stochasticity in population growth dominates the oscillations and masks all the information about single cell growth statistics. The analytically calculated transition point, which roughly corresponds to 13% variability in single-cell growth rate, falls within physiologically relevant parameters. Additionally, we show that the oscillations can stochastically emerge even when the initial state contains multiple cells with out-of-phase division cycles. We show that the amplitude and phase of these oscillations are stochastic and vary across repeated measurements with the same initial conditions. We provide analytic expressions as well as numerical estimates for the typical oscillation amplitude and the number of generations before the amplitude falls below a given measurement threshold for in multiple growth conditions. Published by the American Physical Society 2024

The exploration of pasteurization processes and mechanisms of inactivation of Bacillus cereus ATCC 14579 using radio frequency energy

Radio frequency (RF) heating has been utilized to investigate sterilization techniques, but the mechanism of sterilization via RF heating, particularly on Bacillus cereus (B. cereus), has not been thoroughly examined. In this paper, sterilization processes and potential bactericidal mechanisms of B. cereus using RF were investigated. The best heating and sterilization efficiency was achieved at (Electrode gap 130 mm, conductivity of bacterial suspension 0.1 S/m, volume of bacterial suspension 40 mL). Heating a suspension of B. cereus to 90 °C in 80 s using RF reduced the number of viable bacteria by 4.87 logarithms. At the cellular level, there was a significant leakage of nucleic acids and proteins from the bacterial cells. Additionally, the integrity of the cell membrane was severely damaged, with a decrease in ATP concentration of 2.08 mM, Na, K-ATPase activity to 10.7 (U/109 cells), and Ca, Mg-ATPase activity to 11.6 (U/109 cells). At the molecular level, transcriptomics analysis showed that RF heating of B. cereus to 65 °C produced 650 more differentially expressed genes (DEGs) compared with RF heating to 45 °C. The GO annotation analysis indicated that the majority of differentially expressed genes (DEGs) were predominantly associated with cellular components. KEGG metabolic analysis showed enrichment in microbial metabolism in diverse environments, etc. This study investigated the potential bactericidal mechanism of B. cereus using RF, and provided some theoretical basis for the research of the sterilization of B. cereus.

Antibacterial effect of Cu2O/TiO2 visible-light photocatalytic composite on Xanthomonas campestris.

In this study, a Cu2O/TiO2 (CuTi) visible-light photocatalytic composite was employed for the treatment of Xanthomonas campestris and X. campestris-infected Brassica napus seedlings. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values against X. campestris were determined to be 8 and 32 μg ml-1, respectively. Transmission electron microscopy analysis demonstrated a direct correlation between the extent of bacterial cell damage and the concentration of CuTi. Noteworthily, a bactericidal rate of 100% was achieved at a concentration of 150 μg ml-1 over a treatment duration of 120 min. Moreover, alterations in active oxidants and antioxidants, including reactive oxygen species, glutathione reductase, superoxide dismutase, peroxidase, and catalase within the bacterial cells, were examined to elucidate the underlying mechanism of inhibition by the CuTi. The B. napus infected by X. campestris was treated with CuTi, and the efficacy was validated through determination of plant resistance indexes. The combined data confirmed that the CuTi is characterized by a low dose, fast onset, good effect, and higher safety for killing X. campestris, and it is expected to be developed as an antimicrobial agent for vegetables.

First report of Erwinia papayae associated with papaya mushy canker disease in Guam.

Carica papaya (papaya) in Guam, USA may experience soft rot symptoms, often referred to as mushy canker disease. Disease symptoms first appear as expanding water-soaked dark-green stem lesions or leaf spotting with chlorotic halos. Defoliation at petiole-stem junctions and crown necrosis leads to plant death. Papaya diseases caused by Erwinia spp. are documented in nearby tropic regions such as the Northern Mariana Islands (Trujillo and Schroth 1982), the Philippines (Dela Cueva et al. 2017), Japan (Hanagasaki et al. 2020), and Indonesia (Suharjo et al., 2021). The pathogen was isolated from symptomatic papaya stem sections (cv. Red Lady) from a nursery at the University of Guam Agriculture and Life Sciences building in April 2023. Approximately 20% of seedlings collapsed from stem soft rot, with nearly all plants showing varying degrees of water-soaked lesions on leaves or stems. Stem tissue from lesion margins was excised, surface sterilized with 70% EtOH, and macerated in sterile water. Macerate was plated onto nutrient agar (NA) and incubated at 28°C, yielding colonies that were clear to white in color, smooth, circular and mucoid on NA plates for five suspect isolates (JGD231-235). Strains produced blue diffusible pigment on King's B (KB) media, were Gram-negative rods, and exhibited swimming motility on semi-solid (0.5% agar) NA plates. Crown stab inoculation of ten papaya plants (cv. Red Lady) with isolates resulted in mushy canker symptoms within seven days, while negative control plants stabbed with a sterile probe remained asymptomatic. Koch's postulates were fulfilled by drench-inoculating spontaneous rifampicin-resistant (100µg/ml) mutants, JGD233r and JGD235r, onto ten papaya plants (cv. Solo Sunrise). Nine days post-inoculation, bacterial strains were recovered from symptomatic stem tissue macerate plated on rifampicin (100µg/ml) NA and incubated at 28°C. No symptoms or bacterial cells were recovered from the tissue of negative control plants. Cell morphology, culture phenotypes, and disease symptoms suggested the isolates were Erwinia spp., and blue pigment production on KB further suggested E. papayae (Gardan et al. 2004). Partial 16S rDNA sequences of Guam strains JGD231-235 (sequenced using PCR forward primer 5' - AGAGTTTGATCMTGGCTCAG - 3' and reverse primer 5' - GGTTACCTTGTTACGACTT - 3', GENEWIZ (South Plainfield, NJ)) were deposited into GenBank (OR577627- 631). Highest NCBI BLAST results for all strains showed a 16S rDNA sequence identity of 98.17-98.91% with those of Erwinia sp. I-leaf (LC590218) and E. mallotivora BT-MARDI (HQ456230). A maximum likelihood phylogenetic tree based on concatenated partial atpD, infB, and rpoB sequences of strains JGD232 (PP669340, PP669346, PP669343), JGD233 (PP669341, PP669347, PP669344), and JGD235 (PP669342, PP669348, PP669345) (Brady et al. 2008) constructed using MEGA11 (Tamura et al. 2021) showed all strains formed a monophyletic group with Erwinia sp. I-leaf (Hanagasaki et al. 2020) and E. papayae NCPPB 4294T (Gardan et al. 2004), supported with 98% bootstrap. This note documents the first occurrence of E. papayae as a papaya pathogen in Guam. Papaya cultivation supports sustainable food security for Guam (Bevacqua and Sayama 2023), and Erwinia spp. pathogens threaten papaya on other Pacific islands like Hawaii. These findings convey the need for effective quarantine practices, local disease management, and further research on this pathogen.

Regulation of extracellular electron transfer by sustained existence of Fe²⁺/Fe³⁺ redox couples on iron oxide-functionalized woody biochar anode surfaces in bioelectrochemical systems

Sluggish extracellular electron transfer between the exoelectrogens and anode interface limits the application of bioelectrochemical systems (BECs) for energy generation. In this study, an innovative anode coated with oxidized biochar and co-functionalized with iron nanoparticles (FBC/Fe2O3) was developed to enhance microbial reactions through tuned physicochemical and electrical properties. The designed anode features a highly porous, heterogeneous structure with a large accessible surface area of 10.141 m²/g, promoting better habitation and metabolism of exoelectrogens. The synergistic effect of iron nanoparticles and oxidized functional groups increased the hydrophilicity of the anode surface, augmenting its affinity for bacterial outer membrane c-cysts and facilitating microbial adhesion at a density of 3.106 × 10⁹ CFU/cm². The iron moieties on the FBC/Fe2O3 electrode surface act as electron mediators, utilizing Fe²⁺/Fe³⁺ redox couples, as evidenced by X-ray photoelectron spectroscopy (XPS) data. This enhancement improved extracellular electron transfer (EET) between bacterial cells and the anode surface, resulting in a faster and bifurcated EET process through both direct transfer via outer membrane c-cysts and mediated transfer via the redox couples of Fe moieties. The assembled double-chamber microbial fuel cell (DC-MFC) with the FBC/Fe2O3 anode achieved a maximum power density of 528.75 mW/m² and a chemical oxygen demand (COD) removal efficiency of 47.5 % within 24 h of operation.

Antibacterial and cytocompatible silver coating for titanium Boston Keratoprosthesis.

The Boston Keratoprosthesis (BKPro) serves as a medical solution for restoring vision in complex cases of corneal blindness. Comprising a front plate made of polymethylmethacrylate (PMMA) and a back plate of titanium (Ti), this device utilizes the beneficial biomaterial properties of Ti. While BKPro demonstrates promising retention rates, infection emerges as a significant concern that impacts its long-term efficacy. However, limited research exists on enhancement of BKPros through intrinsic infection-preventing mechanisms. In this regard, metal ions, especially the well-known Ag+ ions, are a promising alternative to obtain implants with innate antibacterial properties. However, little information is available about the effects of Ag in corneal tissue, especially within human corneal keratocytes (HCKs). In this work, an electrodeposition treatment using a constant pulse is proposed to attach Ag complexes onto rough Ti surfaces, thus providing antibacterial properties without inducing cytotoxicity. Complete physicochemical characterization and ion release studies were carried out with both control and Ag-treated samples. The possible cytotoxic effects in the short and long term were evaluated in vitro with HCKs. Moreover, the antibacterial properties of the silver-treated surfaces were tested against the gram-negative bacterial strain Pseudomonas aeruginosa and the gram-positive strain Staphylococcus epidermidis, that are common contributors to infections in BKPros. Physicochemical characterization confirmed the presence of silver, predominantly in oxide form, with low release of Ag+ ions. Ag-treated surfaces demonstrated no cytotoxicity and promoted long-term proliferation of HCKs. Furthermore, the silver-treated surfaces exhibited a potent antibacterial effect, causing a reduction in bacterial adhesion and evident damage to the bacterial cell walls of P. aeruginosa and S. epidermidis. The low release of Ag+ ions suggested reactive oxygen species (ROS)-mediated oxidative stress imbalance as the bactericidal mechanism of the silver deposits. In conclusion, the proposed electrodeposition technique confers antibacterial protection to the Ti backplate of BKPro, mitigating implant-threatening infections while ensuring non-cytotoxicity within the corneal tissue.

Determinants of maturation of the Staphylococcus aureus autoinducing peptide.

The accessory gene regulatory (Agr) system is required for virulence factor gene expression and pathogenesis of Staphylococcus aureus. The Agr system is activated in response to the accumulation of a cyclic autoinducing peptide (AIP), which is matured and secreted by the bacterium. The precursor of AIP, AgrD, consists of the AIP flanked by an N-terminal [Formula: see text]-helical Leader and a charged C-terminal tail. AgrD is matured to AIP by the action of two proteases, AgrB and MroQ. AgrB cleaves the C-terminal tail and promotes the formation of a thiolactone ring, whereas MroQ cleaves the N-terminal Leader in a manner that depends on the four-amino acid linker immediately following a conserved IG helix breaker motif. However, the attributes of AgrD that dictate the sequence of events in peptide maturation are not fully defined. Here, we used engineered AgrD peptide intermediates to ascertain the sufficiency of MroQ for N-terminal peptide cleavage, peptide export, and generation of mature AIP. We found that MroQ promotes the removal of the N-terminal Leader peptide from both linear and cyclic peptide intermediates, while peptide cyclization remained essential for signaling. The expression of the Leader peptide in isolation was sufficient for MroQ-dependent cleavage proximal to the four-amino-acid linker. In addition, active site mutations within AgrB destabilized full-length AgrD and thiolactone-containing intermediates and prevented the release of the Leader peptide. Altogether, our data support a tandem peptide maturation event involving both MroQ and AgrB that appears to couple protease activity and export of bioactive AIP.IMPORTANCEThe accessory gene regulatory (Agr) system is important for S. aureus pathogenesis. Activation of the Agr system requires recognition of a cyclic peptide pheromone, which must be fully matured to exert its biological activity. The complete events in cyclic peptide maturation and export from the bacterial cell remain to be fully defined. We and others recently discovered that the membrane peptidase MroQ is required for pheromone maturation. This study builds off the identification of MroQ and considers the attributes of the pheromone pro-peptide that are required for MroQ-mediated processing as well as uncovers features important for peptide stability and export. Overall, the findings in this study have implications for understanding bacterial pheromone maturation and virulence.

Antimicrobial Hydroxyethyl-Cellulose-Based Composite Films with Zinc Oxide and Mesoporous Silica Loaded with Cinnamon Essential Oil.

Background: Cellulose derivatives are gaining much attention in medical research due to their excellent properties such as biocompatibility, hydrophilicity, non-toxicity, sustainability, and low cost. Unfortunately, cellulose does not exhibit antimicrobial activity. However, derivatives like hydroxyethyl cellulose represent a proper matrix to incorporate antimicrobial agents with beneficial therapeutic effects. Methods: Combining more antimicrobial agents into a single composite material can induce stronger antibacterial activity by synergism. Results: Therefore, we have obtained a hydroxyethyl-cellulose-based material loaded with zinc oxide nanoparticles and cinnamon essential oil as the antimicrobial agents. The cinnamon essential oil was loaded in mesoporous silica particles to control its release. Conclusions: The composite films demonstrated high antibacterial activity against Staphylococcus aureus and Escherichia coli strains, impairing the bacterial cells' viability and biofilm development. Such antimicrobial films can be used in various biomedical applications such as topical dressings or as packaging for the food industry.

Biological activity and chemical characteristics studies of new oligomannose produced by Erwinia gerundensis

Natural polymers have attracted considerable attention in recent decades among scientists due to their potential therapeutic uses, particularly as antimicrobial and antitumor agents. In this research, novel EPSs were extracted from garlic rhizosphere bacteria. The antibacterial and antitumor activities of the polymer were evaluated through biological assays. The antibacterial activity was tested against gram-positive microorganisms (such as Listeria monocytogenes, Bacillus cereus, and Staphylococcus aureus) and gram-negative organisms (such as Shigella sonnei and Escherichia coli). The most significant inhibition zone was observed with Listeria monocytogenes and S. typhi, measuring 35 mm, while the most miniature antibacterial effect was seen with Staphylococcus aureus at 23.67 mm.Furthermore, the inhibitory effect of the crude polymer was assessed using a broth medium with two strains of E. coli and Bacillus cereus. Electron microscope images displayed varying degrees of damage to bacterial cells in the treated broth. The antitumor activity was determined using the MTT test on colon carcinoma cells (HCT-116), hepatocellular carcinoma cells (HepG-2), and CaCO2 (intestinal carcinoma cells), with IC50 values of 188.86±6.17 µg/mL, 221.66±8.02 µg/mL, and 203.65±7.43 µg/mL, respectively, after 48 h. The bacteria responsible for polymer production were isolated from garlic plant rhizospheres and identified as Erwinia gerundensis CCASU-2024–69 through 16S rRNA sequencing. FTIR and NMR techniques determined the crude EPS's main components and functional groups, including carbonyl, carboxylic, methylene, and silanol. GC–MS analysis revealed 34 bioactive compounds, while HPLC analysis indicated that the EPS was a hetero-monosaccharide consisting of d-xylose, d-glucose, l-arabinose, ribose, and d-mannose. This research study represents the initial exploration into the exopolysaccharide derived from Erwinia gerundensis. To assess the interaction between the exopolysaccharide and the active sites of Bacillus cereus and E. coli, molecular docking experiments were conducted using five monosaccharides: d-xylose, d-glucose, l-arabinose, ribose, and d-mannose. The data obtained from the molecular docking analysis strongly correlates with the findings from biological studies.Furthermore, these highly active compounds exhibit a favorable proposed ADMET profile. This particular exopolysaccharide shows potential as a natural antibiotic and holds promise in treating gastrointestinal cancer. A comprehensive assessment of laboratory animals is essential before its potential use as a prebiotic in nutrition.