Antimicrobial Compounds Research Articles

Atividade antimicrobiana dos extratos hidroalcoólicode Eugenia uniflora L. (Myrtaceae) e Schinus molle L.(Anacardiaceae)

The indiscriminate use of antimicrobials available in the market today has been contributing to the increase in the quantity of resistant pathogens. In recent years, significant attention has been given to the use of antimicrobial compounds of natural origin. This growing demand for new bioactive compounds stems from the knowledge that some medicinal plants often exhibit antimicrobial activity. Thus, the aim of this study was to evaluate the antimicrobial effect of hydroalcoholic extracts from the leaves of E. uniflora (Surinam cherry) and S. molle (Brazilian pepper tree) against clinically relevant microorganisms. The leaves were collected from adult plants, identified at the Herbarium of the University of Vale do Sapucaí, where a voucher specimen was deposited. The extract was prepared using the maceration technique in 70% ethanol. Antimicrobial activity was assessed using the disc diffusion method according to the Kirby-Bauer methodology. The microorganisms used were reference strains of: Escherichia coli ATCC8739, Staphylococcus aureus ATCC6538, Pseudomonas aeruginosa ATCC9027, Salmonella typhimurium ATCC14028, Candida albicans ATCC90028, Candida glabrata MYA2950, Candida Krusei ATCC6258, Candida parapsilosis ATCC22019, and Candida utilis ATCC9950. The extracts showed antifungal and antibacterial activity against the studied microorganisms. These findings contribute to the potential future use of these plants as antimicrobial agents.

Microbiota of the ocular surface in infectious/ inflammatory eye diseases

The review article presents current data on the microbiota (MBT) of the ocular surface in infectious and inflammatory eye diseases. Saprophytic MBT increases the resistance of the ocular surface to pathogenic bacteria. Commensal microorganisms regulate host metabolism, immune system development, and defense of the host against pathogen invasion. Meanwhile, ocular surfaces can change due to various environmental factors, processes in the human body, and in particular, due to ophthalmological diseases. Damaged epithelium of the cornea and conjunctiva (e. g. caused by dryness, the use of contact lenses, antibiotics, etc.) can lead to an increase in the number of bacteria on the ocular surface and disruption of the protective film containing antimicrobial compounds that lubricates the epithelium. In recent years, a connection has been shown between changes in the composition of the ocular MBT and a number of infectious and inflammatory ophthalmological diseases. In particular, it turned out that factors influencing the formation of tear fluid can change the MBT of the ocular surface, and when its composition deteriorates, ocular surface may become dry. An increase in the number of pathogenic microorganisms when wearing contact lenses, especially gram-negative ones, can lead to changes in the MBT and the development of keratitis. In inflammatory eye diseases, gram-positive microflora is most often isolated (in 94 % of cases), of which coagulaze negative staphylococci are most often recorded. In bacterial eye infections. conditionally pathogenic microflora often occurs (44.5 %). Apparently, intestinal MBT plays a very significant role in the development of some inflammatory eye diseases such as anterior and posterior uveitis.

Unveiling the Potency: Synthesis and Assessment of Antimicrobial Potential of Some Bis(indolyl)methane Derivatives

Background: The urgent need for new antimicrobial compounds arises from the growing threat of multidrug-resistant human pathogens responsible for infectious diseases. The indole moiety, a prevalent heterocyclic ring system found in nature, is a key structural element in many pharmaceutical agents due to its wide range of biological activities. Bis(in-dolyl)methanes, in particular, have emerged as promising candidates for antibacterial activ-ity. Aim: This study aimed to evaluate the antibacterial activity of nine bis(indolyl)methane derivatives against a range of pathogenic bacterial strains responsible for various human diseases. Methods: The compounds were synthesized using a solvent-free method, and their antibac-terial activity was evaluated using the disk diffusion assay. The minimum inhibitory con-centration (MIC) of the active compounds identified in the disk diffusion assay was deter-mined by the microtiter broth dilution method in 96-well microtiter plates. Bacterial strains in the mid-log phase of growth were utilized. Bacterial suspensions equivalent to 0.5 McFar-land standards were prepared by suspending the bacterial inoculum in sterile water. A work-ing concentration of 100 μg/mL was achieved by diluting the test compounds in 100% DMSO. Results: The antimicrobial activity of nine synthetic compounds was evaluated against nine medically significant pathogenic strains. These include Pseudomonas aeruginosa, Bacillus cereus, and Shigella flexneri, known for producing toxins that cause acute foodborne ill-nesses, as well as Escherichia coli K12 and Enterococcus faecalis, which can disrupt the intestinal barrier in immunocompromised individuals. The results suggest that these com-pounds have the potential to be effective antimicrobial agents. Conclusion: Our findings demonstrate the promising antimicrobial activity of the synthe-sized compounds, with 1-ethyl-3-((1-ethyl-1H-indol-3-yl)(phenyl)methyl)-1H-indole emerging as the most potent, significantly inhibiting most tested bacterial strains. These results highlight the potential for developing novel compounds for antibacterial treatment.

Complete Genome Sequence and In Vitro Probiotic Assessment of Bacillus subtilis DC-11 Isolated from Traditionally Fermented Idli Batter.

In this study, we reported in vitro probiotic assessment and complete genome sequence of Bacillus subtilis DC-11 isolated from traditionally fermented Idli Batter. The strain was evaluated for probiotic properties, biofilm formation, and antimicrobial compound production. The phenotypic safety was determined by accessing the strain's ability to produce enterotoxins, degrade mucin, and antibiotic sensitivity. Whole genome sequencing (WGS) was performed to identify the strain and determine genetic safety by analyzing the presence of plasmids, antibiotic resistance genes, and virulence factors. In the results, B. subtilis DC-11 showed 88.98% viability in gastric juice, and 98.60% viability in intestinal juice. It showed 18.33 ± 0.44% autoaggregation, 32.53 ± 3.11% adhesion to xylene, 0.98 ± 0.05 OD unit's adhesion to mucin (crystal violet equivalence at 550nm), 21.2 ± 2.3% adhesion to Caco-2 cells, and - 22.3 ± 0.65mV zeta potential. The highest co-aggregation was recorded with Escherichia coli (23.62 ± 0.70%). The strain was found negative for enterotoxin production, mucin degradation, and antibiotic resistance to the commonly used therapeutic antibiotics. It formed a good biofilm and capable of producing antimicrobial peptide subtilosin A with a molecular mass of 3400Da. The peptide has inhibited the growth of methicillin-resistant Staphylococcus aureus (18.6 ± 0.58mm). In genetic safety, no plasmids, antibiotic-resistant genes, and virulence factors were detected. Moreover, the strain showed close similarity with B. subtilis ATCC 6051 and proteins involved in probiotic attributes. In conclusion, B. subtilis DC-11 is safe potential probiotic candidate.

Antimicrobial Biphasic Polymer Coatings Enabled by Fast Diffusion of Active Compounds.

The recent COVID-19 pandemic and the prospect of future global pandemics highlight the long-standing need to passively eliminate viruses and bacteria on surfaces. Conventional antimicrobial surfaces and coatings are typically constrained by a trade-off between antimicrobial efficacy and physical durability. A biphasic polyurethane coating has been developed that breaks this trade-off by incorporating a durability-imparting polycarbonate (PC) discrete phase with a continuous poly(ethylene glycol) (PEG) transport phase that absorbs, stores, and releases antimicrobial active compounds for extended microbial inactivation. The biphasic polymer was shown to absorb carboxylic acid and quaternary ammonium antimicrobial active compounds, maintained their levels after five years of simulated cleaning, and inactivated up to 99.99% of Human Coronavirus 229E and Influenza A H1N1. Furthermore, the levels of antimicrobial active compounds on the biphasic coating could be augmented by cleaning the substrate with a disinfectant. The practicality of biphasic coatings for automotive and commercial aerospace environments was demonstrated by showing control of hardness and stain resistance through biphasic composition, showing environmental durability through heat, humidity, and light exposure, and passing flammability protocols.

Evaluation of Antimicrobial Activity of Aqueous and Acetone Root Extracts from Cordia dichotoma

The emergence of antibiotic resistance has renewed interest in exploring plant-based antimicrobial compounds. This study investigated the antimicrobial potential of root extracts from Cordia dichotoma, a traditional medicinal plant widely distributed across Asia. Root samples were collected and extracted using two solvents (acetone and distilled water) through both maceration and Soxhlet extraction methods. Preliminary phytochemical screening revealed the presence of alkaloids, phenolic compounds, glycosides, tannins, and flavonoids across different extracts. The antimicrobial activity was evaluated against both Gram-positive (Bacillus pumilus) and Gram-negative (Escherichia coli) bacteria using the well diffusion method. The acetone maceration extract demonstrated superior antimicrobial activity with 90% inhibition against both test organisms, showing zones of inhibition of 52.5 mm and 51 mm against B. pumilus and E. coli, respectively. The Soxhlet acetone extract showed moderate activity with 58% inhibition against B. pumilus and 52% against E. coli. Aqueous extracts exhibited comparatively lower antimicrobial activity, with the Soxhlet extract showing 44% inhibition against B. pumilus and 58% against E. coli, while the maceration extract showed 50% and 37% inhibition, respectively. These findings suggest that acetone is a more effective solvent for extracting antimicrobial compounds from C. dichotoma roots, with the maceration process yielding better results than Soxhlet extraction. This study provides scientific validation for the traditional use of C. dichotoma in treating infectious diseases and suggests its potential as a source of novel antimicrobial compounds.

Description of Wickerhamia europaea sp. nov. and revisitation of the ascospore number of W. fluorescens.

During the course of two independent studies, six conspecific yeast strains were recovered from flowers, soil, bird faeces and wood of different geographical origins. The six strains share identical DNA sequences in two barcoding regions, the D1/D2 domain of the LSU rRNA gene and the internal transcribed spacer (ITS) region (ITS1-5.8S rRNA gene-ITS2). According to sequence comparisons and phylogenetic analysis, they represent an undescribed Wickerhamia species. The novel species is not only genetically distinct from W. fluorescens, the single species of the genus but can also be distinguished from it by some phenotypic characters. We propose Wickerhamia europaea sp. nov. (holotype: NCAIM Y.01938; isotype: CBS 18675; MycoBank no.: 856571) to accommodate the above noted strains. Under certain fermentation conditions, we detected the production of phenyllactic acid, a potential broad-spectrum antimicrobial compound against food-borne pathogens, by the type strain of the novel species, although in smaller concentrations than in the case of W. fluorescens. Comparing our observations on the formation and properties of the ascospores of Wickerhamia europaea sp. nov. and the ambiguous data on the number of ascospores per ascus of W. fluorescens, we suggest a possible explanation to reconcile the different data regarding the number of ascospores per ascus formed by W. fluorescens.

Investigation of antibacterial mode of action of ω-aminoalkoxylxanthones by NMR-based metabolomics and molecular docking.

The knowledge of the mode of action of an antimicrobial is essential for drug development and helps to fight against bacterial resistance. Thus, it is crucial to use analytical techniques to study the mechanism of action of substances that have potential to act as antibacterial agents OBJECTIVE: To use NMR-based metabolomics combined with chemometrics and molecular docking to identify the metabolic responses of Staphylococcus aureus following exposure to commercial antibiotics and some synthesized ω-aminoalkoxylxanthones. Intracellular metabolites of S. aureus were extracted after treatment with four commercial antibiotics and three synthesized ω-aminoalkoxylxanthones. NMR spectra were obtained and 1HNMR data was analyzed using both unsupervised and supervised algorithms (PCA and PLS-DA, respectively). Docking simulations on DNA topoisomerase IV protein were also performed for the ω-aminoalkoxylxanthones. Through chemometric analysis, we distinguished between the control group and antibiotics with extracellular (ampicillin) and intracellular targets (kanamycin, tetracycline, and ciprofloxacin). We identified 21 metabolites, including important metabolites that differentiate the groups, such as betaine, acetamide, glutamate, lysine, alanine, isoleucine/leucine, acetate, threonine, proline, and ethanol. Regarding the xanthone-type derivatives (S6, S7 and S8), we observed a greater similarity between S7 and ciprofloxacin, which targets bacterial DNA replication. The molecular docking analysis showed high affinity of the ω-aminoalkoxylxanthones with the topoisomerase IV enzyme, as well as ciprofloxacin. NMR-based metabolomics has shown to be an effective technique to assess the metabolic profile of S. aureus after treatment with certain antimicrobial compounds, helping the investigation of their mechanism of action.

Lapachol, a natural food component, interacts with human serum albumin: Insights of its impact on the pharmacokinetics of clinically used drugs

Lapachol (LAP), a natural 1,4-naphthoquinone used in popular medicine of South American, is an antioxidant and antimicrobial compound used as a food additive; however, its interactive profile with the main protein carrier of compounds in the human bloodstream (human serum albumin, HSA) was not still characterized. Additionally, the impact of LAP in binding clinically drugs to albumin is still unknown. Thus, the present work describes the interaction HSA:LAP using different biophysical techniques, i.e., 1H saturation-transfer difference nuclear magnetic resonance (1H STD-NMR), isothermal titration calorimetry (ITC), steady-state and time-resolved fluorescence measurements combined with molecular docking calculations. LAP interacts with subdomain region IIA (site I), mainly driven by enthalpy effects, while subdomain region IB (site III) was identified as the second binding site, mainly driven by entropy effects. The binding is spontaneous, strong (binding constant average, Kaverage ≈ 4.45 × 105 M−1), and there is a positive cooperativity in the presence of ibuprofen, with the LAP structure fully buried into the protein cavities. Overall, LAP might impact the residence time (pharmacokinetic profile) of drugs that bind to subdomains regions IIA and IB of albumin, e.g., warfarin, phenylbutazone, diflunisal, naproxen, camptothecin, doxorubicin, daunorubicin, suramin, and tyrosine kinase inhibitors.

Sennosides A and B could contribute to the antimicrobial efficiency of Senna alexandrina Mill. against pathogenic bacteria in vitro and in vivo models

The search of new antimicrobial compounds is increasing in due with increasing bacterial infections. Discovering effective antibacterial medications is crucial for improving healthcare and combating bacterial infections. Senna alexandrina Mill. known as Tinnevelly senna, used as herbal extract in traditional medicine and found be rich in anthraquinone glycosides like sennoside A (SA) and sennoside B (SB), shows significant biological activity as a potential therapeutic agent. This study assessed the antibacterial effects of senna extracts on Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus bacteria, both in vitro and in vivo. HPLC analysis identified sennosides as the major compounds in senna extracts, with the highest concentration found in the leaves, followed by the pods, flowers, stems, and roots. The leaf extract showed the highest sennoside content (SA 27.21 mg/g and SB 29.1 mg/g) compared to other plant parts. FT-IR analysis confirmed the presence of sennosides through the detection of carboxylic acids and OH functional groups in S. alexandrina extracts. Extracts rich in sennosides displayed potent in vitro antibacterial activity (1000 µg/mL) by generating ROS, penetrating and becoming disruptive to bacterial functions. Similarly, in Caenorhabditis elegans model, they inhibited bacterial growth and colonization and enhanced physiological functions in the worms. Senna extract (1000 µg/mL) improved intestinal barrier's structural stability in C. elegans by outcompeting pathogenic bacteria and prolonged survival rates of those infected with P. aeruginosa and S. aureus to 56.6 % and 62.4 %, respectively, confirming the potent antibacterial efficacy of senna leaf methanolic extracts due to their high sennoside content in both in vitro and in vivo models.

Evaluation of antioxidant, antimicrobial, antidiabetic, anti-tyrosinase, and neuroprotective effects of β-ionone: In vitro and in silico analysis

β-Ionone is a bioactive phytochemical that has been extracted from many flowers, vegetables, and fruits. β-Ionone is an intriguing lead molecule from which several derivatives have been generated and exhibiting a variety of biological effects. Here, we investigated the β-Ionones’ antioxidant, anti-cholinesterases (AChE and BChE), anti-α-amylase, anti-α-glucosidase, and anti-tyrosinase activities. The antibacterial and antifungal effects were also studied. Moreover, in silico studies using molecular docking were carried out to understand the obtained results. The antioxidant activity performed by six different assays including phosphomolybdenum, CUPRAC, FRAP, DPPH, ABTS and metal chelating assay showed that β-Ionone exhibits a promising antioxidant activity. Besides, a good inhibition of AChE and BChE, as well as α-glucosidase, α-amylase, and tyrosinase was obtained. Molecular docking evidenced that β-Ionone correctly occupied the active site of the five studied enzymes through various kind of interactions which corroborate the in vitro outcomes. Moreover, in silico ADMET assessment showed that β-Ionone presented a good ADMET profile. Gram positive bacteria, specifically S. aureus (DIZ = 25 ± 1.5 mm; MIC = 6.25 mg/mL; CMB = 6.25 mg/mL) and B. cereus (DIZ = 21.5 ± 1 mm; MIC = 0.78 mg/mL; CMB = 0.78 mg/mL), showed greater susceptibility. Regarding Gram negative ones, P. aeruginosa exhibited also marked sensitivity (DIZ = 20.33 ± 1.5 mm; MIC = 12.5 mg/mL; CMB = 12.5 mg/mL). Additionally, β-Ionone can limit the growth of C. albicans (DIZ = 23 ± 1 mm; MIC = 1.56 mg/mL; CMB = 1.56 mg/mL). A bactericidal and fungicidal efficacy could be suggested as the MBC/MIC towards all the four inhibited pathogens was equal to 1. To sum up, data suggested that β-Ionone could have potential applications as an antioxidant, antimicrobial, and antifungal compound, as well as a potential inhibitor of tyrosinase, α-amylase, α-glucosidase, and cholinesterases. Furthermore, it can serve as a lead chemical in the creation of a new semisynthetic drug intended in order to treat numerous illnesses, including diabetes, Alzheimer’s disease, and pigmentation disorders

Tissue nano-transfection of antimicrobial genes drives bacterial biofilm killing in wounds and is potentially mediated by extracellular vesicles

The emergence of bacteria that are resistant to antibiotics is on track to become a major global health crisis. Therefore, there is an urgent need for new treatment options. Here, we studied the implementation of tissue-nanotransfection (TNT) to treat Staphylococcus aureus-infected wounds by delivering gene cargos that boost the levels of naturally produced antimicrobial peptides. The Cathelicidin Antimicrobial Peptide gene (CAMP), which produces the antimicrobial peptide LL-37, was used as model gene cargo. In vitro evaluation showed successful transfection and an increase in the transcription and translation of CAMP-coding plasmid in mouse primary epithelial cells. Moreover, we found that the extracellular vesicles (EVs) derived from the transfected cells (in vitro and in vivo) carried significantly higher concentrations of CAMP transcripts and LL-37 peptide compared to control EVs, possibly mediating the trafficking of the antimicrobial contents to other neighboring cells. The TNT platform was then used in vivo on an excisional wound model in mice to nanotransfect the CAMP-coding plasmid on the edge of infected wounds. After 4 days of daily treatment, we observed a significant decrease in the bacterial load in the CAMP-treated group compared to the sham group. Moreover, histological analysis and bacterial load quantification also revealed that TNT of CAMP on S. aureus-infected wounds was effective in treating biofilm progression by reducing the bacterial load. Lastly, we observed a significant increase in macrophage recruitment to the infected tissue, a robust increase in vascularization, as well as and an increased expression of IL10 and Fli1. Our results demonstrate that TNT-based delivery of gene cargos coding for antimicrobial compounds to the wound is a promising approach for combating biofilm infections in wounds.

Phenotypic and Genomic Insights Into Bacillus spp. and Peribacillus spp. of Spanish Olive Groves With Biotechnological Potential.

Spore-forming organisms are an integral component of the rhizosphere, providing plants with significant advantages. Previous studies determined the antimicrobial activity of the olive sporobiota, identifying five candidates of particular relevance, belonging to the Bacillus subtilis, Peribacillus simplex and Bacillus cereus clade. This study aimed to determine their biotechnological properties, safety aspects, spore structure and resistance, and interaction with the environment through a combined microbiological and genomic approach. We report on the ability of these strains to produce hydrolytic and surface-active enzymes and provide evidence for differences in population behaviour through the formation of strong sessile or floating biofilms. Electron microscopic analysis revealed for the first time the presence of an exosporium layer in olive sporobiota isolates belonging to the P. simplex and B. cereus clade, including numerous pili-like structures on the latter. Spores showed significant differences in their resistance to wet heat, oxidising agents, and UV exposure. Whole genome sequencing of isolate Peribacillus frigoritolerans yielded information on its antimicrobial compound biosynthesis and environmental safety. Overall, our findings provide insights into the phenotypic, morphological and genetic variations of spore-formers from Spanish olive groves, which can be useful for the development of bioactive compounds in sustainable agriculture.

Design, Synthesis and Fungicidal Activity of N-(5-Phenyl-1,3,4-Thiadiazol-2-yl)-N-((1-Phenyl-1H-1,2,3-Triazol-4-yl) Methyl) Benzamide Derivatives

Objective: Plant pathogens are serious hazards to agricultural production, but existing drugs have problems such as increased resistance of pathogenic bacteria and environmental pollution, and there is a need to find high-efficiency, low-toxicity fungicides with novel chemical structures. Methods: 5-phenyl-1,3,4-thiadiazol-2-amine was used as the starting material, and 20 new thiadiazole-linked compounds were designed and synthesized. Their in vitro inhibitory activities against plant pathogenic fungi were tested using a mycelium growth inhibition assay, and the relationship between the antifungal activity of the target compounds and their molecular structures was preliminarily discussed. Results: Bioassay results revealed that most of the title compounds exhibited excellent in vitro fungicidal activity, in which compound D16 showed the highest activity against Rhizoctonia solani (EC50 = 0.0028 μmol·L−1), D12 against Botrytis cinerea (EC50 = 0.0024 μmol·L−1), and D5 against Stemphylium lycopersici and Curvularia lunata (EC50 = 0.0105 μmol·L−1, 0.005 μmol·L−1). The structure activity relationship (SAR) was also discussed and the results are of great significance for the structural optimization and development of more effective thiadiazole antibacterial compounds. Conclusion: The results of this study are important for structural optimization and development of more potent thiadiazole antimicrobial compounds.

Bacillus velezensis SS-20 as a potential and efficient multifunctional agent in biocontrol, saline-alkaline tolerance, and plant-growth promotion

The versatile strain Bacillus velezensis SS-20 was studied to determine its agricultural benefits, including its ability to antagonize fungi, promote plant growth, and tolerate saline-alkaline conditions. Firstly, strain SS-20 was found to be an antagonist of plant pathogenic fungi such as Magnaporthe oryzae, Rhizoctonia solani, and Fusarium oxysporum, with control effects up to 82.07 %, 46.57 %, and 23.09 %, respectively. The hyphae of pathogenic fungi treated with SS-20 and its fermentation product were abnormal, swollen, deformed, and distorted. Meanwhile, strain SS-20 dissolved inorganic phosphorus (phosphate solubilization efficiency, 45.95 %), and produced siderophore (siderophore units, 54.18 ± 4.19 %), and poly-γ-glutamic acid (γ-PGA) (13.35 ± 2.61 g/L). Strain SS-20 significantly increased plant height, aboveground fresh weight, and root dehydrogenase activity compared to the control treatment under non-saline conditions (p < 0.05). In addition, strain SS-20 showed significant saline-alkaline tolerance, surviving in 10 % NaCl and pH 9.5, and enhanced plant growth under simulated saline-alkali conditions. Whole-genome sequencing analysis revealed that the chromosome of B. velezensis SS-20 consists of 3,929,792-bp with 46.5 % guanine-cytosine content and 4015 coding sequences. The antiSMASH analysis identified 12 gene clusters within strain SS-20 that encode antimicrobial compounds such as surfactin, fengycin, butirosin A/butirosin B, macrolactin H, bacillibactin, difficidin, and bacilysin, thereby corroborating the strain's biocontrol capabilities. Genes related to plant growth promotion, including siderophores, γ-PGA, indole acetic acid production, phosphate solubilization, glycine-betaine production, and Na+/H+ antiporters, were also annotated. In conclusion, B. velezensis SS-20 represents a promising biotic resource for enhancing plant growth and protecting against environmental stresses.

O-Acetylhomoserine Sulfhydrylase as a Key Enzyme of Direct Sulfhydrylation in Microbial Methionine Biosynthesis

Methionine biosynthesis in most microorganisms proceeds in two alternative ways. Each pathway is catalyzed by independent enzymes and is tightly regulated by methionine. The transulfurylation pathway involves the formation of a cystathionine, and cysteine acts as a source of sulfur. The enzymes of this metabolic pathway are characterized in detail. The direct sulfhydrylation pathway involves the synthesis of homocysteine with the participation of an inorganic sulfur source directly from O-acetylhomoserine and is predominant in most classes of bacteria. The subject of this review is the properties and functioning of one of the least studied enzymes of the direct sulfhydrylation pathway – O-acetylhomoserine sulfhydrylase. A deep understanding of the mechanisms controlling the substrate and reaction specificity of O-acetylhomoserine sulfhydrylase is a necessary step in the rational redesign of the enzyme in order to create a promising catalyst for the synthesis s of methionine and its derivatives, as well as, in combination with crystallographic data, for the development of new antimicrobial compounds based on effective enzyme inhibitors.

Testing low-risk bioactive compounds on Halyomorpha halys: an improved pipeline of analyses to investigate their effects on the bacterial endosymbiont Candidatus Pantoea carbekii.

The brown marmorated stink bug Halyomorpha halys has become an invasive insect pest of many crops. A promising control strategy to manage the proliferation of H. halys is based on the suppression of its obligate and vertically transmitted uncultivated symbiotic bacterium Candidatus Pantoea carbekii through surface-sterilization of H. halys eggs. Indeed, the application of antimicrobial formulations on the eggs of H. halys could cause mortality of endosymbiont and consequently of newly emerged nymphs. In this study, a microbial live/dead assay was applied directly on H. halys eggs to evaluate Ca. P. carbekii loss of viability after treatments with seven commercial formulations including fungicides (copper hydroxide, sulphur, sweet orange essential oil) and plant biostimulants (flavonoids and chestnut tannin extract) compared with two disinfectants for civil and industrial use (sodium hypochlorite/hydrated sodium/tetraborate decahydrate and peracetic acid/hydrogen peroxide). Impact of mode of application was also evaluated, as surface treatment of egg masses was performed through spraying and dipping in laboratory conditions. Antimicrobial activity data were finally complemented with observations of egg hatching and vitality of the nymphs. The optimization of live/dead staining is useful for evaluating Ca. P. carbekii mortality directly on eggs, providing a rapid and reliable culture-independent approach. Sodium hypochlorite, copper, sulphur, tannins and sweet orange essential oil showed an antimicrobial effect against Ca. P. carbekii and a H. halys egg hatching reduction and nymph's vitality. The antimicrobial and insecticidal effects of these commercial products should be further studied to assess their in-field efficiency as well as the impact of these substances on non-target organisms. The approach followed in this study could be considered a robust pipeline of analyses to evaluate the effectiveness of antimicrobial eco-friendly compounds in symbiotic control of H. halys. © 2024 Society of Chemical Industry.

Design, Synthesis, and Activity Evaluation of C-23-Modified 5-O-Mycaminosyltylonolide Derivatives.

The widespread use of tylosin family drugs in clinical practice has led to bacterial resistance and reduced therapeutic efficacy. We designed and synthesized a series of new semisynthetic derivatives of tylosin with 5-O-mycaminosyltylonolide as the mother nucleus, mainly by introducing a variety of amino groups at its C-23 position. Some of the compounds showed high antibacterial activity against Gram-negative and Gram-positive bacteria. These findings indicate that the best compound, c9, possessed significant antibacterial activity (MIC = 0.5 ug/mL), excellent bactericidal efficacy, and a low induction rate of drug resistance against Staphylococcus aureus and Escherichia coli; it also showed good antibacterial activity against drug-resistant bacteria. In addition, compound c9 has a low toxicity in vitro and in vivo. In conclusion, compound c9 could be a potential antimicrobial lead compound that could also contribute to the development of macrolide antibiotics.

Endophytic Fungi Co-Culture: An Alternative Source of Antimicrobial Substances

Antimicrobial resistance is becoming a critical issue due to the widespread and indiscriminate use of antibiotics and antifungals to treat common infections, leading to a growing shortage of effective drugs. Moreover, the increase in antimicrobial resistance is enhancing the pathogenicity and virulence of various pathogens. Microorganisms are key sources of chemically diverse specialized metabolites, which are produced in the final stages of their growth cycle. These metabolites hold significant value in chemical, pharmaceutical, and agrochemical industries. One of the major challenges researchers face in this field is the frequent isolation of already-known substances when classical protocols are used. To address this, several innovative strategies have been developed. The co-culture approach is a powerful tool for activating silent biosynthetic gene clusters, as it simulates natural microbial environments by creating artificial microbial communities. This method has shown promising results, with new compounds being isolated and the yields of target substances being improved. In this context, this review provides examples of antimicrobial compounds obtained from co-cultures of endophytic fungi, conducted in both liquid and solid media. Additionally, the review discusses the advantages and challenges of the co-culture technique. Significance and Impact of the Study: Microbial co-culture is a valuable strategy for discovering new natural products with antimicrobial activity, as well as for scaling up the production of target substances. This review aims to summarize important examples of endophyte co-cultures and highlights the potential of endophytic fungi co-culture for pharmacological applications.

Antibiotic-Producing Bacteria Collected from Seawater

Background: Microorganisms are a known source of antibiotics. The study aimed to identify and screen antibiotic-producing microbes isolated from seawater. Method: Three of the fifty (50) bacteria isolated from seawater showed positive for antibiotic activity. The antimicrobial activity of Pseudomonas guguanensis (KD1) was screened against the ESKAPE pathogens using agar-well diffusion assays. P. guguanensis (KD1) was selected for the fermentation and extraction of antimicrobial compounds using solvent extraction assays. Results: P. guguanensis (KD1) produced the highest antibacterial activity after 36 h of cultivation, inhibiting S. aureus, E. faecium, A. baumannii and E. cloacae. According to sensitization assay, K. pneumoniae was impermeable to all the cell-free supernatants of P. guguanensis (KD1). Using agar-well diffusion assays, ethyl acetate extracts from the supernatant recorded zones of inhibition against S. aureus, E. faecium, and E. cloacae, producing zones of 20.1 ± 0.432, 17.8 ± 0.121 and 16 ± 0.162 mm, respectively. Acetonitrile extract from the supernatant inhibited A. baumannii and S. aureus, forming zones of inhibition 18.2 ± 0.323 mm and 18 ± 0.234. The minimum inhibitory concentration and minimum bactericidal concentration recorded for the ethyl acetate extract and acetonitrile extract ranged from 1.56 to 6.25 mg/mL and 12.5–25 mg/mL, respectively. Conclusions: P. guguanensis (KD1) offers a potential source of antibiotics for infections caused by multidrug-resistant bacteria.