Antimicrobial Compounds Research Articles

An In-Vitro Study of the Cytotoxicity of Chitosan Nanoparticles-Containing Orthodontic Primer

Background: Demineralization is an anticipated side effect of fixed orthodontic treatment. Incorporating antimicrobial compounds into orthodontic adhesive material may be an effective method for averting white spots. The objective of this study was to evaluate the cytotoxicity of an orthodontic primer modified with varying quantities of chitosan nanoparticles. Materials and methods: 0%, 1%, 5%, and 10% concentrations of Chitosan nanoparticles have been combined with Transbond TM XT primer. Three discs of eight millimeters in diameter and two millimeters in thickness were constructed for each group, for a total of twelve discs. Results: included the application of scanning electron microscopy (SEM) and X-ray diffraction (XRD) to confirm the Nano powder's properties. The data was statistically examined using one-way analysis of variance (ANOVA), and the results indicated statistically non-significant differences between groups (p˃0.05). In conclusion, the addition of chitosan nanoparticles to the orthodontic adhesive system's primer exhibited an acceptable level of cytotoxicity and was within the appropriate ISO limits (70% cell viability).

Isolation and Screening of Potent Antibiotic-Producing Actinomycete

This study delves into the realm of actinomycetes, with a specific focus on their ability to produce antibiotics. Actinomycetes, a subset of gram-positive bacteria, are well-known for generating various secondary metabolites, including antibiotics. Indeed, a majority of today's antibiotics trace their origins back to actinomycetes, notably the Streptomyces genus. The research aims to isolate actinomycetes from soil samples and assess their effectiveness against different pathogenic bacteria and fungi, with the goal of extracting natural compounds with potential medical uses. 23 actinomycete morphotypes were isolated from diverse soil sources such as agricultural fields, garbage dumps, and gardens. These isolates were then screened for their antimicrobial activity against various test microorganisms, including Escherichia coli (MTCC 2939), Bacillus subtilis (MTCC 1305), Candida albicans (MTCC 183), and Aspergillus flavus (MTCC 873). Notably, isolate BT 22 demonstrated superior antibacterial and antifungal properties compared to other isolates. Further analysis confirmed the isolate's identity as belonging to the Streptomyces genus, known for its prolific production of bioactive compounds. These findings highlight the potential of actinomycetes, particularly Streptomyces, as a valuable source of natural products with a wide range of applications in medicine and industry. The discovery of novel antimicrobial compounds from these organisms offers promise in combating antibiotic resistance and advancing therapeutic strategies.

Rationally Designed Pooled CRISPRi-Seq Uncovers an Inhibitor of Bacterial Peptidyl-tRNA Hydrolase.

Bacterial mutant libraries in which antibiotic targets are downregulated are useful tools to functionally characterize novel antimicrobials. These libraries are used for chemical-genetic profiling as target-compound interactions can be inferred by differential fitness of mutants during pooled growth. Mutants that are functionally related to the antimicrobial mode of action are usually depleted from the pool upon exposure to the drug. Although powerful, this method can fail when the unequal proliferation of mutant strains before exposure causes mutants to fall below the detection level in the library pool. To address this issue, we constructed an arrayed essential gene mutant library (EGML) in the antibiotic-resistant bacterium Burkholderia cenocepacia using CRISPR interference (CRISPRi) and analyzed the growth parameters of individual mutant strains. We then modelled depletion levels during pooled growth and used the model to rationally design an optimized CRISPR interference-mediated pooled library of essential genes (CIMPLE). By adjusting the initial inoculum of the knockdown mutants, we achieved coverage of the bacterial essential genome with mutant sensitization. We exposed CIMPLE to a recently discovered antimicrobial of a novel class and discovered it inhibits the peptidyl-tRNA hydrolase, an essential bacterial enzyme. In summary, we demonstrate the utility of CIMPLE and CRISPRi-Seq to uncover the mechanism of action of novel antimicrobial compounds.

A New Guanidine-Core Small-Molecule Compound as a Potential Antimicrobial Agent against Resistant Bacterial Strains.

The guanidine core has been one of the most studied functional groups in medicinal chemistry, and guanylation reactions are powerful tools for synthesizing this kind of compound. In this study, a series of five guanidine-core small molecules were obtained through guanylation reactions. These compounds were then evaluated against three different strains of Escherichia coli, one collection strain from the American Type Culture Collection (ATCC) of E. coli ATCC 35218, and two clinical extended-spectrum beta-lactamase (ESBL)-producing E. coli isolates (ESBL1 and ESBL2). Moreover, three different strains of Pseudomonas aeruginosa were studied, one collection strain of P. aeruginosa ATCC 27853, and two clinical multidrug-resistant isolates (PA24 and PA35). Among Gram-positive strains, three different strains of Staphylococcus aureus, one collection strain of S. aureus ATCC 29213, and two clinical methicillin-resistant S. aureus (MRSA1 and MRSA2) were evaluated. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) experiments were reported, and the drop plate (DP) method was used to determine the number of viable suspended bacteria in a known beaker volume. The results from this assessment suggest that guanidine-core small molecules hold promise as therapeutic alternatives for treating infections caused by clinical Gram-negative and Gram-positive bacteria, highlighting the need for further studies to explore their potential. The results from this assessment suggest that the chemical structure of CAPP4 might serve as the basis for designing more active guanidine-based antimicrobial compounds, highlighting the need for further studies to explore their potential.

Advancements in Aerogel Technology for Antimicrobial Therapy: A Review.

This paper explores the latest advancements in aerogel technology for antimicrobial therapy, revealing their interesting capacity that could improve the current medical approaches for antimicrobial treatments. Aerogels are attractive matrices because they can have an antimicrobial effect on their own, but they can also provide efficient delivery of antimicrobial compounds. Their interesting properties, such as high porosity, ultra-lightweight, and large surface area, make them suitable for such applications. The fundamentals of aerogels and mechanisms of action are discussed. The paper also highlights aerogels' importance in addressing current pressing challenges related to infection management, like the limited drug delivery alternatives and growing resistance to antimicrobial agents. It also covers the potential applications of aerogels in antimicrobial therapy and their possible limitations.

Growth fitness, virulence, and heat tolerance of Salmonella Typhimurium variants resistant to food preservation methods

To study potential ramifications of antimicrobial resistance, we carried out adaptive laboratory evolution assays (ALE) to isolate three resistant variants (RVs) of Salmonella enterica Typhimurium, employing three different types of food preservation methods: 1) an emergent technology, plasma-activated water (PAW), leading to variant RV-PAW; a traditional method, heat, leading to variant RV-HT, and a natural antimicrobial compound, carvacrol, leading to variant RV-CAR. The variant resistant to plasma-activated water, RV-PAW, had mutations in rpoA and rpoD; it showed increased tolerance to heat in orange juice but ultimately did not pose a significant threat, as it exhibited a fitness cost at refrigeration temperature (8 °C), whereas its virulence against Caenorhabditis elegans decreased. The variant resistant to heat, RV-HT, had mutations in flhC, dnaJ: it exhibited a fitness cost at high growth temperatures (43 °C) and induced morphofunctional alterations in C. elegans. The variant resistant to carvacrol, RV-CAR, had mutations in sseG, flhA, wbaV, lon; this variant not only exhibited significantly higher thermotolerance in both laboratory media and food models but also effectively increased its growth fitness at refrigeration temperatures while retaining its virulence, evidenced by the highest percentage of Smurf phenotype in C. elegans.To address these challenges, we applied a process combining thermal treatment with citral, with the aim of leveraging the sublethal damage caused in RVs by heat treatments in orange juice. This approach achieves enhanced microbial inactivation without having to escalate the intensity of the thermal treatment. The result was particularly encouraging in the case of RV-CAR, the most challenging strain, for which we improved lethality by up to 3 log10 inactivation cycles.

Inhibitory activity of Alpinia galanga (Kulanjan) against pathogenic bacteria

Infectious disease are the world’s leading cause of premature deaths, killing almost 50 000 people every day. With the continuous use of antibiotics microbes have become resistant. This has created immense clinical problems in the treatment of infectious diseases. Therefore, there is a need to develop alternative antimicrobial drugs for the treatment of infectious diseases. Plant materials remain an important recourse to combat serious diseases in the world. They are used directly as therapeutic agents, as well as starting materials for the synthesis of drugs or as models for pharmacologically active compounds.The search for potent antibacterial agents has now been shifted to plants. One approach is to screen local medicinal plants for possible antimicrobial properties. According to WHO (1993), 80% of the world’s population is dependent on the traditional medicine and a major part of the traditional therapies involves the use of plant extracts or their active constituents. Yet a scientific study of plants to determine their antimicrobial active compounds is a comparatively new field. There are many published reports on the effectiveness of traditional herbs against pathogenic bacteria, viruses and fungi and as a result plants are still recognized as the bedrock for modern medicine to treat infectious diseases. Keeping in view of the importance of herbs traditionally used for the treatment of infectious diseases, this study is designed to evaluate the antimicrobial activity of Alpinia galanga used in the Indian system of medicine for the treatment various diseases. Results showed broad spectrum antimicrobial activity of Methanolic extract of Alpinia galanga roots.

Effectiveness of Garcinia mangostana Mangosteen Peel Extract in Inhibiting Gram-Negative Bacteria in Lobster (Panulirus homarus) Aquaculture Waters

This study aims to examine the effectiveness of mangosteen peel extract (Garcinia mangostana) in inhibiting the growth of Gram-negative bacteria in lobster (Panulirus homarus) aquaculture waters. The main problem in lobster farming is bacterial infections that can cause disease and mass mortality. Mangosteen peel extract is known to contain potent antimicrobial compounds. This research employs an experimental method with various concentrations of mangosteen peel extract to test its effect on the growth of Gram-negative bacteria. Based on result, the mangosteen peel inhibition zone against Gram-negative bacteria from lobster aquaculture waters measures 0.25±0.05 cm (25 mm), indicating weak inhibition activity. This suggests that mangosteen peel could be used as an immunostimulant alternative to antibiotics in combating diseases in lobsters. Further research is needed to determine the optimal dosage of mangosteen peel extract to achieve strong inhibition activity against bacteria.

Isolation and identification of Xanthomonas citri subsp. malvacearum, cotton bacterial blight disease agent and determination of the antibacterial activity of various plant essential oils

Cotton is one of the most important industrial crops produced in large areas in Turkey. Cotton bacterial blight disease agent Xanthomonas citri subsp. malvacearum (Syn. Xanthomonas axonopodis pv. malvacearum) is a seed-borne pathogen. Plant essential oils are natural antimicrobial compounds that have the potential to be used as an alternative to chemical control of seed-borne phytopathogens. In this study, the bacterial pathogen X. citri subsp. malvacearum was isolated from cotton plants showing typical disease symptoms during the 2023 growing season in Diyarbakır provinces and the antibacterial effect of essential oils obtained from 11 different medicinal plants (Thymus serpyllum, Origanum syriacum, Thymus syriacus, Origanum onites, Cistus laden, Salvia aramiensis, Laurus nobilis, Hypericum perforatum, Rosmarinus officinalis, Origanum majorana and Thymbra spicata) were determined by disk diffusion method. Bacterial isolates, obtained from cotton plants showing typical disease symptoms, were identified as X. citri subsp. malvacearum by biochemical and pathogenicity tests and also MALDI-TOF analysis. The essential oils used in the study showed antibacterial activity against the bacterial agent by forming an inhibition zone with a diameter of 6.33-46.33 mm in the nutrient media. T. serpyllum and T. spicata (43.33 mm), O. syriacum (43.00 mm), T. syriacus (38.33 mm) and O. onites (37.3 mm), were identified as the most effective essential oils respectively. The essential oils of H. perforatum (9.67 mm), L. nobilis (9.0 mm) and S. aramiensis (6.33 mm) showed relatively lower antibacterial activity against the disease agent. The results showed that essential oils of Thymus spp., Thymbra spp. and Origanum spp. have the potential to be used as an alternative to chemical control against seed-borne bacterial plant pathogens.

Inhibitory activity of natural antimicrobial compounds against histamine-forming bacterial isolates from cheese

This study was conducted to investigate the presence of histamine-forming bacteria in cheeses, and to assess the impact of naturally-occurring antimicrobials on isolates' viability and histamine-forming potential. Cheese isolates' ability to produce histamine was evaluated by incubation in the presence of the histamine precursor; qualitative detection with a pH indicator and a quantitative analysis by high-performance liquid chromatography. Eight of the 114 isolates were able to produce histamine, but only one was capable of generating histamine at high concentrations. Histamine-producing isolates were identified by matrix-assisted laser desorption ionisation-time of flight mass spectrometry. Isolated strain C_MRSV_25A_4 was the microorganism with the highest capacity to produce histamine, and was identified as Lacticaseibacillus rhamnosus. The antimicrobial potential of natural antimicrobials was tested against this isolate. The results showed that carvacrol, cinnamaldehyde, eugenol, thymol and nisin exhibited remarkable bactericidal activity. These compounds’ inhibitory potential was evaluated against the histamine-generating ability of strain C_MRSV_25A_4 at three concentrations of interest: minimum bactericidal concentration (MBC), MBC/2 and MBC/4. The results on histamine-forming capability at sub-bactericidal concentrations were promising. Given these results, we propose novel antimicrobial formulations based on natural antimicrobials as efficient strategies to reduce potential microbial contamination and histamine accumulation throughout cheese production.

A Snapshot, Using a Multi-Omic Approach, of the Metabolic Cross-Talk and the Dynamics of the Resident Microbiota in Ripening Cheese Inoculated with Listeria innocua.

Raw milk cheeses harbor complex microbial communities. Some of these microorganisms are technologically essential, but undesirable microorganisms can also be present. While most of the microbial dynamics and cross-talking studies involving interaction between food-derived bacteria have been carried out on agar plates in laboratory-controlled conditions, the present study evaluated the modulation of the resident microbiota and the changes of metabolite production directly in ripening raw milk cheese inoculated with Listeria innocua strains. Using a proxy of the pathogenic Listeria monocytogenes, we aimed to establish the key microbiota players and chemical signals that characterize Latteria raw milk cheese over 60 days of ripening time. The microbiota of both the control and Listeria-inoculated cheeses was analyzed using 16S rRNA targeted amplicon sequencing, while direct analysis in real time mass spectrometry (DART-HRMS) was applied to investigate the differences in the metabolic profiles of the cheeses. The diversity analysis showed the same microbial diversity trend in both the control cheese and the inoculated cheese, while the taxonomic analysis highlighted the most representative genera of bacteria in both the control and inoculated cheese: Lactobacillus and Streptococcus. On the other hand, the metabolic fingerprints revealed that the complex interactions between resident microbiota and L. innocua were governed by continuously changing chemical signals. Changes in the amounts of small organic acids, hydroxyl fatty acids, and antimicrobial compounds, including pyroglutamic acid, hydroxy-isocaproic acid, malic acid, phenyllactic acid, and lactic acid, were observed over time in the L. innocua-inoculated cheese. In cheese that was inoculated with L. innocua, Streptococcus was significantly correlated with the volatile compounds carboxylbenzaldheyde and cyclohexanecarboxylic acid, while Lactobacillus was positively correlated with some volatile and flavor compounds (cyclohexanecarboxylic acid, pyroxidal acid, aminobenzoic acid, and vanillic acid). Therefore, we determined the metabolic markers that characterize a raw milk cheese inoculated with L. innocua, the changes in these markers with the ripening time, and the positive correlation of flavor and volatile compounds with the resident microbiota. This multi-omics approach could suggest innovative food safety strategies based on the enhanced management of undesirable microorganisms by means of strain selection in raw matrices and the addition of specific antimicrobial metabolites to prevent the growth of undesirable microorganisms.

Current insights into the biocontrol and biotechnological approaches for postharvest disease management of Botrytis cinerea

Postharvest decay in fruits and vegetables caused by fungal pathogens such as Botrytis cinerea leads to substantial economic losses. The decay caused by B. cinerea can be mitigated through the application of synthetic chemicals. However, due to its toxic residual effects on human health and environment stimulated the researchers to explore alternate effective and safe methods for the postharvest B. cinerea disease management. This article explains the current understanding of B. cinerea pathogenesis and the identification of antagonists used in the management of postharvest B. cinerea decay. This article also explains the mechanism of postharvest biocontrol agents (BCAs) and bioactive compounds derived from microorganisms and other plant resources with a particular focus on current advancements in molecular genomics such as (genetic engineering, transgenes and RNAi technology), omics and nanotechnology. Moreover, encapsulation of BCAs with nanoparticles increases their efficiency by delivering the BCAs to a specific host in a controlled and effective manner, with the aim of combating B. cinerea. Advanced molecular genetics allows for the identification and characterization of genes responsible for producing antifungal compounds produced by BCAs, which can be used to engineer strains with increased production of these compounds, making them more effective in controlling fungal diseases. Similarly, crops can be modified genetically which can show more resistance against the B. cinerea. However, more research will be needed to find the novel antimicrobial compounds derived from BCAs and estimation of developing beneficial microbial consortia for postharvest disease management, as well as genetic approaches, such as the use of CRISPR/Cas9 technology.

Disinfectant efficacy of glabridin against dried and biofilm cells of Listeria monocytogenes and the impact of residual organic matter

Glabridin is an antimicrobial compound which can be extracted from plants, such as liquorice (Glycyrrhiza glabra) roots. Although its activity against foodborne pathogens and spoilage microorganisms has already been reported, the investigation of potential applications as a surface disinfectant is still largely unexplored. Hence, this study evaluated the disinfectant efficacy of glabridin against Listeria monocytogenes. The activity of glabridin was first tested in vitro in a nutrient-rich medium against eight strains of L. monocytogenes, including food isolates and the model strain EGDe. The tested strains showed similar susceptibility with minimal inhibitory and bactericidal concentrations of 12.5 µg/mL and 25 µg/mL, respectively. Subsequently, L. monocytogenes L6, FBR17 and EGDe were selected to assess the efficacy of glabridin against dried cells (according to the European standard EN 13697:2015 + A1:2019) and biofilm cells on stainless steel surfaces. Moreover, the impact of food residual organic matter was investigated using skim milk, cantaloupe and smoked salmon solution as soiling components. Our results showed that applying 200 µg/mL of glabridin resulted in a substantial reduction (>3 log10) of dried and biofilm cells of L. monocytogenes in standard conditions (i.e. low level of residual organic matter). Cantaloupe soiling components slightly reduced the activity of glabridin, while the efficacy of glabridin when tested with salmon and skim milk residuals was substantially affected. Comparative analysis using standardized protein contents provided evidence that the type of food matrices and type of proteins may impact the activity of glabridin as a disinfectant. Overall, this study showed low strain variability for the activity of glabridin against L. monocytogenes and shed light on the possible application of this natural antimicrobial compound as a surface disinfectant.

Controlled release and antibacterial activity of corn starch-based films containing nanocellulose and thymol

The use of nanomaterials such as cellulose nanofiber (CNF) and antimicrobial compounds such as thymol (Thy), in starch films may improve the functional properties of films as active packaging films. This study quantifies the retention of thymol in corn starch (CS) and CS films containing cellulose nanofibers (CS/CNF) and investigates the migration of thymol from the films into a food simulant. A kinetic study was performed to evaluate the release of thymol from films into fatty acid food simulant (95% v/v ethanol) at 40 °C. The antibacterial activity of films was investigated via liquid culture assay. It was found that the addition of thymol significantly affects the surface morphology and cross-section of the films. CS/Thy and CS/CNF/Thy films retained thymol at 2.88 ± 0.50 and 11.21 ± 0.75 mg per g of CS/Thy and CS/CNF/Thy films, respectively. The release of thymol was affected by the presence of an intercalating network of CNF, which exhibited Fickian diffusion behavior. The release of thymol reached equilibrium within 48 h for CS/Thy, and 72 h for CS/CNF/Thy films. The CS/CNF/Thy film had a greater inhibitory effect than the CS/Thy film against Listeria monocytogenes and Salmonella Typhimurium. These findings demonstrate the potential applications of these films in improving the shelf life of perishable food products.

Green-Synthesized Characterization, Antioxidant and Antibacterial Applications of CtAC/MNPs-Ag Nanocomposites.

The emergence of antibiotic resistance, caused by the improper use of antibiotics, is a significant challenge in combating infectious diseases, leading to millions of annual fatalities. The occurrence of antimicrobial side effects catalyzes the investigation of novel antimicrobial compounds and sources of drugs. Consequently, the research on biological activity that is conducted on plants, plant extracts, and compounds that are produced from plant components is of utmost significance. In this study, CtAC/MNPs were obtained by the reaction of activated carbon (AC) obtained from the fruits of the Celtis tournefortii (Ct) plant and magnetic nanoparticles (MNPs), and a CtAC/MNPs-Ag nanocomposite was synthesized by the reduction in silver ions added to the reaction. The synthesized CtAC/MNPs and CtAC/MNPs-Ag nanocomposites were analyzed spectroscopically (FTIR, XRD), microscopically (SEM, EDX), optically (DLS), electrochemically (zeta potential) and magnetically (VSM). The antibacterial activities of CtAC/MNPs and CtAC/MNPs-Ag nanocomposites against S. aureus and E. coli were investigated by microdilution method using minimal inhibitory concentration (MIC) and disk diffusion methods. Antioxidant activity study, including total phenolic content and DPPH and cuprac assays, revealed the remarkable effect of the CtAC/MNPs-Ag nanocomposite. This study has the advantages of obtaining CtAC/MNPs and CtAC/MNPs-Ag nanocomposites in a short time without requiring energy, and most importantly, the reaction takes place without using any toxic substances. In addition, according to the data obtained in the study, the CtAC/MNPs-Ag nanocomposite is thought to shed light on biomedical research.

Chemical Behavior and Bioactive Properties of Spinorphin Conjugated to 5,5'-Dimethyl- and 5,5'-Diphenylhydantoin Analogs.

The discovery of new peptides and their derivatives is an outcome of ongoing efforts to identify a peptide with significant biological activity for effective usage as a possible therapeutic agent. Spinorphin peptides have been documented to exhibit numerous applications and features. In this study, biologically active peptide derivatives based on novel peptide analogues of spinorphin conjugated with 5,5'-dimethyl (Dm) and 5,5'-diphenyl (Ph) hydantoin derivatives have been successfully synthesized and characterized. Scanning electron microscopy (SEM) and spectral methods such as UV-Vis, FT-IR (Fourier Transform Infrared Spectroscopy), CD (Circular Dichroism), and fluorimetry were used to characterize the microstructure of the resulting compounds. The results revealed changes in peptide morphology as a result of the restructuring of the aminoacidic sequences and aromatic bonds, which is related to the formation of intermolecular hydrogen bonds between tyrosyl groups and the hydantoin moiety. Electrochemical and fluorescence approaches were used to determine some physicochemical parameters related to the biological behavior of the compounds. The biological properties of the spinorphin derivatives were evaluated in vivo for anticonvulsant activity against the psychomotor seizures at different doses of the studied peptides. Both spinorphin analog peptides with Ph and Dm groups showed activity against all three phases of the seizure in the intravenous Pentylenetetrazole Seizure (ivPTZ) test. This suggests that hydantoin residues do not play a crucial role in the structure of spinorphin compounds and in determining the potency to raise the seizure threshold. On the other hand, analogs with a phenytoin residue are active against the drug-resistant epilepsy test (6-Hz test). In addition, bioactivity analyses revealed that the new peptide analogues have the potential to be used as antimicrobial and antioxidant compounds. These findings suggest promising avenues for further research that may lead to the development of alternative medicines or applications in various fields beyond epilepsy treatment.

Ancient and remote quartzite caves as a novel source of culturable microbes with biotechnological potential

Quartzite caves located on table-top mountains (tepuis) in the Guyana Shield, are ancient, remote, and pristine subterranean environments where microbes have evolved peculiar metabolic strategies to thrive in silica-rich, slightly acidic and oligotrophic conditions. In this study, we explored the culturable fraction of the microbiota inhabiting the (ortho)quartzite cave systems in Venezuelan tepui (remote table-top mountains) and we investigated their metabolic and enzymatic activities in relation with silica solubilization and extracellular hydrolytic activities as well as the capacity to produce antimicrobial compounds. Eighty microbial strains were isolated with a range of different enzymatic capabilities. More than half of the isolated strains performed at least three enzymatic activities and four bacterial strains displayed antimicrobial activities. The antimicrobial producers Paraburkholderia bryophila CMB_CA002 and Sphingomonas sp. MEM_CA187, were further analyzed by conducting chemotaxonomy, phylogenomics, and phenomics. While the isolate MEM_CA187 represents a novel species of the genus Sphingomonas, for which the name Sphingomonas imawarii sp. nov. is proposed, P. bryophila CMB_CA002 is affiliated with a few strains of the same species that are antimicrobial producers. Chemical analyses demonstrated that CMB_CA002 produces ditropolonyl sulfide that has a broad range of activity and a possibly novel siderophore. Although the antimicrobial compounds produced by MEM_CA187 could not be identified through HPLC-MS analysis due to the absence of reference compounds, it represents the first soil-associated Sphingomonas strain with the capacity to produce antimicrobials. This work provides first insights into the metabolic potential present in quartzite cave systems pointing out that these environments are a novel and still understudied source of microbial strains with biotechnological potential.

Cellulamides: A New Family of Marine-Sourced Linear Peptides from the Underexplored Cellulosimicrobium Genus.

Bioprospecting the secondary metabolism of underexplored Actinomycetota taxa is a prolific route to uncover novel chemistry. In this work, we report the isolation, structure elucidation, and bioactivity screening of cellulamides A and B (1 and 2), two novel linear peptides obtained from the culture of the macroalga-associated Cellulosimicrobium funkei CT-R177. The host of this microorganism, the Chlorophyta Codium tomentosum, was collected in the northern Portuguese coast and, in the scope of a bioprospecting study focused on its associated actinobacterial community, strain CT-R177 was isolated, taxonomically identified, and screened for the production of antimicrobial and anticancer compounds. Dereplication of a crude extract of this strain using LC-HRMS(/MS) analysis unveiled a putative novel natural product, cellulamide A (1), that was isolated following mass spectrometry-guided fractionation. An additional analog, cellulamide B (2) was obtained during the chromatographic process and chemically characterized. The chemical structures of the novel linear peptides, including their absolute configurations, were elucidated using a combination of HRMS, 1D/2D NMR spectroscopy, and Marfey's analysis. Cellulamide A (1) was subjected to a set of bioactivity screenings, but no significant biological activity was observed. The cellulamides represent the first family of natural products reported from the Actinomycetota genus Cellulosimicrobium, showcasing not only the potential of less-explored taxa but also of host-associated marine strains for novel chemistry discovery.

Leuconostoc gelidum Is the Major Species Responsible for the Spoilage of Cooked Sausage Packaged in a Modified Atmosphere, and Hop Extract Is the Best Inhibitor Tested.

Cooked sausages packaged in a modified atmosphere (MAP: 20% CO2, 70% N2, <0.2% O2) with evident yellow stains were analyzed. The aims of this work were to study the microbial cause of the spoilage and to evaluate different antimicrobial compounds to prevent it. Leuconostoc gelidum was identified as the primary cause of the yellow coating in spoiled cooked sausage, as confirmed by its intentional inoculation on slices of unspoiled sausage. Leuconostoc gelidum was the main bacteria responsible for the yellow coating in spoiled cooked sausage, as confirmed by its intentional inoculation on slices of unspoiled sausage. The yellow color was also evident during growth in the model system containing cooked sausage extract, but the colonies on MRS agar appeared white, demonstrating that the food substrate stimulated the production of the yellow pigment. The spoilage was also characterized by different volatile compounds, including ketones, ethanol, acetic acid, and ethyl acetate, found in the spoiled cooked sausage packages. These compounds explained the activity of Leuc. gelidum because they are typical of heterofermentative LAB, cultivated either on food substrates or in artificial broths. Leuc. gelidum also produced slight swelling in the spoiled packages. The efficacy of different antimicrobials was assessed in model systems composed of cooked sausage extract with the antimicrobials added at food product concentrations. The data showed that sodium lactate, sodium acetate, and a combination of sodium lactate and sodium diacetate could only slow the growth of the spoiler-they could not stop it from occurring. Conversely, hop extract inhibited Leuc. gelidum, showing a minimal inhibitory concentration (MIC) of approximately 0.008 mg CAE/mL in synthetic broth and 4 mg CAE/kg in cooked sausage slices. Adding hop extract at the MIC did not allow Leuc. gelidum growth and did not change the sensorial characteristics of the cooked sausages. To our knowledge, this is the first report of the antimicrobial activities of hop extracts against Leuc. gelidum either in vitro or in vivo.

Antimicrobial assay and controlled drug release studies with novel eugenol imprinted p(HEMA)-bacterial cellulose nanocomposite, designed for biomedical applications

In this study, a novel bio-composite material that allow sustained release of plant derived antimicrobial compound was developed for the biomedical applications to prevent the infections caused by microorganisms resistant to commercial antimicrobials agents. With this aim, bacterial cellulose (BC)-p(HEMA) nanocomposite film that imprinted with eugenol (EU) via metal chelated monomer, MAH was prepared. Firstly, characterization studies were utilized by FTIR, SEM and BET analysis. Then antimicrobial assays, drug release studies and in vitro cytotoxicity test were performed. A significant antimicrobial effect against both Gram (+) Staphylococcus aureus and Gram (-) Escherichia coli bacteria and a yeast Candida albicans were observed even in low exposure time periods. When antimicrobial effect of EU compared with commercially used agents, both antifungal and antibacterial activity of EU were found to be higher. Then, sustained drug release studies showed that approximately 55% of EU was released up to 50 h. This result proved the achievement of the molecular imprinting for an immobilization of molecules that desired to release on an area in a long-time interval. Finally, the in vitro cytotoxicity experiment performed with the mouse L929 cell line determined that the synthesized EU-imprinted BC nanocomposite was biocompatible.