Selective Antimicrobial Activity Research Articles

Selective and complementary antimicrobial and antiviral activity of silver, copper, and selenium nanoparticle suspensions in deep eutectic solvent

Metallic and nonmetallic nanoparticles are bioactive compounds that exhibit broad resistance to bacteria, fungi, and even viruses. In this paper, a deep eutectic solvent (DES) based on betaine, glucose, and ethylene glycol was used to obtain suspensions of silver, copper, and selenium nanoparticles. Depending on the nanoparticle precursor used, Ag, Cu, and Se nanoparticles (NPs) with an average particle size of 50−100 nm were prepared, and the properties of the products were confirmed by the STEM, XPS, DLS, and UV-VIS methods. The use of a DES, without the need for additional reactants, allowed the production of stable nanoparticles with increased bioactivity against microorganisms. The obtained systems showed high bioactivity against strains of S. aureus, E. coli, and C. albicans. Nanosuspensions, by generating reactive oxygen species (ROSs), caused enzyme inactivation and the inhibition of the metabolic processes of microorganisms. Particle-generated cell degradation processes were investigated through ROS generation assays, API assays, the determination of the MIC/MBC, and cell decomposition rate assays in the early logarithmic growth phase. Copper nanoparticles derived from copper(II) acetate were also highly active against the human influenza A/H1N1 viruses, human coronavirus (HCoV-OC43, Betacoronavirus 1), and vesicular stomatitis virus (VSV, Rhabdoviridae), showing a virus titer reduction of more than 93.7−99.96%.

Synthesis, Characterization, and Biological Investigation of Antimony(III) Halide Complexes With Different Coordination Architectures Constructed From Thiophene Thiosemicarbazones

ABSTRACTIn this study, we report the synthesis, characterization, and biological investigation of antimony(III) halide complexes with various coordination architectures constructed from thiophene thiosemicarbazones. Antimony(III) thiophene‐2‐carbaldehyde thiosemicarbazone complexes (1, 2, 4, and 5) exhibit a square pyramidal geometry, with ligands coordinated to the central antimony atom in two distinct binding modes. In contrast, antimony(III) 2‐acetylthiophene thiosemicarbazone complexes (3, 6, and 7) adopt a seesaw geometry. These complexes (1–7) represent the first reported examples of antimony(III) halide thiosemicarbazone compounds. The unique coordination environments observed in these complexes are of significant importance within the realm of antimony chemistry. These synthesized complexes exhibit different coordination geometries as well as potential biological activities. The antiproliferative activity against the human breast adenocarcinoma (MCF‐7) cell line and antimicrobial activity against Gram‐positive and Gram‐negative bacteria were assessed. Antimony(III) thiophene‐2‐carbaldehyde thiosemicarbazone complexes (1, 2, 4, and 5) showed significant antiproliferative activity with IC50 values ranging from 8.5 to 19.1 μM, while antimony(III) 2‐acetylthiophene thiosemicarbazone complexes (3, 6, and 7) had higher IC50 values. Additionally, the antimony complexes demonstrated selective antimicrobial activity against Gram‐negative bacteria.

Antimicrobial Peptide with a Bent Helix Motif Identified in Parasitic Flatworm Mesocestoides corti.

The urgent need for antibiotic alternatives has driven the search for antimicrobial peptides (AMPs) from many different sources, yet parasite-derived AMPs remain underexplored. In this study, three novel potential AMP precursors (mesco-1, -2 and -3) were identified in the parasitic flatworm Mesocestoides corti, via a genome-wide mining approach, and the most promising one, mesco-2, was synthesized and comprehensively characterized. It showed potent broad-spectrum antibacterial activity at submicromolar range against E. coli and K. pneumoniae and low micromolar activity against A. baumannii, P. aeruginosa and S. aureus. Mechanistic studies indicated a membrane-related mechanism of action, and circular dichroism spectroscopy confirmed that mesco-2 is unstructured in water but forms stable helical structures on contact with anionic model membranes, indicating strong interactions and helix stacking. It is, however, unaffected by neutral membranes, suggesting selective antimicrobial activity. Structure prediction combined with molecular dynamics simulations suggested that mesco-2 adopts an unusual bent helix conformation with the N-terminal sequence, when bound to anionic membranes, driven by a central GRGIGRG motif. This study highlights mesco-2 as a promising antibacterial agent and emphasizes the importance of structural motifs in modulating AMP function.

Engineered Hybrid Lantibiotic that Selectively Combats Infections Caused by Staphylococcus aureus.

The rapid emergence of antibiotic-resistant strains of Staphylococcus aureus presents a substantial challenge to global public health, underscoring the urgent need for novel antibiotics with diverse mechanisms of action. In this study, we conducted mutagenesis on the C-terminal region of the lantibiotic ripcin C to enhance its antimicrobial efficacy against S. aureus. The resulting optimized variant, ripcin CP23A, demonstrated potent and selective antimicrobial activity, with a minimal inhibitory concentration of 2-4 mg/L against S. aureus. Beyond its strong antimicrobial properties, ripcin CP23A exhibited significant antibiofilm activity against methicillin-resistant S. aureus (MRSA). Mechanistic studies revealed that, in addition to targeting lipid II, ripcin CP23A disrupts bacterial membranes, a capability absent in ripcin C, which may contribute to its superior antimicrobial and antibiofilm effects. Moreover, ripcin CP23A displayed favorable biosafety and plasma stability profiles. Notably, in a mouse model of MRSA-induced mastitis, ripcin CP23A effectively reduced bacterial load, alleviated inflammation, and preserved the normal histomorphology of mammary glands. This study introduces ripcin CP23A as a promising antibiotic candidate for the treatment of MRSA-related infections.

Unveiling MurM inhibitors in Enterococcus faecalis V583: a promising approach to tackle antibiotic resistance

Enterococcus faecalis is commonly found in the GI tract of humans and animals. It causes various infections, especially in hospital environments, and shows growing antibiotic resistance. This study utilized a subtractive proteomics approach to find out the potential drug targets in E. faecalis. Unique metabolic pathways were analysed and compared to the host to minimize adverse effects. Among twenty nine pathogenic specific and seventy three host-pathogen common pathways identified using the KEGG database, sixty seven essential proteins were found through the DEG BLAST search. PSORTB predicted that forty cytoplasmic proteins could be suitable as druggable targets. Further analysis identified fourteen proteins with virulence properties using the VFDB BLAST. Among these, seven proteins with more than ten antigenic sites were subjected to DrugBank BLAST, identifying three novel and four existing drug targets. One of the crucial drug targets, MurM, was selected due to its critical role in peptidoglycan biosynthesis. The reason for selecting MurM is crucial for addressing antibiotic resistance, disrupting bacterial cell wall synthesis, and attaining selective antimicrobial activity. MurM belongs to the mixed αβ class with two functional domains. The possible binding site residues of MurM are Trp31, Lys35, Trp38, Arg215, and Tyr219. Virtual screening identified potential lead candidates for MurM, and four were selected based on their physiochemical, pharmacokinetic, and structural properties. This study provides valuable insights into identifying and analysing a potential drug target, the MurM protein, and its inhibitors in E. faecalis V583.

Chebulinic acid isolated from aqueous extracts of Terminalia chebula Retz inhibits Helicobacter pylori infection by potential binding to Cag A protein and regulating adhesion.

Terminalia chebula Retz, known as the King of Tibet, is considered a functional food in China, celebrated for its antioxidant, immune-modulating, antibacterial, and anti-inflammatory properties. Chebulinic acid, derived from aqueous extracts of Terminalia chebula Retz, is known for its anti-inflammatory properties. However, its potential as an anti-Helicobacter pylori (HP) agent has not been fully explored. Herein, we extracted the main compound from Terminalia chebula Retz using a semi-preparative liquid chromatography (LC) system and identified compound 5 as chebulinic acid through Ultra-high performance liquid chromatography-MS/MS (UPLC-MS/MS) and Nuclear Magnetic Resonance (NMR). To evaluate its role, we conducted minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays, scanning electron microscope (SEM) imaging, inhibiting kinetics curves, urea fast test, cell counting kit-8 (CCK-8) assay, western blot analysis, griess reagent system, and molecular docking. Our results showed that chebulinic acid effectively inhibited the growth of the HP strain ATCC 700392, damaged the HP structure, and exhibited selective antimicrobial activity without affecting normal epithelial cells GES-1. Importantly, it suppressed the expression of Cytotoxin-associated gene A (Cag A) protein, a crucial factor in HP infection. Molecular docking analysis predicted a strong affinity (-9.7 kcal/mol) between chebulinic acid and Cag A protein. Overall, our findings suggest that chebulinic acid acts as an anti-adhesive agent, disrupting the adhesion of HP to host cells, which is a critical step in HP infection. It also suppresses the Cag A protein. These results highlight the potential of chebulinic acid against HP infections.

Micellar mediated preparation of cadmium sulfide (CdS) nanoparticles: Influence of cleavable spacer based cationic gemini surfactant

Cleavable spacer (s = diamido) based cationic gemini surfactant (with different alkyl tail lengths (m) abbreviated as g1; m = 12, g2; m = 14 or g3; m = 16), in aqueous micellar solution, was used to control the size and morphology of cadmium sulfide (CdS) nanoparticles (NPs), via modified chemical precipitation technique. The purity and stability of all CdS NPs were characterized by EDAX, FT-IR, TGA and zeta potential (ζ). By varying the geminis, significant size reduction (2–6 nm), enhanced capping capacity, and higher energy band gap (∼4.1 eV) have been found in CdS-g1 compared to other NPs, by using Dynamic Light Scattering (DLS), TEM, XRD and UV–visible spectroscopy. Photoluminescence (PL) spectra revealed an emission at 525 and 630 nm, showing the effect of geminis m concerning surface states of NP. Additionally, antioxidant and antimicrobial (on Gram-negative (E. coli and P. aeruginosa) and Gram-positive (S. aureus and B. subtilis) strains) activities of CdS NPs were examined by DPPH radical scavenging and agar plating-spot disc inoculation method, respectively. The results recommended a significant antioxidant activity in CdS-g1 with 45.6 %, while, selective antimicrobial activity was obtained on E. coli and S. aureus in all NP systems.

Acute toxicity assessment of bioactive constituents from Salvia algeriensis (Desf.) extracts: a promising natural agent against clinical bacterial isolates and pathogenic fungi

Salvia species are emerging as promising therapeutic agents due to their diverse bioactivity against various pathologies. This study was conducted to investigate the phytochemical profile, antimicrobial activity, and acute Toxicity of hydromethanolic extracts from Salvia algeriensis (Desf.) leaves, flowers, and roots. Chemical reaction tests and chromatographic analysis were employed to determine the chemical composition, while microdilution was used to determine the tested microorganisms' minimum inhibitory concentration (MIC). The acute Toxicity of the leaf extract was carried out following the rules and guidelines of OECD 425. Toxicity parameters in Swiss albino mice were evaluated after a single dose of 500 mg/kg and 2000 mg/kg. According to the preliminary phytochemical screening results, terpenoids and polyphenols (flavonoids and tannins) were found in all plant parts, but coumarins were only found in the root extract. The HPLC-DAD analysis revealed the presence of 16 phenolic compounds in varying amounts across the three extracts, of which rosmarinic acid, quercetin, caffeic acid, and 3-hydroxybenzoic acid were the most abundant. Selective antimicrobial activity was noticed, with the root extract demonstrating the most substantial effect against the two fungal strains tested. MIC values ranged from 0.3 to 10 mg/mL, and Gram-positive bacteria generally showedgreater susceptibility compared to Gram-negative bacteria. The LD50 was found to be greater than 2000 mg/kg. There were no overt clinical symptoms of Toxicity. Body weights, organ weights, and temperatures were not significantly altered, and hematological analysis showed no significant differences. Salvia algeriensis (Desf.) extracts emerge as potential candidates for natural, non-toxic antimicrobial agents. Keywords: Acute Toxicity; antimicrobial; HPLC-DAD; polyphenols; Salvia

In vitro and In vivo Activity of a New N-Oxide Derivative for Acne Vulgaris Treatment.

Furoxan and benzofuroxan are compounds containing an N-oxide function, known for their diverse pharmacological properties, including antimicrobial and antiinflammatory effects. This study aimed to investigate these activities using an in-house library of N-oxide compounds. Twenty compounds were tested against both Gram-positive and Gram-negative bacteria, including Cutibacterium acnes (C. acnes), a microorganism implicated in the development of acne vulgaris. One compound, (E)-4-(3-((2-(3-hydroxybenzoyl)hydrazone)methyl)phenoxy)-3- (phenylsulfonyl)-1,2,5-oxadiazol-2-N-oxide (compound 15), exhibited selective antimicrobial activity against C. acnes, with a Minimum Inhibitory Concentration (MIC) value of 2 μg/mL. Indirect measurement of Nitric Oxide (NO) release showed that compound 15 and isosorbide dinitrate, when treated with L-cysteine, produced nitrite levels of 20.1% and 9.95%, respectively. Using a NO scavenger (PTIO) in combination with compound 15 in a culture of C. acnes resulted in reduced antimicrobial activity, indicating that NO release is part of its mechanism of action. Cytotoxicity assessments using murine macrophages showed cellular viability above 70% at concentrations up to 0.78 μg/mL. Measurements of Interleukin-1 beta (IL1-β) and Tumor Necrosis Factor-alpha (TNF-α) indicated that compound 15 did not reduce the levels of these pro-inflammatory cytokines. Sustained NO production by inducible Nitric Oxide Synthase (iNOS) in macrophages or neutrophils has been found to be involved in the inflammatory process in acne vulgaris and lead to toxicity in surrounding tissues. Nitrite levels in the supernatant of murine macrophages were found to be decreased at a concentration of 0.78 μg/mL of compound 15, indicating an anti-inflammatory effect. In vivo studies were conducted using Balb/c nude mice inoculated subcutaneously with C. acnes. Cream and gel formulations of compound 15 were applied to treat the animals, along with commercially available anti-acne drugs, for 14 days. Animals treated with a cream base containing 5% of compound 15 exhibited less acanthosis with mild inflammatory infiltration compared to other groups, highlighting its anti-inflammatory properties. Similar results were observed in the benzoyl peroxide group, demonstrating that compound 15 presented comparable anti-inflammatory activity to the FDA-approved drug. These promising results suggest that compound 15 has a dual mechanism of action, with selective antimicrobial activity against C. acnes and notable anti-inflammatory properties, making it a potential prototype for developing new treatments for acne vulgaris.

Enhancing Selective Antimicrobial and Antibiofilm Activities of Melittin through 6-Aminohexanoic Acid Substitution.

Leucine residues are commonly found in the hydrophobic face of antimicrobial peptides (AMPs) and are crucial for membrane permeabilization, leading to the cell death of invading pathogens. Melittin, which contains four leucine residues, demonstrates broad-spectrum antimicrobial properties but also significant cytotoxicity against mammalian cells. To enhance the cell selectivity of melittin, this study synthesized five analogs by replacing leucine with its structural isomer, 6-aminohexanoic acid. Among these analogs, Mel-LX3 exhibited potent antibacterial activity against both Gram-positive and Gram-negative bacteria. Importantly, Mel-LX3 displayed significantly reduced hemolytic and cytotoxic effects compared to melittin. Mechanistic studies, including membrane depolarization, SYTOX green uptake, FACScan analysis, and inner/outer membrane permeation assays, demonstrated that Mel-LX3 effectively permeabilized bacterial membranes similar to melittin. Notably, Mel-LX3 showed robust antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and multidrug-resistant Pseudomonas aeruginosa (MDRPA). Furthermore, Mel-LX3 effectively inhibited biofilm formation and eradicated existing biofilms of MDRPA. With its improved selective antimicrobial and antibiofilm activities, Mel-LX3 emerges as a promising candidate for the development of novel antimicrobial agents. We propose that the substitution of leucine with 6-aminohexanoic acid in AMPs represents a significant strategy for combating resistant bacteria.

QSAR Reveals Decreased Lipophilicity of Polar Residues Determines the Selectivity of Antimicrobial Peptide Activity.

Antimicrobial resistance has increased rapidly, causing daunting morbidity and mortality rates worldwide. Antimicrobial peptides (AMPs) have emerged as promising alternatives to traditional antibiotics due to their broad range of targets and low tendency to elicit resistance. However, potent antimicrobial activity is often accompanied by excessive cytotoxicity toward host cells, leading to a halt in AMP therapeutic development. Here, we present multivariate analyses that correlate 28 peptide properties to the activity and toxicity of 46 diverse African-derived AMPs and identify the negative lipophilicity of polar residues as an essential physiochemical property for selective antimicrobial activity. Twenty-seven active AMPs are identified, of which the majority are of scorpion or frog origin. Of these, thirteen are novel with no previously reported activities. Principal component analysis and quantitative structure-activity relationships (QSAR) reveal that overall hydrophobicity, lipophilicity, and residue side chain surface area affect the antimicrobial and cytotoxic activity of an AMP. This has been well documented previously, but the present QSAR analysis additionally reveals that a decrease in the lipophilicity, contributed by those amino acids classified as polar, confers selectivity for a peptide to pathogen over mammalian cells. Furthermore, an increase in overall peptide charge aids selectivity toward Gram-negative bacteria and fungi, while selectivity toward Gram-positive bacteria is obtained through an increased number of small lipophilic residues. Finally, a conservative increase in peptide size in terms of sequence length and molecular weight also contributes to improved activity without affecting toxicity. Our findings suggest a novel approach for the rational design or modification of existing AMPs to increase pathogen selectivity and enhance therapeutic potential.

1,3,6-Trigalloylglucose: A Novel Potent Anti-Helicobacter pylori Adhesion Agent Derived from Aqueous Extracts of Terminalia chebula Retz.

1,3,6-Trigalloylglucose is a natural compound that can be extracted from the aqueous extracts of ripe fruit of Terminalia chebula Retz, commonly known as "Haritaki". The potential anti-Helicobacter pylori (HP) activity of this compound has not been extensively studied or confirmed in scientific research. This compound was isolated using a semi-preparative liquid chromatography (LC) system and identified through Ultra-high-performance liquid chromatography-MS/MS (UPLC-MS/MS) and Nuclear Magnetic Resonance (NMR). Its role was evaluated using Minimum inhibitory concentration (MIC) assay and minimum bactericidal concentration (MBC) assay, scanning electron microscope (SEM), inhibiting kinetics curves, urea fast test, Cell Counting Kit-8 (CCK-8) assay, Western blot, and Griess Reagent System. Results showed that this compound effectively inhibits the growth of HP strain ATCC 700392, damages the HP structure, and suppresses the Cytotoxin-associated gene A (Cag A) protein, a crucial factor in HP infection. Importantly, it exhibits selective antimicrobial activity without impacting normal epithelial cells GES-1. In vitro studies have revealed that 1,3,6-Trigalloylglucose acts as an anti-adhesive agent, disrupting the adhesion of HP to host cells, a critical step in HP infection. These findings underscore the potential of 1,3,6-Trigalloylglucose as a targeted therapeutic agent against HP infections.

Tuning the antimicrobial activity of microbial glycolipid biosurfactants through chemical modification.

Sophorolipids, glycolipid biosurfactants derived from microorganisms such as Starmerella bombicola, possess distinctive surface-active and bioactive properties, holding potential applications in cosmetics, pharmaceuticals and bioremediation. However, the limited structural variability in wild-type sophorolipids restricts their properties and applications. To address this, metabolic engineering efforts have allowed to create a portfolio of molecules. In this study, we went one step further by chemically modifying microbially produced sophorosides, produced by an engineered S. bombicola. Twenty-four new sophoroside derivatives were synthesized, including sophoroside amines with varying alkyl chain lengths (ethyl to octadecyl) on the nitrogen atom and their corresponding quaternary ammonium salts. Additionally, six different microbially produced glycolipid biosurfactants were hydrogenated to achieve fully saturated lipid tails. These derivatives, along with microbially produced glycolipids and three benchmark biosurfactants (di-rhamnolipids, alkyl polyglucosides, cocamidopropyl betaine), were assessed for antimicrobial activity against bacteria (Bacillus subtilis, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, Pseudomonas aeruginosa) and yeast (Candida albicans). Results indicated that microbially produced glycolipids, such as bola sophorosides, acidic sophorolipids and acidic glucolipids exhibit selective antimicrobial activity against the test organisms. Conversely, lactonic sophorolipids, sophoroside amines and quaternary ammonium salts display a broad antimicrobial activity. N-octyl, N-dodecyl and N-octadecyl derivatives exhibit the lowest minimal inhibitory concentrations, ranging from 0.014 to 20.0mgmL-1. This study demonstrates the potential synergy of thoughtful biotechnology and targeted chemistry to precisely tailor glycolipid biosurfactants to meet specific requirements across applications.

Monoterpenes as Medicinal Agents: Exploring the Pharmaceutical Potential of p-Cymene, p-Cymenene, and γ-Terpinene

This review highlights the therapeutic propeties of monoterpenes, particularly γ-terpinene, p-cymene, and p-cymenene, found in essential oils derived from various plants. These compounds are known for their analgesic, anticancer, anti-inflammatory, and antimicrobial properties. γ-Terpinene is recognized for its potent antioxidant propeties and is a constituent of oils from plants such as cumin and thyme. p-cymene, found in over 100 plant species, is noted for its antiviral and antibacterial properties and is considered safe by IFRA standards. p-Cymenene, with its distinct aroma, is detected in parsley and turmeric oils and is known for its antibacterial and antioxidant activities. The antimicrobial properties of γ-terpinene and p-cymene are highlighted, demonstrating their effectiveness in treating various skin conditions and reducing airborne microbes. Their selective antimicrobial activity preserves the integrity of the microbiome, offering a balanced approach to infection control. The anti-inflammatory properties of γ-terpinene are emphasized, with studies indicating its role in modulating cytokine production, underscoring its potential in the treatment of inflammation. Additionally, its antinociceptive effects suggest that it is a safe analgesic. In cancer treatment, the antiproliferative effects of γ-terpinene and p-cymene are being explored, highlighting their potential for targeted cancer therapy. This review aims to consolidate knowledge about these monoterpenes and promote a deeper understanding of their medical applications and safety. The knowledge gained is expected to stimulate further research, potentially leading to innovative applications in pharmaceutical and medical fields and harnessing the potential of -terpinene, p-cymene, and p-cymenene.

Antimicrobial and Anti-inflammatory Cyclic Tetrapeptides from the Co-cultures of Two Marine-Derived Fungi.

Violaceotides B-E (1-4), four new cyclic tetrapeptides, along with seven known compounds, were identified from the sponge-associated Aspergillus insulicola IMB18-072 co-cultivated with the marine-derived Alternaria angustiovoidea IMB20-805. Their structures were elucidated by extensive analysis of spectroscopic data, including HRESIMS, 1D and 2D NMR, and MS/MS data. The absolute configurations were determined by the advanced Marfey's method. Compounds 2, 3, and violaceotide A (5) displayed selective antimicrobial activities against the aquatic pathogenic bacteria Edwardsiella tarda and E. ictaluri. In addition, compounds 1-5 showed inhibitory activities against the LPS-induced expression of the inflammatory mediator IL-6 in RAW264.7 cells at a concentration of 10 μM.

The soil-borne white root rot pathogen Rosellinia necatrix expresses antimicrobial proteins during host colonization.

Rosellinia necatrix is a prevalent soil-borne plant-pathogenic fungus that is the causal agent of white root rot disease in a broad range of host plants. The limited availability of genomic resources for R. necatrix has complicated a thorough understanding of its infection biology. Here, we sequenced nine R. necatrix strains with Oxford Nanopore sequencing technology, and with DNA proximity ligation we generated a gapless assembly of one of the genomes into ten chromosomes. Whereas many filamentous pathogens display a so-called two-speed genome with more dynamic and more conserved compartments, the R. necatrix genome does not display such genome compartmentalization. It has recently been proposed that fungal plant pathogens may employ effectors with antimicrobial activity to manipulate the host microbiota to promote infection. In the predicted secretome of R. necatrix, 26 putative antimicrobial effector proteins were identified, nine of which are expressed during plant colonization. Two of the candidates were tested, both of which were found to possess selective antimicrobial activity. Intriguingly, some of the inhibited bacteria are antagonists of R. necatrix growth in vitro and can alleviate R. necatrix infection on cotton plants. Collectively, our data show that R. necatrix encodes antimicrobials that are expressed during host colonization and that may contribute to modulation of host-associated microbiota to stimulate disease development.

Rombocin, a Short Stable Natural Nisin Variant, Displays Selective Antimicrobial Activity against Listeria monocytogenes and Employs a Dual Mode of Action to Kill Target Bacterial Strains.

Nisin, with its unique mode of action and potent antimicrobial activity, serves as a remarkable inspiration for the design of novel antibiotics. However, peptides possess inherent weaknesses, particularly their susceptibility to proteolytic degradation, such as by trypsin, which limits their broader applications. This led us to speculate that natural variants of nisin produced by underexplored bacterial species can potentially overcome these limitations. We carried out genome mining of two Romboutsia sedimentorum strains, RC001 and RC002, leading to the discovery of rombocin A, which is a 25 amino acid residue short nisin variant that is predicted to have only four macrocycles compared to the known 31-35 amino acids long nisin variants with five macrocycles. Using the nisin-controlled expression system, we heterologously expressed fully modified and functional rombocin A in Lactococcus lactis and demonstrated its selective antimicrobial activity against Listeria monocytogenes. Rombocin A uses a dual mode of action involving lipid II binding activity and dissipation of the membrane potential to kill target bacteria. Stability tests confirmed its high stability at different pH values, temperatures, and in particular, against enzymatic degradation. With its gene-encoded characteristic, rombocin A is amenable to bioengineering to generate novel derivatives. Further mutation studies led to the identification of rombocin K, a mutant with enhanced bioactivity against L. monocytogenes. Our findings suggest that rombocin A and its bioengineered variant, rombocin K, are promising candidates for development as food preservatives or antibiotics against L. monocytogenes.

Antimicrobial sesterterpenoids with a unique 5/8/6/5 tetracyclic carbon-ring-system and diepoxide polyketides from a deep sea-sediment-sourced fungus Chaetomium globosum SD-347.

Two new sesterterpenoids, sesterchaetins A and B (1 and 2), and two new diepoxide polyketides, chaetoketoics A and B (3 and 4), were characterized from the culture extract of Chaetomium globosum SD-347, a fungal strain derived from deep sea-sediment. Their structures and absolute configurations were unambiguously determined by detailed NMR, mass spectra, and X-ray crystallographic analysis. Compounds 1 and 2 contained a distinctive 5/8/6/5 tetracyclic carbon-ring-system, which represented a rarely occurring natural product framework. The new isolates 1-4 exhibited selective antimicrobial activities against human and aquatic pathogenic bacteria and plant-pathogenic fungi.

Biotransformed bear bile powder alleviates diet-induced nonalcoholic fatty liver disease in mice by regulating the gut microbiota and reversing lipid metabolism

BackgroundThe pathogenesis of metabolic syndrome was strongly associated with compromised metabolism homeostasis and gut microbiota imbalance. NAFLD is a progressive metabolic liver disease for which effective interventions are lacking. Bile acids exhibited appreciable metabolic regulatory effects and selective antimicrobial activity. Aim of the studyThis study was designed to investigate the effect of BBBP, which mainly contained bile acids, on NAFLD from the perspectives of gut microbiota and metabolomics. Materials and methodsThe present study was initiated on the anti-NAFLD effect of BBBP in HFD-fed mice. The efficacy of BBBP was evaluated by mice phenotypes, liver histopathological analysis and serum lipid and glucose levels. The activation of bile acid receptors such as Nr1h4, Nr1i2 and S1pr2 were detected by qRT-PCR analysis. Subsequently, untargeted metabolomics coupled with microbiomics was used to explore the mechanism of BBBP against NAFLD. Human L02 hepatocytes induced by OA and PA were used to investigate the effect of GABA on reducing lipid accumulation in vitro. ResultsBBBP significantly and dose-dependently alleviated the obese phenotype, lipid accumulation and liver injury in mice subjected to 18 weeks HFD diet. Untargeted metabolomics and microbiomics analysis revealed that BBBP could alleviate the disturbance of lipid and amino acid metabolism and the imbalance of gut microbiota. Furthermore, BBBP oral gavage activated liver bile acid receptors, as indicated by elevated mRNA levels of Nr1h4, Nr1i2 and S1pr2. Surprisingly, we determined that BBBP, which mainly contained bile acids that possessed antimicrobial activity, could promote the growth of Lactobacillus. Correlation analysis showed a remarkable correlation between Lactobacillus and endogenous metabolites such as valine, serine, glutamine, et al. Among them, GABA which could be produced by Lactobacillus significantly reduced the lipid accumulation in L02 cells. ConclusionsThe role of BBBP in regulating lipid metabolism might be achieved by activating bile acid receptors, or partially by promoting the levels of Lactobacillus and its metabolites such as GABA. Our study provided evidence that BBBP could be a novel therapeutic candidate for the treatment of NAFLD.

Antimicrobial and Cytotoxic Secondary Metabolites from a Marine-Derived Fungus Penicillium Citrinum VM6.

Investigation of an antimicrobial and cytotoxic ethyl acetate extract prepared from solid fermentation of the marine-derived fungus Penicillium citrinum VM6 led to the isolation of eight metabolites (1-8), including one citrinin dimer dicitrinone F (1). Of these, compound 7 was isolated for the first time from the Penicillium genus and compound 1 with carbon-bridged C-7/C-7' linkage is rarely reported. All compounds (1-8) exhibited selective antimicrobial activity against the tested Gram-positive bacteria and Candida albicans with MICs of 32-256µg/mL. Compounds 1 and 8 exhibited cytotoxicity against all tested cell lines A549, MCF7, MDA-MB-231, Hela, and AGS with IC50 values of 6.7 ± 0.2 to 29.6 ± 2.2µg/mL, whereas compound 5 had selective cytotoxicity against the MCF7 cell lines with IC50 of 98.1 ± 7.8µg/mL.