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Background: Staphylococcus aureus is a common pathogenic microorganism in humans and animals. Type II NADH oxidoreductase (NDH-2) is the only NADH:quinone oxidoreductase present in this organism and represents a promising target for the development of anti-staphylococcal drugs. Recently, myricetin, a natural flavonoid from vegetables and fruits, was found to be a potential inhibitor of NDH-2 of S. aureus. The objective of this study was to evaluate the inhibitory properties of myricetin against NDH-2 and its impact on the growth and expression of virulence factors in S. aureus. Results: A screening method was established to identify effective inhibitors of NDH-2, based on heterologously expressed S. aureus NDH-2. Myricetin was found to be an effective inhibitor of NDH-2 with a half maximal inhibitory concentration (IC50) of 2 μM. In silico predictions and enzyme inhibition kinetics further characterized myricetin as a competitive inhibitor of NDH-2 with respect to the substrate menadione (MK). The minimum inhibitory concentrations (MICs) of myricetin against S. aureus strains ranged from 64 to 128 μg/mL. Time–kill assays showed that myricetin was a bactericidal agent against S. aureus. In line with being a competitive inhibitor of the NDH-2 substrate MK, the anti-staphylococcal activity of myricetin was antagonized by MK-4. In addition, myricetin was found to inhibit the gene expression of enterotoxin SeA and reduce the hemolytic activity induced by S. aureus culture on rabbit erythrocytes in a dose-dependent manner. Conclusions: Myricetin was newly discovered to be a competitive inhibitor of S. aureus NDH-2 in relation to the substrate MK. This discovery offers a fresh perspective on the anti-staphylococcal activity of myricetin. [ABSTRACT FROM AUTHOR]

One of the important monitoring indicators of the air pollution is atmospheric fine particulate matter (PM2.5), which can induce lung inflammation after inhalation. Coelonin can alleviate PM2.5‐induced macrophage damage through anti‐inflammation. However, its molecular mechanism remains unclear. We hypothesized that macrophage damage may involve the release of inflammatory cytokines, activation of inflammatory pathways, and pyrosis induced by inflammasome. In this study, we evaluated the anti‐inflammation activity of coelonin in PM2.5‐induced macrophage and its mechanism of action. Nitric oxide (NO) and reactive oxygen species (ROS) production were measured by NO Assay kit and dichlorofluorescein‐diacetate (DCFH‐DA), and apoptosis were measured by Flow cytometry and TUNEL staining. The concentration of inflammatory cytokines production was measured with cytometric bead arrays and ELISA kits. The activation of NF‐κB signaling pathway and NLRP3 inflammasome were measured by immunofluorescence, quantitative reverse transcription‐polymerase chain reaction and western blot. As expected, coelonin pretreatment reduced NO production significantly as well as alleviated cell damage by decreasing ROS and apoptosis. It decreased generation of interleukin (IL)‐6 and tumor necrosis factor (TNF)‐α in PM2.5‐induced RAW264.7 and J774A.1 cells. Moreover, coelonin markedly inhibited upregulating the expression of toll‐like receptor (TLR)4 and cyclo‐oxygenase (COX)‐2, blocked activation of p‐nuclear factor‐kappa B (NF‐κB) signaling pathway, and suppressed expression of NLRP3 inflammasome, ASC, GSDMD, IL‐18 and IL‐1β. In conclusion, the results showed that coelonin could protect against PM2.5‐induced macrophage damage via suppressing TLR4/NF‐κB/COX‐2 signaling pathway and NLRP3 inflammasome activation in vitro. [ABSTRACT FROM AUTHOR]

Abstract Background Pelgipeptin, a potent antibacterial and antifungal agent, is a non-ribosomally synthesised lipopeptide antibiotic. This compound consists of a β-hydroxy fatty acid and nine amino acids. To date, there is no information about its biosynthetic pathway. Results A potential pelgipeptin synthetase gene cluster (plp) was identified from Paenibacillus elgii B69 through genome analysis. The gene cluster spans 40.8 kb with eight open reading frames. Among the genes in this cluster, three large genes, plpD, plpE, and plpF, were shown to encode non-ribosomal peptide synthetases (NRPSs), with one, seven, and one module(s), respectively. Bioinformatic analysis of the substrate specificity of all nine adenylation domains indicated that the sequence of the NRPS modules is well collinear with the order of amino acids in pelgipeptin. Additional biochemical analysis of four recombinant adenylation domains (PlpD A1, PlpE A1, PlpE A3, and PlpF A1) provided further evidence that the plp gene cluster involved in pelgipeptin biosynthesis. Conclusions In this study, a gene cluster (plp) responsible for the biosynthesis of pelgipeptin was identified from the genome sequence of Paenibacillus elgii B69. The identification of the plp gene cluster provides an opportunity to develop novel lipopeptide antibiotics by genetic engineering.

New classes of antibiotics with different mechanisms of action are urgently required for combating antimicrobial resistance. Blestriacin, a dihydro-biphenanthrene with significant antibacterial activity, was recently isolated from the fibrous roots of Bletilla striata. Here, we report the further characterization of the antimicrobial potential and mode of action of blestriacin. The phenanthrene compound inhibited the growth of all tested clinical isolates of Staphylococcus aureus including methicillin-resistant S. aureus (MRSA). The minimum inhibitory concentrations (MICs) of blestriacin against these pathogens ranged from 2 to 8 μg/mL. Minimum bactericidal concentration (MBC) tests were conducted, and the results demonstrated that blestriacin was bactericidal against S. aureus. This effect was confirmed by the time-kill assays. At bactericidal concentrations, blestriacin caused loss of membrane potential in B. subtilis and S. aureus and disrupted the bacterial membrane integrity of the two strains. The spontaneous mutation frequency of S. aureus to blestriacin was determined to be lower than 10-9. The selection and whole genome sequencing of the blestriacin –resistant mutants of S. aureus indicated that the development of blestriacin resistance in S. aureus involves mutations in multi-genes. All these observations can be rationalized by the suggestion that membrane is a biological target of blestriacin. [ABSTRACT FROM AUTHOR]

In a project aiming to isolate strains with the ability to produce nonribosomal peptides, a Gram-negative, endospore-forming, rod-shaped strain, designated B5T, was isolated from a soil sample collected from Tianmu Mountain national natural reserve in Hangzhou, China. Strain B5T contained meso-diaminopimelic acid in the cell wall peptidoglycan. The major cellular fatty acids were anteiso-C15:0 and iso-C15:0. The DNA G+C content was 42.5 mol%. The phylogenetic analysis based on 16S rRNA gene sequence indicated that strain B5T fell within the genus Bacillus, with highest sequence similarity values to Bacillus barbaricus DSM 14730T (96.4%) and Bacillus macauensis JCM 13285T (95.5%). The isolate, however, could be distinguished from Bacillus strains with validly published names by low 16S rRNA gene sequence similarity values, distinct phenotypic and chemotaxonomic characteristics. On the basis of these polyphasic evidences, it is demonstrated that the isolate B5T represents a novel species of the genus Bacillus, for which the name Bacillus tianmuensis sp. nov. is proposed. The type strain is B5T (=DSM 22111T=CGMCC 1.8879T). [ABSTRACT FROM AUTHOR]

Importance: The use of plant extracts is increasing as an alternative to synthetic compounds, especially antibiotics. However, there is no sufficient knowledge on the mechanisms and potential risks of antibiotic resistance induced by these phytochemicals. In the present study, we found that stable drug resistant mutants of E. coli emerged after repetitive exposure to sanguinarine and demonstrated that the AcrB efflux pump contributed to the emerging of induced and intrinsic resistance of E. coli to this phytochemical. Our results offered some insights into comprehending and preventing the onset of drug-resistant strains when utilizing products containing sanguinarine., Competing Interests: The authors declare no conflict of interest.

One of the important monitoring indicators of the air pollution is atmospheric fine particulate matter (PM 2.5 ), which can induce lung inflammation after inhalation. Coelonin can alleviate PM 2.5 -induced macrophage damage through anti-inflammation. However, its molecular mechanism remains unclear. We hypothesized that macrophage damage may involve the release of inflammatory cytokines, activation of inflammatory pathways, and pyrosis induced by inflammasome. In this study, we evaluated the anti-inflammation activity of coelonin in PM 2.5 -induced macrophage and its mechanism of action. Nitric oxide (NO) and reactive oxygen species (ROS) production were measured by NO Assay kit and dichlorofluorescein-diacetate (DCFH-DA), and apoptosis were measured by Flow cytometry and TUNEL staining. The concentration of inflammatory cytokines production was measured with cytometric bead arrays and ELISA kits. The activation of NF-κB signaling pathway and NLRP3 inflammasome were measured by immunofluorescence, quantitative reverse transcription-polymerase chain reaction and western blot. As expected, coelonin pretreatment reduced NO production significantly as well as alleviated cell damage by decreasing ROS and apoptosis. It decreased generation of interleukin (IL)-6 and tumor necrosis factor (TNF)-α in PM 2.5 -induced RAW264.7 and J774A.1 cells. Moreover, coelonin markedly inhibited upregulating the expression of toll-like receptor (TLR)4 and cyclo-oxygenase (COX)-2, blocked activation of p-nuclear factor-kappa B (NF-κB) signaling pathway, and suppressed expression of NLRP3 inflammasome, ASC, GSDMD, IL-18 and IL-1β. In conclusion, the results showed that coelonin could protect against PM 2.5 -induced macrophage damage via suppressing TLR4/NF-κB/COX-2 signaling pathway and NLRP3 inflammasome activation in vitro., (© 2023 Wiley Periodicals LLC.)

Objective: To investigate the chemical constituents isolated from the fibrous roots of Bletilla striata, and to research their antibacterial activities., Methods: The native products were isolated and purified by silica gel, Sephadex LH-20 column chromatography and preparative HPLC. Their structures were elucidated on the basis of various spectroscopic analysis, and their antibacterial activities were tested by microbroth dilution method in a 96-well microtiter plate., Results: Seven compounds were isolated from the ethanol extract of the fibrous roots of Bletilla striata, and identified as p-hydroxybenzaldehyde( 1),2,7-dihydroxy-4-methoxy-9,10-dihydrophenanthrene( 2),4,5-dihydroxy-2-methoxy-9,10-dihydrohenanthrpene( 3),2-dihydroxy-4,7-dimethoxyphenan-threne( 4), militarine( 5), dactylorhin A( 6) and gastrodin( 7). Among them, compounds 2 ~ 4 showed moderate antibacterial activities against several Gram-positive bacterial strains( MIC 8 ~ 128 μg / m L),such as Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis and Bacillus subtilis., Conclusion: The fibrous roots and tubers of Bletilla striata contain similar compounds, including glucosyloxybenzyl 2-isobutylmalates,and phenanthrene compounds, which showed antimicrobial activities against Gram-positive bacterial strains. And compounds 3,4 are isolated from Bletilla genus for the first time.

The main factors which affected the isolation, purification and cultivation of Pinellia cordata protoplasts from leaves were studied. The results indicated that the optimum enzyme solution for P. cordata leaves was 13% CPW + 1.0% Cellulose +0.1% Pectolase, at pH 6.0, temperature (25-28 degrees C ) for 4 h. The sucrose density gradient centrifugation was adopted to purificate the protoplasts collected, when 25% sucrose was used as mediator, centrifugating at 500 rpm for 10 min. When the protoplasts were shallow liquid and liquid-solid double layer cultured on the medium of MS + 0.5 mg x L(-1) 6-BA + 0.25 mg x L(-1) NAA + 13% mannitol at the density of 2.5 x 104 protoplasts/mL, or fed and nursed cultured at the density of 100-500 protoplasts/mL, cell division could be observed for 3 days; granular calli appeared for 30 days. Calli was proliferated on the medium of MS + 0.5 mg x L(-1) 6-BA + 0.25 mg x L(-1) NAA solidified by 0.55% agar, and differentiated and regenerated after 5-6 months. Plant generation of P. cordata is successfully established.

The coiled-coil neck domain of pulmonary surfactant protein D (SP-D) is required for trimeric association and the subsequent assembly of functional dodecamers of SP-D. It is also necessary and sufficient for trimerization of a heterologous collagen sequence. To investigate whether it is capable of driving trimerization of heterologous non-collagenous proteins, we expressed and purified a fusion of a heterologous non-collagenous sequence (thioredoxin) to the coiled-coil neck domain of human SP-D here. While western blot analysis detected a small population of stable trimers of the fusion protein, chemical cross-linking and SEC-HPLC indicated that the fusion protein was predominantly a trimer. In contrast, purified thioredoxin without the fusion was found only as monomers and dimers. We also measured the thermal stabilities (with circular dichroism) and degradation rates of these two proteins. Our data showed that the fusion protein had a melting temperature that was 13 K higher than that of thioredoxin and a longer degradation half life than thioredoxin. Our findings indicate that the coiled-coil neck domain of SP-D enables the trimerization and stabilization of the heterologous non-collagenous thioredoxin. It may provide new clues for further study on the application of this human original coiled-coil domain in protein engineering to construct trimeric functional fusion proteins.

A new antagonistic strain of actinomycete, designated AP19-2, was isolated from the feces of giant pandas inhabiting the Foping National Nature Reserve in China. Cultural characteristic studies strongly suggested that this strain is a member of the genus Streptomyces. The nucleotide sequence of the 16S rRNA gene of strain AP19-2 evidenced profound similarity (97-99%) with other Streptomyces strains. Two pure active molecules were isolated from a fermentation broth of Streptomyces sp. strain AP19-2 via extraction, concentration, silica gel G column chromatography, and HPLC. The chemical structures of the two related compounds (referred to as chromomycin A2 and chromomycin A3) were established on the basis of their Infrared spectra (IR), High Resolution Electrospray Ionization Mass Spectrometry (HR-ESI-MS), and Nuclear Magnetic Resonance (NMR) data, and by comparison with published data.