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1.
J Nat Prod ; 83(1): 111-117, 2020 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-31904958

RESUMO

Seven new trialkyl-substituted benzene derivatives named benwamycins A-G (1-7), together with three known congeners, 8-10, were isolated from culture broth of the soil-derived Streptomyces sp. KIB-H1471. Their structures were elucidated by using 1D and 2D NMR analyses in combination with HRESIMS data. The absolute configurations of 1-9 were determined by chemical conversion and comparison of circular dichroism spectra and confirmed for 1 by single-crystal X-ray crystallography. Compounds 6 and 7 have a unique γ-pyrone-like ring on one side chain. Compounds 2 and 6 inhibited human T cell proliferation with IC50 values of 14.3 and 12.5 µM, respectively, without obvious cytotoxicity for naïve human T cells. Compounds 3 and 6 could weakly enhance insulin-stimulated glucose uptake.

2.
Huan Jing Ke Xue ; 40(10): 4685-4690, 2019 Oct 08.
Artigo em Chinês | MEDLINE | ID: mdl-31854839

RESUMO

Antibiotic resistance genes (ARGs) are considered to be emerging environmental contaminants. ARGs are frequently detected in municipal solid waste landfill and its leachate. In this study, high-throughput quantitative PCR techniques were used to investigate the dynamics of ARGs during the treatment process of landfill leachate. The results showed that ARGs in leachate were diverse and abundant, and leachate treatment could effectively reduce their abundance; the absolute abundance of ARGs was reduced to 9.2×1010 copies·L-1, which was five orders of magnitude less than the abundance of the influent. However, the range and abundance of antibiotic resistance genes in the leachate effluents were still high compared to the natural environment. Therefore, the secondary contamination of ARGs might be caused by leachate being directly discharged into municipal sewage system. In this regard, ecological and environmental risk is an inconvenient truth. Furthermore, strong correlations indicate that heavy metals and mobile genetic elements (MGEs) in landfill leachate might influence the transfer of ARGs.


Assuntos
Antibacterianos , Resistência Microbiana a Medicamentos , Resíduos Sólidos , Poluentes Químicos da Água , Bactérias/genética , Resistência Microbiana a Medicamentos/genética , Genes Bacterianos , Instalações de Eliminação de Resíduos
3.
Food Funct ; 10(10): 6568-6581, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31552989

RESUMO

Formation of a gel matrix, involving interactions between proteins, lipids, and water, plays an essential role in the textural properties of processed meats. This study investigated the effects of sodium pyrophosphate (SPP) on the textural properties and oxidative stability of myofibrillar protein (MP)-stabilized emulsion gels under different pH conditions (5.0-9.0). The SPP-modified MP emulsion gels showed an improved elasticity, strength, water-holding capacity, and oxidative stability at pH 6.0 and 7.0. This improvement should be mainly attributed to the enhanced protein-protein crosslinks via ionic interaction between phosphate groups and -NH3+ of amino acids, which were homogeneously formed among adsorbed and/or unadsorbed proteins, entrapping fractions of MPs (myosin heavy chain, actin, and troponin T) within the network. Therefore, the oil droplets were better adherent to the gel matrix. Nevertheless, increased electrostatic repulsion between protein molecules due to excessive phosphates attached to MPs at pH 8.0 and 9.0, as well as protein precipitation at pH 5.0, caused the collapse of the MP-stabilized emulsion gel structure, and thus, overall decreased the gel properties and oxidative stability. LC-MS/MS results confirmed that phosphate groups were successfully introduced to MPs through C-O-P bonds at pH 6.0, and the phosphorylation sites were found to be on serine residues (Ser14, Ser79, Ser96, Ser148, Ser2427, and Ser5272), threonine residues (Thr118 and Thr926), and tyrosine residues (Tyr215 and Tyr425). The results provided a new aspect for better understanding the effect of polyphosphates in meat protein/oil composite systems.

4.
Nat Commun ; 10(1): 4036, 2019 09 06.
Artigo em Inglês | MEDLINE | ID: mdl-31492848

RESUMO

The skeleton of tropane alkaloids is derived from ornithine-derived N-methylpyrrolinium and two malonyl-CoA units. The enzymatic mechanism that connects N-methylpyrrolinium and malonyl-CoA units remains unknown. Here, we report the characterization of three pyrrolidine ketide synthases (PYKS), AaPYKS, DsPYKS, and AbPYKS, from three different hyoscyamine- and scopolamine-producing plants. By examining the crystal structure and biochemical activity of AaPYKS, we show that the reaction mechanism involves PYKS-mediated malonyl-CoA condensation to generate a 3-oxo-glutaric acid intermediate that can undergo non-enzymatic Mannich-like condensation with N-methylpyrrolinium to yield the racemic 4-(1-methyl-2-pyrrolidinyl)-3-oxobutanoic acid. This study therefore provides a long sought-after biosynthetic mechanism to explain condensation between N-methylpyrrolinium and acetate units and, more importantly, identifies an unusual plant type III polyketide synthase that can only catalyze one round of malonyl-CoA condensation.


Assuntos
Malonil Coenzima A/metabolismo , Proteínas de Plantas/metabolismo , Policetídeo Sintases/metabolismo , Pirróis/metabolismo , Alcaloides de Solanáceas/metabolismo , Tropanos/metabolismo , Sequência de Aminoácidos , Biocatálise , Cromatografia Líquida/métodos , Cristalografia por Raios X , Malonil Coenzima A/química , Modelos Químicos , Estrutura Molecular , Filogenia , Proteínas de Plantas/classificação , Proteínas de Plantas/genética , Policetídeo Sintases/química , Policetídeo Sintases/genética , Pirróis/química , Homologia de Sequência de Aminoácidos , Alcaloides de Solanáceas/química , Espectrometria de Massas em Tandem/métodos , Tropanos/química
5.
Sensors (Basel) ; 19(6)2019 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-30889902

RESUMO

Traditional industry is seeing an increasing demand for more autonomous and flexible manufacturing in unstructured settings, a shift away from the fixed, isolated workspaces where robots perform predefined actions repetitively. This work presents a case study in which a robotic manipulator, namely a KUKA KR90 R3100, is provided with smart sensing capabilities such as vision and adaptive reasoning for real-time collision avoidance and online path planning in dynamically-changing environments. A machine vision module based on low-cost cameras and color detection in the hue, saturation, value (HSV) space is developed to make the robot aware of its changing environment. Therefore, this vision allows the detection and localization of a randomly moving obstacle. Path correction to avoid collision avoidance for such obstacles with robotic manipulator is achieved by exploiting an adaptive path planning module along with a dedicated robot control module, where the three modules run simultaneously. These sensing/smart capabilities allow the smooth interactions between the robot and its dynamic environment, where the robot needs to react to dynamic changes through autonomous thinking and reasoning with the reaction times below the average human reaction time. The experimental results demonstrate that effective human-robot and robot-robot interactions can be realized through the innovative integration of emerging sensing techniques, efficient planning algorithms and systematic designs.

6.
Environ Toxicol Chem ; 38(4): 760-768, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30657202

RESUMO

Organophosphate flame retardants (OPFRs) have been found in human samples and associated with adverse health effects. In the present study, OPFR and dialkyl and diaryl phosphate (DAP) concentrations in human urine were determined and differences in the concentrations in urine from males and females were investigated. Urine samples from 22 male and 26 female university students, paired dust samples from the dormitories (13 each for males and females), and 10 dust samples from university teaching buildings were analyzed. The tri-o-cresyl phosphate (TOCP), tri-p-cresyl phosphate (TPCP), and tris(2-chloroisopropyl)phosphate (TCIPP) concentrations were significantly higher (p = 0.049, 0.023, and 0.027, respectively) in urine from the female students than in urine from the male students. Similar differences were found between males and females in terms of OPFR exposure and OPFR concentrations in urine for three-fourths of the OPFRs. Questionnaire answers and calculations indicated that disparities in OPFR concentrations in urine were mainly caused by females spending much more time than males in dormitories. Organophosphate flame retardants may pose degrees of health risk similar to those of polybrominated diphenyl ethers (PBDEs), and this must be considered when making decisions about controlling flame retardants. We are not aware of any previous studies that simultaneously monitor OPFRs and DAPs in human urine in China. Environ Toxicol Chem 2019;38:760-768. © 2019 SETAC.

7.
Nat Prod Res ; 33(2): 219-225, 2019 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29495881

RESUMO

Actinomycin Z6 (1), a new member of the actinomycin family, along with three congeners of the Z-type (Z1, Z3, Z5) actinomycins, are produced from Streptomyces sp. KIB-H714. Their structures were authenticated by comprehensive spectroscopic data interpretation. Different from all the reported Z-type actinomycins, the ß-ring of the new compound actinomycin Z6 includes an additional ring linked between the actinoyl chromophore and ß-peptidolactone. In Z3 and Z5, the L-threonine in ß-depsipeptide is replaced by the unusual 4-chlorothreonine, an amino acid rarely found in actinomycin family. All isolates were evaluated for cytotoxicity against five human tumor cell lines and for inhibitory activity against Candida albicans and Staphylococcus aureus.


Assuntos
Anti-Infecciosos/farmacologia , Antineoplásicos/farmacologia , Dactinomicina/análogos & derivados , Dactinomicina/farmacologia , Streptomyces/química , Anti-Infecciosos/química , Antineoplásicos/química , Candida albicans/efeitos dos fármacos , Linhagem Celular Tumoral , Dactinomicina/química , Avaliação Pré-Clínica de Medicamentos/métodos , Humanos , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Oxigênio/química , Espectrometria de Massas por Ionização por Electrospray , Staphylococcus aureus/efeitos dos fármacos , Relação Estrutura-Atividade , Treonina/análogos & derivados , Treonina/química
8.
Org Biomol Chem ; 17(3): 477-481, 2019 01 16.
Artigo em Inglês | MEDLINE | ID: mdl-30565634

RESUMO

Toxoflavin (1), fervenulin (2), and reumycin (3), known to be produced by plant pathogen Burkholderia glumae BGR1, are structurally related 7-azapteridine antibiotics. Previous biosynthetic studies revealed that N-methyltransferase ToxA from B. glumae BGR1 catalyzed the sequential methylation at N6 and N1 in pyrimido[5,4-e]-as-triazine-5,7(6H,8H)-dione (4) to generate 1. However, the N8 methylation of 4 in the biosynthesis of fervenulin remains unclear. To explore the N-methyltransferases required for the biosynthesis of 1 and 2, we identified and characterized the fervenulin and toxoflavin biosynthetic gene clusters in S. hiroshimensis ATCC53615. On the basis of the structures of intermediates accumulated from the four N-methyltransferase gene inactivation mutants and systematic enzymatic methylation reactions, the tailoring steps for the methylation order in the biosynthesis of 1 and 2 were proposed. The N-methylation order and routes for the biosynthesis of fervenulin and toxoflavin in S. hiroshimensis are more complex and represent an obvious departure from those in B. glumae BGR1.


Assuntos
Metiltransferases/metabolismo , Pirimidinonas/metabolismo , Streptomyces/metabolismo , Triazinas/metabolismo , Biocatálise , Relação Dose-Resposta a Droga , Metiltransferases/química , Estrutura Molecular , Pirimidinonas/química , Streptomyces/química , Streptomyces/enzimologia , Relação Estrutura-Atividade , Triazinas/química
9.
J Antibiot (Tokyo) ; 71(12): 1040-1043, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30218038

RESUMO

Chemical investigation of a strain Streptomyces sp. KIB-H1318 isolated from soil sample led to the discovery of three new phenoxazinone-related alkaloids 1-3, as well as two known analogs exfoliazone (4) and viridobrunnine A (5). Their structures were determined on the basis of extensive spectroscopic analysis. The antimicrobial activity and cytotoxicity of the isolates were assayed. Exfoliazone and viridobrunnine A exhibited minor antibacterial activity against Escherichia coli ATCC 8099, Bacillus subtilis ATCC 6633, and Staphylococcus aureus ATCC 6538. Compound 2 exhibited low cytotoxicity against two human cancer cell lines HeLa and SW480 with the IC50 values of 36.8 and 37.8 µM, respectively.


Assuntos
Alcaloides/química , Oxazinas/química , Streptomyces/química , Alcaloides/isolamento & purificação , Antibacterianos/isolamento & purificação , Antibacterianos/farmacologia , Antineoplásicos/química , Antineoplásicos/isolamento & purificação , Bacillus subtilis/efeitos dos fármacos , Linhagem Celular Tumoral , Escherichia coli/efeitos dos fármacos , Humanos , Testes de Sensibilidade Microbiana , Oxazinas/isolamento & purificação , Staphylococcus aureus/efeitos dos fármacos
10.
Chemosphere ; 205: 71-79, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29684693

RESUMO

Brominated flame retardants (BFRs) can accumulate in humans and are associated with adverse health effects. The study was conducted to determine the differences in Polybrominated diphenyl ethers (PBDEs) and alternative brominated flame retardant (Alt-BFR) concentrations between men and women. We analyzed hair samples from 14 male and 20 female university students, paired dust samples from their dormitories (10 for males and 8 for females), and six dust samples from university teaching buildings. The total PBDE concentrations in hair from females were significantly (three times) higher (p = 0.012) than that from males (means 372 and 109 ng/g, respectively). The mean total PBDE concentrations in classroom and dormitory dust were 36100 and 2012 ng/g, respectively. The PBDE patterns were different in the male and female hair samples, as were the patterns in the classroom and dormitory dust. There are no reports concerning human exposure to BFRs through dust that was assessed considering academic and residential environments simultaneously. The differences between BFR exposure for males and females and the differences between BFR concentrations in hair samples from males and females were consistent for 71.4% of the compounds. However, using only dormitory dust in the calculations gave consistent differences only for 28.6% of the compounds, suggesting that the BFR concentration differences in hair were mainly because females spent much more time than males in classrooms.


Assuntos
Poluição do Ar em Ambientes Fechados/análise , Poeira/análise , Exposição Ambiental/análise , Retardadores de Chama/análise , Cabelo/química , Éteres Difenil Halogenados/análise , Feminino , Humanos , Masculino
11.
J Antibiot (Tokyo) ; 71(7): 672-676, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29651143

RESUMO

Two new glycosylated piericidins, glucopiericidinol A3 (1) and 7-demethyl-glucopiericidin A (2), along with four known analogs were isolated from the culture broth of Streptomyces sp. KIB-H1083. The chemical structures of new compounds were elucidated by spectroscopic analyses. Their cytotoxicity on HL-60, SMMC-772, A-549, MCF-7, and SW480 cell lines, as well as antimicrobial activities was evaluated. The results showed that glucopiericidin A (4) has potent cytotoxicity against HL-60, SMMC-772, A-549, and MCF-7 cell lines with IC50 values of 0.34, 0.65, 0.60, and 0.50 µM, respectively. For the antimicrobial activity, piericidin A (6) showed most powerful inhibitory activities against Xanthomonas oryzae pv. oryzicola, and Penicillium decumbens.


Assuntos
Antibacterianos/isolamento & purificação , Antibacterianos/farmacologia , Streptomyces/química , Antibióticos Antineoplásicos/isolamento & purificação , Antibióticos Antineoplásicos/farmacologia , Antifúngicos/isolamento & purificação , Antifúngicos/farmacologia , Linhagem Celular Tumoral , Endófitos/química , Fermentação , Humanos , Espectroscopia de Ressonância Magnética , Testes de Sensibilidade Microbiana , Penicillium/efeitos dos fármacos , Xanthomonas/efeitos dos fármacos
12.
J Nat Prod ; 80(10): 2615-2619, 2017 10 27.
Artigo em Inglês | MEDLINE | ID: mdl-28990780

RESUMO

Our natural products discovery program utilizes endophytic actinomycetes associated with plants and employs biological assays and HPLC-based metabolite profiles as the preliminary screen to identify strains of interest, followed by large-scale fermentation and isolation, leading to new and/or bioactive natural products. Six new trialkyl-substituted aromatic acids, namely, lorneic acids E-J (1-6), together with two known analogues (7 and 8), were isolated and identified from the culture extract of Streptomyces sp. KIB-H1289, an endophytic actinomycete obtained from the inner tissue of the bark of Betula mandshurica Nakai. The structures were characterized by interpretation of their spectroscopic data, mainly 1D and 2D NMR. Among them, compound 5 contains a unique disulfide bond that is presumably derived from N-acetylcysteine. All isolated metabolites were evaluated for their inhibitory activity on tyrosinase.


Assuntos
Actinobacteria/química , Derivados de Benzeno/isolamento & purificação , Acetilcisteína/metabolismo , Derivados de Benzeno/química , Betula/microbiologia , Produtos Biológicos/química , Produtos Biológicos/isolamento & purificação , Cromatografia Líquida de Alta Pressão , Endófitos/química , Estrutura Molecular , Monofenol Mono-Oxigenase/antagonistas & inibidores , Ressonância Magnética Nuclear Biomolecular , Casca de Planta/química , Streptomyces/química
13.
Org Lett ; 19(14): 3911-3914, 2017 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-28703597

RESUMO

Euphordraculoates A (1) and B (2), featuring tigliane diterpenoids with two new carbon skeletons, were characterized as metabolites of Euphorbia dracunculoides and semisynthetic products, respectively. Their structures were determined by spectroscopic analyses and X-ray crystallography. The respective biosynthetic and chemical formation mechanisms for 1 and 2 from a known tigliane 3 was proposed. The detailed decarbonization mechanism from 3 to 2 was further explored by 18O-labeling experiment. Compound 2 could inhibit Wnt pathway in a dose- and time-dependent manner.


Assuntos
Euphorbia/química , Carbono , Diterpenos , Estrutura Molecular , Isótopos de Oxigênio , Via de Sinalização Wnt
14.
Nat Prod Bioprospect ; 7(4): 329-334, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28634711

RESUMO

Tamoxifen resistance (TamR) is the underlying cause of treatment failure in many breast cancer patients receiving tamoxifen. In order to look for noncytotoxic natural products with the ability to reverse TamR, an extract from strain Streptomyces sp. KIB-H0495 was detected to be active. Subsequent large scale fermentation and isolation led to the isolation of four α-pyrone derivatives including two new compounds, violapyrones J (2) and K (3), and two known analogues, violapyrones B (1) and I (4). Further bioactivity assays indicated that only 1 and 3 exerted potent resensitization effects on MCF-7/TamR cells at a concentration of 1 µM. Owing to the simple structures of 1 and 3, these two compounds might have potential for further investigation as novel tamoxifen resensitization agent in breast cancer chemotherapy.

15.
J Hazard Mater ; 321: 47-53, 2017 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-27607932

RESUMO

Lab scale and single stage high solid anaerobic digestion of sewage sludge spiked with freshly synthesized nanoscale zero valent iron (nZVI) and commercial iron powder (IP) under mesophilic condition (37±1°C) was performed. The effects of both additives on methane yield, and pharmaceutical and personal care product (PPCP) removal were investigated. Results showed that methane yield was increased by 25.2% and 40.8% in the presence of nZVI (0.1%) and IP (1.6%), respectively. Removal efficiencies of chemical oxygen demand were 54.4% and 66.2% in the presence of nZVI and IP, respectively, which were higher compared to the control group (44.6%). In addition, most PPCPs could be partly or completely removed during the anaerobic digestion process. The application of nZVI and IP showed positive impact on the removal of chlorinated PPCPs (p<0.05), but did not show significant impact on other PPCPs (p>0.05). Our finding suggests that the application of nZVI and IP in anaerobic digestion could be a promising way to enhance methane yield but had less improvement on PPCP degradation.


Assuntos
Cosméticos/análise , Ferro/química , Metano/biossíntese , Nanopartículas/química , Preparações Farmacêuticas/análise , Esgotos , Poluentes Químicos da Água/análise , Bactérias Anaeróbias/metabolismo , Reatores Biológicos/microbiologia , Pós , Esgotos/química , Esgotos/microbiologia , Purificação da Água/métodos
16.
Nat Commun ; 7: 13083, 2016 10 07.
Artigo em Inglês | MEDLINE | ID: mdl-27713400

RESUMO

The pyridine ring is a potent pharmacophore in alkaloid natural products. Nonetheless, its biosynthetic pathways are poorly understood. Rubrolones A and B are tropolone alkaloid natural products possessing a unique tetra-substituted pyridine moiety. Here, we report the gene cluster and propose a biosynthetic pathway for rubrolones, identifying a key intermediate that accumulates upon inactivation of sugar biosynthetic genes. Critically, this intermediate was converted to the aglycones of rubrolones by non-enzymatic condensation and cyclization with either ammonia or anthranilic acid to generate the respective pyridine rings. We propose that this non-enzymatic reaction occurs via hydrolysis of the key intermediate, which possesses a 1,5-dione moiety as an amine acceptor capable of cyclization. This study suggests that 1,5-dione moieties may represent a general strategy for pyridine ring biosynthesis, and more broadly highlights the utility of non-enzymatic diversification for exploring and expanding natural product chemical space.


Assuntos
Alcaloides/biossíntese , Piridinas/metabolismo , Streptomyces/metabolismo , Aminação , Genes Bacterianos , Família Multigênica , Oxirredução , Streptomyces/genética , ortoaminobenzoatos/metabolismo
17.
Aquat Toxicol ; 176: 10-23, 2016 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-27104239

RESUMO

In this study, the effect of environmental metal exposure on the accumulation and subcellular distribution of metals in the digestive gland of clams with special emphasis on metallothioneins (MTs) was investigated. Specimens of indigenous Moerella iridescens were collected from different natural habitats in Maluan Bay (China), characterized by varying levels of metal contamination. The digestive glands were excised, homogenized and six subcellular fractions were separated by differential centrifugation procedures and analyzed for their Cu, Zn, Cd and Pb contents. MTs were quantified independently by spectrophotometric measurements of thiols. Site-specific differences were observed in total metal concentrations in the tissues, correlating well with variable environmental metal concentrations and reflecting the gradient trends in metal contamination. Concentrations of the non-essential Cd and Pb were more responsive to environmental exposure gradients than were tissue concentrations of the essential metals, Cu and Zn. Subcellular partitioning profiles for Cu, Zn and Cd were relatively similar, with the heat-stable protein (HSP) fraction as the dominant metal-binding compartment, whereas for Pb this fraction was much less important. The variations in proportions and concentrations of metals in this fraction along with the metal bioaccumulation gradients suggested that the induced MTs play an important role in metal homeostasis and detoxification for M. iridescens in the metal-contaminated bay. Nevertheless, progressive accumulation of non-essential metals (Cd, and especially Pb) resulting from "spillover" was observed in putative metal- sensitive (e.g., mitochondria and heat-denaturable protein (HDP)) or lysosome/microsome fractions, demonstrating that metal detoxification was incomplete and increased the toxicological risk to M. iridescens inhabiting the metal-impacted environments. Through multiple stepwise regression analysis, the induction of MTs was statistically correlated with the HSP concentrations of Cu, and to a lesser extent with Zn, and ultimately to the Cd concentrations, exhibiting significant dose-dependent relationships. Overall, these findings not only revealed the fates of accumulated metals, but scientifically favored an improved understanding of the detoxification at the subcellular level in response to metal accumulation, supporting the focus of metabolic availability assessment on the intracellular processes or events occurring within organisms.


Assuntos
Bivalves/efeitos dos fármacos , Metalotioneína/metabolismo , Metais/toxicidade , Poluentes Químicos da Água/toxicidade , Animais , Baías , Bivalves/metabolismo , Exposição Ambiental , Sedimentos Geológicos/análise , Metais/análise , Metais/química , Espectrofotometria , Poluentes Químicos da Água/química
18.
Org Lett ; 18(6): 1254-7, 2016 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-26926531

RESUMO

Rubrolones are tropolonoid natural products with a unique carbon skeleton. Extensive secondary metabolite analysis of the endophytic Streptomyces sp. KIB-H033 revealed a new class of rubrolone analogue possessing a rare benzoic acid-pyridine inner salt moiety. Precursor feeding with [(13)C]-acetate revealed a labeling pattern consistent with tropolone moiety construction via type-II PKS chemistry followed by complex oxidative rearrangements. This bacterial biosynthetic route represents a surprising departure from fungal tropolone assembly during stipitatic acid biosynthesis.


Assuntos
Produtos Biológicos/síntese química , Piridinas/síntese química , Streptomyces/química , Alcaloides/metabolismo , Produtos Biológicos/química , Cátions , Estrutura Molecular , Piridinas/química , Tropolona/análogos & derivados
19.
Appl Microbiol Biotechnol ; 100(5): 2267-77, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26552797

RESUMO

The glutarimide-containing polyketides represent a fascinating class of natural products that exhibit a multitude of biological activities. We have recently cloned and sequenced the biosynthetic gene clusters for three members of the glutarimide-containing polyketides-iso-migrastatin (iso-MGS) from Streptomyces platensis NRRL 18993, lactimidomycin (LTM) from Streptomyces amphibiosporus ATCC 53964, and cycloheximide (CHX) from Streptomyces sp. YIM56141. Comparative analysis of the three clusters identified mgsA and chxA, from the mgs and chx gene clusters, respectively, that were predicted to encode the PimR-like Streptomyces antibiotic regulatory proteins (SARPs) but failed to reveal any regulatory gene from the ltm gene cluster. Overexpression of mgsA or chxA in S. platensis NRRL 18993, Streptomyces sp. YIM56141 or SB11024, and a recombinant strain of Streptomyces coelicolor M145 carrying the intact mgs gene cluster has no significant effect on iso-MGS or CHX production, suggesting that MgsA or ChxA regulation may not be rate-limiting for iso-MGS and CHX production in these producers. In contrast, overexpression of mgsA or chxA in S. amphibiosporus ATCC 53964 resulted in a significant increase in LTM production, with LTM titer reaching 106 mg/L, which is five-fold higher than that of the wild-type strain. These results support MgsA and ChxA as members of the SARP family of positive regulators for the iso-MGS and CHX biosynthetic machinery and demonstrate the feasibility to improve glutarimide-containing polyketide production in Streptomyces strains by exploiting common regulators.


Assuntos
Antibacterianos/metabolismo , Expressão Gênica , Genes Reguladores , Macrolídeos/metabolismo , Piperidonas/metabolismo , Streptomyces/genética , Streptomyces/metabolismo
20.
Mar Pollut Bull ; 101(2): 707-15, 2015 Dec 30.
Artigo em Inglês | MEDLINE | ID: mdl-26481412

RESUMO

To investigate the impacts and processes of CO2-induced acidification on metal mobilization, laboratory-scale experiments were performed, simulating the scenarios where carbon dioxide was injected into sediment-seawater layers inside non-pressurized chambers. Coastal sediments were sampled from two sites with different contamination levels and subjected to pre-determined pH conditions. Sediment samples and overlying water were collected for metal analysis after 10-days. The results indicated that CO2-induced ocean acidification would provoke increased metal mobilization causing adverse side-effects on water quality. The mobility of metals from sediment to the overlying seawater was correlated with the reduction in pH. Results of sequential extractions of sediments illustrated that exchangeable metal forms were the dominant source of mobile metals. Collectively, our data revealed that high metal concentrations in overlying seawater released from contaminated sediments under acidic conditions may strengthen the existing contamination gradients in Maluan Bay and represent a potential risk to ecosystem health in coastal environments.


Assuntos
Dióxido de Carbono/química , Sedimentos Geológicos/química , Metais/química , Água do Mar/química , China , Ecossistema , Sedimentos Geológicos/análise , Concentração de Íons de Hidrogênio , Metais/análise , Oceanos e Mares , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Qualidade da Água
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