High-throughput screening for Streptomyces antibiotic biosynthesis activators

A genomic cosmid library of Streptomyces clavuligerus was constructed and transferred efficiently by conjugation to Streptomyces lividans, and 12 distinct groups of overlapping cosmid clones that activated the silent actinorhodin biosynthesis gene cluster were identified. This generally applicable high-throughput screening procedure greatly facilitates the identification of antibiotic biosynthesis activators.     

Karyology of the genus Faberia (Cichorieae–Asteraceae) and its systematic implications

Faberia Hemsl., a small genus of six species in the tribe Cichorieae, Asteraceae, has been karyologically investigated for the first time. All four studied species were revealed to have the somatic chromosome number 2n = 34, and thus the basic number of the genus was assumed to be x = 17. This rather high basic number has been previously reported very rarely in the tribe, occurring otherwise only in Warionia Benth. & Coss., a monospecific genus endemic to northwestern Africa, and in the American species of Lactuca L. The chromosome morphology was very similar among the four species, with the majority being median centromeric (m) and a few submedian centromeric (sm). In all the karyotypes the chromosomes were medium‐sized (6.33–1.61 μm), and showed a steady gradation in length from the longest to the shortest, with no evidence of bimodality. Our results strongly support the recognition of Faberia as an independent genus and the inclusion of Faberiopsis Shih & Y. L. Chen in Faberia.     

An ATP signalling pathway in plant cells: extracellular ATP triggers programmed cell death in Populus euphratica

We elucidated the extracellular ATP (eATP) signalling cascade active in programmed cell death (PCD) using cell cultures of Populus euphratica. Millimolar amounts of eATP induced a dose‐ and time‐dependent reduction in viability, and the agonist‐treated cells displayed hallmark features of PCD. eATP caused an elevation of cytosolic Ca²⁺ levels, resulting in Ca²⁺ uptake by the mitochondria and subsequent H₂O₂ accumulation. P. euphratica exhibited an increased mitochondrial transmembrane potential, and cytochrome c was released without opening of the permeability transition pore over the period of ATP stimulation. Moreover, the eATP‐induced increase of intracellular ATP, essential for the activation of caspase‐like proteases and subsequent PCD, was found to be related to increased mitochondrial transmembrane potential. NO is implicated as a downstream component of the cytosolic Ca²⁺ concentration but plays a negligible role in eATP‐stimulated cell death. We speculate that ATP binds purinoceptors in the plasma membrane, leading to the induction of downstream intermediate signals, as the proposed sequence of events in PCD signalling was terminated by the animal P2 receptor antagonist suramin.     

Modification of hydroxypropyl guar gum with ethanolamine

A new guar gum derivative containing amino group was synthesized through nucleophilic substitution of p-toluenesulfonate activated hydroxypropyl guar gum with ethanolamine. For the preparation of p-toluenesulfonate esters hydroxypropyl guar gum, the results showed that the reaction rate was optimal at 25°C and the reaction could reach equilibrium state when it was carried out for 10h at 25°C. For the nucleophilic substitution of tosyl group with ethanolamine, the reaction was completed after 10h reaction at 50°C. The structures of products were characterized by NMR and FT-IR spectroscopy. The results showed that the p-toluenesulfonate esters can be effectively substituted by ethanolamine to form the hydroxyethyl amino hydroxypropyl guar gum (EAHPG). The content of nitrogen of EAHPG was determined by acid-base titration and element analysis.     

Carboxymethyl chitin/organic rectorite composites based nanofibrous mats and their cell compatibility

In this study, carboxymethyl chitin (CMC) - organic rectorite (OREC)/poly (vinyl alcohol) (PVA) composite nanofibrous mats were successfully prepared via electrospinning. SAXRD pattern showed that the interlayer distance of OREC was increased from 3.68 to 4.08nm, which verified that polymer chains were intercalated into the interlayer of OREC. Field emission scanning electron microscopy, Fourier transform infrared spectra and energy-dispersive X-ray spectroscopy were used to characterize the morphology and microcosmic structure of nanofibrous mats. Thermal properties of mats were determined by differential scanning calorimetry. To evaluate the cell compatibility of mats, mouse lung fibroblast (L929) was chosen for cell attachment and spreading assay. The results shows that nanofibrous mats contained OREC have better thermal properties. Besides, the addition of OREC has little effect on the cell compatibility of nanofibrous mats.     

Network identification and flux quantification of glucose metabolism in Rhodobacter sphaeroides under photoheterotrophic H(2)-producing conditions

The nonsulfur purple bacteria that exhibit unusual metabolic versatility can produce hydrogen gas (H(2)) using the electrons derived from metabolism of organic compounds during photoheterotrophic growth. Here, based on (13)C tracer experiments, we identified the network of glucose metabolism and quantified intracellular carbon fluxes in Rhodobacter sphaeroides KD131 grown under H(2)-producing conditions. Moreover, we investigated how the intracellular fluxes in R. sphaeroides responded to knockout mutations in hydrogenase and poly-β-hydroxybutyrate synthase genes, which led to increased H(2) yield. The relative contribution of the Entner-Doudoroff pathway and Calvin-Benson-Bassham cycle to glucose metabolism differed significantly in hydrogenase-deficient mutants, and this flux change contributed to the increased formation of the redox equivalent NADH. Disruption of hydrogenase and poly-β-hydroxybutyrate synthase resulted in a significantly increased flux through the phosphoenolpyruvate carboxykinase and a reduced flux through the malic enzyme. A remarkable increase in the flux through the tricarboxylic acid cycle, a major NADH producer, was observed for the mutant strains. The in vivo regulation of the tricarboxylic acid cycle flux in photoheterotrophic R. sphaeroides was discussed based on the measurements of in vitro enzyme activities and intracellular concentrations of NADH and NAD(+). Overall, our results provide quantitative insights into how photoheterotrophic cells manipulate the metabolic network and redistribute intracellular fluxes to generate more electrons for increased H(2) production.     

Complete Genome Sequence of Bacillus thuringiensis Serovar Sichuansis Strain MC28

Bacillus thuringiensis is an important microbial insecticide used in the control of agricultural pests. Here we report the finished, annotated genome sequence of Bacillus thuringiensis serovar Sichuansis strain MC28, which can form parasporal crystals consisting of Cry4Cc1, Cry30Fa1, Cry53Ab1, Cry54Aa1, Cry54Ab1, Cry68Aa1, Cry69Aa1, Cry69Aa2, Cry70Ba1, Cyt1Da1, and Cyt2Aa3. It is also highly toxic to lepidopterous and dipterous insects.     

New mechanistic explanation for the localization of ulcers in the rat duodenum: role of iron and selective uptake of cysteamine

Cysteamine, a coenzyme A metabolite, induces duodenal ulcers in rodents. Our recent studies showed that ulcer formation was aggravated by iron overload and diminished in iron deficiency. We hypothesized that cysteamine is selectively taken up in the duodenal mucosa, where iron absorption primarily occurs, and is transported by a carrier-mediated process. Here we report that cysteamine administration in rats leads to cysteamine accumulation in the proximal duodenum, where the highest concentration of iron in the gastrointestinal tract is found. In vitro, iron loading of intestinal epithelial cells (IEC-6) accelerated reactive oxygen species (ROS) production and increased [(14)C]cysteamine uptake. [(14)C]Cysteamine uptake by isolated gastrointestinal mucosal cells and by IEC-6 was pH-dependent and inhibited by unlabeled cysteamine. The uptake of [(14)C]cysteamine by IEC-6 was Na(+)-independent, saturable, inhibited by structural analogs, H(2)-histamine receptor antagonists, and organic cation transporter (OCT) inhibitors. OCT1 mRNA was markedly expressed in the rat duodenum and in IEC-6, and transfection of IEC-6 with OCT1 siRNA decreased OCT1 mRNA expression and inhibited [(14)C]cysteamine uptake. Cysteamine-induced duodenal ulcers were decreased in OCT1/2 knockout mice. These studies provide new insights into the mechanism of cysteamine absorption and demonstrate that intracellular iron plays a critical role in cysteamine uptake and in experimental duodenal ulcerogenesis.     

A bursal pentapeptide (BPP-I), a novel bursal-derived peptide, exhibits antiproliferation of tumor cell and immunomodulator activity

The bursa of Fabricius (BF) is the central humoral immune organ unique to birds. Here, we isolated a novel bursal pentapeptide I (BPP-I), LGPGP, from BF. BPP-I could play inhibition effect on MCF-7 but not on CEF or Vero cell proliferation in vitro, and enhance antitumor factor p53 protein expression. Also, BPP-I stimulated antibody production in a dose-dependent manner in hybridoma cell. Furthermore, BPP-I could induce various immune responses in mice immunization experiments, including increase antibody production and cytokines IL-4 and IFN-γ level, and induce T-cell immunophenotyping. These results suggest that BPP-I is a potential immunomodulator of antitumor and immunity. The study could provide some novel insights on the probable candidate reagent for the antitumor and immune improvement.