Enzymatic Synthesis of GDP-alpha-L-fucofuranose by MtdL and Hyg20

Two mutases, MtdL and Hyg20, are reported. Both are able to functionally drive the biosynthesis of GDP-alpha-L-fucofuranose. Both enzymes catalyze similar functions, catalytically enabling the bidirectional reaction between GDP-beta-L-fucopyranose and GDP-alpha-L-fucofuranose using only divalent cations as cofactors. This realization is but one of a number of important insights into fucofuranose biosynthesis presented herein

Angucycline Glycosides from Mangrove-Derived Streptomyces diastaticus subsp SCSIO GJ056

Nine new angucycline glycosides designated urdamycins N1-N9 (1-9), together with two known congener urdamycins A (10) and B (11), were obtained from a mangrove-derived Streptomycesdiastaticus subsp. SCSIO GJ056. The structures of new compounds were elucidated on the basis of extensive spectroscopic data analysis. The absolute configurations of 6-9 were assigned by electronic circular dichroism calculation method. Urdamycins N7 (7) and N8 (8) represent the first naturally occurring (5R, 6R)-angucycline glycosides, which are diastereomers of urdamycins N6 (6) and N9 (9), respectively

Antifouling Potentials and Metabolite Profiles of Two Marine-derived Fungal Isolates

Extracts of the culture broths of Aspergillus sydowii SCSIO 00305 and Penicillium chrysogenum SCSIO 00258 exhibited a relatively broad spectrum of antifouling activity against various biofoulers. The main chemical components of their bioactive fractions were analyzed and identified by LC-MS and from literature data. Two bioactive fractions comprised of 1 alpha-methoxyroquefortine C, meleagrin, roquefortine C and isoroquefortine C exhibited more significant anti-barnacle activity than meleagrin in field bioassays, suggesting that the combination of different bioactive compounds could display a stronger antifouling activity than a single compound in the complicated marine ecological environments

Spawning, larval development and juvenile growth of the tropical sea cucumber Holothuria leucospilota

The tropical sea cucumber Holothuria leucospilota (Echinodermata: Holothuroidea) is one of the most widespread sea cucumber species with high economic value. To develop the artificial breeding methods of H. leucospilota, we conducted the first detailed study on the processes of spawning, embryonic and larval development, and juvenile growth of the species. The results showed that the suitable breeding season of H. leucospilota in the Daya Bay might be from June to October and that at least 30 days were needed for embryos to develop into juveniles at a temperature of 29-33 degrees C, a salinity of 27-30 parts per thousand, and a pH of 7.9-8.2. The survival rate of the juveniles were approximately 8.5%, the average growth rate during days 31-49 of culture was 0.11mm per day and increased to 0.72mm per day during days 73-120. The body color of the juveniles was transparent yellow at approximately 55 days of culture, and it began to darken at 79 days later. These results indicated that an artificial culture method of H. leucospilota was realized. Our research might contribute a feasible way to the artificial breeding, natural resource restoration, and sustainable use of tropical sea cucumbers

Functional Characterization of a New Antarctic Microbial Esterase EST112-2 and Its Use in the Preparation of Chiral Tertiary Alcohol (S)-Linalool

Chiral tertiary alcohols (TAs) are key building blocks for the synthesis of many crucial flavor compounds and pharmaceuticals. The two enantiomers of tertiary alcohol, linalool, differ in odor. So, sustainable strategies for the manufacture of optically pure TAs represented by linalool, are highly desirable. But the enzymatic synthesis of chiral tertian' alcohols through kinetic resolution was not easily achieved, possibly because of the steric hindrance from the chemical structures of tertiary alcohols. Herein, we identified and functionally characterized a new microbial esterase EST112-2 from the antarctic sediments and utilized esterase EST112-2 as a green biocatalyst in the synthesis of chiral tertiary alcohol (S)-linalool through asymmetric hydrolysis of racemic linalyl acetate. Parameters such as pH, temperature, co-solvents, substrate concentrations, enzyme loading and reaction time were optimized for the kinetic resolutions. Desired chiral product (S)-linalool was finally obtained with an enantiomeric excess of over 66% and a yield of over 72% after process optimization. The enantiomeric excess of (S)-linalool prepared by esterase EST112-2 was much higher than that from previous reports

Overexpression of a type III PKS gene affording novel violapyrones with enhanced anti-influenza A virus activity

Background: Type III polyketide synthases (PKSs) are simple homodimer ketosynthases that distribute across plants, fungi, and bacteria, catalyzing formation of pyrone-and resorcinol-types aromatic polyketides with various bioactivities. The broad substrate promiscuity displayed by type III PKSs makes them wonderful candidates for expanding chemical diversity of polyketides. Results: Violapyrone B (VLP B, 10), an alpha-pyrone compound produced by deepsea-derived Streptomyces somaliensis SCSIO ZH66, is encoded by a type III PKS VioA. We overexpressed VioA in three different hosts, including Streptomyces coelicolor M1146, Streptomyces sanyensis FMA as well as the native producer S. somaliensis SCSIO ZH66, leading to accumulation of different violapyrone compounds. Among them, S. coelicolor M1146 served as the host producing the most abundant violapyrones, from which five new (2-4, 7 and 12) and nine known (1, 5, 6, 8-11, 13 and 14) compounds were identified. Anti-influenza A (H1N1) virus activity of these compounds was then evaluated using ribavirin as a positive control (IC50 = 112.9 mu M), revealing that compounds 11-14 showed considerable activity with IC50 values of 112.7, 26.9, 106.7 and 28.8 mu M, respectively, which are significantly improved as compared to that of VLP B (10) (IC50 > 200 mu M). The productions of 10 and 13 were increased by adding P450 inhibitor metyrapone. In addition, site-directed mutagenesis experiment led to demonstration of the residue S242 to be essential for the activity of VioA. Conclusions: Biological background of the expression hosts is an important factor impacting on the encoding products of type III PKSs. By using S. coelicolor M1146 as cell factory, we were able to generate fourteen VLPs compounds. Anti-H1N1 activity assay suggested that the lipophilic nature of the alkyl chains of VLPs plays an important role for the activity, providing valuable guidance for further structural optimization of VLPs

Protective Effects of Enteral Nutrition Supplemented with Crassostrea hongkongensis Polysaccharides Against 5-Fluorouracil-Induced Intestinal Mucosal Damage in Rats

Chemotherapeutics, including 5-fluorouracil (5-FU), often damage the intestinal mucosal barrier and cause intestinal mucositis (IM). Supplementation with immunoregulatory polysaccharides from Crassostrea hongkongensis has been shown to positively influence the effectiveness and toxicity of 5-FU. Therefore, we studied the effects of oyster polysaccharides on 5-FU-induced intestinal mucosal damage in rats. The C30-60% ethanol-precipitated fraction of polysaccharides promoted IEC-6 cell proliferation and exhibited a maximal effect at a 0.0195 mg/mL concentration. Moreover, treatment with C30-60% polysaccharide-based nutrition formula (OPNF) partially prevented the 5-FU-induced degenerative changes in the histology and ultrastructure of small intestinal mucosa. In addition, the endotoxin level of rats fed with 5-FU and OPNF decreased to the normal control level. Furthermore, the 5-FU-induced increase of proinflammatory cytokine interleukin (IL)-2 and the decrease of anti-inflammatory cytokine IL-10 level in the peripheral blood were significantly attenuated by OPNF administration. In conclusion, Oyster C30-60% polysaccharides can ameliorate 5-FU-induced IM by partially preventing mucosal damage, reducing inflammation, and promoting immunity

Butyratibacter algicola gen. nov., sp nov., a marine bacterium from the culture broth of Picochlorum sp 122

A Gram-stain-negative, motile, non-spore-forming, ovoid or rod-shaped bacterium, designated strain B15(T), was isolated from the culture broth of a marine microalga, Picochlorum sp. 122. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain B15(T) forms a stable cluster with Lutibaculum baratangense KCTC 22669(T) (95.4% 16S rRNA gene sequence similarity), Tepidamorphus gemmatus CB-27A(T) (94.9 %) and Microbaculum marinum HSF11(T) (94.6 %) in the family Rhodobiaceae. Optimal growth of strain B15(T) was observed at 33 degrees C, pH 8-9 and in the presence of 3% (w/v) NaCl. The only detected ubiquinone of strain B15(T) was Q-10, and the G+C content of the genomic DNA was 66.3 mol%. The major fatty acid profile comprised C-19 : 0 cyclo omega 8c, C-18 : 1 omega 7c/omega 6c and C-17 : 1 iso I/anteiso B. The major polar lipids of strain B15(T) were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, two unidentified aminolipids, and one unidentified lipid. Comprehensive analyses based on polyphasic characterization of strain B15(T) indicated that it represents a novel species of a new genusin the family Rhodobiaceae, for which the name Butyratibacter algicola gen. nov., sp. nov. is proposed. The type strain of the type species is B15(T) (= KCTC 52552(T) = MCCC 1K03221(T))

Modulation of Tropical Cyclogenesis Location and Frequency over the Indo-Western North Pacific by the Intraseasonal Indo-Western Pacific Convection Oscillation during the Boreal Extended Summer

The influence of the intraseasonal Indo-western Pacific convection oscillation (IPCO) on tropical cyclone (TC) genesis location and frequency over the Indo-western North Pacific (WNP) during the boreal extended summer (May-October) is explored. Observational analysis shows that the impacts of the intraseasonal IPCO on TCs over the Indo-WNP include an evident "phase lock of TC genesis location'' and distinct differences in TC frequency. In the WNP, in the positive intraseasonal IPCO phase, the atmosphere gains heat through the release of latent heat in cumulus convective condensation, and the anomalous cyclonic circulation weakens the western Pacific subtropical high (WPSH) and enhances TC genesis, thereby tending to produce many more TCs. Moreover, the diminished WPSH and the westward shift of the centers of anomalous cyclonic circulations lock TC genesis locations to the west WNP and lower latitudes (around 5 degrees-20 degrees N), especially in the South China Sea. The almost opposite situation occurs in a negative phase. In the north Indian Ocean, the total TC genesis frequencies in the two intraseasonal IPCO phases are approximate. However, in the positive intraseasonal IPCO phase, the environmental conditions to the north of 13 degrees N are similar to those in the WNP except without the WPSH control, whereas south of 13 degrees N the situation is reversed, leading to a northward shift of the TC genesis location (around 13 degrees-20 degrees N). The negative phase reflects an opposite situation

大亚湾浮游植物粒级结构对温排水和营养盐输入的响应

大亚湾核电站温排水对其邻近海域的生态效应日益突出。文章结合现场调查和室内模拟实验,研究了夏季和冬季大亚湾海域沿温排水温度梯度的浮游植物粒径结构特征,探讨了营养物质的输入可能对其产生的影响,以期深入了解浮游植物对升温以及富营养化作用的响应机制。结果表明,适温条件对浮游植物的生长起促进作用,在极高温(36.0℃)环境下则产生抑制作用,在排水口邻近高温区夏季和冬季浮游植物叶绿素a含量均呈较低分布。交互模拟实验发现不同季节浮游植物对于温度和营养盐的敏感性存在差异,夏季营养盐对浮游植物生长的促进作用比温度明显,冬季温度的作用则更为显著。现场观测和模拟实验均显示,水温升高和营养盐加富均可造成小粒级浮游植物(<20μm)所占比例的增加;因此,升温和营养盐输入均可能导致浮游植物粒级结构呈小型化趋势,并对食物网能量流动与物质循环、生态系统的结构稳定性以及海洋渔业的产量造成潜在影响