Extension of cell membrane boosting squalene production in the engineered Escherichia coli

Squalene is a lipophilic and non-volatile triterpene with many industrial applications for food, pharmaceuticals, and cosmetics. Metabolic engineering focused on optimization of the production pathway suffer from little success in improving titers because of a limited space of the cell membrane accommodating the lipophilic product. Extension of cell membrane would be a promising approach to overcome the storage limitation for successful production of squalene. In this study, Escherichia coli was engineered for squalene production by overexpression of some membrane proteins. The highest production of 612 mg/L was observed in the engineered E. coli with overexpression of Tsr, a serine chemoreceptor protein, which induced invagination of inner membrane to form multilayered structure. It was also observed an increase in unsaturated fatty acid in membrane lipids composition, suggesting cellular response to maintain membrane fluidity against squalene accumulation in the engineered strain. This study potentiates the capability of E. coli for squalene production and provides an effective strategy for the enhanced production of such compounds.     

清醒狗短暂缺血心肌复灌注时舒缩功能的变化

在狗的心脏上装入微超声探头和高精度微压力传感器,手术后两星期,在清醒状态下给予左冠状动脉旋支阻断三分钟。在复灌注过程中,观察到血液动力学指标与收缩期心室壁厚度(WT)迅速恢复正常;但在 dWT/dt—WT 环形图上出现舒张早期异常相,其形状与缺血过程不同。低氧和急遽冠状动脉过度充盈可以产生此种异常图形。我们推测,心肌缺血可能促使一些产物的形成,复灌注时它使冠脉过度舒张,冠脉灌注增加,从而造成舒张早期急遽充盈而形成了此种异常的形图。     

长春和北京地区引起婴幼儿肺炎的3型与7型腺病毒的分子流行病学研究

对长春和北京地区连续12年(1976年冬至1988年春)引起小儿肺炎的3、7型腺病毒102株标本,进行了限制性内切酶核酸电泳图谱分析。56株7型腺病毒经BamHⅠ、BclⅠ、BglⅠ、XbaⅠ、SmaⅠ、HindⅢ分析后,表现为两个基因组型——Ad7 b和Ad7 d。46株3型腺病毒被Bg1 Ⅱ、BamHⅠ酶解后,表现为 3个基因组型——Ad 3Ⅰ、Ad 3Ⅱ、Ad 3Ⅲ。各基因组型的分布情况是:56株7型腺病毒中,43株为Ad 7 b(76.8％),流行于1976年冬至1986年春;13株是Ad 7 d(23.2％),出现于1982年,与Ad 7 b共同流行;1986年～1988年分析的5株病毒都是Ad 7d。43株3型腺病毒中,Ad3Ⅰ42株(91.0％),分布于12年中;Ad 3Ⅱ、Ad 3Ⅲ各2株,散在分布。此结果表明,国内这12年中引起小儿肺炎的3型腺病毒至少有3个基因组型,7型腺病毒至少有两个基因组型。Ad3Ⅰ和Ad7 b是流行优势基因组型。但自80年代初开始出现Ad7 d以来,有逐年增多的趋势,最近两年的标本又都是Ad7 d,很可能它将取代Ad7 b而成为流行的优势基因组型.     

撕裂蜡孔菌HG2011对光叶紫花苕结瘤固氮的影响及其潜在机制

【目的】 在我国南方尤其是西南地区,光叶紫花苕(Vicia villosa Roth.)作为重要的青饲和绿肥两用豆科作物被广泛种植,有助于提高土壤氮素和后茬作物的产量品质。接种有益微生物是促进豆科作物生物固氮和生长的重要措施之一。为此,本文研究了一株自主分离获得的白腐真菌¾¾撕裂蜡孔菌(Careporia lacerata HG2011)对光叶紫花苕结瘤固氮和生长的影响,并揭示其潜在机制。【方法】 采用微生物培养、植物培养和田间试验,研究C. lacerata磷铁活化能力、代谢产物构成、与根瘤菌Rhizobium sophorae S3的相互作用,及其对光叶紫花苕结瘤、生长、产量、品质和土壤有效磷铁的影响。【结果】 C. lacerata和根瘤菌之间无拮抗作用。液相色谱-质谱(liquid chromatography-mass spectrometry, LC-MS)分析发现,C. lacerata发酵液含有氨基酸、有机酸和类黄酮等化感物质,能增强根瘤菌的趋化性并促进生物膜形成。此外,C. lacerata还能释放生长素、赤霉素、水杨酸和铁载体,活化难溶性有机和无机磷。在植物培养试验中,单独接种C. lacerata或根瘤菌均能促进光叶紫花苕生长,但以共接种处理效果最佳。C. lacerata定殖于光叶紫花苕根际,导致根长、根系表面积和结瘤数显著增加。田间试验发现,接种C. lacerata显著提高了光叶紫花苕单株根瘤数、根瘤质量和固氮酶活性,以及土壤有效磷铁含量和磷酸酶活性,产量比常规施肥处理增加12.15%且品质无显著变化。【结论】 C. lacerata能够在光叶紫花苕根际定殖,通过分泌化感物质、生长素和活化土壤磷铁等机制促进结瘤固氮和生长发育。C. lacerata易于培养,菌剂制备成本低廉,施用简便,对提高豆科作物产量品质具有一定应用价值。     

抗白粉病小麦染色体组型的分子标记与生化标记分析

应用与小麦第六同源群有关的分子和生化标记,包括ＤＮＡ探针ｐＳｃ５·３Ｈ３和ｐＳＲ１６７以及同工酶Ｅｓｔ－５和ａ－Ａｍｙ－１,对来自六倍体小黑麦Ｂｅａｇｌｅ与普通小麦科冬５８杂交后代Ｆ１花粉植株的抗白粉病株系Ｍ２４．Ｍ０９及Ｍ１７进行了分析。结果表明,Ｍ２４、Ｍ０９及Ｍ１７不同程度地含有黑麦染色体成分,而且电泳谱带差别较大,据此推断,Ｍ０９为６ＲＬ的易位系。因此,生化和分子标记不仅可以用于确定外源片段的存在,而且可以帮助确定染色体组型和外源片段的位置     

Galectin‐3 mediates pulmonary vascular endothelial cell dynamics via TRPC1/4 under acute hypoxia

Galectin‐3 (Gal‐3) has been implicated in various biological functions, yet little is known about its role in regulating the dynamics of pulmonary vascular endothelial cells. Gal‐3 was shown to be increased in hypoxic model rats by sequencing analysis. We exposed pulmonary vessel endothelial cells (PVECs) to hypoxia or Gal‐3 stimulation, following which cell apoptosis and autophagy were measured with the relevant methods. The results demonstrated that hypoxia elevated nuclear factor‐κB (NF‐κB) activity and Gal‐3 expression. Gla‐3 decreased the expression of Bcl‐2, Alix, Beclin‐1, Atg5, and LC3A/B. The messenger RNA and protein levels of transient receptor potential channel 1/4 (TRPC1/4) and calpain were reduced after Gal‐3 treatment. Gal‐3 also activated protein kinase B/glycogen synthase kinase‐3 β/mammalian target of rapamycin signaling pathways in PVECs. These results suggest that a hypoxia‐mediated increase in Gal‐3 promotes apoptosis and inhibits autophagy by inhibiting the TRPC1/4 pathway and activating the protein kinase B/glycogen synthase kinase‐3 β/mammalian target of rapamycin signaling pathway in PVECs. Furthermore, these results may provide us with a new direction to explore the pathogenesis of pulmonary artery hypertension.     

大豆异黄酮对骨质疏松大鼠模型的作用探讨

目的研究大豆异黄酮促进骨质疏松大鼠骨形成的作用及其肠道微生态的变化。方法从60只SPF级SD雌性大鼠中随机挑选50只建立去卵巢骨质疏松大鼠模型,余下10只为假手术组。将建模成功的大鼠随机分为5组,模型组、大豆异黄酮高、中、低剂量组(320 mg/kg、160 mg/kg、80 mg/kg的大豆异黄酮)、阿仑膦酸钠组(1 mg/kg阿仑膦酸钠),每日1次,治疗10周。比较治疗前后大鼠骨密度、血清1型前胶原N端前肽(P1NP)、骨碱性磷酸酶(BALP)、血清骨钙素(BGP)水平和肠道微生物变化。结果治疗后,模型组大鼠骨密度、血清P1NP、BALP、BGP水平均低于假手术组(P<0.05),阿仑膦酸钠组和大豆异黄酮高、中、低剂量组均高于模型组(P<0.05)。治疗后,阿仑膦酸钠组和大豆异黄酮高、中、低剂量与模型组比较股骨组织病变减轻;厚壁菌门、梭菌纲、芽孢杆菌纲、毛螺菌科、乳杆菌科、普氏菌科、肠球菌科、毛螺菌属、乳杆菌属、罗氏菌属、布劳特氏菌属、粪球菌属、普氏菌属水平相对丰度模型组均低于假手术组(P<0.05),阿仑膦酸钠组和大豆异黄酮高、中、低剂量组均高于模型组(P<0.05)。拟杆菌门、变形菌门、拟杆菌纲、γ变形菌纲、毛菌纲、拟杆菌科、肠杆菌科、拟杆菌属、别样棒菌属、肠杆菌属模型组均高于假手术组(P<0.05),阿林磷酸钠组和大豆异黄酮高、中、低剂量组均低于模型组(P<0.05)。LEfSe分析结果显示,与模型组比较,阿仑膦酸钠组和大豆异黄酮高、中、低剂量组治疗后丁酸球菌属、放线菌属、拟杆菌科、拟杆菌属水平降低,消化球菌科、韦荣氏菌科、普氏菌属水平升高。结论大豆异黄酮可提高骨密度,提高血清骨形成指标水平,促进骨质疏松大鼠骨形成,还可改善大鼠肠道菌群。     

Crumbs proteins stabilize the cone mosaics of photoreceptors and improve vision in zebrafish

Although the unique organization of vertebrate cone mosaics was first described long ago,both their underlying molecular basis and physiological significance are largely unknown.Here,we demonstrate that Crumbs proteins,the key regulators of epithelial apical polarity,establish the planar cellular polarity of photoreceptors in zebrafish.Via heterophilic Crb2a-Crb2b interactions,the apicobasal polarity protein Crb2b restricts the asymmetric planar distribution of Crb2a in photoreceptors.The planar polarized Crumbs proteins thus balance intercellular adhesions and tension between photoreceptors,thereby stabilizing the geometric organization of cone mosaics.Notably,loss of Crb2b in zebrafish induces a nearsightedness-like phenotype in zebrafish accompanied by an elongated eye axis and impairs zebrafish visual perception for predation.These data reveal a detailed mechanism for cone mosaic homeostasis via previously undiscovered apical-planar polarity coordination and propose a pathogenic mechanism for nearsightedness.