土壤杆菌固氮生理特性研究

对根癌土壤杆菌C58/pGV3850菌株的固氮生理特性研究结果表明,该菌具有自生固氮活性,其固氮活性的最适pH为8.0,温度为30℃.固氮活性在对数生长后期(14h)最高,延缓期和静止期乙炔还原活性较低.该菌株好氧,通过氧呼吸和吸氢酶的作用达到避氧固氮.当通入氧气超过呼吸耗氧时,对固氮活性产生抑制作用.在培养过程中增加NH_4~+浓度,固氮活性会降低,当达到15mmol/L时完全丧失固氮活性,表现NH_4~+阻遏固氮酶蛋白合成.在乙炔还原测定系统中加入NH_4~+并不影响乙炔还原反应,说明没有NH_4~+关闭现象.培养过程中加入MSX(2.5mg/ml)能解除10mmol/L NH_4~+对固氮酶合成的阻遏作用.固定的游离氮不能以NH_4~+形式分泌于胞外.固氮过程中放出大量氢气,培养16小时产氢量达65μmol H_2/mg蛋白.在限碳条件下(0.2%蔗糖)其吸氢酶活力可达520nmol H_2·ml~(-1)·h~(-1).     

大豆（Glycing soja）苗期光合呼吸和蒸腾作用中的能量代谢

本文研究了大豆(Glying soja)苗期在光合、呼吸和蒸腾作用中的能量代谢,结果表明,大豆苗期的能量输入为990Kcal.m~(-2)·h~(-1),能量吸收为40.42Kcal.m~(-2)·h~(-1),能量固定为14.71Kcal.m~(-2)·h~(-1),能量损耗为28.61Kcal.m~(-2)·h~(-1),能量积累为11.71Kcal。m~(-2)·h~(-1)。 由此可见,绝大多数的能量损耗于大豆苗期的能量代谢过程,其中,蒸腾作用中的能量损耗为25.71Kcal.m~(-2)·h~(-1),光呼吸和暗呼吸作用中的能量损耗为3.00Kcal.m~(-2)·h~(-1)。因此,大豆苗期能量利用效率仅为1.18％。     

固定化光合细菌利用有机物产氢的研究

应用固定化细胞技术包埋荚膜红假单胞菌(Rhodopseudomonas capsulata)菌株386．研究在光照下利用有机物产氢的特性。实验观察到,光照培养120小时,悬浮培养物的产氢量为68．2ml·比产氢速率为104．1ml H2/g(生物量)·h;用琼脂包埋后．其产氢能力得到改善,产氢量和比产氢速率分别达到128．4ml和l 9s．8mlH2/g·h。该菌株除可利用苹果酸外,还可利用葡萄糖、乳酸、丙酸等基质高效地产氢。基质浓度只有控制在适当水平时,才具有较高的基质转化产氢效率。此外．菌体生物量、菌龄、培养液pH、光照强度、光照／黑暗时间比以及温度对产氢过程均有不同程度的影响。     

沼泽红假单胞菌乙酸光合放氢研究

依据光合细菌生长代谢特性和有机废水降解主要产物类型,11种有机物被用于沼泽红假单胞菌（Rhodopseudomonas palustris）Z菌株的光合产氢研究,其中,乙酸反应体系产氢活性最高。在此基础上,研究了该菌株的生长与产氢动力学行为,探求了影响该菌株光合放氢的主要限制性影响因素。结果表明,该菌株产氢与生长部分相关。种子培养基和菌龄对产氢活性有明显影响。细胞最适产氢和生长所需要的光照强度和温度基本一致。当种子来源于硫酸铵高菌龄预培养物或谷氨酸钠对数期预培养物时,该菌株产氢活性显著增加,产氢延滞期明显缩短。氧浓度和接种量对产氢活性也有显著影响。供氢体和氮源浓度直接决定细胞的生长与光放氢活性。在低于70 mmol/L乙酸钠和15 mmol/L谷氨酸钠时,产氢活性随底物浓度的增加而增强。谷氨酸钠浓度高于15mmol/L时,由于游离NH₄⁺的出现,产氢活性受到抑制,但却明显刺激细胞的生长。在标准状况下,该菌株的最大产氢速率可达19.4 mL·L^-1·h^-1。     

固氮鱼腥藻(Anabaena azotica Ley HB686)的固氮和放氢作用

固氮鱼腥藻(水生686)整体水平在光照下同时有释氢和放氧的现象。氢的释放量与乙炔还原活性有平行的关系。在暗期,释氢量极少。 固氮鱼腥藻在光照下具有较强的吸氢作用,这是由于氢酶有吸氢的特性。我们看到H_2和O_2的浓度对氢酶的活性有一定的影响。氢酶催化分子氢和分子氧的反应的Km值分别为1.6mM和0.5mM。 分子氢能明显地支持乙炔还原作用,当以空气为气相的反应体系中含有10％分子氢时,大大地提高乙炔还原的活性。 铵离子不仅抑制乙炔还原,而且对释氢作用也有明显的抑制。随着铵离子浓度的增加抑制作用愈为显著。当铵离子浓度达到10mM时,乙炔还原和释氢都几乎全被抑制。说明放氢与固氮酶的活性有密切的联系。 DCMU(2×10~(-5)M)对乙炔还原活性和释氢的抑制约20％,DNP(5×10~(-4)M)表现出更强烈的抑制。     

木糖发酵产氢菌的筛选及其生长产氢特性研究

利用改进的Hungate厌氧技术, 从牛粪堆肥中分离出一株能有效利用木糖发酵产氢的中温菌HR-1。通过16S rRNA系统发育树分析表明, 菌株 HR-1 与丙酮丁醇梭菌Clostridium acetobutylicum ATCC 824 相似性最高为96%, 结合生理生化和生长特性分析表明, HR-1是梭菌属Clostridium的一个新种, 命名为Clostridium sp. HR-1。菌株HR-1为单胞生长的规则杆状菌(0.3 mm ~0.6 mm)×(1.4 mm~2.3 mm), 革兰氏染色为阴性, 无荚膜、无鞭毛、表面光滑、无明显凸起, 专性厌氧菌。HR-1可在10°C~45°C, pH 4.0~10.0条件下生长; 37°C和pH 8.0分别为其最适生长条件。发酵PYG的主要发酵产物有氢气、二氧化碳、乙酸、丁酸及少量乙醇。HR-1可以利用有机氮源和无机氮源生长并产氢, 酵母提取物是其最佳产氢氮源。HR-1在木糖浓度为3 g/L和初始pH 6.5条件下, 其比产氢量为1.84 mol-H2/mol-木糖, 最大比产氢速率为10.52 mmol H2/h·g-细胞干重。HR-1可以亦利用葡萄糖、半乳糖、纤维二糖、甘露糖和果糖等碳源生长并发酵产氢, 发酵葡萄糖时比产氢量为2.36 mol-H2/mol-葡萄糖。     

胞外蛋白酶和脂酶活性作为球孢白僵菌毒力指标的可靠性分析

通过测定17株不同来源球孢白僵菌(Beauveria bassiana)的胞外蛋白酶活性(PU,μmol·ml~(-1)·min~(-1))和脂酶活性(LU,μmol·ml~(-1)·h~(-1))及其对血黑蝗(Melanoplussanguinipes)的毒力,分析用酶活性作为毒力指标的可靠性.结果表明,菌株间毒力和酶活性差异较大,LT_(50)的变化范围为5.27~16.89d,PU和LU分别为0.47~3.37×10~(-2)和0.00~56.75.将PU与LU分别对接种后各日累计死亡率及LT_(50)进行回归分析,发现各菌株PU与其毒力相关显著,但LU却与毒力相关不显著.对接种后7d的死亡率,PU可表达其变异的67%,也是最大表达率.因此,PU可作为大量菌株初筛的参考性毒力指标,但应谨慎使用,不能以PU测定完全取代常规的毒力测定.脂酶活性不宜作为所试菌种的毒力参考指标.     

蚕豆植株中酰脲分布和叶片中酰脲水解活性

蚕豆根、茎和叶含有0.31～0.70 μmol酰脲·g~(-1)FW,并受结瘤和生长发育的影响。摘除正在生长的器官可观察到同腋位叶片酞脲含量暂时升高现象。 叶片中酰脲主要是尿囊酸。尿囊素酶和脲酶活性分别为0.30 μmol尿囊酸·g~(-1)FW·h~(-1)和0.19 μmol NH_3·g~(-1)FW·h~(-1)。尿囊酸含量和尿囊素酶活性日变化相似,只是后者峰值比前者出现早。     

固氮螺菌氢代谢与固氮作用的关系I.固氮螺菌放氢现象与吸氢能力的研究

本文研究了固氮螺菌(Azosptrillum brastlense)的放氢现象和吸氢酶活性以及与固氮作用的关系。测定了57株固氮螺菌的放氢现象及其固氮酶活性,其中不放氢41株,微放氢14株,其放氢量为2·63—31.00n mol C2H4／ml菌液·小时。放氢量较多的2株R38{和R256A都是从水稻根表上分离获得,其放氢量分别为185.75n mol H2／ml 菌液·小时和547．00 moIH2／ml 菌液·小时。测定了53株螺菌的吸氢酶活性,它们均具有吸氢能力,其吸氢量各异,0-63-27·38n mol H2／ml菌液。小时。生长在含有NH4CI培养基上的固氮螺菌既没有固氮能力,也不产氢。在无氮培养基上所产生的氢是固氮过程中放出的氢。实验结果指出,C2H2抑制氢酶的活性。当吸氢的菌株与放氢菌株混合培养时,其固氮酶活性比单株纯培养高,有氢存在时,固氮酶活性比不加氢时高。     

sp. B49发酵糖蜜制氢条件

研究1株产氢细菌Ethanoligenens sp. B49利用废糖蜜为基本原料进行生物制氢的条件,及外加氮素营养物对废糖蜜生物制氢的影响。结果表明,在10.3～20.6 g·L^-1的化学需氧量（COD）范围内,经过驯化的Ethanoligenens sp. B49细胞具有较好的生物利用能力,细胞生长量和产氢能力随着废糖蜜COD的提高而增加。当废糖蜜COD超过20.6 g·L^-1时Ethanoligenens sp. B49的细胞生长受到抑制,同时产氢能力下降,COD超过41.2 g·L^-1时细胞基本不具有生长和产氢能力。Ethanoligenens sp. B49利用废糖蜜产氢的最佳COD为20.6 g·L^-1。在20.6 g·L^-1COD条件下外加有机氮源可以促进Ethanoligenens sp. B49利用废糖蜜制氢的能力,促进作用顺序为酵母粉>牛肉膏>蛋白胨>脲素。添加4 g·L^-1的酵母粉时,Ethanoligenens sp. B49细胞具有最好的生长活性和产氢能力。优化营养条件后,单位体积产氢量从44.82 mmol·L ^-1提高到78.97 mmol·L^-1,提高了76.2%。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.