Effect of high temperature on growth,nitrogen fixation,and chlorophyll content of five species of Azolla Anabaena symbiosis

Summary Cultures of Azolla sp. ST-SI, A. microphylla BR-GI, A. mexicana BR-GL, A. caroliniana WT-V, and A. filiculoides BR -H were grown in N-free International Rice Research Institute growth medium in the glasshouse at 38±1 °C (day) and 25±1 °C (night) under a light intensity of 350 Em²s^–1 for 27 days. Biomass, chlorophyll contents and nitrogenase activity (acetylene reduction assay) were recorded on the 19th and 27th day. For comparison the same parameters were studied in Azolla spp. under normal growth conditions at 26±1 °C (day) and 19±1 °C (night). Azolla sp. STSI and A. microphylla BR-GI had produced a larger biomass by the 19th and the 27th day of incubation than A. caroliniana WTV and A. filiculoides which showed poor growth. Under normal growth conditions A. caroliniana WTV and A. filiculoides BRH produced less biomass than the other Azolla spp. cultures tested. A. mexicana BR-GL had a higher total chlorophyll content in both incubation periods than A. caroliniana WT-V and A. filiculoides BR-H. The N content was high in Azolla sp. ST-SI, A. microphylla BR-GI, and A. mexicana BR-GL compared with the low N content of A. filiculoides BR-H and A. caroliniana WT-V. At the higher temperature (38±1 °C/25±1 °C) Azolla sp. ST-SI and A. microphylla BR-GI consistently showed a higher growth rate than A. filiculoides BR-H and A. caroliniana WTV, while the growth rate of A. mexicana BR-GL was intermediate.The study was carried out at C.F. Kettering Research Laboratory, Yellowsprings, OH - 45387, USA     

鱼腥蓝细菌PCC 7120异形胞的分离

鱼腥蓝细菌PCC 7120是一种光合自养型丝状蓝细菌.缺氮条件下,菌丝上5％～10％的营养细胞分化为异形胞,发挥固氮作用.异形胞是研究生物固氮和细胞分化的理想材料.为研究异形胞生理功能及其发育过程中的基因表达变化,需要从菌丝中分离高质量的异形胞.用2 mg/mL溶菌酶与0.1％ Triton X-100同时处理菌丝30 min,得到了完整性好、纯度高的异形胞.     

附植藻类-黑藻体系克澡效应初探

向鲜重约10g的扦插黑藻顶枝端表面分别接种1．00、2．00和4．00g鲜重附植藻类，组成3个附植藻类一黑藻体系处理组，另设置未接种附植藻类的单一黑藻体系处理组，研究了各处理组种植水对水华鱼腥藻的化感作用。研究结果表明，附植藻类-黑藻体系和单一黑藻体系均对水华鱼腥藻产生了显著的化感抑制作用；附植藻类-黑藻体系抑制作用强于单一的黑藻体系；附植藻类接种量大的处理组。抑制作用较强，其中接种4．00g鲜重附植藻类的体系对水华鱼腥藻产生了极显著的化感抑制作用，叶绿素a去除率达97．65％。     

氯化钠影响下蓝藻Anabaena 7120的固氮活性和去铵阻抑

正常培养液中NaCl浓度增高时,蓝藻固氮活性明显下降,去铵阻抑速率也减慢。NaCl浓度越高,阻抑程度越大。如果NaCl浓度过高,固氮酶活性即完全丧失,铵阻抑效应也不能消除。低光照度、光合抑制剂、O_2、N_2以及N_2+CO_2都加剧高浓度NaCl对蓝藻固氮酶活性和去铵阻抑的阻抑,而外源蔗糖、H_2和H_2+O_2则有一定程度的促进。     

Fate of Azolla spp. and urea nitrogen applied to wetland rice (Oryza sativa L.)

Summary Using ¹⁵N, the fate of N applied to wetland rice either as Azolla or urea was studied in a field at the International Rice Research Institute (IRRI). In bigger plots nearby, yield response and N uptake were also determined with unlabelled N sources. Azolla microphylla was labelled by repeated application of labelled ammonium sulfate. Labelled and unlabelled N were used alternately in applications of Azolla or urea 0 and 42 days after transplanting, in order to determine the effect of the time of application on the availability of Azolla N. The quantities of Azolla N incorporated were 23% more than those of urea N (30 kg N ha^–1) in the isotope plots or 7% less in the yield response plots. Grain yield and total N uptake by the rice plants in the yield-response plots were higher in the urea-treated plots than in the Azolla-treated plots, but the physiological effect of Azolla N (grain yield response/increase in N uptake) was higher than that of rea. The labelled N balance was studied after the first and second crops of rice. Losses of labelled N after the first crop were higher from urea (30%–32%) than from Azolla (0%–11 %). Losses in N applied as a side dressing 42 days after transplanting were less than those of N applied basally. No further losses of ¹⁵N occurred after the first crop. The recovery of Azolla ¹⁵N in the first crop of rice was 39% from the basal application and 63% from the side dressing. The recovery of urea ¹⁵N was 27% from the basal application and 48% from the side dressing. Recoveries of residual N from both Azolla and urea during the second rice crop were similar. Laboratory incubation of the Azolla used and the changes in labelled exchangeable N in the soil showed that at least 65% of Azolla N (4.7% N content) was mineralized within 10 days.     

鱼腥蓝细菌PCC 7120中两个磷酸酶N端结构域活性分析

为了研究鱼腥蓝细菌(A nabaena sp.)PCC 7120中两个PP2C类蛋白磷酸酶PrpJ1和PrpJ2的磷酸酶活性,将编码两个蛋白N端至跨膜区的基因片段重组到质粒中,转化大肠杆菌进行原核表达,获得了可溶性的PrpJ1up和PrpJ2up蛋白.并且以pNPP为底物测定了所得蛋白的磷酸酶活性,双倒数作图法结果显示PrpJ1up蛋白的KK为0.30 mmol/L,Vmax为7.10 nmol/min;PrpJ2up蛋白的Km为0.24 mmol/L,Vmax为0.43 nmol/min.     

藻蓝蛋白α亚基裂合酶的分子克隆和酶动力学研究

为了比较研究不同藻种中藻蓝蛋白裂合酶CpcE/F的结构与功能的差异,对Anabaena sp.PCC 7120中的CpcE/F进行克隆,并进行大量表达,将表达的裂合酶CpcE/F用于藻蓝胆素(PCB)与Mastigocladus laminosus PCC 7603藻蓝蛋白α-亚基(α-PC)脱辅基蛋白(CpcA)的体外重组,得到天然活性的α-PC,从而表明CpcE/F所编码的蛋白质是α-PC生物合成的裂合酶,并对CpcE/F的酶动力学进行了初步研究。     

水华鱼腥藻超弱发光初探

首次用BPCL微弱发光测量仪测得蓝藻门中的水华鱼腥藻发射的自然超弱光,结果表明:水华鱼腥藻的光子计数率-时间曲线遵循双曲线衰减规律,这一点说明生物光子是具有一定相干性的;藻类浓度(个·mL-1)与超弱光光子计数率呈显著正相关(r=0.96)。     

可见分光光度法测定水华鱼腥藻

采用可见分光光度法测定水华鱼腥藻（Anabaena flos-aquae)藻液的吸光度A。这种方法与细菌计数法、叶绿素a含量测定法和荧光分光光度法相比较，即简便又准确，且可获得十分理想的线性相关性，其测得的A值可以作为水华鱼腥藻现存量的指标。     

铜绿微囊藻·螺旋鱼腥藻和水华束丝藻竞争优势的研究

用铜绿微囊藻、螺旋鱼腥藻和水华束丝藻进行单独培养和共培养,研究其生长特性和培养液N、P含量变化,探讨其竞争优势.结果表明:单独培养时,水华束丝藻生长优势最显著,其次是螺旋鱼腥藻;共培养时,水华束丝藻完全被抑制,P含量较高时,螺旋鱼腥藻生长占优,P含量较低时,铜绿微囊藻占优.铜绿微囊藻和螺旋鱼腥藻均向水体中分泌或释放较多的含N化学物质,而水华束丝藻几乎不分泌或释放含N物质.铜绿微囊藻、螺旋鱼腥藻、水华束丝藻和混合藻吸收的N、P比值分别为12.1、14.8、12.5和15.2,推测此比值是它们生长最适N、P比.该研究为解释自然水体中蓝藻水华优势种演替的原因提供了新证据.