The effect of bacterial strain and temperature changes on the nitrogenase activity of Lotus pedunculatus root nodules

After 40 days of growth at 25°C, Lotus pedunculatus cav., cv. Maku plants infected with Rhizobium loti strain NZP2037 displayed similar relative growth rates but had twice the nodule mass and only one third the whole plant dry weight of plants infected with Bradyrhizobium sp. (Lotus) strain CC814s. In the NZP2037 symbiosis, the rate of CO₂ evolution (per g dry weight of nodulated root) was 1.6 times as high as that in the CC814s symbiosis while the rate of C₂H₂ reduction (per g dry weight of nodule) was only 48% of that in the CC814s symbiosis. Studies of the effect of short term temperature changes on the gas exchange characteristics (CO₂ and H₂ evolution, C₂H₂ reduction) of these symbioses revealed wide differences in the optima for C₂H₂ reduction. Nodules infected with NZP2037 displayed maximal C₂H₂ reduction rates [157 μmol (g dry weight nodule)^?1 h^?1] at 12°C, whereas nodules infected with CC814s were optimal at 30°C [208 μmol (g dry weight nodule)^?1 h^?1]. These short term studies suggested that differences in temperature optima for N₂ may have partially accounted for the poorer effectivity, at 25°C, of strain NZP2037 when compared with strain CC-814s. The relative efficiency [RE = 1 – (H₂ evolution/C₂H₂ reduction)] of N₂ fixation varied widely with temperature in the two symbioses, but there was a general trend toward higher RE with lower temperatures. The ratio of CO₂ evolution: C₂H₂ reduction (mol/mol) in nodulated roots infected with CC814s was constant (ca 10 CO₂/C₂H₂) between 5°C and 30°C, whereas in plants infected with NZP2037 it reached a minimal value of 3.3 CO₂/C₂H₂ at 10°C and was 19 CO₂/C₂H₂ at the growing temperature (25°C).     

海冰微生物Pseudoalteromonas sp. ANT319耐盐性初步研究

南极海冰微生物在适应极端环境的长期进化过程中,获得了特殊的生理生化特性和基因表达调控机制。为了更多的了解南极微生物的逆境适应机制,以隶属南极海冰微生物典型菌属Pseudoalteromonas的ANT319为研究对象,探讨了该菌株在3%~12%的盐度梯度下的抗盐生长情况、蛋白质含量变化、细胞膜透性、丙二醛含量变化和不同盐度对菌株细胞内超氧化物歧化酶(SOD)、过氧化氢酶(CAT)和过氧化物酶(POD)3种抗氧化酶活性的影响。结果表明,此菌株的最适生长盐度为9%,随着盐度的升高,细胞内蛋白质含量升高,膜透性逐渐增加,SOD和POD的酶活性呈现先升高后降低的变化趋势,在9%盐度下达到最高,CAT活性和MDA则基本上保持不变。可见,随着盐度的增加,细胞膜逐渐受到破坏,同时生物体对盐迫作出应激反应,产生较多蛋白来清除不良因素下产生的有害活性氧,包括生物体内抗氧化酶在内的蛋白含量及其活性的增加,研究结果初步揭示了海冰细菌的耐盐机制。     

Biochemical alterations in Bradyrhizobium sp USDA 3187 induced by the fungicide Mancozeb

We have previously shown that fungicide Mancozeb causes a 50% decrease in Bradyrhizobium sp USDA 3187 growth rate and affects the bacteria-root symbiotic interaction. In order to elucidate the fungicide toxicity mechanism we determined the effects of Mancozeb on cell chemical composition, glutathione (GSH) content (molecule involved in the detoxification process), glutathione S-transferase (GST) activity and on polyamine, exopolysaccharides, capsular polysaccharides and lipopolysaccharides. Mancozeb produced biochemical alterations in membrane composition, polysaccharides and polyamines. In spite of the increment of GSH content and GST activity, they are not enough to prevent the growth diminution.     

用rep—PCR技术研究中国花生根瘤菌的多样性

采用细菌基因组重复序列ＰＣＲ技术（简称ｒｅｐＰＣＲ）中常用的ＲＥＰＰＣＲ和ＥＲＩＣＰＣＲ,对从中国１１个省、市的２３个点、２４个花生品种采集的根瘤中分离的５９株花生根瘤菌Ｂｒａｄｙｒｈｉｚｏｂｉｕｍｓｐ．（Ａｒａｃｈｉｓ）进行多样性研究,同时对来自国外的６株花生根瘤菌及１４株参比慢生根瘤菌也进行了比较。得到的低相似性结果表明中国花生根瘤菌基因组存在显著的多样性。ＲＥＰＰＣＲ揭示,在相似性５０％上分为１１个群,而ＥＲＩＣＰＣＲ却得到２４个分群。这两种结果对菌株的分群有差异,暗示这两种短重复序列在慢生根瘤菌基因组中的分布的不同。没有发现菌株间基因组的多样性分布与花生品种、地理来源之间的必然联系。将两者电泳图谱结合并分析,得到介于上述两者间的结果。此结果进一步反映了菌株基因组间存在的多样性。同时还表明ｒｅｐＰＣＲ不仅是研究生物多样性的快速简便方法,还可应用于菌株的鉴别和生态学研究。     

亚栖热菌透性化细胞的耦合固定化研究

将海藻酸盐凝胶包埋法与交联法和聚电解质静电自组装覆膜法相耦合,对含有海藻糖合酶活性的亚栖热菌的透性化细胞进行了固定化研究。结果表明,利用重氮树脂和聚苯乙烯磺酸钠对海藻酸凝胶微球交替覆膜,可以显著提高凝胶微球在磷酸盐缓冲液中的稳定性,以碳二亚胺对固定化细胞进行交联处理则可以提高固定化细胞中海藻糖合酶的热稳定性。透性化细胞经包埋－交联－覆膜耦合固定化后,酶活回收率为32％,最适酶反应pH值由6.5左右升至7.0左右,最适反应温度未变,仍为60℃。所得固定化细胞间歇反应时,催化麦芽糖转化为海藻糖的转化率可达60％,重复使用4次（每次50℃、反应24h）,酶活损失小于20％,转化率可保持在50％以上。     

Competitive interaction between non-nodulating and nodulating strains for nodulation of cowpea (Vigna unguiculata)

Abstract: We have examined the effect of a non-nodulating mutant (JRW3-Sm^D) on the nodulation ability of cowpea rhizobia ( Bradyrhizobium sp.) strains JRW3 and IRC256. Nodulation of cowpea ( Vigna unguiculata ) by a nodulating Rhizobium strain is suppressed by the presence of a non-nodulating mutant. The msgnitude of suppression for nodule formation by nodulating strains varied between 40% and 80% depending on the strain and the time of inoculation.     

Occurrence of two forms of glutamate synthase in Chlamydomonas reinhardii

A simple and rapid radiochemical assay for measuring glutamate synthase activity in permeable cells and cell free extracts of Chlamydomonas is described. Using this method, separate NADH- and ferredoxin-specific enzymes were detected and these were resolved by gel filtration. The properties of the two enzymes differed markedly with respect to MW and affinity for 2-oxoglutarate and glutamine. Activity measurements on cells grown under different physiological conditions revealed a strict coordinate synthesis of the two enzymes. The possible significance of these observations in relation to light and dark NH₃, assimilation in the alga is discussed.     

花生根瘤菌与钼、硼复配的初步研究

针对四川花生主产区土壤缺硼、钼现状和花生对硼、钼的需肥特性,研究根瘤菌与Mo、B复配的可行性。供试慢生花生根瘤菌Spr2-9、Spr4-5耐硼、钼试验结果表明,根瘤菌耐硼能力远低于耐钼能力。“根瘤菌 Mo B”复合菌肥研制试验表明:根瘤菌不宜与硼复配,宜与Mo复配,与钼复配的适宜最高钼浓度以0.4%为宜。     

Pathway of ammonia assimilation in illuminated Lemna minor

Plants of duckweed (Lemna minor) were grown under constant illumination and with a controlled supply of ammonium-N so as to maintain a constant low concentration. In two kinetic experiments (differing in illumination and N level) with ¹⁵N-ammonia, plants were periodically harvested and their free amino acids analysed for ¹⁵N abundance. Attempts were then made to fit the data by computer simulation models. Only models which had at least two or more intracellular compartments gave adequate fits. Two two-compartment models were tested fully. Both had in compartment 1 the glutamine synthetase-glutamate synthase cycle and in compartment 2 a second site of glutamine synthesis. In one model the glutamate for compartment 2 was derived by transport from compartment 1; in the second model it was synthesized from ammonia by glutamate dehydrogenase at a rate equivalent to 10% of the total N uptake. This second model was rejected after it was found that plants previously treated with methionine sulphoximine and aza-serine (inhibitors of the glutamate synthase cycle) were unable to incorporate ¹⁵N. In spite of wide differences in labelling pattern between the two experiments the first model gave acceptable fits to both when different pool sizes were allowed for. Operation of the glutamate synthase cycle was confirmed by the correspondence between model and data for labelling of glutamine amide, glutamine amino and glutamic acid. Consideration of enzyme distributions suggested that compartment 1 (the glutamate synthase system) is the chloroplasts and compartment 2 the cytosol. Analysis of asparagine and neutral amino acids made it possible to construct balance sheets for N uptake in the two experiments. They suggest that all glutamine synthesized in the chloroplast is used for glutamate and asparagine synthesis and that the cytosol enzyme meets the need of the cell for glutamine per se. The high turnover rates for asparagine indicate that this compound is an important intermediate even under steady state conditions, and carries between 20 and 50% of the products of N assimilation.     

不同耐盐性水稻幼苗根氨同化酶对盐胁迫的反应

在盐胁迫下,检测了耐盐性不同的水稻(Oryza sativa L.)品种根部氨同化酶及其相关参数的变化.结果表明,根的可溶性蛋白、谷氨酰胺合成酶(GS)及依赖于NADH的谷氨酸合酶(NADH-GOGAT)活性在高盐浓度下不同程度地降低,其影响大小依次为早花二号(盐敏感品种)、金珠一号(正常栽培品种)、津稻779(耐盐品种),与其耐盐性相一致.在盐胁迫条件下,在耐盐性较高的水稻品种中,GS和GOGAT活性比盐敏感品种高,NH4 浓度维持在较低的水平.Native-PAGE和活性染色结果表明,GSrb更容易受到外界环境的影响.在高浓度盐的胁迫下,早花二号、金珠一号的依赖于NADH的谷氨酸脱氢酶(AADH-GDH)活性都有较显著的升高,津稻779却无明显的变化,这和NH4 含量的变化相一致.盐不同程度地导致可溶性糖(TSS)在金珠一号和津稻779根部积累,而在早花2号的根部,可溶性糖的水平则随盐浓度的不同而表现出不同的变化.在所检测的品种中,脯氨酸的含量均有不同程度的升高,但在高盐浓度下,盐敏感品种的含量较低.这些结果提示,不同的水稻品种对盐胁迫的敏感程度与该品种GS以及GOGAT活性的高低有关.     

不同耐盐性水稻幼苗根氨同化酶对盐胁迫的反应

在盐胁迫下,检测了耐盐性不同的水稻(Oryza sativa L.)品种根部氨同化酶及其相关参数的变化。结果表明,根的可溶性蛋白、谷氨酰胺合成酶(GS)及依赖于NADH的谷氨酸合酶(NADH-GOGAT)活性在高盐浓度下不同程度地降低,其影响大小依次为早花二号(盐敏感品种)、金珠一号(正常栽培品种)、津稻779(耐盐品种),与其耐盐性相一致。在盐胁迫条件下,在耐盐性较高的水稻品种中, GS和GOGAT活性比盐敏感品种高,NH4 浓度维持在较低的水平。Native-PAGE和活性染色结果表明,GSrb更容易受到外界环境的影响。在高浓度盐的胁迫下,早花二号、金珠一号的依赖于NADH的谷氨酸脱氢酶(NADH-GDH)活性都有较显著的升高,津稻779却无明显的变化,这和NH4 含量的变化相一致。盐不同程度地导致可溶性糖(TSS)在金珠一号和津稻779根部积累,而在早花2号的根部,可溶性糖的水平则随盐浓度的不同而表现出不同的变化。在所检测的品种中,脯氨酸的含量均有不同程度的升高,但在高盐浓度下,盐敏感品种的含量较低。这些结果提示,不同的水稻品种对盐胁迫的敏感程度与该品种GS以及GOGAT活性的高低有关。     

花生根瘤菌的数值分类

从我国 １１个省、 １６种土壤类型、 ２０多个花生（Ａｒａｃｈｉｓ ｈｙｐｏｇａｅａ Ｌ．）品种上分离到的花生根瘤菌［Ｂｒａｄｙｒｈｉｚｏｂｉｕｍ ｓｐ．（Ａｒａｃｈｉｓ）］中选取５０个代表菌株、并与从津巴布韦引进的４株花生根瘤菌及７株慢生根瘤菌常用的参比菌株共６１株菌进行了１２８项表型特征的测定。数值分类的结果表明,全部菌株在７５％水平上相聚,并在７６％和７７％的水平上分别聚成两大群（群Ⅰ、群Ⅱ）,每大群以较高的相似性（８５％- ９４％）各聚成６个亚群。所用数值分类方法不能将花生根瘤菌和大豆根瘤菌在属的水平上分开,但亚群和未归入亚群的菌株可能暗示亚种或种存在,同时本文结果还表现出花生根瘤菌的地域分布差异及其多样性。     

Microbial Resolution of Racemic Carvomenthols

By selected microorganisms dl-carvomenthyl acetate, dl-isocarvomenthyl acetate and dl-neo isocarvomenthyl acetate were asymmetrically hydrolyzed to l-carvomenthol with d-carvomenthyl acetate, l-isocarvomenthol with d-isocarvomenthyl acetate and d-neo isocarvomenthol with l-neo isocarvomenthyl acetate respectively; dl-neo carvomenthyl acetate was not hydrolyzed.     

Purification and properties of glutamate synthase from Streptomyces lincolnensis

Ｉｎｍｏｓｔｐｒｏｃａｒｙｏｔｅｓ,ｔｈｅｅｎｚｙｍｅｇｌｕｔａｍａｔｅｓｙｎｔｈａｓｅ[Ｌｇｌｕｔａｍａｔｅ:ＮＡＤ(Ｐ)+ｏｘｉｄｏｒｅｄｕｃｔａｓｅ(ｔｒａｎｓａｍｉｎａｔｉｎｇ)(ＥＣ1.4.1.13ｏｒ14)](ＧＯＧＡＴ),ｔｏｇｅｔｈｅｒｗｉｔｈｇｌｕｔａｍｉｎｅｓｙｎｔｈｅｔａｓｅ[Ｌｇｌｕｔａｍａｔｅ:ａｍｍｏｎｉａｌｉｇａｓｅ(ＡＤＰｆｏｒｍｉｎｇ)(ＥＣ6.3.1.2)](ＧＳ),ｈａｓｂｅｅｎｃｏｎｓｉｄｅｒｅｄｔｏｂｅａｎａｌｔｅｒｎａｔｉｖｅｔｏｇｌｕｔａｍａｔｅｄｅｈｙｄｒｏｇｅｎａｓｅｉｎａｍｍｏｎｉａ…     

用发光酶基因(luxAB)标记法研究慢生花生根瘤菌的竞争结瘤能力

luxAB基因标记是一种新型基因标记技术,在很多研究领域都有着良好的应用前景。研究通过三亲本杂交将luxAB基因成功地向慢生型花生根瘤菌进行了转移,并获得了一株带LuxAB基因标记的菌株Cspr7-1。对Cspr7-1进行性状、标记基因的遗传稳定性检测,结果表明,LuxAB基因不仅能有效表达,而且性状稳定。在无氮水培条件下进行标记菌株与土著根瘤菌的竞争结瘤试验。结果证实,Cspr7-1在植物根系上的占瘤率平均达到61.3％,比土著根瘤菌的竞争结瘤能力强,而且Cspr7-1在主根上的侵染能力远较侧根上的强,平均高出22.3％-39.6％。     

不同耐盐品种棉花根系主要指标对盐分胁迫的响应

以盐敏感品种‘中棉所45’(CCRI45)、弱耐盐品种‘新陆早17号’(XLZ17)、中等耐盐品种‘新陆早13号’(XLZ13)和耐盐品种‘中棉所35’(CCRI35)为试验材料,利用根系分析系统研究盐分胁迫下棉花根系形态特征及其与棉株耐盐性的关系.结果表明:盐分胁迫显著降低棉花根和叶的干质量以及K^+/Na^+,其中耐盐品种CCRI35和中等耐盐品种XLZ13的根干质量、叶干质量以及根中K^+/Na^+分别比盐敏感品种CCRI45提高了69.3%~104.4%、24.8%~45.3%和25.0%~45.8%;盐分胁迫显著抑制棉花根系生长发育,其中CCRI 35和XLZ13的总根长、根系总表面积、根系总体积以及0~10 cm土层中直径为0~1.2 mm内的根长、根表面积和根体积均显著高于CCRI45,分别增加了15.2%~85.8%、12.0%~68.5%、31.7%~217.8%、27.2%~73.9%、39.6%~74.3%和99.0%~309.7%.主成分分析表明,比根长、浅层根长比例和细根比例受基因型差异的影响较为明显,是区分不同耐盐品种棉花根系形态差异的主要指标.逐步回归分析显示,比根长、0~10 cm土层的粗根根长、细根根表面积、粗根根表面积、粗根体积、中根比例,以及10~20 cm粗根根长、粗根表面积、粗根体积等根系参数对盐分响应敏感.耐盐棉花品种可通过维持表层根长比例、细根比例和比根长的增加来适应盐分胁迫.