螺藻旋Spirulina platensis整体细胞放氢特性的研究

螺旋藻Spirulina platensis具有氢酶。由氢酶催化的放H_2活性受到培养基中硝酸盐的抑制。这是由于氢酶与硝酸还原酶之间存在还原能力的竞争。以脲素取代硝酸盐可以部分地解除其抑制作用。放H_2活性随着暗中时间的延长而成倍加强。在氮气或氩气中比在空气中的放氢活性分别高出244％和287％。氧气抑制放H_2活性,约5％O_2达到半抑制浓度。CO对,放H_2的半抑制浓度为2％。当光照强度大于2000lx时完全抑制放H_2活性。光合放氧与放氢的矛盾可以通过光、暗交替处理,由暗中的耗氧呼吸以加协调。     

浑球红假单胞菌在暗处发酵生长时的固氮酶、吸氢酶以及放氢机制的研究

光合细菌浑球红假单胞菌(Rhodopesudomonas sphaeroides)能在黑暗厌氧条件下生长。首次发现发酵生长的浑球红假单胞菌有固氮酶和吸氧酶的活性。试验比较了在光营养、黑暗厌氧呼吸和好氧呼吸生长方式下该菌的放氢作用,认为黑暗厌氧呼吸过程中的放氢是氢酶催化的放氢。     

蓝藻(Anabaena 7120)的光合放氢和参与放氢的酶

蓝藻Anabaena 7120放氢是一个依赖于光的过程,暗中几乎测不出放氢活性。静置方式培养的蓝藻预先进行强化培养是测得高放氢活性的重要条件。年轻的蓝藻放氢活性比年老的高。氯化铵和一系列光合作用抑制剂对蓝藻放氢有抑制作用,弱光加剧氯化铵对放氢的抑制。在弱光加光合抑制剂的条件下,受氯化铵抑制的放氢活性恢复速度比强光下慢。CO_2、N_2、NaN_3和KNO_3与放氢竞争电子而抑制蓝藻的放氢。C_2H_2促进蓝藻放氢,CO则抑制放氢,C_2H_2和CO一起加入时,放氢受到的促进显著比单加C_2H_2的大。经分子氢预处理过的蓝藻,其放氢活性在光下可以得到明显的促进。     

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。     

铁和镍对光合细菌生长和产氢的影响

基于金属元素在生物体功能发挥中的作用以及它们参与光合细菌光合放氢的重要性,着重进行了铁和镍对沼泽红假单胞菌（Rhodopseudomonas palustris）Z菌株和一株红杆菌（Rhodobactersp.）细胞生长、光合放氢和光合色素合成影响的研究。结果表明,高浓度Fe3+可显著提高两菌株光放氢能力和生物合成能力,最适浓度的Fe3+可使其产氢能力分别达对照组的1.32倍和2.8倍,产氢得率分别为360.6mL/g和385.9 mL/g,生物量分别为对照组的1.42倍和1.54倍。9μmol/L Ni2+的添加可使两菌株产氢能力分别达对照组的1.48倍和1.96倍,产氢得率分别为429.7mL/g和456.3 mL/g。而当Ni2+浓度为12μmol/L时,两菌株的产氢活性受到不同程度的抑制,产氢得率分别降低46.7%和19.4%。在铁浓度相同时,添加6μmol/L Ni2+能明显促进两菌株的生长。而当Ni2+浓度大于6μmol/L时,细胞生长受到抑制。Fe3+和Ni2+对Rhodobactersp.菌株类胡萝卜色素有显著影响。研究结果显示, 426nm色素峰随铁浓度的增加和镍的添加而消失,同时,产氢活性提高。     

光合放氢与氢气能源

光合作用所吸收的日光能,首先贮存于ATP和NADPH_2两种称为同化力之中,然后除了用于CO_2还原外,在某些光合生物中还可用于还原H_2O或有机物分子中,并以分子态氢的形式释放出来,后者就是某些植物(主要是藻类)和细菌的光合放氢作用。现在已知,几乎所有的光合细菌都可以放氢,50%以上的藻类在一定条件下也可以放氢。如蓝绿藻既能进行光合固氮,又能进行光合放氢。这不仅说明了光     

荚膜红假单孢菌(Rhodopseudomonas capsulata)氢酶性质的初步研究

荚膜红假单孢菌(Rhodopseudomonas capsulata F.)含有可溶性和膜结合态两种状态的氢酶,以膜结合态为主要存在形式,其活性占整个氢酶活性的65％左右,表面活性剂Triton X-100能把它从膜上溶解下来、两种状态的氢酶均具有催化吸氢和放氢活性,并在吸氢反应的最适pH值、电子受体,热稳定性等方面都是很相似,但吸氢活性远高于放氢活性。两种状态的氢酶对氧都较敏感,曝露于氧往往使活性钝化,钝化了的氢酶又可被氢再活化,不过可溶性氢酶曝氧时间较长(3天后),氢就不再使其活性恢复。温度和气相对两种状态氢酶活性的贮存也表现各异,氢气相下,可溶性氢酶在4℃最稳定,而膜结合态氢酶则为20℃。NaCl对膜结合态氢酶的吸氢活性具有抑制作用,NaCl=0.5M时,抑制其活性达60％左右。     

测定氢酶吸氢活性的光谱分析法

固氮酶催化放氢是影响生物固氮效率的重要因素之一。经过吸氢酶吸收固氮酶释放的氢,一方面可以增加还原力来源,同时经氧化后可以消除系统内的氧,保护固氮酶免受氧伤害,从而提高固氮效率。测定氢酶吸氢的方法有多种,例如:同位素氚与水的交换法、检压法、电极法、气相层析法和光谱分析法。由于前三种方法操作较繁琐,目前国内较多的是使用气相层析法。而用光谱分析法定量地测定氢酶的吸氢活性是一种比气相法更为快速和灵敏的     

镍在浑球红假单胞菌氢酶合成中的作用（简报）

在固氮酶能表达的生长条件下,镍可促进浑球红假单胞菌菌株601的氢酶合成,而在含氨培养基上则没有影响。镍促进氢酶合成的最适浓度为10μmol/L,并具有金属专一性,其他二价金属离子对氢酶合成没有作用。镍在促进氢酶吸氢的同时,抑制菌体的放氢,但对固氮酶的乙炔还原活性则几乎没有影响。     

光合细菌产氢因子的研究进展

光合细菌在固氮的同时释放氢气。产氢与固氮是同步进行的。固氮酶与氢酶共同影响光合细菌的产氢活性,而外源生理条件又影响着固氮酶与氢酶的活性,其中有机碳阻抑吸氢酶表达,促进产氢;氨则抑制固氮活性而降低产氢量;氧气的存在使固氮酶与氢酶都失活,从而抑制放氢反应的进行。     

缺钼培养的蓝藻Anabaena 1720放氢的研究

培养液中缺钼时,蓝藻Anabaena 7120的放氢受到削弱,其削弱程度比固氮活性的削弱小。此种蓝藻的放氢对CO和氧都敏感,预先以乙炔处理时,其放氢即受抑制,而在光下以分子氢预处理则促进放氢。这类蓝藻光下放氢比暗中高,当添加光合抑制剂或氯化铵于反应系统时,其放氢便明显下降。     

Aerobic hydrogen production by the heterocystous cyanobacteria Anabaena spp. strains CA and 1F.

Aerobic photoproduction of H2 was demonstrated in Anabaena spp. strains CA and 1F when cells were growing under nitrogen-fixing conditions. The rates of production, measured either by the hydrogen electrode or in a flow system by gas chromatography, were 10 to 15% of the rate of photosynthetic O2 evolution or 50 to 80% of the rates of acetylene reduction. Strains CA and 1F differed in several respects. In strain CA, H2 production was immediately partially sensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea, whereas strain 1F was not immediately affected. Strain CA also showed a consistently higher rate of H2 production than did strain 1F. H2 production in strain CA was also markedly influenced by the light intensity used for growth, although the growth rates indicated that the light intensities used were essentially saturating.     

蓝藻Anabaena7120的固氮活力及其和光合作用的关系

蓝藻Anabaena 7120经用Ar+CO_2、空气和Ar处理后,固氮活性有明显不同。Ar+CO_2处理的活性比空气处理的高出数倍,而Ar处理的则比空气中的低很多。以上三种处理的Anabaena 7120固氮对不同生理条件反应不一样,固氮活性高者对CO和O_2的敏感程度小些、受到CO_2和N_2的抑制程度也轻。但是分子氢对三者固氮作用的支持效用相同,并且也是和氢酶活动有联系。弱光下固氮活力低的蓝藻固氮活性下降得更大些。光合抑制剂和结合态氮对固氮活力高的蓝藻固氮活性的抑制显著比固氮活力低者小。三者的放氢和放氧能力也不同,固氮活力高者放氧高而放氢量小些,低固氮活力的蓝藻正好相反。     

硝酸钾缓解氯化钠胁迫蓝藻Anabaena 7120固氮的生理基础

营养液中添加适量ＫＮＯ３可在一定程度上缓解ＮａＣｌ对鱼腥藻固氮活性的抑制作用。暗处理或加光合抑制剂时,ＫＮＯ３对ＮａＣｌ胁迫的缓解作用便消失。供给外源蔗糖、提高ＣＯ２浓度、同时供给ＣＯ２和Ｎ２时,ＫＮＯ３对缓解ＮａＣｌ胁迫的作用则增高．同时供给Ｏ２和Ｈ２对ＫＮＯ３的缓解作用增高影响较小,而在厌氧（Ａｒ或Ｎ２中）或单加氧下,ＫＮＯ３的缓解效应则明显减弱或消失．     

Effects of Preillumination on Dark Nitrogen Fixation and Respiration by Anabaena Cylindrica

In whole filaments of Anabaena cylindrica dark nitrogen-fixingactivity (measured as acetylene reduction) and respiration increasedwith the light intensity of a fixed period of preillumination,saturating at ca. 10,000 lux. With saturating light during preillumination,the amount and duration of dark nitrogen-fixing activity increasedwith length of preillumination, but respiration declined rapidlyin the dark. At dark respiration rates below 250 nmol O₂ uptake mg protein^–1?h^–1(State 1) no significant nitrogen-fixing activity is observed.From 250 to 550 nmol O₂ uptake?mg protein^–1?h^–1(State 2), nitrogen-fixing activity depends on O₂ uptake whileabove 550 nmol O₂ uptake?mg protein^–1?h^–1 (State3), nitrogen-fixing activity no longer increases with furtherincrease in O₂ uptake rate. (Received June 18, 1983; Accepted November 10, 1983)     

Comparative Amperometric Study of Uptake Hydrogenase and Hydrogen Photoproduction Activities between Heterocystous Cyanobacterium Anabaena cylindrica B629 and Nonheterocystous Cyanobacterium Oscillatoria sp. Strain Miami BG7

Heterocystous filamentous cyanobacterium Anabaena cylindrica B629 and nonheterocystous filamentous cyanobacterium Oscillatoria sp. strain Miami BG7 were cultured in media with N₂ as the sole nitrogen source; and activities of oxygen-dependent hydrogen uptake, photohydrogen production, photooxygen evolution, and respiration were compared amperometrically under the same or similar experimental conditions for both strains. Distinct differences in these activities were observed in both strains. The rates of hydrogen photoproduction and hydrogen accumulation were significantly higher in Oscillatoria sp. strain BG7 than in A. cylindrica B629 at every light intensity tested. The major reason for the difference was attributable to the fact that the heterocystous cyanobacterium had a high rate of oxygen-dependent hydrogen consumption activity and the nonheterocystous cyanobacterium did not. The activity of oxygen photoevolution and respiration also contributed to the difference. Oscillatoria sp. strain BG7 had lower O₂ evolution and higher respiration than did A. cylindrica B629. Thus, the effect of O₂ on hydrogen photoproduction was minimized in Oscillatoria sp. strain BG7.     

Hydrogen uptake in Anabaena sp. strain CA does not protect nitrogenase from inactivation by hyperbaric oxygen

Abstract Two mutants of Anabaena sp. strain CA were used to demonstrate that oxygen-dependent hydrogen uptake was not the primary means to protect the nitrogenase enzyme complex from the deleterious effects of hyperbaric oxygen in vivo. Exposure to air caused the immediate and irreversible inactivation of nitrogenase activity in an oxygen-sensitive mutant, designated strain 22Y. Inactivation was concomitant with the destruction of the molybdo-iron (MoFe) protein of the nitrogenase complex. The mutant 22Y expressed an O₂-stable, Ni²⁺-stimulated hydrogen uptake of up to 2.7 μM H₂ per mg dry wt per h. Conversely, after exposure to 1% CO₂-99% O₂ for 3 h, both wild-type strain CA and a hydrogen uptake deficient (Hup⁻) mutant, strain N9AR, recovered 70–80% of their original acetylene reduction capacity with no apparent perturbations in the MoFe protein.     

甘露醇对氯化钠胁迫下蓝藻Anabaena 7120固氮活性的增强效应

营养液中添加外源的甘露醇后,蓝藻Ａｎａｂａｅｎａ ７１２０固氮受ＮａＣｌ胁迫的程度减弱。在光合作用不能进行或受到削弱,能量供应受阻、厌氧环境中和分子氧条件下,甘露醇的良好作用减小或消失。改善能涛和碳架供应,增强氢的利用或满足合成固氮酶蛋白所需物质需求时,甘露醇缓解ＮａＣｌ胁迫蓝藻固氮的程度明显增大。