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首页> 外文期刊>Journal of bacteriology >H2 metabolism in the photosynthetic bacterium Rhodopseudomonas capsulata: H2 production by growing cultures.
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H2 metabolism in the photosynthetic bacterium Rhodopseudomonas capsulata: H2 production by growing cultures.

机译：光合细菌荚膜红假单胞菌中的H2代谢：通过生长培养物产生H2。

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Purple photosynthetic bacteria produce H2 from organic compounds by an anaerobic light-dependent electron transfer process in which nitrogenase functions as the terminal catalyst. It has been established that the H2-evolving function of nitrogenase is inhibited by N2 and ammonium salts, and is maximally expressed in cells growing photoheterotrophically with certain amino acids as sources of nitrogen. In the present studies with Rhodopseudomonas capsulata, nutritional factors affecting the rate and magnitude of H2 photoproduction in cultures growing with amino acid nitrogen sources were examined. The highest H2 yields and rates of formation were observed with the organic acids: lactate, pyruvate, malate, and succinate in media containing glutamate as the N source; under optimal conditions with excess lactate, H2 was produced at rates of ca. 130 ml/h per g(dry weight) of cells. Hydrogen production is significantly influenced by the N/C ratio in the growth substrates; when this ratio exceeds a critical value, free ammonia appears in the medium and H2 is not evolved. In the "standard" lactate + glutamate system, both H2 production and growth are "saturated" at a light intesity of ca. 600 ft-c (6,500 lux). Evolution of H2, however, occurs during growth at lithe intensities as low as 50 to 100 ft-c (540 to 1,080 lux), i.e., under conditions of energy limitation. In circumstances in which energy conversion rate and supplies of reducing power exceed the capacity of the biosynthetic machinery, energy-dependent H2 production presumably represents a regulatory device that facilitates "energy-idling." It appears that even when light intensity (energy) is limiting, a significant fraction of the available reducing power and adenosine 5'-triphosphate is diverted to nitrogenase, resulting in H2 formation and a bioenergetic burden to the cell.
机译：紫色的光合细菌通过依赖于厌氧性的依赖光的电子转移过程从有机化合物中产生H2，其中固氮酶充当末端催化剂。已经确定，固氮酶的H 2进化功能受到N 2和铵盐的抑制，并在以某些氨基酸作为氮源光异养生长的细胞中最大表达。在目前关于荚膜红假单胞菌的研究中，研究了影响氨基酸氨基酸源生长的培养物中H2光产生速率和幅度的营养因素。在以谷氨酸为氮源的培养基中，乳酸，丙酮酸，苹果酸和琥珀酸等有机酸可观察到最高的H2产率和形成速率。在乳酸过量的最佳条件下，氢气的生成速度约为每克（干重）细胞130毫升/小时。氢气的产生显着受生长基质中N / C比的影响;当该比率超过临界值时，介质中会出现游离氨，并且不会释放出H2。在“标准”乳酸+谷氨酸系统中，H 2的产生和生长都在约200的轻度强度下“饱和”。 600英尺-英尺（6,500 lux）。然而，H 2的放出发生在生长在低至50至100 ft-c（540至1,080 lux）的光强下，即在能量限制的条件下。在能量转换率和降低功率的供应超过生物合成机械的能力的情况下，与能量有关的H2产生可能代表一种调节装置，可促进“能量空转”。似乎即使光强度（能量）受到限制，可用还原能力和5'-三磷酸腺苷的很大一部分仍转移到了固氮酶上，导致了H2的形成和细胞的生物能负担。

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