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首页> 外文期刊>Journal of bacteriology >Nitrogen metabolism in the phototrophic bacteria Rhodocyclus purpureus and Rhodospirillum tenue.
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Nitrogen metabolism in the phototrophic bacteria Rhodocyclus purpureus and Rhodospirillum tenue.

机译：养光细菌紫红霉菌和红螺螺旋藻中的氮代谢。

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摘要

Studies of the nitrogen nutrition and pathways of ammonia assimilation in Rhodocyclus purpureus and Rhodospirillum tenue have shown that these two seemingly related bacteria differ considerably in aspects of their nitrogen metabolism. When grown photoheterotrophically with malate as carbon source, R. purpureus utilized only NH4+ or glutamine as sole nitrogen sources and was unable to fix N2. By contrast, R. tenue was found to utilize a variety of amino acids as nitrogen sources and was a good N2 fixer. No nitrogenase activity was detected in cells of R. purpureus grown on limiting ammonia, whereas cells of R. tenue grown under identical conditions reduced acetylene to ethylene at high rates. Regardless of the nitrogen source supporting growth, extracts of cells of R. purpureus contained high levels of glutamate dehydrogenase, whereas R. tenue contained only trace levels of this enzyme. Alanine dehydrogenase activity was absent from both species. We conclude that R. purpureus is incapable of fixing molecular nitrogen and employs the glutamate dehydrogenase pathway as the primary means of assimilating NH4+ under all growth conditions. R. tenue, on the other hand, employs the glutamine synthetase/glutamate synthase pathway for the incorporation of NH4+ supplied exogenously or as the product of N2 fixation.
机译：对紫红霉菌和红螺螺旋藻的氮营养和氨同化途径的研究表明，这两种看似相关的细菌在氮代谢方面存在很大差异。当以苹果酸为碳源光异养生长时，紫癜仅利用NH4 +或谷氨酰胺作为唯一的氮源，无法固定N2。相比之下，人们发现R. tenue利用多种氨基酸作为氮源，并且是很好的N2固定剂。在限制氨气条件下生长的紫癜菌的细胞中未检测到固氮酶活性，而在相同条件下生长的ten虫的细胞在高速率下将乙炔还原为乙烯。不管支持生长的氮源如何，紫癜的细胞提取物中都含有高水平的谷氨酸脱氢酶，而紫ten中仅含有微量的这种酶。两种物种都没有丙氨酸脱氢酶活性。我们得出的结论是，紫癜河菌无法固定分子氮，并利用谷氨酸脱氢酶途径作为在所有生长条件下吸收NH4 +的主要手段。另一方面，R。tenue利用谷氨酰胺合成酶/谷氨酸合酶途径掺入外源或作为N2固定产物的NH4 +。

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