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首页> 外文期刊>BMC Microbiology >Inhibition of bacteriochlorophyll biosynthesis in the purple phototrophic bacteria Rhodospirillumrubrum and Rhodobacter capsulatus grown in the presence of a toxic concentration of selenite
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Inhibition of bacteriochlorophyll biosynthesis in the purple phototrophic bacteria Rhodospirillumrubrum and Rhodobacter capsulatus grown in the presence of a toxic concentration of selenite

机译：在有毒浓度的亚硒酸盐存在下生长的紫色光养细菌Rhodospirillumrubrum和Rhodobacter荚膜菌中细菌叶绿素生物合成的抑制

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Background In many works, the chemical composition of bacterially-produced elemental selenium nanoparticles (Se0-nanoparticles) was investigated using electron dispersive X-ray analysis. The results suggest that these particles should be associated with organic compounds. However, a complete analysis of their chemical composition is still missing. Aiming at identifying organic compounds associated with the Se0-nanoparticles produced by the purple phototrophic bacteria Rhodospirillum rubrum and Rhodobacter capsulatus (α group of the proteobacteria), we used MALDI-TOF spectrometry. Results This technic revealed that numerous signals obtained from particles produced by both species of bacteria were from metabolites of the photosynthetic system. Furthermore, not only bacteriochlorophyll a, bacteriopheophytin a, and bacteriopheophorbide a, which are known to accumulate in stationary phase cultures of these bacteria grown phototrophically in the absence of selenite, were identified. The particles were also associated with intermediary metabolites of the bacteriochlorophyll a biosynthesis pathway such as protoporphyrin IX, protoporphyrin IX monomethyl ester, bacteriochlorophyllide a and, most likely, Mg-protoporphyrin IX-monomethyl ester, as well as with oxidation products of the substrates of protochlorophyllide reductase and chlorin reductase. Conclusion Accumulation of intermediary metabolites of the bacteriochlorophyll biosynthesis pathway in these purple phototrophic bacteria was attributed to inhibition of oxygen-sensitive enzymes involved in this pathway. Consistent with this interpretation it has been reported that these bacteria reduce selenite intracellularly, that they contain high levels of glutathione and that the reduction of selenite with glutathione is a very fast reaction accompanied by the production of reactive oxygen species. As many enzymes involved in the biosynthesis of bacteriochlorophyll contain [Fe-S] clusters in their active site, which are known to be degraded in the presence of reactive oxygen species as well as in the presence of molecular oxygen, we concluded that the substrates of these enzymes accumulate in cells during selenite reduction. Association of metabolites of bacteriochlorophyll biosynthesis and degradation with the Se0-nanoparticles produced by Rhodospirillum rubrum and Rhodobacter capsulatus is proposed to result from coating of the nanoparticles with the intracytoplasmic membrane of these bacteria, where the photochemical apparatus is concentrated.
机译：背景技术在许多工作中，使用电子弥散X射线分析法研究了细菌生产的元素硒纳米颗粒（Se0-纳米颗粒）的化学组成。结果表明这些颗粒应与有机化合物结合。但是，仍然缺少对其化学成分的完整分析。为了鉴定与紫色光养细菌Rhodospirillum rubrum和Rhodobacter荚膜菌（变形杆菌的α组）产生的Se0纳米粒子相关的有机化合物，我们使用了MALDI-TOF光谱法。结果该技术表明，从两种细菌产生的颗粒中获得的许多信号均来自光合系统的代谢产物。此外，不仅鉴定了已知的叶绿素a，细菌脱镁叶绿素a和细菌脱镁叶绿素a，它们在不存在亚硒酸盐的情况下在营养养分生长的细菌的固定相培养物中积累。颗粒还与细菌叶绿素a生物合成途径的中间代谢产物相关，例如原卟啉IX，原卟啉IX单甲酯，细菌叶绿素a和最有可能的Mg-原卟啉IX单甲酯，以及原叶绿素底物的氧化产物。还原酶和二氢卟酚还原酶。结论这些紫色光养细菌中细菌叶绿素生物合成途径的中间代谢产物的积累归因于该途径中涉及的氧敏感性酶的抑制。与这种解释一致，据报道这些细菌在细胞内还原亚硒酸盐，它们含有高含量的谷胱甘肽，并且谷胱甘肽对亚硒酸盐的还原是非常快速的反应，伴随着活性氧的产生。由于许多参与细菌叶绿素生物合成的酶在其活性位点均含有[Fe-S]簇，已知这些簇会在存在活性氧以及存在分子氧的情况下被降解，因此我们得出结论：这些酶在亚硒酸盐还原过程中会积聚在细胞中。细菌叶绿素生物合成和降解的代谢产物与由红螺旋螺旋藻和荚膜红球藻产生的Se0-纳米颗粒的关联被认为是由这些细菌的胞质膜上的纳米颗粒包被而形成的，光化学装置在该颗粒上被浓缩。

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