Metabolic stasis in an ancient symbiosis: genome-scale metabolic networks from two Blattabacterium cuenoti strains, primary endosymbionts of cockroaches
Metabolic stasis in an ancient symbiosis: genome-scale metabolic networks from two Blattabacterium cuenoti strains, primary endosymbionts of cockroaches
复制标题
古代共生中的代谢停滞：来自两种蟑螂主要内共生菌的基因组规模代谢网络
作者：
C. González;Eugeni Belda;Rafael Patiño;A. Moya;J. Peretó;A. Latorre
背景蟑螂是陆生昆虫，它们以氨而非尿酸的形式显着消除废氮。 Blattabacteruenoti (Mercier 1906) 菌株 Bge 和 Pam 分别是德国小蠊和美洲大蠊蟑螂的专性主要内共生菌。两种细菌内共生体的基因组最近已被测序，使得基于基因组规模约束的代谢网络重建成为可能。代谢网络的数学表达以及随后通过通量平衡分析（FBA）对表型特征进行定量研究代表了对这些不可培养细菌的有效功能方法。结果我们报告了Blattabacter菌株Bge（iCG238）和Pam（iCG230）的代谢模型，包括296和289个生化反应，分别与238和230个基因以及364和358个代谢物相关。这两个模型都反映了这些微生物的惊人相似性和奇点。 FBA 用于分析模型的特性、潜力和局限性，假设一些环境限制，例如有氧条件和这些细菌系统的氨净产量，正如实验观察到的那样。此外，使用 iCG238 模型进行的计算机模拟已经能够定义一组碳源和氮源，这也将支持 Pam 菌株在生物量生产方面的可行表型，该菌株缺乏三羧酸循环的前三个步骤。 FBA揭示了一种代谢条件，使得这些酶促步骤变得可有可无，从而为它们的消除提供了可能的进化解释。我们还通过计算模拟证实了代谢网络的脆弱性及其宿主依赖性。 结论 经过 1.4 亿年的内共生体在不同蟑螂谱系中的进化，Bge 和 Pam 菌株中最小化的蜚蠊杆菌代谢网络惊人地相似。对这两种细菌的重建网络进行的 FBA 有助于完善基因组的功能分析，使我们能够推测稍微不同的宿主代谢环境如何推动它们的平行进化。
BackgroundCockroaches are terrestrial insects that strikingly eliminate waste nitrogen as ammonia instead of uric acid. Blattabacterium cuenoti (Mercier 1906) strains Bge and Pam are the obligate primary endosymbionts of the cockroaches Blattella germanica and Periplaneta americana, respectively. The genomes of both bacterial endosymbionts have recently been sequenced, making possible a genome-scale constraint-based reconstruction of their metabolic networks. The mathematical expression of a metabolic network and the subsequent quantitative studies of phenotypic features by Flux Balance Analysis (FBA) represent an efficient functional approach to these uncultivable bacteria.ResultsWe report the metabolic models of Blattabacterium strains Bge (iCG238) and Pam (iCG230), comprising 296 and 289 biochemical reactions, associated with 238 and 230 genes, and 364 and 358 metabolites, respectively. Both models reflect both the striking similarities and the singularities of these microorganisms. FBA was used to analyze the properties, potential and limits of the models, assuming some environmental constraints such as aerobic conditions and the net production of ammonia from these bacterial systems, as has been experimentally observed. In addition, in silico simulations with the iCG238 model have enabled a set of carbon and nitrogen sources to be defined, which would also support a viable phenotype in terms of biomass production in the strain Pam, which lacks the first three steps of the tricarboxylic acid cycle. FBA reveals a metabolic condition that renders these enzymatic steps dispensable, thus offering a possible evolutionary explanation for their elimination. We also confirm, by computational simulations, the fragility of the metabolic networks and their host dependence.ConclusionsThe minimized Blattabacterium metabolic networks are surprisingly similar in strains Bge and Pam, after 140 million years of evolution of these endosymbionts in separate cockroach lineages. FBA performed on the reconstructed networks from the two bacteria helps to refine the functional analysis of the genomes enabling us to postulate how slightly different host metabolic contexts drove their parallel evolution.
什么是通量平衡分析？
影响因子：
46.9
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