Experimental Ecology and Evolution Research Group, Department of Bioorganic Chemistry, Max Planck Institute for Chemical Ecology, Jena 07745, Germany.
Department of Ecology, School of Biology/Chemistry, University of Osnabrück, Osnabrück 49076, Germany.
Environ Microbiol. 2019 Apr;21(4):1306-1320. doi: 10.1111/1462-2920.14539. Epub 2019 Mar 4.
Bacteria frequently engage in cross-feeding interactions that involve an exchange of metabolites with other micro- or macroorganisms. The often obligate nature of these associations, however, hampers manipulative experiments, thus limiting our mechanistic understanding of the ecophysiological consequences that result for the organisms involved. Here we address this issue by taking advantage of a well-characterized experimental model system, in which auxotrophic genotypes of E. coli derive essential amino acids from prototrophic donor cells using intercellular nanotubes. Surprisingly, donor-recipient cocultures revealed that the mere presence of auxotrophic genotypes was sufficient to increase amino acid production levels of several prototrophic donor genotypes. Our work is consistent with a scenario, in which interconnected auxotrophs withdraw amino acids from the cytoplasm of donor cells, which delays feedback inhibition of the corresponding amino acid biosynthetic pathway and, in this way, increases amino acid production levels. Our findings indicate that in newly established mutualistic associations, an intercellular regulation of exchanged metabolites can simply emerge from the architecture of the underlying biosynthetic pathways, rather than requiring the evolution of new regulatory mechanisms.
细菌经常进行交叉喂养相互作用，涉及与其他微生物或宏观生物交换代谢物。然而，这些关联的强制性往往阻碍了操纵实验，从而限制了我们对涉及的生物体产生的生态生理后果的机械理解。在这里，我们利用一个经过充分表征的实验模型系统来解决这个问题，其中大肠杆菌的营养缺陷型基因型利用细胞间纳米管从营养型供体细胞中获得必需氨基酸。令人惊讶的是，供体-受体共培养表明，仅仅存在营养缺陷型基因型就足以提高几种营养型供体基因型的氨基酸生产水平。我们的工作与以下情况一致，即相互连接的营养缺陷型从供体细胞的细胞质中提取氨基酸，这会延迟相应氨基酸生物合成途径的反馈抑制，从而增加氨基酸的生产水平。我们的发现表明，在新建立的互利共生关系中，交换代谢物的细胞间调节可以简单地从基础生物合成途径的结构中出现，而不需要新的调节机制的进化。
