Department of Biochemical Engineering and Biotechnology, Indian Institute of Technology Delhi, Hauz Khas, New Delhi 110016, India.
Biotechnol Bioeng. 2012 May;109(5):1205-16. doi: 10.1002/bit.24403. Epub 2011 Dec 25.
Elucidation of the chemical logic of life is one of the grand challenges in biology, and essential to the progress of the upcoming field of synthetic biology. Treatment of microbial cells explicitly as a "chemical" species in controlled reaction (growth) environments has allowed fascinating discoveries of elemental formulae of a few species that have guided the modern views on compositions of a living cell. Application of mass and energy balances on living cells has proved to be useful in modeling of bioengineering systems, particularly in deriving optimized media compositions for growing microorganisms to maximize yields of desired bio-derived products by regulating intra-cellular metabolic networks. In this work, application of elemental mass balance during growth of Magnetospirillum gryphiswaldense in bioreactors has resulted in the discovery of the chemical formula of the magnetotactic bacterium. By developing a stoichiometric equation characterizing the formation of a magnetotactic bacterial cell, coupled with rigorous experimental measurements and robust calculations, we report the elemental formula of M. gryphiswaldense cell as CH(2.06)O(0.13)N(0.28)Fe(1.74×10(-3)). Remarkably, we find that iron metabolism during growth of this magnetotactic bacterium is much more correlated individually with carbon and nitrogen, compared to carbon and nitrogen with each other, indicating that iron serves more as a nutrient during bacterial growth rather than just a mineral. Magnetotactic bacteria have not only invoked some interest in the field of astrobiology for the last two decades, but are also prokaryotes having the unique ability of synthesizing membrane bound intracellular organelles. Our findings on these unique prokaryotes are a strong addition to the limited repertoire, of elemental compositions of living cells, aimed at exploring the chemical logic of life.
阐明生命的化学逻辑是生物学的重大挑战之一，也是即将到来的合成生物学领域发展的关键。在受控反应（生长）环境中，明确将微生物细胞视为“化学”物质，可以发现一些物种的基本元素配方，这些发现为现代活细胞成分观提供了指导。将质量和能量平衡应用于活细胞已被证明在生物工程系统建模中非常有用，特别是在通过调节细胞内代谢网络来优化微生物生长的培养基成分，以最大限度地提高所需生物衍生产品的产量。在这项工作中，在生物反应器中生长磁螺菌时应用元素质量平衡，发现了磁螺菌的化学公式。通过开发一个描述磁细菌细胞形成的化学计量方程，结合严格的实验测量和强大的计算，我们报告了 M. gryphiswaldense 细胞的元素配方为 CH(2.06)O(0.13)N(0.28)Fe(1.74×10(-3))。值得注意的是，我们发现与其他元素相比，在这种磁细菌的生长过程中，铁代谢与碳和氮的相关性更高，这表明铁在细菌生长过程中更像是一种营养物质，而不仅仅是一种矿物质。在过去的二十年中，磁细菌不仅在天体生物学领域引起了一些关注，而且还是具有合成膜结合细胞内细胞器的独特能力的原核生物。我们对这些独特原核生物的发现，为探索生命的化学逻辑提供了有限的活细胞元素组成的有力补充。
