School of Oceanography, University of Washington, Seattle, WA 98195, USA.
School of Oceanography, University of Washington, Seattle, WA 98195, USA.
Protist. 2019 Jul;170(3):328-348. doi: 10.1016/j.protis.2019.05.004. Epub 2019 May 28.
Diatoms perform an estimated 20% of global photosynthesis, form the base of the marine food web, and sequester carbon into the deep ocean through the biological pump. In some areas of the ocean, diatom growth is limited by the micronutrient cobalamin (vitamin B), yet the biochemical ramifications of cobalamin limitation are not well understood. In a laboratory setting, we grew the diatom Thalassiosira pseudonana under replete and low cobalamin conditions to elucidate changes in metabolite pools. Using metabolomics, we show that the diatom experienced a metabolic cascade under cobalamin limitation that affected the central methionine cycle, transsulfuration pathway, and composition of osmolyte pools. In T. pseudonana, 5'-methylthioadenosine decreased under low cobalamin conditions, suggesting a disruption in the diatom's polyamine biosynthesis. Furthermore, two acylcarnitines accumulated under low cobalamin, suggesting the limited use of an adenosylcobalamin-dependent enzyme, methylmalonyl CoA mutase. Overall, these changes in metabolite pools yield insight into the metabolic consequences of cobalamin limitation in diatoms and suggest that cobalamin availability may have consequences for microbial interactions that are based on metabolite production by phytoplankton.
硅藻进行全球光合作用的约 20%，构成海洋食物网的基础，并通过生物泵将碳隔离到深海中。在海洋的某些区域，硅藻的生长受到微量元素钴胺素（维生素 B）的限制，但对钴胺素限制的生化后果还了解甚少。在实验室环境中，我们在富含和低钴胺素条件下培养硅藻假微型海链藻，以阐明代谢物库的变化。通过代谢组学，我们发现，在钴胺素限制下，硅藻经历了代谢级联反应，影响了中心蛋氨酸循环、转硫途径和渗透物库的组成。在假微型海链藻中，5'-甲基硫代腺苷在低钴胺素条件下减少，表明其多胺生物合成受到破坏。此外，两种酰基辅酶 A 在低钴胺素条件下积累，表明腺苷钴胺素依赖性酶甲基丙二酰辅酶 A 变位酶的使用受限。总的来说，这些代谢物库的变化为我们提供了关于硅藻钴胺素限制的代谢后果的深入了解，并表明钴胺素的可用性可能会对基于浮游植物代谢产物产生的微生物相互作用产生影响。
