Institute of Molecular Systems Biology, Department of Biology, ETH Zürich, Zürich, Switzerland.
Department of Civil, Environmental and Geomatic Engineering, Institute of Environmental Engineering, ETH Zürich, Zürich, Switzerland.
mSystems. 2024 Apr 16;9(4):e0022724. doi: 10.1128/msystems.00227-24. Epub 2024 Mar 27.
Cyanobacteria fix carbon dioxide and release carbon-containing compounds into the wider ecosystem, yet they are sensitive to small metabolites that may impact their growth and physiology. Several cyanobacteria can grow mixotrophically, but we currently lack a molecular understanding of how specific nutrients may alter the compounds they release, limiting our knowledge of how environmental factors might impact primary producers and the ecosystems they support. In this study, we develop a high-throughput phytoplankton culturing platform and identify how the model cyanobacterium sp. PCC 6803 responds to nutrient supplementation. We assess growth responses to 32 nutrients at two concentrations, identifying 15 that are utilized mixotrophically. Seven nutrient sources significantly enhance growth, while 19 elicit negative growth responses at one or both concentrations. High-throughput exometabolomics indicates that oxidative stress limits growth but may be alleviated by antioxidant metabolites. Furthermore, glucose and valine induce strong changes in metabolite exudation in a possible effort to correct pathway imbalances or maintain intracellular elemental ratios. This study sheds light on the flexibility and limits of cyanobacterial physiology and metabolism, as well as how primary production and trophic food webs may be modulated by exogenous nutrients.IMPORTANCECyanobacteria capture and release carbon compounds to fuel microbial food webs, yet we lack a comprehensive understanding of how external nutrients modify their behavior and what they produce. We developed a high throughput culturing platform to evaluate how the model cyanobacterium sp. PCC 6803 responds to a broad panel of externally supplied nutrients. We found that growth may be enhanced by metabolites that protect against oxidative stress, and growth and exudate profiles are altered by metabolites that interfere with central carbon metabolism and elemental ratios. This work contributes a holistic perspective of the versatile response of to externally supplied nutrients, which may alter carbon flux into the wider ecosystem.
蓝藻固定二氧化碳并将含碳化合物释放到更广泛的生态系统中，但它们对可能影响其生长和生理的小分子代谢物很敏感。一些蓝藻可以混合营养生长，但我们目前缺乏对特定营养素如何改变它们释放的化合物的分子理解，这限制了我们对环境因素如何影响初级生产者及其支持的生态系统的认识。在这项研究中，我们开发了一种高通量浮游植物培养平台，并确定了模式蓝藻 sp. PCC 6803 对营养补充的反应。我们评估了 32 种营养素在两种浓度下的生长反应，确定了 15 种可以混合营养利用的营养素。七种营养源显著促进生长，而 19 种营养源在一种或两种浓度下都产生负生长反应。高通量外代谢组学表明，氧化应激限制了 sp. PCC 6803 的生长，但抗氧化代谢物可以缓解这种限制。此外，葡萄糖和缬氨酸可能会强烈改变代谢物的分泌，以努力纠正途径失衡或维持细胞内元素比例。这项研究揭示了蓝藻生理学和新陈代谢的灵活性和局限性，以及初级生产和营养食物链如何可能被外源营养素调节。
