Alternative CO2 concentrating mechanisms in different green algal species related to phosphorus limitation and pH

微藻承担了地球上近一半的二氧化碳封存，它们越来越多地被用于生物质生产，为我们的发电厂提供燃料，并固定它们的烟雾-二氧化碳。因此，藻类二氧化碳的固定是一个重要的过程，在许多物种中都有二氧化碳浓缩机制(CCM)的支持。在淡水(和海洋)生态系统中，二氧化碳浓度较低，约为15μM，这需要CCM来提高二氧化碳固定酶Rubisco的羧化速率。这种活性过程需要很高的无机磷(PI)浓度，就像中性小球藻一样，在PI充足的条件下具有高亲和力的CO2吸收系统，但在PI限制的条件下无法实现其完全的CCM能力。最近，我发现了嗜酸性衣藻的一种对比模式，它实现了在等电点充满和等电点限制条件下的高亲和力二氧化碳吸收系统。这对嗜酸杆菌吸收二氧化碳是一个活跃过程的观点提出了质疑。此外，我还用第三种CCM策略确定了另一种藻类。因此，我建议结合PI浓度和pH研究这三种藻类的C-获取，以获得对不同CO2和PI条件下藻类功能反应的机械性洞察。我与联合基因组研究所(美国)、内布拉斯加州大学(美国)和莫纳什大学(澳大利亚)的合作使包括生态学、生理学、分子生物学和遗传学在内的多学科方法得以实现，以阐明绿色微藻中潜在的碳固定机制。

Micro-algae are responsible for nearly one-half of all CO2 sequestration on the planet and they are increasingly used for biomass production to fuel our power plants and fix their fume-CO2. Algal CO2 fixation is thus a vital process that is supported by a CO2-concentrating mechanism (CCM) in many species. In freshwater (and marine) ecosystems CO2 concentrations are low, circa 15 μM, which requires a CCM to enhance carboxylation rates of the CO2-fixing enzyme Rubisco. This active process is assumed to require high inorganic phosphorus (Pi) concentrations, as found in the neutrophile Chlorella emersonii that has a high affinity CO2 uptake system under Pi replete conditions, but cannot realise its full CCM capacity under Pi limiting conditions. Recently, I discovered a contrasting pattern for the acidophile Chlamydomonas acidophila which realises a high affinity CO2 uptake system under both Pi replete and Pi limiting conditions. This questions the notion that CO2 uptake in C. acidophila is an active process. In addition, I have identified another algae with a third CCM strategy. I therefore propose to study the C-acquisition in these three algal species in conjunction with Pi concentration and pH to obtain mechanistic insight into algal functional responses to different conditions of CO2 and Pi. My collaboration with the Joint Genome Institute (USA), the University of Nebraska (USA), and Monash University (Australia) enables a multi-disciplinary approach that includes ecology, physiology, molecular biology and genetics to elucidate mechanisms underlying carbon sequestration in green micro-algae.