Abstract：
The phototrophic capability of Candidatus Accumulibacter (Accumulibacter), a common polyphosphate accumulating organism (PAO) in enhanced biological phosphorus removal (EBPR) systems, was investigated in this study. Accumulibacter is phylogenetically related to the purple bacteria Rhodocyclus from the family Rhodocyclaceae, which belongs to the class Betaproteobacteria. Rhodocyclus typically exhibits both chemoheterotrophic and phototrophic growth, however, limited studies have evaluated the phototrophic potential of Accumulibacter. To address this gap, short and extended light cycle tests were conducted using a highly enriched Accumulibacter culture (95%) to evaluate its responses to illumination. Results showed that, after an initial period of adaptation to light conditions (approximately 4-5 h), Accumulibacter exhibited complete phosphorus (P) uptake by utilising polyhydroxyalkanoates (PHA), and additionally by consuming glycogen, which contrasted with its typical aerobic metabolism. Mass, energy, and redox balance analyses demonstrated that Accumulibacter needed to employ phototrophic metabolism to meet its energy requirements. Calculations revealed that the light reactions contributed to the generation of, at least more than 67% of the ATP necessary for P uptake and growth. Extended light tests, spanning 21 days with dark/light cycles, suggested that Accumulibacter generated ATP through light during initial operation, however, it likely reverted to conventional anaerobic/aerobic metabolism under dark/light conditions due to microalgal growth in the mixed culture, contributing to oxygen production. In contrast, extended light tests with an enriched Tetrasphaera culture, lacking phototrophic genes in its genome, clearly demonstrated that phototrophic P uptake did not occur. These findings highlight the adaptive metabolic capabilities of Accumulibacter, enabling it to utilise phototrophic pathways for energy generation during oxygen deprivation, which holds the potential to advance phototrophic-EBPR technology development.
摘要：
念珠菌蓄积菌（accumulibacter）的光养能力，增强生物除磷(EBPR)系统中常见的聚磷酸盐积累生物(PAO)，在这项研究中进行了调查。累积杆菌属在系统发育上与红霉素科的紫色细菌Rhodocyclus有关，属于Betaproteobacteria类。Rhodocyclus通常表现出化学异养和光养生长，然而,有限的研究已经评估了累积杆菌的光养潜力。为了解决这个差距，使用高度富集的累积杆菌培养物（95％）进行了短期和长期的光周期测试，以评估其对光照的反应。结果表明,在适应光照条件的初始阶段(大约4-5小时)后，通过利用聚羟基链烷酸酯（PHA），积累杆菌表现出完全的磷（P）吸收，另外通过消耗糖原，这与它典型的有氧代谢形成了对比。弥撒,能源,和氧化还原平衡分析表明，积累杆菌需要采用光养代谢来满足其能量需求。计算表明，光反应有助于产生，P摄取和生长所需的ATP至少超过67％。扩展光测试,跨越21天，有黑暗/光明周期，提示累积杆菌在初始手术期间通过光照产生ATP，然而,由于混合培养物中的微藻生长，在黑暗/光照条件下，它可能会恢复到常规的厌氧/有氧代谢。有助于氧气生产。相比之下,具有丰富的Tetrasphaera文化的扩展光测试，基因组中缺乏光养基因，清楚地表明，光养P的摄取没有发生。这些发现突出了积累杆菌的适应性代谢能力，使其能够在缺氧期间利用光养途径产生能量，具有推进光养EBPR技术发展的潜力。
