Li Tingting, Xu Longqian, Li Wenxuan, Wang Chengxian, Gin Karina Yew-Hoong, Chai Xiaoli, Wu Boran
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, 1239 Siping Road, Shanghai, 200092, China.
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China; State Environmental Protection Key Laboratory of Ecological Effect and Risk Assessment of Chemicals, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
Water Res. 2024 May 15;255:121465. doi: 10.1016/j.watres.2024.121465. Epub 2024 Mar 13.
Dissolved organic carbon (DOC) can alter the availability of background nutrients by affecting the proliferation of heterotrophic bacteria, which exerts a notable influence on algal growth and metabolism. However, the mechanism of how allochthonous DOC (aDOC) precipitates shifts in bacterial-algal interactions and modulates the occurrence of cyanobacteria blooms remains inadequately elucidated. Therefore, this study investigated the relationship between bacteria and algae under aDOC stimulation. We found that excess aDOC triggered the breakdown and reestablishment of the equilibrium between Microcystis and heterotrophic bacteria. The rapid proliferation of heterotrophic bacteria led to a dramatic decrease in soluble phosphorus and thereby resulted in the inhibition of the Microcystis growth. When the available DOC was depleted, the rapid death of heterotrophic bacteria released large amounts of dissolved phosphorus, which provided sufficient nutrients for the recovery of Microcystis. Notably, Microcystis rejuvenated and showed higher cell density compared to the carbon-absent group. This phenomenon can be ascribed that Microcystis regulated the compositions of extracellular polymeric substances (EPS) and the expression of relevant proteins to adapt to a nutrient-limited environment. Using time of flight secondary ion mass spectrometry (TOF-SIM) and proteomic analysis, we observed an enhancement of the signal of organic matter and metal ions associated with P complexation in EPS. Moreover, Microcystis upregulated proteins related to organic phosphorus transformation to increase the availability of phosphorus in various forms. In summary, this study emphasized the role of DOC in algal blooms, revealing the underestimated enhancement of Microcystis nutrient utilization through DOC-induced heterotrophic competition and providing valuable insights into eutrophication management and control.
溶解有机碳（DOC）可通过影响异养细菌的增殖来改变背景养分的有效性，这对藻类的生长和代谢产生显著影响。然而，外源DOC（aDOC）如何促使细菌-藻类相互作用发生转变并调节蓝藻水华的发生机制仍未得到充分阐明。因此，本研究调查了在aDOC刺激下细菌与藻类之间的关系。我们发现过量的aDOC引发了微囊藻与异养细菌之间平衡的打破与重新建立。异养细菌的快速增殖导致可溶性磷急剧减少，从而抑制了微囊藻的生长。当可用的DOC耗尽时，异养细菌的快速死亡释放出大量溶解磷，为微囊藻的恢复提供了充足的养分。值得注意的是，与无碳组相比，微囊藻恢复活力并表现出更高的细胞密度。这种现象可以归因于微囊藻调节细胞外聚合物（EPS）的组成和相关蛋白质的表达以适应营养受限的环境。通过飞行时间二次离子质谱（TOF-SIM）和蛋白质组学分析，我们观察到EPS中与磷络合相关的有机物和金属离子信号增强。此外，微囊藻上调了与有机磷转化相关的蛋白质，以提高各种形式磷的可用性。总之，本研究强调了DOC在藻华形成中的作用，揭示了通过DOC诱导的异养竞争对微囊藻养分利用的增强作用被低估，为富营养化的管理和控制提供了有价值的见解。
