A Diazotrophs-Lettuce Symbiosis Platform based on the Carbon Dots-Microalgae Hybrid System

Diazotrophs-plant symbiosis model system has been developed, but the nitrogen-fixation efficiency of engineered systems remains suboptimal compared with wild-type counterparts. In this study, carbon dots (CDs) with benzoquinone and phenazine structures, prepared from o-phenylenediamine (o-PD) and catechol (CAT), were selected as an electron donor and an electron relay to construct a CDs/microalgae hybrid nitrogen-fixation system. The photocurrent response confirmed the photoelectron-donor capability of the CDs. Nostoc commune Vauch was chosen as the diazotroph. The hybrid system produced 1.32-fold more ethylene than pure microalgae. When integrated with a lettuce hydroponic platform, the system enabled lettuce to utilize atmospheric nitrogen as an ammonia fertilizer. The net photosynthetic rate, total fresh weight, total chlorophyll content, and total soluble protein content of lettuce grown in the established platform increased by 1.20-, 1.12-, 1.14-, and 1.32-fold, respectively, contributing to the sustainable development of agriculture.