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Outline
Cereibacter azotoformans has been widely applied in the water quality regulation and disease prevention of aquaculture owing to its efficient nitrogen and phosphorus removal capacity as well as its probiotic effects on aquatic animals. However, whether this bacterium possesses both capabilities of denitrification and polyphosphate accumulation (DPA) remains unclear. [Objective] To identify the DPA phenotype of C. azotoformans and to elucidate its underlying molecular regulation mechanism. [Methods] Using the C. azotoformans strain ATCC 17025 as a model, we first examined its metabolic characteristics under DPA-inducing conditions to determine the presence of a DPA phenotype. Subsequently, gene deletion, DNA affinity purification sequencing (DAP-seq), and physiological and biochemical analyses were employed to systematically investigate the regulatory role of the NtrX/Y two-component system in DPA of the model strain. [Results] The C. azotoformans strain exhibited a typical DPA phenotype: releasing phosphate during the anaerobic stage and excessively absorbing phosphate in synergy with denitrification during the anoxic stage. At the end of the experiment, the nitrate degradation rate reached 95%, and the phosphate removal rate exceeded 90%. The deletion of ntrY resulted in the loss of the DPA phenotype. Particularly, the environmental phosphate concentration continuously increased rather than decreased, and the peak synthesis of intracellular polyhydroxyalkanoates (PHAs) was significantly impaired compared with that of the wild type (0.11 mg/mL). DAP-seq analysis revealed that NtrX directly targeted key denitrification genes (nirK and norB/C) as well as the PHAs synthesis gene phaC, thereby coordinately regulating denitrification and polyphosphate metabolism. [Conclusion] This study demonstrates that the anoxygenic phototrophic bacterium C. azotoformans possesses excellent DPA capabilities, and it reveals a central regulatory role of the NtrX/Y two-component system in this process. These findings offer a new theoretical basis for the development of microbial resources for simultaneous nitrogen and phosphorus removal.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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