兼性好氧反硝化嗜盐菌海杆菌属W-8的脱氮性能及其机制

Denitrification characteristics and mechanism of a facultative aerobic denitrifying halophilic bacterial strain Marinobacter sp. W-8

摘要:

目的 针对高盐高硝态氮废水脱氮效率低的难题，分离筛选高效脱氮的耐盐菌株，对其进行鉴定，并挖掘其高效脱氮的机制。方法 利用形态学观察和16S rRNA基因测序进行菌种分类鉴定；通过不同形态氮的测定评价菌株的脱氮性能；通过RT-qPCR检测和电子传递链酶活的测定，探究菌株在低氧或低氧低C/N比条件下高效脱氮的机制。结果 从高盐土壤中筛选到一株兼性好氧反硝化嗜盐菌，命名为W-8，鉴定为海杆菌属(Marinobacter sp.)。该菌在好氧和厌氧条件下均能进行反硝化，尤其在低氧环境(溶解氧浓度<1.2 mg/L)中展现出优异的反硝化能力。静置培养48 h后，对97.85 mg/L NO₃^--N的去除率达到95.56%，总氮去除率为87.63%。低氧条件下，narG和narI基因表达显著上调，电子传递链复合体Ⅰ和Ⅱ的活性增强，促进了NO₃^-的高效还原；norB基因表达显著上调，促进了NO的还原。在低氧条件下，低C/N比进一步增强了复合体Ⅱ的活性，降低了菌株对碳源的需求。W-8在厌氧条件下以反硝化代谢为主，生成气态氮的比例达到87.63%；而在好氧条件下，反硝化与同化作用共同参与脱氮过程。结论 Marinobacter sp. W-8兼具耐盐和高效反硝化的能力，无需曝气或严格厌氧条件，对碳源需求低，能够显著减少污泥产生，这为高效、低成本脱氮提供了理论和实践依据。

关键词:兼性好氧反硝化;脱氮性能;基因表达;电子传递链

Abstract:

Objective To address the low denitrification efficiency in high-salinity, and high-nitrate nitrogen wastewater, this study aimed to isolate and identify salt-tolerant denitrifying a strain with high efficiency. And elucidate its underlying mechanisms for enhanced nitrogen removal.Methods Morphological characterization and the analysis of its 16S rRNA gene sequence were employed for strain identification. Denitrification performance of bacterial strains was evaluated by measuring different forms of nitrogen. Exploring the mechanism of efficient denitrification of bacterial strains through the RT-qPCR analysis and the measurement of electron transport chain enzyme activity under low oxygen or low oxygen and low C/N ratio conditions.Results A halotolerant, facultative aerobic denitrifying bacterium, named W-8, was isolated from saline soil. The strain was identified as Marinobacter sp. This strain can perform denitrification under both aerobic and anaerobic conditions, particularly demonstrating a significant denitrifying activity under low-oxygen conditions (dissolved oxygen concentration<1.2 mg/L). After 48 h of culture under static conditions, W-8 achieved the NO₃^--N (97.85 mg/L) removal efficiency of 95.56% and the total nitrogen removal efficiency of 87.63%. Under low dissolved oxygen, the expression of narG and narI was significantly upregulated, and the activities of electron transport chain complex I and II were enhanced, which promoted the efficient reduction of NO₃^-. The expression of norB was significantly upregulated, promoting the reduction of NO. Under low-oxygen conditions, W-8 further improved the activity of the complex II under a low C/N ratio, reducing carbon source requirements. Under anaerobic conditions, W-8 mainly metabolized NO₃^--N through denitrification, with a gaseous nitrogen production ratio of 87.63%. Under aerobic conditions, this strain achieved nitrogen removal through denitrification combined with assimilation.Conclusion Marinobacter sp. W-8 demonstrates exceptional salt tolerance and high-efficiency denitrification. It can significantly reduce sludge production without the need for aeration or strict anaerobic conditions and has a lower demand for carbon sources. It shows great application potential and provides a theoretical and practical basis for efficient, low-cost denitrification.

Key words:facultative aerobic denitrification;denitrification performance;gene expression;electronic transport chain