寒旱区湖泊沉积物中固氮微生物群落特征——以包头南海湖为例

为了探究寒旱区湖泊中固氮菌的地区差异性，利用固氮菌特异性功能基因nif H对南海湖沉积物中的固氮菌进行测定并分析其与环境因子之间的相互作用关系.结果表明：不同湖区优势固氮菌群落组成存在差异，整体上由3门（蓝藻门、厚壁菌门、变形菌门）10属（蓝藻菌属、着色菌属、梭菌属、鱼腥藻属、红螺菌属、厌氧粘细菌属、荚硫菌属、柱孢藻属、根瘤菌属、假单胞菌属）组成；寒旱区特有的冰封期长、紫外线照射强等环境条件导致沉积物中的主导固氮菌为蓝藻门下的微生物.冗余分析结果表明：较高的C/N和TP是固氮菌生存的必要营养条件，可以促进固氮反应的顺利进行，较高的TN和NH₃-N含量及较低的pH值会抑制表层沉积物部分固氮微生物的生长，较高的pH值尤其会抑制鱼腥藻属、荚硫菌属、蓝藻菌属、红螺菌属的生长.本研究通过探讨寒旱区固氮微生物在沉积物中的分布来研究固氮作用的潜在功能，进一步补充其在氮循环中的重要作用.

Community characteristics of nitrogen-fixing microorganisms in lake sediment-taking Nanhaihu lake as example

In order to explore the regional differences of the nitrogen-fixing bacteria in lakes of cold-arid areas, the nitrogen-fixing bacteria in the sediments of Nanhai Lake and the interaction relationship between the bacteria and the environmental factors were analyzed using the nitrogen-fixing bacteria specific functional gene nif H. The results demonstated that there existed differences in the composition of the dominant nitrogen-fixing bacterial community among various parts of the Lake, with the dominant bacterial community being mainly composed of 3 phyla (Cyanobacteria, Firmicutes and Proteobacteria) and 10 genera (Cyanobacteria, Chromatium, Clostridium, Anabaena, Rhodospirillum, Anaeromyxobacter, Thiocapsa, Cylindrospermopsis, Rhizobium and Pseudomonas). And Cyanobacteria turned out to be the leading bacteria at the phyla level due to the specific environmental conditions of the cold-arid areas like, the long freezing period and strong ultraviolet radiation. Based on the redundancy analysis, a high level of C/N and TP was shown to be the necessary nutrients for the survival of the nitrogen-fixing bacteria by speeding up the nitrogen-fixing reactions therein, while high levels of TN and NH₃-N, and low pH values could inhibit the growth of nitrogen-fixing bacteria in the surface sediments. To be precise, a high pH value would inhibit the growth of Anabaena, Thiocapsa, Cyanobacteria and Rhodospirillum. In this essay, the potential function of the nitrogen fixation was studied by exploring the distributions of nitrogen-fixing microorganisms in the sediments of cold-arid areas, which could better explain the important role that the nitrogen-fixing microorganisms play in the nitrogen cycle.