河口生态系统氨氧化菌生态学研究进展

由amoA基因编码的氨单加氧酶(AMO)所调控的氨氧化作用,是硝化作用的限速步骤和中心环节,而含有amoA基因的氨氧化细菌(AOB)和氨氧化古菌(AOA)多样性与环境因子关系密切,对缓解河口生态系统因人类活动造成的富营养化等环境问题具有特别重要的意义。水、陆和海交汇形成高度变异的具环境因子梯度的河口生态系统,是研究AOA和AOB生态学的天然实验室。河口AOA与AOB的群落组成、丰富度特征和生物有效性,与河口主要环境因子盐度、富营养化程度、植被、温度、碳、氮、硫、铁等,尤其是对盐度和富营养化有着较为强烈的响应。AOA和AOB多样性变化规律及其与河口特有的环境因子之间的相关性,应当是今后我国河口氨氧化菌研究的方向和重点。包括:(1)建立有效的氨氧化菌活性评价方法;(2)研究AOA的同化作用方式;(3)依据氨氧化菌分类和组成对河口环境变化的适应进化机制,建议可作为指示河口环境质量变化的生物标记;(4)将传统的分离培养方法与现代分子生物学研究方法相结合,筛选我国河口高效的氨氧化菌,并将其应用于生产。

Research progress on ammonia-oxidizing microorganisms in estuarine ecosystem

With the development of urbanization and the highly intensified agriculture in the world, the massive anthropogenic loading of particular nitrogen compounds into rivers, and the environmental quality of many estuarine ecosystems in China are deteriorating through eutrophication. Ammonia oxidation, which is regulated by ammonia monooxygenase (AMO), is the critical and rate-limiting step in the nitrification. The diversity of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) containing AMO encoded by the amoA gene can be impacted by environmental factors. Transformation and removal of the land-accumulated nitrogen in estuarine ecosystems could significantly reduce eutrophication. The steep physico-chemical gradients in estuary linking freshwater, terrestrial and marine systems serve as an important natural laboratory for studying ammonia-oxidizing microorganisms. Previous studies have reviewed the characteristics of AOA and AOB composition, their abundance, and nitrification levels in the estuarine ecosystems, as well as their responses to environmental factors. There are strong correlations between the ammonia oxidizers' diversity and environmental parameters,e.g. salinity, eutrophication, vegetation, temperature, carbon, nitrogen, sulphur and iron in estuarine ecosystems, especially in salinity and eutrophication. Future directions and work of ammonia oxidizers with estuary ecosystems in China should be focused on as follows: (1) set up effective assessment method of nitrification induced by ammonia-oxidizers; (2) elucidate which kind of assimilation style, heterotrophic, autotrophic or mixotrophic is characteristic of AOA; (3) confirm that ammonia-oxidizer compositions could be used as biological indicators to indicate the environmental quality in estuaries; (4) cultivate and identify the most biologically effective ammonia-oxidizers from estuaries by combining traditional cultivation methods with modern molecular biotechnology techniques, and finally apply them to practical production.