Biodiversity of Nitrate-Reducing Microbes in Grassland Soils by Massive Cultivation and Genomics (acronym: BE-Cult)

BE-Cult项目研究了生物多样性探索（BEs）在所有草地vip（非常深入研究的地块）中管理较少和集约化的草地土壤中硝酸盐氨化（同质异化硝酸盐还原为铵，DNRA）细菌的生物多样性。长期以来，人们对DNRA细菌在土壤中保持氮(N)的相关性没有太大的认识，它们对土壤中氧化亚氮释放的定量贡献也没有进行研究。因此，对土壤中以硝酸盐为电子受体的反硝化菌的生物多样性和生态生理有了大量的了解。这段历史的结果是，但对DNRA细菌在陆地氮循环中的生态生理学和意义知之甚少。与DNRA细菌相反，dentrifiers从硝酸盐中产生N气体，从而促进土壤中N的损失，而DNRA细菌形成铵，铵留在土壤中，是一种主要的植物养分。这两种细菌群都会形成温室气体一氧化二氮，从而导致全球变暖。BE-Cult的主要目的是评估土地利用强度对这一重要的氮循环土壤微生物群的影响。通过高通量培养方法（包括用于快速菌株鉴定的MALDI TOF MS，以及对分离物进行分组的各种生理测试），将根据系统发育和硝酸盐生理特征对10,000多个硝酸盐还原分离物进行表征和聚类。从该菌株收集中，将选择100个分离株并获得基因组草图。基于基因组信息，将开发新的功能基因标记引物，以量化从vip土壤DNA提取物中分离出的这些分离物，并与合作伙伴一起，通过对元转录组进行针对性分析来评估它们的相关性（即与树齿菌相比的活性）。最后，这些数据将用于功能基因丰度、生理性状以及非生物和生物位点参数的多变量分析，以解释DNRA细菌在土壤中的分布模式并确定其生态位。

The project BE-Cult adresses the biodiversity of nitrate ammonifying (syn. dissimilatory nitrate reducing to ammonium, DNRA) bacteria in soils of less and intensively managed grasslands of the Biodiversity Exploratories (BEs) at all grassland VIPs (very intensively studied plots). The relevance for keeping nitrogen (N) through DNRA bacteria in the soil has been long-time not much appreciated and their quantitive contribution to relase of nitrous oxide from soils has not been investigated. Thus, a lot information is available about biodiversity and eco-physiology of denitrifiers, which use also nitrate as electron acceptor in soil. The consequence of this history is that but not very much is known about the ecophysiology and significance of DNRA bacteria in terrestrial N cycling. In contrast to DNRA bacteria, dentrifiers produce N gases from nitrate and thus facilitate N loss in soils, whereas DNRA bacteria form ammonium that remains in soil and is a major plant nutrient. Both bacterial groups form the greenhouse gas nitrous oxide and thus contribute to global warming. The main aim of BE-Cult is to assess the impact of land use intensities on this important group N cycling soil microbes. By a high throughput cultivation approach (including MALDI TOF MS for rapid strain identification, and various physiological tests to group isolates) over 10,000 nitrate reducing isolates will be charcterized and clustered according to phylogeny and nitrate physiology. From this strain collection, 100 isolates will be selected and draft genomes will be gained. Based on genome information, new primers for functional gene markers will be developed to quantify these isolates in soil DNA extracts from VIPs and together with partners their relevance (i.e their activity compared to dentrifiers) will be assesed by targeted analyses of meta-transcriptomes. Finally, the revealed data will be used in multivariate analyses of functional gene abundances, physiological traits, and as well abiotic and biotic site parameters to explain the distribution patterns of DNRA bacteria in soils and to define their ecological niches.