Influence of salinity on novel (moderately) thermophilic nitrite-oxidizing bacteria

盐度对新型（中度）嗜热亚硝酸氧化细菌的影响

• 批准号: 432963485
• 负责人: Privatdozentin Dr. Eva Spieck
• 金额: --
• 依托单位: Department of Microbiology
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/432963485?language=en
• 关键词: Influence; salinity; novel; moderately; thermophilic

Nitrification, the biological oxidation of ammonia to nitrite and further to nitrate, is of environmental importance to avoid accumulation of harmful ammonia and nitrite, which can result in human and aquatic animal health risk. In WWTPs its functioning has to be maintained even under adverse conditions caused for example by elevated temperature or salinity. Especially the fastidious nitrite-oxidizing bacteria (NOB) that perform the second step of nitrification are not sufficiently investigated. From geothermal systems and warm sewage, Nitrospira and different Chloroflexi NOB were already cultivated, but metagenome data indicated the presence of a highly diverse community of putative NOB by specific sequences of the key enzyme, the nitrite oxidoreductase (NXR). In the first phase of this project, directed cultivation approaches led to the description of new (moderately) thermophilic species of Nitrospira and Nitrolancea. Additionally, several novel NOB candidates growing at elevated temperature (37-50°C) from diverse phyla (Ca. Dadabacteria, Actinobacteria, Chloroflexi, Acidobacteria, (Delta)-Proteobacteria, Nitrospirae) were selectively enriched and correlated with specific nxrA/B and 16S rRNA gene sequences as well as distinct morphotypes, but their 16S rRNA gene similarities to the next taxonomically described bacteria are rather low (80-94%). Molecular characterization of metagenome assembled genomes (MAGs) gave first insights into their carbon, nitrogen and oxygen metabolism including the finding of rubisco genes for some Chloroflexi and Actinobacteria, supporting their chemolithoautotrophic lifestyle and differentiating them from denitrifiers. In the past, new NOB isolates were obtained by various selecting factors (nitrite concentration, temperature, DO, pH), whereas in the second part of the project, salinity stress (especially nitrate) will be the main driver for niche separation in combination with high temperature. Preliminary results indicated high NaCl tolerances of Dehalococcoides-like NOB and novel Actinobacteria and reduced abundance of Nitrospira. It is the goal to highly enrich/isolate novel salt- and heat-tolerant NOB by cell sorting, to characterize them physiologically and to screen metagenomes for new metabolic pathways. RNA based gene expression and metatranscriptome data obtained under different growth conditions will verify activity of novel nxr genes and give insights into tolerance mechanisms. Most promising candidates will be tested for their ability to grow in bioreactor systems under salt and temperature stress for biotechnological applications. With regard to a warming world, there is a growing interest in nitrification under thermal conditions and it has to be ensured that agricultural nitrification inhibitors will still affect a shifting community of nitrifying microorganisms. Furthermore, thermophilic bacteria as survivors of early Earth are interesting with regard to evolutionary aspects.

硝化作用是将氨氧化成亚硝酸盐并进一步氧化成硝酸盐，对于避免有害氨和亚硝酸盐的积累具有重要的环境意义，这可能导致人类和水生动物的健康风险，即使在不利条件下，污水处理厂也必须维持其功能。尤其是由地热系统进行第二步硝化作用的挑剔的亚硝酸盐氧化细菌（NOB）引起的。在温暖的污水中，Nitrospira 和不同的 Chloroflexi NOB 已经被培养出来，但宏基因组数据表明，通过关键酶亚硝酸盐氧化还原酶 (NXR) 的特定序列，存在高度多样化的假定 NOB 群落。定向培养方法导致了 Nitrospira 和 Nitrolancea 新的（中等）嗜热物种的描述。此外，一些新的 NOB 候选物在高温下生长。来自不同门（Ca. Dadabacteria、Actinobacteria、Chloroflexi、Acidobacteria、Delta）-Proteobacteria、Nitrospirae）的 (37-50°C) 被选择性富集并与特定的 nxrA/B 和 16S rRNA 基因序列以及不同的形态型相关，但它们的 16S rRNA 基因与下一个分类学描述的细菌的相似性相当低(80-94%) 宏基因组组装基因组 (MAG) 的分子特征首次深入了解了它们的碳、氮和氧代谢，包括发现了一些绿柔菌和放线菌的 rubisco 基因，支持它们的化能自养生活方式并将它们与反硝化菌区分开来。过去，新的 NOB 分离株是通过各种选择因素（亚硝酸盐浓度、温度、DO、pH）获得的，而在该项目的第二部分中，盐度胁迫（尤其是硝酸盐）与高温相结合将成为生态位分离的主要驱动力。初步结果表明，类脱卤球菌和新型放线菌的耐盐性较高，而硝化螺菌的丰度降低，这是高度富集/分离新型放线菌的目标。通过细胞分选对耐盐和耐热的 NOB 进行生理学表征，并筛选宏基因组以寻找新的基于 RNA 的基因表达和在不同生长条件下获得的宏转录组数据。将验证新型 nxr 基因的活性，并深入了解耐受机制。将测试它们在生物反应器系统中在盐和温度胁迫下生长的能力，以用于生物技术应用。此外，嗜热细菌作为早期地球的幸存者，在进化方面也很有趣。