Anaerobic quaternary amine degradation: from single bacterium to salt marsh ecosystem.

甘氨酸甜菜碱（GBT）等季胺（QAs）在海洋生物中普遍存在。GBT被海洋生物用作一种相容性溶质，以应对环境条件的变化，例如盐度的增加，因为GBT不会干扰细胞代谢。由于环境变化，如病毒攻击和放牧，QA化合物经常被释放到海洋生态系统中。这些化合物的降解，特别是在潮间带沿海地区的降解，极大地促进了对气候有影响的痕量气体的产生。这些包括强大的温室气体甲烷和挥发性甲基化胺，它们被认为与海洋环境中的云形成有关。据估计，沿海沉积物约占全球海洋甲烷排放量的75%（每年8-13 Tg），其中大部分可能来自QA的降解。虽然我们知道微生物主要负责GBT降解为甲烷和挥发性甲胺，但我们对降解途径中涉及的基因和酶知之甚少。此外，尚未确定负责转化的那些微生物的身份。我们目前对这两个方面的知识仍然是推测性的，至少部分原因是缺乏明确的研究。这一及时的建议旨在填补我们对海洋碳循环知识的这一重大空白。利用培养的模式微生物，我们的目的是确定的关键基因和编码酶的厌氧降解GBT。利用分子生态学技术和由此产生的数据，从模式微生物的研究，我们的目标是进一步确定的关键微生物球员参与厌氧生产的甲烷和甲胺从GBT在海洋环境中。这项工作将产生关于我们对微生物GBT转化的理解的新知识，因此将填补我们对海洋碳循环知识的严重空白。

Quaternary amines (QAs) such as glycine betaine (GBT) are ubiquitous in marine organisms. GBT is used by marine organisms as a compatible solute in response to changes in environmental conditions, such as increasing salinity, because GBT does not interfere with cell metabolism. QA compounds are frequently released into the ocean ecosystems due to environmental changes, such as viral attack and grazing. The degradation of these compounds, especially in intertidal coastal areas, contributes significantly to the production of climate-active trace gases. These include the potent greenhouse gas methane and volatile methylated amines, which are thought to be involved in cloud formation in the marine environment. Coastal sediments are estimated to contribute approximately 75% of the global oceanic methane emissions (8-13 Tg per year) and much of this is likely to be derived from the degradation of QAs. Although we know that microorganisms are mainly responsible for the degradation of GBT to methane and volatile methylamines, we know little about the genes and enzymes involved in the degradation pathway. Furthermore, the identity of those microorganisms responsible for the transformation has not yet been determined. Our current knowledge of these two aspects remains speculative, at least partially due to the lack of definitive research.This timely proposal aims to fill in this major gap in our knowledge of marine carbon cycle. Using cultivated model microorganisms, we aim to define the key genes and the encoding enzymes in the anaerobic degradation of GBT. Using molecular ecology techniques and the resultant data from the study of the model microorganisms, we aim to further determine the key microbial players involved in the anaerobic production of methane and methylamines from GBT in the marine environment. The work will generate novel knowledge about our understanding of microbial GBT transformations and will therefore fill in a serious gap in our knowledge of the marine carbon cycle.