Coordination Funds

海洋细菌在全球碳循环中发挥着至关重要的作用：虽然藻类每年将二氧化碳转化为碳水化合物的速度为50亿吨，但细菌酶降解藻类生物量并回收这些碳-迄今为止未知的数量。因此，细菌的活动决定了有多少二氧化碳从大气中被移除并储存在海洋中（碳汇），以及有多少被重新引导到碳循环中。在这个黑匣子上发光，也就是说，因此，阐明决定藻类聚糖命运的潜在机制、基因和酶库，对于我们全面了解海洋在气候紧急情况中的作用是必不可少的。考虑到这些问题，我们结合了我们在细菌多样性，微生物生态学，（Meta）基因组学，（Meta）蛋白质组学，生物化学，酶学和结构生物学方面的协同专业知识，并着手解开春季浮游植物水华期间关键细菌种群的生理和功能。我们的研究表明，藻类多糖是由许多高度专业化的细菌菌株，其中每一个目标的糖中间体的不同子集的连续作用降解。我们可以证明，数百种碳水化合物活性酶参与了单个藻类聚糖的循环。此外，我们最近发现了特定的复杂的藻类聚糖结构，与不太复杂的多糖不同，它们难以消化，因此在藻类水华期间几乎不被细菌降解。这些研究工作的FOR 2406导致超过25个联合同行评审的出版物。在研究单位POMPU的第三阶段和最后阶段，我们将加强我们对海洋拟杆菌中心多糖利用机制所涉及的蛋白质功能的关注。深入的分子生物学分析，所谓的多糖利用位点（普尔斯）和生化特性的关键蛋白质将使我们能够确定α-甘露聚糖，硫酸木聚糖和海带多糖利用的海洋战略。这些蛋白基因组学分析的可培养的，环境相关的关键细菌在体外条件下定义将补充我们的比较在原位研究的颗粒相关和自由生活的细菌在浮游植物水华。我们将阐明海洋颗粒物的复杂微生物组的组成，相互作用和功能及其特定的聚糖循环过程。我们在FOR 2406中的跨学科和整体方法对于解开海洋多糖利用的基本分子机制至关重要，因此最终将使我们能够破译迄今为止未知的全球碳循环方面。

Marine bacteria play an essential role in global carbon cycling: Whilst algae convert carbon dioxide into carbohydrates at a rate of 50 gigatons per year, it is bacterial enzymes that degrade the algal biomass and recycle this carbon – in hitherto unknown quantities. Bacterial action thus dictates how much carbon dioxide is removed from the atmosphere and stored in the ocean (carbon sink) and how much is rechannelled into the carbon cycle. Shedding light on this black box, i.e., elucidating the underlying mechanisms, genes and enzyme repertoires that determine the fate of algal glycans is therefore mandatory for our overall understanding of the ocean’s role in the climate emergency. With these premisses in mind, we bundled our synergistic expertise in bacterial diversity, microbial ecology, (meta)genomics, (meta)proteomics, biochemistry, enzymology, and structural biology, and set out to unravel the physiologies and functions of key bacterial populations during spring phytoplankton blooms. Our studies revealed that algal polysaccharides are degraded by the successive action of numerous highly specialized bacterial strains, each of which targets a different subset of sugar intermediates. We could demonstrate that hundreds of carbohydrate-active enzymes are involved in the cycling of individual algal glycans. Moreover, we recently discovered specific intricate algal glycan structures which, unlike less complex polysaccharides, are difficult to digest and therefore hardly degraded by bacteria during algal blooms. These research efforts of FOR 2406 resulted in more than 25 joint peer-reviewed publications to date. In the third and final phase of the research unit POMPU we will strengthen our focus on protein functions involved in central polysaccharide utilization mechanisms of marine Bacteroidetes. In-depth molecular biological analyses of so-called polysaccharide utilization loci (PULs) and biochemical characterizations of identified key proteins will allow us to determine marine strategies of alpha-mannan-, sulfated xylan- and laminarin utilization. These proteogenomic analyses of cultivable, environmentally relevant key bacteria under defined in vitro conditions will complement our comparative in situ studies on particle-associated and free-living bacteria during phytoplankton blooms. We will elucidate the composition, interaction and function of complex microbiomes of marine particles and their specific glycan-cycling processes. Our interdisciplinary and holistic approach in FOR 2406 is crucial to unravel fundamental molecular mechanisms of marine polysaccharide utilization and will thus ultimately enable us to decipher hitherto unknown facets of global carbon cycling.