From culture to community: the physiology, regulation and community functions of alginate degradation by marine Gammaproteobacteria and Bacteroidetes

细菌对丰富的海洋多糖（如藻酸盐）的降解是海洋中有机物生物化的基础。然而，仍然知之甚少的海藻酸盐降解的调节，海藻酸盐降解细菌的身份和丰度，以及海藻酸盐的能力如何影响天然细菌组合的功能多样性。目前的后续建议，我的“EigeneStelle”项目解决了彻底调查海洋细菌藻酸盐利用的监管，基因组和社区水平。这依赖于已建立的溶藻模型分离株、共培养和微宇宙系统，以及对天然浮游细菌群落的分子调查。对已建立的交替单胞菌和移动杆菌模型分离株中的藻酸盐加工基因进行定量实时PCR，将阐明与生长期和聚合物大小相关的藻酸盐分解基因的表达。结合转录组学和高分辨率外代谢组学，这将提供与细菌藻酸盐降解相关的基因调控和代谢过程的整体视图。此外，交替单胞菌和Maribacter模型分离株的荧光标记和实时显微镜将能够跟踪它们在天然群落中的生长和运动，阐明当添加藻酸盐颗粒时，藻酸盐溶解性状是否提供竞争优势。以培养为基础的工作将辅之以分子基因FISH分析，以确定各种海洋生物群中的藻酸盐降解类群。使用来自南部，大西洋和太平洋的环境样品，这将揭示在广泛的地理和环境梯度的海藻酸分解能力的地理模式。此外，GeneFISH将被应用到微宇宙与藻酸盐修正的太平洋和北海的水，以阐明在不同阶段的藻酸盐分解从聚合物到单体的群落演替。该项目将受益于一系列国家和国际合作，并大大有助于了解物种和社区一级的藻酸分解活动，这对全球海洋碳循环有影响。

The bacterial degradation of abundant marine polysaccharides, such as alginate, is fundamental for the remineralization of organic matter in the oceans. However, still little is known about the regulation of alginate degradation, the identity and abundance of alginate-degrading bacteria, and how alginolytic capacities affect the functional diversity of natural bacterial assemblages. The present follow-up proposal on my 'Eigene Stelle' project addresses a thorough investigation of marine bacterial alginate utilization on the regulatory, genomic and community level. This relies on established alginolytic model isolates, co-culture and microcosm systems, as well as molecular investigations of natural bacterioplankton communities. Quantitative real-time PCR of alginate-processing genes in established Alteromonas and Maribacter model isolates will elucidate the expression of alginolytic genes in relation to growth phase and polymer size. In combination with transcriptomics and high-resolution exometabolomics, this will provide a holistic view of gene regulation and metabolic processes associated with bacterial alginate degradation. In addition, fluorescent labelling and real-time microscopy of Alteromonas and Maribacter model isolates will enable to track their growth and motility in natural communities, illuminating whether alginolytic traits provide a competitive advantage when alginate particles are added. The culture-based work will be complemented by molecular GeneFISH analyses to identify alginate-degrading taxa in various oceanic biomes. Using environmental samples from the Southern, Atlantic and Pacific Oceans, this will reveal biogeographic patterns in alginolytic abilities over wide geographical and environmental gradients. Furthermore, GeneFISH will be applied to microcosms with alginate-amended Pacific and North Sea water to elucidate the community succession during different stages of alginate breakdown from polymer to monomer. The project will benefit from a range of national and international collaborations and substantially contribute to the understanding of alginolytic activities on the species and community level, which has implications for global marine carbon cycling.