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

海藻酸盐等丰富的海洋多糖的细菌降解是海洋中有机物再矿化的基础。然而，关于藻酸盐降解的调控，藻酸盐降解细菌的身份和丰度，以及藻酸盐降解能力如何影响天然细菌组合的功能多样性，人们仍然知之甚少。目前，我的“Eigene stella”项目的后续建议将在调控、基因组和群落水平上对海洋细菌藻酸盐的利用进行彻底的调查。这依赖于已建立的褐藻溶解模型分离物、共培养和微观系统，以及对天然浮游细菌群落的分子研究。对已建立的Alteromonas和Maribacter模型分离物中海藻酸处理基因的实时定量PCR分析将阐明海藻酸降解基因的表达与生长阶段和聚合物大小的关系。结合转录组学和高分辨率外代谢组学，这将提供与细菌海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模型分离物的荧光标记和实时显微镜将能够跟踪它们在自然群落中的生长和运动，阐明当添加海藻酸盐颗粒时，藻解特性是否提供了竞争优势。以培养为基础的工作将辅以分子GeneFISH分析，以识别各种海洋生物群系中的海藻酸降解分类群。利用来自南部、大西洋和太平洋的环境样本，这将揭示在广泛的地理和环境梯度上藻酸盐分解能力的生物地理模式。此外，GeneFISH将应用于海藻酸盐修饰的太平洋和北海海水中，以阐明海藻酸盐从聚合物到单体分解不同阶段的群落演替。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群落水平上的藻酸分解活动，这对全球海洋碳循环具有重要意义。

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.