State Key Laboratory of Marine Environmental Science, Fujian Key Laboratory of Marine Carbon Sequestration, College of Ocean and Earth Sciences, Xiamen University, Xiamen, 361102, People's Republic of China.
Department of Molecular Virology & Microbiology, Center for Metagenomics and Microbiome Research, Baylor College of Medicine, Houston, TX, 77030, USA.
Microbiome. 2021 Mar 24;9(1):71. doi: 10.1186/s40168-021-01022-z.
Phytoplankton blooms are frequent events in coastal areas and increase the production of organic matter that initially shapes the growth of opportunistic heterotrophic bacteria. However, it is unclear how these opportunists are involved in the transformation of dissolved organic matter (DOM) when blooms occur and the subsequent impacts on biogeochemical cycles.
We used a combination of genomic, proteomic, and metabolomic approaches to study bacterial diversity, genome traits, and metabolic responses to assess the source and lability of DOM in a spring coastal bloom of Akashiwo sanguinea. We identified molecules that significantly increased during bloom development, predominantly belonging to amino acids, dipeptides, lipids, nucleotides, and nucleosides. The opportunistic members of the bacterial genera Polaribacter, Lentibacter, and Litoricola represented a significant proportion of the free-living and particle-associated bacterial assemblages during the stationary phase of the bloom. Polaribacter marinivivus, Lentibacter algarum, and Litoricola marina were isolated and their genomes exhibited streamlining characterized by small genome size and low GC content and non-coding densities, as well as a smaller number of transporters and peptidases compared to closely related species. However, the core proteomes identified house-keeping functions, such as various substrate transporters, peptidases, motility, chemotaxis, and antioxidants, in response to bloom-derived DOM. We observed a unique metabolic signature for the three species in the utilization of multiple dissolved organic nitrogen compounds. The metabolomic data showed that amino acids and dipeptides (such as isoleucine and proline) were preferentially taken up by P. marinivivus and L. algarum, whereas nucleotides and nucleosides (such as adenosine and purine) were preferentially selected by L. marina.
The results suggest that the enriched DOM in stationary phase of phytoplankton bloom is a result of ammonium depletion. This environment drives genomic streamlining of opportunistic bacteria to exploit their preferred nitrogen-containing compounds and maintain nutrient cycling. Video abstract.
浮游植物水华是沿海地区的频繁事件，增加了有机物的产量，有机物最初塑造了机会性异养细菌的生长。然而，当水华发生时，这些机会主义者如何参与溶解有机物（DOM）的转化以及随后对生物地球化学循环的影响尚不清楚。
我们使用基因组学、蛋白质组学和代谢组学相结合的方法来研究细菌多样性、基因组特征和代谢对赤潮期间 DOM 来源和不稳定性的响应阿克西沃桑圭纳。我们确定了在水华发展过程中显著增加的分子，主要属于氨基酸、二肽、脂质、核苷酸和核苷。在水华的静止阶段，细菌属 Polaribacter、Lentibacter 和 Litoricola 的机会主义成员代表了自由生活和颗粒相关细菌组合的重要比例。从赤潮中分离出 Polaribacter marinivivus、Lentibacter algarum 和 Litoricola marina，并对其基因组进行了分析，结果表明其基因组具有特征，包括基因组尺寸小、GC 含量低且非编码密度低，以及与密切相关的物种相比，转运体和肽酶数量较少。然而，鉴定出的核心蛋白质组在响应源自水华的 DOM 时具有各种基础功能，如各种底物转运体、肽酶、运动性、趋化性和抗氧化剂。我们观察到这三个物种在利用多种溶解有机氮化合物方面具有独特的代谢特征。代谢组学数据表明，氨基酸和二肽（如异亮氨酸和脯氨酸）被 P. marinivivus 和 L. algarum 优先吸收，而核苷酸和核苷（如腺苷和嘌呤）则被 L. marina 优先选择。
结果表明，浮游植物水华静止阶段富含 DOM 是铵耗尽的结果。这种环境驱动了机会主义细菌的基因组简化，以利用其首选的含氮化合物并维持营养循环。
