Helmholtz Institute for Functional Marine Biodiversity at the University of Oldenburg, Oldenburg, Germany.
Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany.
Environ Microbiol. 2021 Jun;23(6):3130-3148. doi: 10.1111/1462-2920.15536. Epub 2021 May 6.
Polysaccharide particles are important substrates and microhabitats for marine bacteria. However, substrate-specific bacterial dynamics in mixtures of particle types with different polysaccharide composition, as likely occurring in natural habitats, are undescribed. Here, we studied the composition, functional diversity and gene expression of marine bacterial communities colonizing a mix of alginate and pectin particles. Amplicon, metagenome and metatranscriptome sequencing revealed that communities on alginate and pectin particles significantly differed from their free-living counterparts. Unexpectedly, microbial dynamics on alginate and pectin particles were similar, with predominance of amplicon sequence variants (ASVs) from Tenacibaculum, Colwellia, Psychrobium and Psychromonas. Corresponding metagenome-assembled genomes (MAGs) expressed diverse alginate lyases, several colocalized in polysaccharide utilization loci. Only a single, low-abundant MAG showed elevated transcript abundances of pectin-degrading enzymes. One specific Glaciecola ASV dominated the free-living fraction, possibly persisting on particle-derived oligomers through different glycoside hydrolases. Elevated ammonium uptake and metabolism signified nitrogen as an important factor for degrading carbon-rich particles, whereas elevated methylcitrate and glyoxylate cycles suggested nutrient limitation in surrounding waters. The bacterial preference for alginate, whereas pectin primarily served as colonization scaffold, illuminates substrate-driven dynamics within mixed polysaccharide pools. These insights expand our understanding of bacterial niche specialization and the biological carbon pump in macroalgae-rich habitats.
多糖颗粒是海洋细菌的重要基质和微生境。然而，在自然栖息地中可能存在的不同多糖组成的颗粒类型混合物中，对特定基质的细菌动态变化仍知之甚少。在这里，我们研究了定植在海藻酸钠和果胶颗粒混合物上的海洋细菌群落的组成、功能多样性和基因表达。扩增子、宏基因组和宏转录组测序表明，海藻酸钠和果胶颗粒上的群落与其自由生活的群落明显不同。出乎意料的是，海藻酸钠和果胶颗粒上的微生物动态变化相似，优势扩增子序列变体（ASV）来自 Tenacibaculum、Colwellia、Psychrobium 和 Psychromonas。相应的宏基因组组装基因组（MAG）表达了多种海藻酸钠裂解酶，其中一些在多糖利用基因座中聚集。只有一个单一的、低丰度的 MAG 表现出果胶降解酶转录丰度的升高。一个特定的 Glaciecola ASV 主导了自由生活部分，可能通过不同的糖苷水解酶在颗粒衍生的低聚物上持续存在。铵的摄取和代谢增加表明氮是降解富含碳的颗粒的重要因素，而甲基柠檬酸和乙醛酸循环的增加表明周围水中存在营养限制。细菌对海藻酸钠的偏好，而果胶主要作为定植支架，揭示了混合多糖库中基质驱动的动态变化。这些发现扩展了我们对细菌生态位特化和富含大型藻类生境中生物碳泵的理解。
