Department of Microbiology and Immunology, Life Sciences Institute, BioProducts Institute, The University of British Columbia, Vancouver, BC, Canada.
Advanced Renewable Materials Lab, Department of Wood Science, BioProducts Institute, The University of British Columbia, Vancouver, BC, Canada.
ISME J. 2021 Mar;15(3):879-893. doi: 10.1038/s41396-020-00820-x. Epub 2020 Nov 2.
Thermal swamps are unique ecosystems where geothermally warmed waters mix with decomposing woody biomass, hosting novel biogeochemical-cycling and lignin-degrading microbial consortia. Assembly of shotgun metagenome libraries resolved 351 distinct genomes from hot-spring (30-45 °C) and mesophilic (17 °C) sediments. Annotation of 39 refined draft genomes revealed metabolism consistent with oligotrophy, including pathways for degradation of aromatic compounds, such as syringate, vanillate, p-hydroxybenzoate, and phenol. Thermotolerant Burkholderiales, including Rubrivivax ssp., were implicated in diverse biogeochemical and aromatic transformations, highlighting their broad metabolic capacity. Lignin catabolism was further investigated using metatranscriptomics of sediment incubated with milled or Kraft lignin at 45 °C. Aromatic compounds were depleted from lignin-amended sediment over 148 h. The metatranscriptomic data revealed upregulation of des/lig genes predicted to specify the catabolism of syringate, vanillate, and phenolic oligomers in the sphingomonads Altererythrobacter ssp. and Novosphingobium ssp., as well as in the Burkholderiales genus, Rubrivivax. This study demonstrates how temperature structures biogeochemical cycling populations in a unique ecosystem, and combines community-level metagenomics with targeted metatranscriptomics to identify pathways with potential for bio-refinement of lignin-derived aromatic compounds. In addition, the diverse aromatic catabolic pathways of Altererythrobacter ssp. may serve as a source of thermotolerant enzymes for lignin valorization.
热沼泽是独特的生态系统，其中地热变暖的水与分解的木质生物质混合，形成新的生物地球化学循环和木质素降解微生物共生体。对 shotgun 宏基因组文库的组装从温泉（30-45°C）和中温（17°C）沉积物中解析出 351 个独特的基因组。对 39 个精制的草图基因组进行注释揭示了与寡营养相关的代谢，包括降解芳香族化合物（如丁香酸盐、香草酸盐、对羟基苯甲酸酯和苯酚）的途径。耐温伯克霍尔德氏菌（包括 Rubrivivax 亚种）参与了多种生物地球化学和芳香族转化，突出了其广泛的代谢能力。通过在 45°C 下用研磨或 Kraft 木质素孵育沉积物的宏转录组学进一步研究了木质素的分解代谢。在 148 小时内，木质素添加的沉积物中的芳香族化合物被耗尽。宏转录组数据显示，预测在鞘氨醇单胞菌属 Altererythrobacter ssp.和新鞘氨醇单胞菌属 Novosphingobium ssp.以及伯克霍尔德氏菌属 Rubrivivax 中指定丁香酸盐、香草酸盐和酚类低聚物代谢的 des/lig 基因上调。本研究展示了温度如何在独特的生态系统中构建生物地球化学循环种群，并将群落水平的宏基因组学与靶向宏转录组学相结合，以确定具有生物精炼木质素衍生芳香族化合物潜力的途径。此外，鞘氨醇单胞菌属 Altererythrobacter ssp.的多种芳香族代谢途径可能成为木质素增值的耐热酶的来源。
