Table4_Responses to organic pollutants in the tropical Pacific and subtropical Atlantic Oceans by pelagic marine bacteria.XLSX

Background and chronic pollution by organic pollutants (OPs) is a widespread threat in the oceans with still uncharacterized effects on marine ecosystems and the modulation of major biogeochemical cycles. The ecological impact and toxicity of this anthropogenic dissolved organic carbon (ADOC) is not related to the presence of a single compound but to the co-occurrence of a myriad of synthetic chemicals with largely unknown effects on heterotrophic microbial communities. We have analyzed the metabolic capacity of metagenome-assembled genomes (MAGs) of natural oceanic communities from the north Pacific (Costa Rica dome) and Atlantic oceans challenged with environmentally relevant levels of ADOC. In the Atlantic, ADOC-exposed MAGs responded transcriptionally more strongly compared to controls than in the Pacific, possibly mirroring the higher relevance of ADOC compounds as carbon source in oligotrophic environments. The largest proportions of transcripts originated from MAGs belonging in the families Rhodobacteraceae and Flavobacteriaceae, known to play a role on consumption of several OPs. In the Atlantic, archaeal Poseidoniales showed the highest transcription levels after 2 h of ADOC exposure, although no increase of relative abundances in the DNA pool was recorded after 24 h, whereas Methylophaga showed the opposite pattern. Both taxa are suggested to be actively involved in the consumption of biogenic alkanes produced by cyanobacteria. We observed similar gene expression profiles of alkane degradation and methylotrophy signature genes. These findings, plus the chemical degradation of alkanes measured in the experiments, provides experimental evidence of the consumption of anthropogenic hydrocarbons and synthetic chemicals at the low concentrations found in the ocean, and modulation of microbiomes by ADOC.

背景及有机污染物（OPs）的长期污染是海洋中普遍存在的威胁，其对海洋生态系统的影响及对主要生物地球化学循环的调节作用尚未得到充分表征。这种人为溶解有机碳（ADOC）的生态影响及毒性并非与单一化合物的存在相关，而是与众多合成化学物质的共现相关，这些化学物质对异养微生物群落的影响大多未知。我们分析了来自北太平洋（哥斯达黎加穹顶）和大西洋自然海洋社区的宏基因组组装基因（MAGs）的代谢能力，这些社区受到了与环境相关水平的ADOC的挑战。在大西洋中，与对照组相比，暴露于ADOC的MAGs在转录水平上表现出更强的反应，这可能反映了ADOC化合物在寡营养环境中的碳源更高的重要性。转录物最大比例来自属于红螺菌科和黄杆菌科的MAGs，这些科已知在消耗多种OPs中发挥作用。在大西洋中，古菌门类Pseudonocardiaceae在ADOC暴露2小时后显示出最高的转录水平，尽管在24小时后DNA库中未记录到相对丰度的增加，而Methylophaga则表现出相反的模式。这两种类群都被认为在消耗蓝藻产生的生物烷烃中起着积极作用。我们观察到烷烃降解和甲基化特征基因的基因表达谱相似。这些发现，加上实验中测量的烷烃化学降解，为在海洋中发现的低浓度人为碳氢化合物和合成化学物质的消耗，以及ADOC对微生物群的调节作用提供了实验证据。