Table_4_Microbial Functional Responses in Marine Biofilms Exposed to Deepwater Horizon Spill Contaminants.XLSX

Marine biofilms are essential biological components that transform built structures into artificial reefs. Anthropogenic contaminants released into the marine environment, such as crude oil and chemical dispersant from an oil spill, may disrupt the diversity and function of these foundational biofilms. To investigate the response of marine biofilm microbiomes from distinct environments to contaminants and to address microbial functional response, biofilm metagenomes were analyzed from two short-term microcosms, one using surface seawater (SSW) and the other using deep seawater (DSW). Following exposure to crude oil, chemical dispersant, and dispersed oil, taxonomically distinct communities were observed between microcosms from different source water challenged with the same contaminants and higher Shannon diversity was observed in SSW metagenomes. Marinobacter, Colwellia, Marinomonas, and Pseudoalteromonas phylotypes contributed to driving community differences between SSW and DSW. SSW metagenomes were dominated by Rhodobacteraceae, known biofilm-formers, and DSW metagenomes had the highest abundance of Marinobacter, associated with hydrocarbon degradation and biofilm formation. Association of source water metadata with treatment groups revealed that control biofilms (no contaminant) harbor the highest percentage of significant KEGG orthologs (KOs). While 70% functional similarity was observed among all metagenomes from both experiments, functional differences between SSW and DSW metagenomes were driven primarily by membrane transport KOs, while functional similarities were attributed to translation and signaling and cellular process KOs. Oil and dispersant metagenomes were 90% similar to each other in their respective experiments, which provides evidence of functional redundancy in these microbiomes. When interrogating microbial functional redundancy, it is crucial to consider how composition and function evolve in tandem when assessing functional responses to changing environmental conditions within marine biofilms. This study may have implications for future oil spill mitigation strategies at the surface and at depth and also provides information about the microbiome functional responses of biofilms on steel structures in the marine built environment.

海洋生物膜（marine biofilms）是一类关键生物组成组分，可将人工建造的钢结构转化为人工鱼礁。排放进入海洋环境的人为污染物（anthropogenic contaminants），例如石油泄漏产生的原油与化学分散剂，可能会破坏这类基础生物膜的多样性与功能。为探究不同环境来源的海洋生物膜微生物组对污染物的响应，并解析微生物的功能应答机制，本研究对两组短期微宇宙（microcosms）体系中的生物膜宏基因组进行了分析：一组采用表层海水（surface seawater, SSW），另一组采用深层海水（deep seawater, DSW）。在分别经原油、化学分散剂以及分散型原油处理后，研究观察到：接受相同污染物胁迫的不同水源来源的微宇宙体系中，其群落分类学组成存在显著差异；且表层海水来源的宏基因组香农多样性（Shannon diversity）更高。海杆菌属（Marinobacter）、科尔韦尔氏菌属（Colwellia）、海洋单胞菌属（Marinomonas）与假交替单胞菌属（Pseudoalteromonas）的系统型（phylotypes）是导致表层与深层海水来源群落产生差异的主要类群。表层海水来源的宏基因组以已知可形成生物膜的红杆菌科（Rhodobacteraceae）为优势类群，而深层海水来源的宏基因组中海杆菌属（Marinobacter）的丰度最高，该属与烃类降解及生物膜形成过程密切相关。将水源元数据与处理组进行关联分析后发现，空白对照组（未添加污染物）的生物膜中，具有统计学显著性的KEGG同源基因（KEGG orthologs, KOs）占比最高。尽管两组实验的所有宏基因组之间存在70%的功能相似性，但表层与深层海水来源宏基因组的功能差异主要由膜转运相关的KEGG同源基因驱动，而二者的功能相似性则归因于翻译、信号转导及细胞过程相关的KEGG同源基因。在各自的实验中，原油处理组与化学分散剂处理组的宏基因组功能相似性达90%，这为这类微生物组的功能冗余性提供了直接证据。在探究微生物功能冗余性时，评估海洋生物膜内微生物组对环境条件变化的功能响应过程中，需同步考量群落组成与功能的协同演化过程，这一点至关重要。本研究可为表层与深层海域的石油泄漏应急缓解策略提供参考，同时也为海洋人工钢结构表面生物膜的微生物组功能响应研究提供了重要的数据支撑。