Data_Sheet_1_Oil Hydrocarbon Degradation by Caspian Sea Microbial Communities.PDF

The Caspian Sea, which is the largest landlocked body of water on the planet, receives substantial annual hydrocarbon input from anthropogenic sources (e.g., industry, agriculture, oil exploration, and extraction) and natural sources (e.g., mud volcanoes and oil seeps). The Caspian Sea also receives substantial amounts of runoff from agricultural and municipal sources, containing nutrients that have caused eutrophication and subsequent hypoxia in the deep, cold waters. The effect of decreasing oxygen saturation and cold temperatures on oil hydrocarbon biodegradation by a microbial community is not well characterized. The purpose of this study was to investigate the effect of oxic and anoxic conditions on oil hydrocarbon biodegradation at cold temperatures by microbial communities derived from the Caspian Sea. Water samples were collected from the Caspian Sea for study in experimental microcosms. Major taxonomic orders observed in the ambient water samples included Flavobacteriales, Actinomycetales, and Oceanospirillales. Microcosms were inoculated with microbial communities from the deepest waters and amended with oil hydrocarbons for 17 days. Hydrocarbon degradation and shifts in microbial community structure were measured. Surprisingly, oil hydrocarbon biodegradation under anoxic conditions exceeded that under oxic conditions; this was particularly evident in the degradation of aromatic hydrocarbons. Important microbial taxa associated with the anoxic microcosms included known oil degraders such as Oceanospirillaceae. This study provides knowledge about the ambient community structure of the Caspian Sea, which serves as an important reference point for future studies. Furthermore, this may be the first report in which anaerobic biodegradation of oil hydrocarbons exceeds aerobic biodegradation.

里海（Caspian Sea）是地球上规模最大的内陆水体，每年接收大量来自人为来源（如工业、农业、石油勘探与开采）及自然来源（如泥火山、石油渗漏）的烃类物质输入。里海同时还会接纳大量农业与市政来源的径流，径流携带的营养物质已导致其深层冷水域发生富营养化及后续的缺氧现象。目前学界对氧气饱和度降低与低温环境对微生物群落降解石油烃类的影响尚未得到充分表征。本研究旨在探究低温环境下，好氧与厌氧条件对源自里海的微生物群落降解石油烃类的影响。研究人员从里海采集水样，用于实验微宇宙（microcosms）体系研究。环境水样中观测到的主要分类阶元包括黄杆菌目（Flavobacteriales）、放线菌目（Actinomycetales）以及海洋螺菌目（Oceanospirillales）。实验微宇宙接种了取自最深层水域的微生物群落，并添加石油烃类进行为期17天的培养。研究测定了烃类降解情况与微生物群落结构的变化。令人意外的是，厌氧条件下的石油烃类降解效率优于好氧条件，这一现象在芳香烃类的降解中尤为明显。与厌氧微宇宙相关的重要微生物类群包括已知的石油降解菌，如海洋螺菌科（Oceanospirillaceae）。本研究阐明了里海原位微生物群落结构的相关信息，可为未来相关研究提供重要参考基准。此外，本研究或许是首次报道厌氧降解石油烃的效率高于好氧降解的研究案例。