Bourke Michael F, Marriott Philip J, Glud Ronnie N, Hasler-Sheetal Harald, Kamalanathan Manoj, Beardall John, Greening Chris, Cook Perran L M
Water Studies Centre, School of Chemistry, Monash University, Wellington Road, Clayton, VIC 3800, Australia.
Australian Centre for Research on Separation Science, School of Chemistry, Monash University, Wellington Road, VIC 3800, Australia.
Nat Geosci. 2017 Jan;10(1):30-35. doi: 10.1038/ngeo2843. Epub 2016 Nov 28.
Permeable sediments are common across continental shelves and are critical contributors to marine biogeochemical cycling. Organic matter in permeable sediments is dominated by microalgae, which as eukaryotes have different anaerobic metabolic pathways to prokaryotes such as bacteria and archaea. Here we present analyses of flow-through reactor experiments showing that dissolved inorganic carbon is produced predominantly as a result of anaerobic eukaryotic metabolic activity. In our experiments, anaerobic production of dissolved inorganic carbon was consistently accompanied by large dissolved H production rates, suggesting the presence of fermentation. The production of both dissolved inorganic carbon and H persisted following administration of broad spectrum bactericidal antibiotics, but ceased following treatment with metronidazole. Metronidazole inhibits the ferredoxin/hydrogenase pathway of fermentative eukaryotic H production, suggesting that pathway as the source of H and dissolved inorganic carbon production. Metabolomic analysis showed large increases in lipid production at the onset of anoxia, consistent with documented pathways of anoxic dark fermentation in microalgae. Cell counts revealed a predominance of microalgae in the sediments. H production was observed in dark anoxic cultures of diatoms ( sp.) and a chlorophyte () isolated from the study site, substantiating the hypothesis that microalgae undertake fermentation. We conclude that microalgal dark fermentation could be an important energy-conserving pathway in permeable sediments.
渗透性沉积物在大陆架上很常见，是海洋生物地球化学循环的重要贡献者。渗透性沉积物中的有机物质主要由微藻主导，作为真核生物，微藻具有与细菌和古菌等原核生物不同的厌氧代谢途径。在此，我们展示了对流通式反应器实验的分析，结果表明溶解无机碳主要是厌氧真核生物代谢活动的产物。在我们的实验中，溶解无机碳的厌氧产生始终伴随着大量溶解氢的产生速率，这表明存在发酵现象。在施用广谱杀菌抗生素后，溶解无机碳和氢的产生仍持续，但在用甲硝唑处理后停止。甲硝唑抑制发酵性真核生物产氢的铁氧化还原蛋白/氢化酶途径，这表明该途径是氢和溶解无机碳产生的来源。代谢组学分析表明，缺氧开始时脂质产量大幅增加，这与微藻中记录的缺氧黑暗发酵途径一致。细胞计数显示沉积物中微藻占主导地位。在从研究地点分离出的硅藻（ 种）和绿藻（ ）的黑暗缺氧培养物中观察到了氢产生现象，证实了微藻进行发酵的假设。我们得出结论，微藻黑暗发酵可能是渗透性沉积物中一种重要的节能途径。
