Origin of Short-Chain Organic Acids in Serpentinite Mud Volcanoes of the Mariana Convergent Margin
Origin of Short-Chain Organic Acids in Serpentinite Mud Volcanoes of the Mariana Convergent Margin
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DOI：
10.3389/fmicb.2019.01729
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发表时间：
2019-07-26
影响因子：
5.2
通讯作者：
Lever, Mark Alexander
中科院分区：
文献类型：
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作者：
Eickenbusch, Philip;Takai, Ken;Lever, Mark Alexander
蛇纹岩系统是微生物生命的潜在栖息地，这是由于经常高浓度的微生物能量底物，如氢（H-2），甲烷（CH 4）和短链有机酸（SCOA）。然而，由于高碱性条件（pH > 10）和高温（>80 ° C），许多蛇纹岩系统也是生理挑战性环境。为了阐明在深层蛇纹质地壳环境中微生物生命的可能性，国际海洋发现计划（IODP）第366次考察队在马里亚纳前弧的Yinazao、Fantangisfia和Asut Tesoru蛇纹质泥火山中进行了钻探。这些泥火山在下面的俯冲板块的温度（分别为80、150、250摄氏度）和蛇纹岩泥的孔隙水pH值（分别为11.0、11.2、12.5）方面有所不同。三个泥火山的甲酸盐和乙酸盐浓度增加，这与俯冲板块的温度呈正相关，并与H（2）浓度的强烈增加相一致，表明与蛇纹作用有关的起源。热力学计算表明，甲酸盐是通过与溶解的无机碳（DIC）+ H-2的平衡反应产生的，并且在低于80摄氏度的温度下，在流体上升期间平衡继续。相比之下，乙酸盐产生的机制尚不清楚。除了甲酸盐，乙酸盐，和H-2的数据，我们目前的浓度的其他SCOAs，甲烷，一氧化碳，硫酸盐，δ C-13-散装碳池的数据，和微生物细胞计数。尽管计算表明广泛的微生物分解代谢反应是有益的，但势能底物的浓度分布和非常低的细胞数量表明微生物生命是稀缺或不存在的。我们讨论了温度，pH值，压力和分散的潜在作用，在限制发生的微生物生命在深蛇纹岩环境。
Serpentinitic systems are potential habitats for microbial life due to frequently high concentrations of microbial energy substrates, such as hydrogen (H-2), methane (CH4), and short-chain organic acids (SCOAs). Yet, many serpentinitic systems are also physiologically challenging environments due to highly alkaline conditions (pH > 10) and elevated temperatures (>80 degrees C). To elucidate the possibility of microbial life in deep serpentinitic crustal environments, International Ocean Discovery Program (IODP) Expedition 366 drilled into the Yinazao, Fantangisfia, and Asut Tesoru serpentinite mud volcanoes on the Mariana Forearc. These mud volcanoes differ in temperature (80, 150, 250 degrees C, respectively) of the underlying subducting slab, and in the porewater pH (11.0, 11.2, 12.5, respectively) of the serpentinite mud. Increases in formate and acetate concentrations across the three mud volcanoes, which are positively correlated with temperature in the subducting slab and coincide with strong increases in H(2 )concentrations, indicate a serpentinization-related origin. Thermodynamic calculations suggest that formate is produced by equilibrium reactions with dissolved inorganic carbon (DIC) + H-2, and that equilibration continues during fluid ascent at temperatures below 80 degrees C. By contrast, the mechanism(s) of acetate production are not clear. Besides formate, acetate, and H-2 data, we present concentrations of other SCOAs, methane, carbon monoxide, and sulfate, delta C-13-data on bulk carbon pools, and microbial cell counts. Even though calculations indicate a wide range of microbial catabolic reactions to be thermodynamically favorable, concentration profiles of potential energy substrates, and very low cell numbers suggest that microbial life is scarce or absent. We discuss the potential roles of temperature, pH, pressure, and dispersal in limiting the occurrence of microbial life in deep serpentinitic environments.