Extracellular enzyme kinetics and thermodynamics along a climate gradient in southern California
Extracellular enzyme kinetics and thermodynamics along a climate gradient in southern California
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DOI：
10.1016/j.soilbio.2017.07.005
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发表时间：
2017-11-01
影响因子：
9.7
通讯作者：
Allison, Steven D.
中科院分区：
文献类型：
--
作者：
Baker, Nameer R.;Allison, Steven D.
微生物分解者产生胞外酶来降解复杂的植物聚合物，使植物C可用于新陈代谢，并最终以CO2的形式呼吸回到大气中。因此，了解细胞外酶动力学和微生物活性如何随气候变化而变化，对于预测未来碳循环如何受到气候变化的影响是有价值的，但在更多的干旱生态系统中调查这种动态的研究在文献中的代表性不足。我们调查了微生物生物量，凋落物化学，胞外酶（V-最大值和Km）和它们的温度敏感性变化沿着地中海气候梯度在南加利福尼亚州。总微生物生物量并没有改变站点之间沿着梯度在干燥或潮湿的季节。相反，胞外酶Vmax和Km作为真菌生物量和底物可用性的函数而变化。我们还发现，大多数酶的Vmax是更敏感的温度在寒冷的网站比温暖的网站，虽然只有在旱季。相比之下，在两个季节中，多种酶的Km对温暖地点的温度更敏感。观察到的酶Vmax和Km的指示细胞外酶积累在干燥的网站沿着梯度，这可能有助于呼吸的大脉冲，在这些干旱系统中的再润湿事件。酶特性沿着梯度的变化表明，随着这些系统在未来变得更加干旱，酶动力学将从较小的，潜在的更活跃的池转移到较大的，潜在的活性较低的酶池，积累在干旱时期。此外，酶分解的速率可能对沿着我们的梯度的最冷位置的温度升高最敏感。(C)2017爱思唯尔有限公司版权所有
Microbial decomposers produce extracellular enzymes to degrade complex plant polymers, making plant C available for metabolism and eventual respiration back to the atmosphere as CO2. Knowledge of how extracellular enzyme kinetics and microbial activity vary with climate is therefore valuable for predicting how future carbon cycling may be affected by climate change, but studies investigating such dynamics in more xeric ecosystems are underrepresented in the literature. We investigated how microbial biomass, litter chemistry, and extracellular enzymes (V-max and K-m) and their temperature sensitivities varied along a Mediterranean Climate gradient in southern Califotnia. Total microbial biomass did not vary among sites along the gradient in either the dry or the wet season. In contrast, extracellular enzyme Vmax and Km varied as a function of fungal biomass and substrate availability. We also found that Vmax of most enzymes was more sensitive to temperature in colder sites than in warmer sites, though only in the dry season. In contrast, Km of multiple enzymes was more sensitive to temperature in warmer sites across both seasons. Observed enzyme Vmax and Km were indicative of extracellular enzyme accumulation in the drier sites along the gradient, which may contribute to the large pulses of respiration that follow rewetting events in these xeric systems. Variation in enzyme characteristics along the gradient indicate that as these systems become more arid in the future, enzyme dynamics will shift from smaller, potentially more active pools to larger, potentially less active enzyme pools that accumulate over dry periods. In addition, rates of enzymatic decomposition will likely be most sensitive to rising temperatures in the coldest sites along our gradient. (C) 2017 Elsevier Ltd. All rights reserved.