Impact of cell density on microbially induced stable isotope fractionation
Impact of cell density on microbially induced stable isotope fractionation
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DOI：
10.1007/s00253-008-1755-0
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发表时间：
2009-01-01
影响因子：
5
通讯作者：
Wick, Lukas Y.
中科院分区：
文献类型：
--
作者：
Kampara, Makeba;Thullner, Martin;Wick, Lukas Y.
基于稳定同位素分馏分析（SIFA）的微生物污染物生物降解定量依赖于已知的，不变的同位素分馏因子。微生物诱导的同位素分馏是由含有轻而不是重同位素的键的优先裂解引起的。然而，在同位素敏感的键断裂之前的许多非同位素敏感的步骤可能影响降解过程的反应动力学并减少所观察到的（即，宏观可检测的）同位素分馏。这给同位素分馏用于微生物降解过程的量化带来了不确定性。在这里，我们报告的细菌细胞密度对观察到的稳定同位素分馏的影响。在非生长条件下进行分批生物降解实验，通过将恶臭假单胞菌mt-2（pWWO）以不同的细胞密度暴露于不同浓度的甲苯来量化甲苯氢同位素分馏。观察到的同位素分馏显着依赖于细胞密度。当细胞密度从5 × 10（5）增加到5 × 10（8）个细胞/mL时，观察到的同位素分馏下降了70%，并沿着单个细胞降解率下降55%。理论估计表明，通过细胞扩散控制的边界层的重叠，单个细胞的摄取驱动扩散取决于细胞密度。我们的数据表明，生物量对SIFA的影响必须考虑，即使在良好的混合系统，如本研究中使用的细胞悬浮液。
Quantification of microbial contaminant biodegradation based on stable isotope fractionation analysis (SIFA) relies on known, invariable isotope fractionation factors. The microbially induced isotope fractionation is caused by the preferential cleavage of bonds containing light rather than heavy isotopes. However, a number of non-isotopically sensitive steps preceding the isotopically sensitive bond cleavage may affect the reaction kinetics of a degradation process and reduce the observed (i.e., the macroscopically detectable) isotope fractionation. This introduces uncertainty to the use of isotope fractionation for the quantification of microbial degradation processes. Here, we report on the influence of bacterial cell density on observed stable isotope fractionation. Batch biodegradation experiments were performed under non-growth conditions to quantify the toluene hydrogen isotope fractionation by exposing Pseudomonas putida mt-2(pWWO) at varying cell densities to different concentrations of toluene. Observed isotope fractionation depended significantly on the cell density. When the cell density rose from 5 x 10(5) to 5 x 10(8)cells/mL, the observed isotope fractionation declined by 70% and went along with a 55% decrease of the degradation rates of individual cells. Theoretical estimates showed that uptake-driven diffusion to individual cells depended on cell density via the overlap of the cells' diffusion-controlled boundary layers. Our data suggest that biomass effects on SIFA have to be considered even in well-mixed systems such as the cell suspensions used in this study.