White Angelicque E, Watkins-Brandt Katie S, Engle Morgan A, Burkhardt Brian, Paytan Adina
College of Earth, Ocean, and Atmospheric Sciences, Oregon State University Corvallis, OR, USA.
Front Microbiol. 2012 Aug 10;3:276. doi: 10.3389/fmicb.2012.00276. eCollection 2012.
Production, transformation, and degradation are the principal components of the cycling of dissolved organic matter (DOM) in marine systems. Heterotrophic Bacteria (and Archaea) play a large part in this cycling via enzymatic decomposition and intracellular transformations of organic material to inorganic carbon (C), nitrogen (N), and phosphorus (P). The rate and magnitude of inorganic nutrient regeneration from DOM is related to the elemental composition and lability of DOM substrates as well as the nutritional needs of the mediating organisms. While many previous efforts have focused on C and N cycling of DOM, less is known in regards to the controls of organic P utilization and remineralization by natural populations of bacteria. In order to constrain the relative time scales and degradation of select dissolved organic P (DOP) compounds we have conducted a series of experiments focused on (1) assessment of the short-term lability of a range of DOP compounds, (2) characterization of labile DOP remineralization rates, and (3) examination of temperature sensitivities of labile DOP remineralization for varying bacterial populations. Results reinforce previous findings of monoester and polyphosphate lability and the relative recalcitrance of a model phosphonate: 2-aminoethylphosphonate. High resolution time-series of P-monoester remineralization indicates decay constants on the order of 0.67-7.04 day(-1) for bacterial populations isolated from coastal and open ocean surface waters. The variability of these rates is predictably related to incubation temperature and initial concentrations of heterotrophic bacteria. Additional controls on DOP hydrolysis included seasonal shifts in bacterial populations and the physiological state of bacteria at the initiation of DOP addition experiments. Composite results indicate that bacterial hydrolysis of P-monoesters exceeds bacterial P demand and thus DOP remineralization efficiency may control P availability to autotrophs.
生产、转化和降解是海洋系统中溶解有机物（DOM）循环的主要组成部分。异养细菌（和古细菌）通过酶促分解以及将有机物质细胞内转化为无机碳（C）、氮（N）和磷（P），在这个循环中发挥着重要作用。DOM无机养分再生的速率和幅度与DOM底物的元素组成和易分解性以及介导生物的营养需求有关。虽然之前许多研究都集中在DOM的碳和氮循环上，但对于细菌自然群体对有机磷利用和再矿化的控制了解较少。为了确定特定溶解有机磷（DOP）化合物的相对时间尺度和降解情况，我们进行了一系列实验，重点关注：（1）评估一系列DOP化合物的短期易分解性；（2）表征易分解DOP的再矿化速率；（3）研究不同细菌群体对易分解DOP再矿化的温度敏感性。结果强化了之前关于单酯和多磷酸盐易分解性以及模型膦酸盐（2-氨基乙基膦酸盐）相对难降解性的发现。P-单酯再矿化的高分辨率时间序列表明，从沿海和开阔海洋表层水体分离出的细菌群体的衰减常数在0.67-7.04天⁻¹的范围内。这些速率的变异性可预测地与培养温度和异养细菌的初始浓度有关。对DOP水解的其他控制因素包括细菌群体的季节性变化以及DOP添加实验开始时细菌的生理状态。综合结果表明，细菌对P-单酯的水解超过了细菌对磷的需求，因此DOP再矿化效率可能控制着自养生物可利用的磷含量。
