School of Civil Engineering and Geosciences, Newcastle University Newcastle upon Tyne, UK ; Department of Biochemistry, North - Eastern Hill University Shillong, Meghalaya, India.
School of Civil Engineering and Geosciences, Newcastle University Newcastle upon Tyne, UK.
Front Microbiol. 2014 Apr 11;5:160. doi: 10.3389/fmicb.2014.00160. eCollection 2014.
Availability of inorganic nutrients, particularly nitrogen and phosphorous, is often a primary control on crude oil hydrocarbon degradation in marine systems. Many studies have empirically determined optimum levels of inorganic N and P for stimulation of hydrocarbon degradation. Nevertheless, there is a paucity of information on fundamental kinetic parameters for nutrient enhanced crude oil biodegradation that can be used to model the fate of crude oil in bioremediation programmes that use inorganic nutrient addition to stimulate oil biodegradation. Here we report fundamental kinetic parameters (Ks and qmax) for nitrate- and phosphate-stimulated crude oil biodegradation under nutrient limited conditions and with respect to crude oil, under conditions where N and P are not limiting. In the marine sediments studied, crude oil degradation was limited by both N and P availability. In sediments treated with 12.5 mg/g of oil but with no addition of N and P, hydrocarbon degradation rates, assessed on the basis of CO2 production, were 1.10 ± 0.03 μmol CO2/g wet sediment/day which were comparable to rates of CO2 production in sediments to which no oil was added (1.05 ± 0.27 μmol CO2/g wet sediment/day). When inorganic nitrogen was added alone maximum rates of CO2 production measured were 4.25 ± 0.91 μmol CO2/g wet sediment/day. However, when the same levels of inorganic nitrogen were added in the presence of 0.5% P w/w of oil (1.6 μmol P/g wet sediment) maximum rates of measured CO2 production increased more than four-fold to 18.40 ± 1.04 μmol CO2/g wet sediment/day. Ks and qmax estimates for inorganic N (in the form of sodium nitrate) when P was not limiting were 1.99 ± 0.86 μmol/g wet sediment and 16.16 ± 1.28 μmol CO2/g wet sediment/day respectively. The corresponding values for P were 63 ± 95 nmol/g wet sediment and 12.05 ± 1.31 μmol CO2/g wet sediment/day. The qmax values with respect to N and P were not significantly different (P < 0.05). When N and P were not limiting Ks and qmax for crude oil were 4.52 ± 1.51 mg oil/g wet sediment and 16.89 ± 1.25 μmol CO2/g wet sediment/day. At concentrations of inorganic N above 45 μmol/g wet sediment inhibition of CO2 production from hydrocarbon degradation was evident. Analysis of bacterial 16S rRNA genes indicated that Alcanivorax spp. were selected in these marine sediments with increasing inorganic nutrient concentration, whereas Cycloclasticus spp. were more prevalent at lower inorganic nutrient concentrations. These data suggest that simple empirical estimates of the proportion of nutrients added relative to crude oil concentrations may not be sufficient to guarantee successful crude oil bioremediation in oxic beach sediments. The data we present also help define the maximum rates and hence timescales required for bioremediation of beach sediments.
在海洋系统中，无机养分（尤其是氮和磷）的可利用性通常是控制原油烃降解的主要因素。许多研究已经经验性地确定了促进烃降解的最佳无机 N 和 P 水平。然而，关于在使用无机养分促进油生物降解的生物修复计划中可以用来模拟原油命运的基本营养物增强原油生物降解的动力学参数的信息却很少。在这里，我们报告了在营养物有限的条件下，硝酸盐和磷酸盐刺激的原油生物降解的基本动力学参数（Ks 和 qmax），以及在不限制 N 和 P 的情况下，与原油有关的基本动力学参数。在所研究的海洋沉积物中，原油降解受到 N 和 P 可用性的双重限制。在未添加 N 和 P 但用 12.5mg/g 油处理的沉积物中，根据 CO2 生成评估的烃降解速率为 1.10±0.03μmol CO2/g 湿沉积物/天，与未添加油的沉积物中的 CO2 生成速率相当（1.05±0.27μmol CO2/g 湿沉积物/天）。当单独添加无机氮时，最大 CO2 生成速率为 4.25±0.91μmol CO2/g 湿沉积物/天。然而，当在 0.5%w/w 油的存在下添加相同水平的无机氮（1.6μmol P/g 湿沉积物）时，测量的最大 CO2 生成速率增加了四倍以上，达到 18.40±1.04μmol CO2/g 湿沉积物/天。当 P 不受限制时，无机 N（以硝酸钠的形式）的 Ks 和 qmax 估计值分别为 1.99±0.86μmol/g 湿沉积物和 16.16±1.28μmol CO2/g 湿沉积物/天。P 的相应值为 63±95nmol/g 湿沉积物和 12.05±1.31μmol CO2/g 湿沉积物/天。N 和 P 的 qmax 值没有显着差异（P<0.05）。当 N 和 P 不受限制时，原油的 Ks 和 qmax 分别为 4.52±1.51mg 油/g 湿沉积物和 16.89±1.25μmol CO2/g 湿沉积物/天。当无机氮浓度高于 45μmol/g 湿沉积物时，烃降解产生的 CO2 生成受到抑制。对细菌 16S rRNA 基因的分析表明，随着无机养分浓度的增加，在这些海洋沉积物中选择了 Alcanivorax 属，而 Cycloclasticus 属在较低的无机养分浓度下更为普遍。这些数据表明，相对于原油浓度简单经验估计添加的养分比例可能不足以保证在含氧海滩沉积物中成功进行原油生物修复。我们提供的数据还有助于定义海滩沉积物生物修复所需的最大速率和因此所需的时间尺度。
