Some bacteria can degrade organic micropollutants (OMPs) as primary carbon sources. Due to typically low OMP concentrations, these bacteria may benefit from supplemental assimilation of natural substrates present in the pool of dissolved organic matter (DOM). The biodegradability of such auxiliary substrates and the impacts on OMP removal are tightly linked to biotransformation pathways. Here, we aimed to elucidate the biodegradability and effect of different DOM constituents for the carbofuran degrader Novosphingobium sp. KN65.2, using a novel approach that combines pathway prediction, laboratory experiments, and fluorescence spectroscopy. Pathway prediction suggested that ring hydroxylation reactions catalysed by Rieske-type dioxygenases and flavin-dependent monooxygenases determine the transformability of the 11 aromatic compounds used as model DOM constituents. Our approach further identified two groups with distinct transformation mechanisms amongst the four growth-supporting compounds selected for mixed substrate biodegradation experiments with the pesticide carbofuran (Group 1: 4-hydroxybenzoic acid, 4-hydroxybenzaldehyde; Group 2: p-coumaric acid, ferulic acid). Carbofuran biodegradation kinetics were stable in the presence of both Group 1 and Group 2 auxiliary substrates. However, Group 2 substrates would be preferable for bioremediation processes, as they showed constant biodegradation kinetics under different experimental conditions (pre-growing KN65.2 on carbofuran vs. DOM constituent). Furthermore, Group 2 substrates were utilisable by KN65.2 in the presence of a competitor (Pseudomonas fluorescens sp. P17). Our study thus presents a simple and cost-efficient approach that reveals mechanistic insights into OMP-DOM biodegradation.

中文翻译：

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耦合途径预测和荧光光谱法评估辅助底物对微污染物生物降解的影响

一些细菌可以降解有机微污染物（OMP）作为主要碳源。由于 OMP 浓度通常较低，这些细菌可能受益于溶解有机物 (DOM) 池中存在的天然底物的补充同化。此类辅助底物的生物降解性以及对 OMP 去除的影响与生物转化途径密切相关。在这里，我们的目的是阐明不同 DOM 成分对呋喃丹降解剂Novosphingobium sp 的生物降解性和效果。KN65.2，采用一种结合途径预测、实验室实验和荧光光谱的新颖方法。路径预测表明，Rieske 型双加氧酶和黄素依赖性单加氧酶催化的环羟基化反应决定了用作模型 DOM 成分的 11 种芳香族化合物的可转化性。我们的方法进一步确定了在选择用于农药克百威混合底物生物降解实验的四种生长支持化合物中具有不同转化机制的两组（组1：4-羟基苯甲酸、4-羟基苯甲醛；组2：对香豆酸、阿魏酸） ）。在存在第 1 组和第 2 组辅助底物的情况下，呋喃丹生物降解动力学稳定。然而，第 2 组底物更适合生物修复过程，因为它们在不同的实验条件下（在克百威与 DOM 成分上预生长 KN65.2）表现出恒定的生物降解动力学。此外，在竞争者（荧光假单胞菌P17）存在的情况下，KN65.2 可以利用第 2 组底物。因此，我们的研究提出了一种简单且经济高效的方法，揭示了 OMP-DOM 生物降解的机制。