Genome-Wide Analysis of Transcriptional Changes and Genes That Contribute to Fitness during Degradation of the Anthropogenic Pollutant Pentachlorophenol by Sphingobium chlorophenolicum.
Genome-Wide Analysis of Transcriptional Changes and Genes That Contribute to Fitness during Degradation of the Anthropogenic Pollutant Pentachlorophenol by Sphingobium chlorophenolicum.
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DOI：
10.1128/msystems.00275-18
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发表时间：
2018-11
期刊：
影响因子：
6.4
通讯作者：
Copley SD
中科院分区：
文献类型：
--
作者：
Flood JJ;Copley SD
五氯苯酚（PCP）、三氯生和2，4-二氯苯氧乙酸（2，4-D）等酚类化合物是一类常见的人类杀生物剂。尽管这些化合物是新奇的，但许多化合物可以被从污染场地分离的微生物降解。然而，这类化学品的降解通常会产生有毒中间体，这可能会导致其难以生物降解。我们已经解决了与五氯酚鞘氨醇菌降解五氯酚相关的压力，通过研究五氯酚暴露后的转录反应，并确定在暴露和降解五氯酚过程中生长所必需的基因。这项工作确定了一些保护细胞免受这种有毒化合物侵害并促进其降解的机制。这一信息可用于工程菌株能够改善五氯苯酚或类似的酚类污染物的生物降解。五氯苯酚（PCP）是一种剧毒农药，于20世纪30年代首次引入。从受PCP污染的沉积物中分离得到的Sphingobium chlorophenolicum已构建了一条能够完全降解PCP的代谢途径。该途径产生四种有毒中间体，包括一种有效的烷基化剂氯化苯醌和三种与O2反应产生活性氧（ROS）的氯化氢醌。RNA-seq分析显示，五氯苯酚引起的整体应激反应类似于对质子动力解偶联和膜破坏的反应，但令人惊讶的是，这种反应几乎与五氯苯酚降解中间体预期产生的反应没有相似之处。Tn-seq被用于识别在PCP存在下对适应性重要的基因。通过比较野生型S.通过对氯酚菌和非五氯酚降解突变体的比较，我们确定了只有在产生五氯酚降解中间产物时才重要的基因。这些包括编码两种酶的基因，这两种酶可能参与保护免受ROS的侵害。除了这些酶外，保护细胞免受氧化应激的其他酶的内源水平似乎也能减轻五氯苯酚的氯化苯醌和氢醌代谢物的毒性影响。RNA-seq和Tn-seq结果的结合确定了防御五氯苯酚毒性的重要机制。五氯苯酚（PCP）、三氯生和2，4-二氯苯氧乙酸（2，4-D）等酚类化合物是一类常见的人为生物杀灭剂。尽管这些化合物是新奇的，但许多化合物可以被从污染场地分离的微生物降解。然而，这类化学品的降解通常会产生有毒中间体，这可能会导致其难以生物降解。我们已经解决了与五氯酚鞘氨醇菌降解五氯酚相关的压力，通过研究五氯酚暴露后的转录反应，并确定在暴露和降解五氯酚过程中生长所必需的基因。这项工作确定了一些保护细胞免受这种有毒化合物侵害并促进其降解的机制。这一信息可用于工程菌株能够改善五氯苯酚或类似的酚类污染物的生物降解。
Phenolic compounds such as pentachlorophenol (PCP), triclosan, and 2,4-dichlorophenoxyacetic acid (2,4-D) represent a common class of anthropogenic biocides. Despite the novelty of these compounds, many can be degraded by microbes isolated from contaminated sites. However, degradation of this class of chemicals often generates toxic intermediates, which may contribute to their recalcitrance to biodegradation. We have addressed the stresses associated with degradation of PCP by Sphingobium chlorophenolicum by examining the transcriptional response after PCP exposure and identifying genes necessary for growth during both exposure to and degradation of PCP. This work identifies some of the mechanisms that protect cells from this toxic compound and facilitate its degradation. This information could be used to engineer strains capable of improved biodegradation of PCP or similar phenolic pollutants. Pentachlorophenol (PCP) is a highly toxic pesticide that was first introduced in the 1930s. The alphaproteobacterium Sphingobium chlorophenolicum, which was isolated from PCP-contaminated sediment, has assembled a metabolic pathway capable of completely degrading PCP. This pathway produces four toxic intermediates, including a chlorinated benzoquinone that is a potent alkylating agent and three chlorinated hydroquinones that react with O2 to produce reactive oxygen species (ROS). RNA-seq analysis revealed that PCP causes a global stress response that resembles responses to proton motive force uncoupling and membrane disruption, while surprisingly, little of the response resembles the responses expected to be produced by the PCP degradation intermediates. Tn-seq was used to identify genes important for fitness in the presence of PCP. By comparing the genes that are important for fitness in wild-type S. chlorophenolicum and a non-PCP-degrading mutant, we identified genes that are important only when the PCP degradation intermediates are produced. These include genes encoding two enzymes that are likely to be involved in protection against ROS. In addition to these enzymes, the endogenous levels of other enzymes that protect cells from oxidative stress appear to mitigate the toxic effects of the chlorinated benzoquinone and hydroquinone metabolites of PCP. The combination of RNA-seq and Tn-seq results identify important mechanisms for defense against the toxicity of PCP. IMPORTANCE Phenolic compounds such as pentachlorophenol (PCP), triclosan, and 2,4-dichlorophenoxyacetic acid (2,4-D) represent a common class of anthropogenic biocides. Despite the novelty of these compounds, many can be degraded by microbes isolated from contaminated sites. However, degradation of this class of chemicals often generates toxic intermediates, which may contribute to their recalcitrance to biodegradation. We have addressed the stresses associated with degradation of PCP by Sphingobium chlorophenolicum by examining the transcriptional response after PCP exposure and identifying genes necessary for growth during both exposure to and degradation of PCP. This work identifies some of the mechanisms that protect cells from this toxic compound and facilitate its degradation. This information could be used to engineer strains capable of improved biodegradation of PCP or similar phenolic pollutants.