Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China; Institute for Ocean Engineering, Tsinghua University, Beijing 100084, PR China.
Shenzhen Public Platform for Screening and Application of Marine Microbial Resources, Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, PR China.
Sci Total Environ. 2021 Jun 1;771:145437. doi: 10.1016/j.scitotenv.2021.145437. Epub 2021 Jan 28.
Bacterial degradation is one of the most efficient ways to remove microcystins (MCs), the most frequently detected toxin in cyanobacterial blooms. Using Novosphingobium sp. ERW19 as a representative strain, our laboratory previously demonstrated that quorum sensing (QS), the cell density-dependent gene regulation system, positively regulates biodegradation of MCs via transcriptional activation of mlr-pathway-associated genes. Increasing evidence indicates that QS is involved in a wide spectrum of regulatory circuits, but it remains unclear which physiological processes in MC degradation besides the expression of MC-degrading genes are also subject to QS-dependent regulation. This study used transcriptome analysis to identify QS-regulated genes during degradation of MCs. A large percentage (up to 32.6%) of the genome of the MC-degrading bacterial strain Novosphingobium sp. ERW19 was significantly differentially expressed in the corresponding QS mutants. Pathway enrichment analysis of QS-regulated genes revealed that QS mainly influenced metabolism-associated pathways, particularly those related to amino acid metabolism, carbohydrate metabolism, and biodegradation and metabolism of xenobiotics. In-depth functional interpretation of QS-regulated genes indicated a variety of pathways were potentially associated with bacterial degradation or physiological responses to MCs, including genes involved in cell motility, cytochrome P450-dependent metabolism of xenobiotics, glutathione S-transferase (GST), envelope stress response, and ribosomes. Furthermore, QS may be involved in regulating the initial and final steps of the catabolic pathway of phenylacetic acid, an intermediate product of MC degradation. Collectively, this global survey of QS-regulated genes in a MC-degrading bacterial strain facilitates a deeper understanding of QS-controlled processes that may be important for bacterial degradation of MCs or may contribute to the physiological responses of bacteria to MCs.
细菌降解是去除微囊藻毒素（MCs）的最有效方法之一，MCs 是蓝藻水华中毒素中最常被检测到的一种。本实验室以前曾使用鞘氨醇单胞菌 ERW19 作为代表性菌株进行研究，证明了群体感应（QS），即细胞密度依赖型基因调控系统，通过转录激活 mlr 途径相关基因正向调控 MCs 的生物降解。越来越多的证据表明，QS 参与了广泛的调控回路，但仍不清楚除了降解 MC 基因的表达外，QS 还调节 MC 降解过程中的哪些生理过程。本研究使用转录组分析鉴定了 MC 降解过程中 QS 调控的基因。MC 降解细菌菌株鞘氨醇单胞菌 ERW19 的基因组中有很大一部分（高达 32.6%）在相应的 QS 突变体中表达显著不同。QS 调控基因的途径富集分析表明，QS 主要影响代谢相关途径，特别是与氨基酸代谢、碳水化合物代谢以及外源性物质的生物降解和代谢相关的途径。对 QS 调控基因的深入功能解释表明，多种途径可能与细菌降解或对 MCs 的生理反应有关，包括参与细胞运动、细胞色素 P450 依赖性外源性物质代谢、谷胱甘肽 S-转移酶（GST）、包膜应激反应和核糖体的基因。此外，QS 可能参与调节 MC 降解中间产物苯乙酸分解代谢途径的起始和终末步骤。总之，对 MC 降解细菌菌株中 QS 调控基因的全面调查有助于更深入地了解 QS 控制的过程，这些过程可能对细菌降解 MCs 很重要，或者可能有助于细菌对 MCs 的生理反应。
