Microcystin-LR Degradation and Gene Regulation of Microcystin-Degrading Novosphingobium sp. THN1 at Different Carbon Concentrations
Microcystin-LR Degradation and Gene Regulation of Microcystin-Degrading Novosphingobium sp. THN1 at Different Carbon Concentrations
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DOI：
10.3389/fmicb.2019.01750
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发表时间：
2019-08
影响因子：
5.2
通讯作者：
Juanping Wang;Chang Wang;Qi Li;Mengyuan Shen;Peng-yuan Bai;Jionghui Li;Yan Lin;N. Gan;Tao Li;Jindong Zhao
中科院分区：
文献类型：
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作者：
Juanping Wang;Chang Wang;Qi Li;Mengyuan Shen;Peng-yuan Bai;Jionghui Li;Yan Lin;N. Gan;Tao Li;Jindong Zhao
Novosphingobium sp. THN1 （THN1）能够降解微囊藻毒素- lr （MC-LR）。为了研究THN1对MC-LR的降解能力及其可能的调控机制，我们分析了碳浓度对降解过程的影响。在MC-LR生物降解过程中，MC-LR降解率先达到峰值，然后下降。培养基中碳含量的降低导致降解峰提前出现。不同碳浓度下，编码微胱氨酸酶的功能基因mlrA的表达量与MC-LR的降解率呈相似趋势（r2 = 0.717, p < 0.05），说明调控mlrA的表达可能在THN1对MC-LR的降解中起重要作用。当碳源限制时，细菌总生物量减少，且与MC-LR降解速率无关。转录组学分析显示，MC-LR降解差异调控了62.16%（2597/4178）的THN1基因。在MC-LR降解过程中，相当数量的差异表达基因（DEGs）编码了与碳、氮和氨基酸相关的蛋白质。在MC-LR降解2 h时，大多数参与碳氮代谢的DEGs（29/33）下调。这表明MC-LR可能调控Novosphingobium sp. THN1的碳氮途径。KEGG通路分析表明，MC-LR降解过程中DEGs的上调主要与氨基酸降解和底物代谢途径有关。特别是，我们从转录组数据中发现，与基因表达0小时相比，在MC-LR降解2小时时，谷胱甘肽代谢相关基因的表达增加，如GST家族蛋白、谷胱甘肽过氧化物酶、S-（羟甲基）谷胱甘肽脱氢酶和谷胱甘肽依赖的二硫键氧化还原酶，这些基因已被报道参与微囊藻毒素降解。
The bacterium Novosphingobium sp. THN1 (THN1) is capable of degrading microcystin-LR (MC-LR). To study the ability of THN1 to degrade MC-LR and its possible mechanism(s) of regulation, we analyzed the effect of carbon concentrations on the degradation process. The MC-LR degradation rate peaked early and then declined during MC-LR biodegradation. Decreased levels of carbon in the medium caused the degradation peak to occur earlier. The expression of the functional gene mlrA, encoding a microcystinase, showed a similar trend to the MC-LR degradation rate at various carbon concentrations (r2 = 0.717, p < 0.05), suggesting that regulation of mlrA expression may play an important role in MC-LR degradation by THN1. The total bacterial biomass decreased when the carbon source was limited and did not correlate with the MC-LR degradation rate. Transcriptomic analysis showed that MC-LR degradation differentially regulated 62.16% (2597/4178) of THN1 genes. A considerable number of differentially expressed genes (DEGs) during MC-LR degradation encoded proteins related to carbon-, nitrogen-, and amino acid-related pathways. At 2 h of MC-LR degradation, most DEGs (29/33) involved in carbon and nitrogen metabolism were downregulated. This indicated that MC-LR may regulate carbon and nitrogen pathways of Novosphingobium sp. THN1. KEGG pathway analysis indicated that the upregulated DEGs during MC-LR degradation were mainly related to amino acid degradation and substrate metabolism pathways. Particularly, we detected increased expression of glutathione metabolism-related genes from transcriptomic data at 2 h of MC-LR degradation compared with the gene expression of 0 h, such as GST family protein, glutathione peroxidase, S-(hydroxymethyl) glutathione dehydrogenase, and glutathione-dependent disulfide-bond oxidoreductase that have been reported to be involved in microcystin degradation.