School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, Lanzhou, People's Republic of China.
School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou, 730070, People's Republic of China.
Appl Microbiol Biotechnol. 2021 Oct;105(20):7841-7855. doi: 10.1007/s00253-021-11586-3. Epub 2021 Sep 21.
Microbial bioremediation of Cr(VI)-contaminated environments has drawn extensive concern. However, the molecular processes underlying the microbial Cr(VI) tolerance and reduction remain unclear. We isolated a Cr(VI)-reducing Lysinibacillus fusiformis strain 15-4 from soil on the Qinghai-Tibet Plateau. When grown in 1 mM and 2 mM Cr(VI)-containing medium, strain 15-4 could reduce 100% and 93.7% of Cr(VI) to Cr(III) after 36 h and 60 h of incubation, respectively. To know the molecular processes in response to Cr(VI), transcriptome sequencing was carried out using RNA-Seq technology. The results annotated a total of 3913 expressed genes in the strain. One thousand ninety-eight genes (28.1%) were significantly (fold change ≥ 2, false discovery rate ≤ 0.05) expressed in response to Cr(VI), of which 605 (55.1%) were upregulated and 493 (44.9%) were downregulated. The enrichment analysis showed that a total of 630 differentially expressed genes (DEGs) were enriched to 122 KEGG pathways, of which 8 pathways were significantly (p < 0.05) enriched in Cr(VI)-treated sample, including ATP-binding cassette (ABC) transporters (97 DEGs), ribosome (40), sulfur metabolism (16), aminoacyl-tRNA biosynthesis (19), porphyrin metabolism (20), quorum sensing (44), oxidative phosphorylation (17), and histidine metabolism (10), suggesting that these pathways play key roles to cope with Cr(VI) in the strain. The highly upregulated DEGs consisted of 29 oxidoreductase, 18 dehydrogenase, 14 cell redox homeostasis and stress response protein, and 10 DNA damage and repair protein genes. However, seven Na:H antiporter complex-coding DEGs and most of transcriptional regulator-coding DEGs were significantly downregulated in the Cr-treated sample. Many of FMN/NAD(P)H-dependent reductase-encoding genes were greatly induced by Cr, suggesting the involvement of these genes in Cr(VI) reduction in strain 15-4. Sulfur and iron ions as well as the thiol-disulfide exchange reactions might play synergistic roles in Cr reduction.Key points• Lysinibacillus fusiformis 15-4 was able to tolerate and reduce Cr(VI) to Cr(III).• Transcriptome analysis revealed that 1098 DEGs and 8 key KEGG pathways significantly responded to Cr(VI).• Sulfur metabolism, protein biosynthesis, and porphyrin metabolism were the key pathways associated with the survival of strain 15-4 in response to Cr(VI).
微生物生物修复铬（VI）污染环境引起了广泛关注。然而，微生物对铬（VI）的耐受性和还原的分子过程仍不清楚。我们从青藏高原土壤中分离到一株能还原铬（VI）的解淀粉芽孢杆菌 15-4 菌株。当在含有 1mM 和 2mM 铬（VI）的培养基中生长时，菌株 15-4 在 36h 和 60h 分别能将 100%和 93.7%的铬（VI）还原为铬（III）。为了了解铬（VI）作用下的分子过程，我们使用 RNA-Seq 技术进行了转录组测序。结果注释了该菌株共表达了 3913 个基因。1098 个基因（28.1%）（倍数变化≥2，错误发现率≤0.05）在铬（VI）作用下显著表达，其中 605 个（55.1%）上调，493 个（44.9%）下调。富集分析表明，630 个差异表达基因（DEGs）共富集到 122 个 KEGG 途径，其中 8 个途径在铬（VI）处理样本中显著富集（p<0.05），包括 ABC 转运体（97 个 DEGs）、核糖体（40 个）、硫代谢（16 个）、氨酰-tRNA 生物合成（19 个）、卟啉代谢（20 个）、群体感应（44 个）、氧化磷酸化（17 个）和组氨酸代谢（10 个），表明这些途径在菌株中对铬（VI）的应对发挥关键作用。高度上调的 DEGs包括 29 个氧化还原酶、18 个脱氢酶、14 个细胞氧化还原稳态和应激反应蛋白和 10 个 DNA 损伤和修复蛋白基因。然而，在铬处理样本中，7 个 Na：H 反向转运体复合物编码的 DEGs 和大多数转录调节因子编码的 DEGs显著下调。许多 FMN/NAD（P）H 依赖型还原酶编码基因被铬强烈诱导，表明这些基因参与了 15-4 菌株中铬（VI）的还原。硫和铁离子以及巯基-二硫键交换反应可能在铬还原中发挥协同作用。
