摘要:16S rRNA基因高通量测序 (16S-seq) 是研究微生物组的常用方法之一。在分析植物或其他高等生物的样品时,线粒体和质体16S rRNA基因也被通用引物扩增,造成测序结果中宿主序列的污染最高达99%以上,不仅提高了成本,而且极大地限制了16S-seq方法分析植物微生物群落结构的灵敏度。Cas-16S-seq的方法是一种利用CRISPR/Cas9靶向切割植物16S rRNA基因序列从而富集扩增产物中细菌序列的方法 (图1) (Song和Xie,2020)。该方法操作简单,可以方便地整合到已有的16S-seq流程中,能高效率地消除共扩增的高丰度植物序列。我们的分析也表明Cas9具有高特异性,通过使用我们开发的生物信息学平台设计的植物特异的gRNA,未检测到脱靶切割细菌16S rRNA的现象。本文以水稻为例,描述了Cas-16S-seq的详细步骤和实验要点,为科研人员使用该方法分析植物微生物组提供参考。
材料和试剂
- 50 ml离心管 (Corning, catalog number: 430829)
- RNase-free 0.2 ml PCR管 (Axygen, catalog number: PCR-02D-C)
- RNase-free 1.5 ml离心管 (Axygen, catalog number: MCT-150-C)
- 丁腈手套 (AMMEX, catalog number: APFNCHD50)
- Alkaline phosphatase, calf intestinal (CIP) (New England Biolabs, catalog number: M0290S)
- Bsa I (New England Biolabs, catalog number: R0535S)
- Cas9 (New England Biolabs, catalog number: M0386S)
- DH5α (Vazym, catalog number: C502-03)
- Protease K (New England Biolabs, catalog number: P8107S)
- T4 DNA ligase (New England Biolabs, catalog number: M0202S)
- T4 polynucleotide kinase (T4 PNK) (New England Biolabs, catalog number: M0201S)
- pUC19-gRNA (Addgene plasmid #137776,质粒图谱见图1)

图1. pUC19-gRNA载体示意图
- 16S rDNA Bacterial Identification PCR Kit (TaKaRa, catalog number: RR176)
- Agencourt AMPure XP beads (Beckman Coulter, catalog number: A63880)
- DNeasy Powersoil Kit (QIAGEN, catalog number: 12888-50)
- Gel Extraction Kit (OMEGA, catalog number: D2500-02)
- HiScribe Quick T7 High Yield RNA Synthesis Kit (New England Biolabs, catalog number: E2050)
- I-5 2× High-Fidelity Master Mix (Molecular Cloning Laboratories, catalog number: I5HM-200)
- QIAGEN plasmid mini kit (QIAGEN, catalog number: 12123)
- RNA Clean & Concentrator Kit (Zymo Research, catalog number: R1017)
- Double-distilled H2O (ddH2O)
- KCl (Fisher Scientific, catalog number: P217-500)
- KH2PO4 (Fisher Scientific, catalog number: P285-500)
- LE Agarose (Hydragene, catalog number: R9012LE-100g)
- NaCl (Fisher Scientific, catalog number: S271-1)
- Na2HPO4 (Fisher Scientific, catalog number: S374-500)
- TWEEN 20 (Fisher Scientific, catalog number: BP337-100)
- 75%乙醇,80%乙醇 (用95%乙醇和0.1‰ DEPC处理水配制)
- 75%医用酒精 (国药试剂)
- 氨苄青霉素 (国药试剂)
- 苯酚 (国药试剂)
- 焦碳酸二乙酯 (DEPC, Sigma, catalog number: D5758)
- 氯仿 (国药试剂)
- 无核酸酶水 (Zymo Research, catalog number: W1001-4)
- 无水乙醇或95%乙醇 (国药试剂,分析纯)
- 无水乙酸钠 (国药试剂,分析纯)
- 液氮
- 磷酸盐缓冲溶液 (见溶液配方)
- 0.1‰ DEPC处理水 (见溶液配方)
- 3 M 醋酸钠 (pH 5.2) (见溶液配方)
仪器设备
- 96孔磁铁架 (BORHEE, catalog number: MAG-96-11)
- 剪刀和镊子
- 研磨钵和研磨棒
- 移液器 (2.5,20,200,1,000 μl) (Labnet, catalog numbers: 540910296, 340930114, 240750135, 440960631)
- NanoDrop One (Thermo Fisher Scientific, catalog number: ND-ONE-W)
- DNA电泳装置
- 超净工作台
- 小型离心机 (Eppendorf, catalog number: 022620498)
- 台式离心机 (Cence, catalog number: TDZ5-WS)
- 涡旋振荡器 (Scientific Industries, catalog number: G560E)
- 水浴锅
- 37 °C恒温培养箱
- PCR热循环仪 (Bio-Rad Laboratories, S1000TM Thermal Cycler, catalog number: 1852148)
- 研钵和研磨棒
- -20 °C冰箱
- pH计 (METTLER TOLEDO, catalog number: FE20K)
软件和数据库
- VSEARCH软件 (version 2.8.1)
实验步骤
Copyright: © 2021 The Authors; exclusive licensee Bio-protocol LLC.
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