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芽孢杆菌KJ82的全基因组测序及分析

Whole Genome Sequencing and Analysis of Bacillus Strain KJ82

  • 摘要: 以克百威为代表的氨基甲酸酯类农药在土壤中残留的问题随着其广泛使用受到越来越多的关注。前期从阿克苏10年以上连作棉田盐碱土壤富集的克百威降解菌群中分离到一株细菌KJ82,现利用PacBio SequelⅡ三代测序平台获得了该菌株的全基因组序列,使用Microbial assembly、HGAP4、Canu、Glimmer等软件对该菌株进行基因组组装、编码基因的预测、功能注释、参考菌株的共线性分析、基因簇分析,预测克百威降解相关功能基因簇。全基因组分析表明,菌株KJ82基因组由1条环状染色体组成,不含质粒,长度为3 754 440 bp,平均GC含量为41.41%,注释出3 896个蛋白编码基因;包含有24个16S-23S-5S rRNA,81个tRNA及77个其余RNA,预测出9个CRISPR序列,4个基因组岛,1个前噬菌体结构;通过基础数据库COG、GO、KEGG/KOG注释,分别匹配到3 005个、2 214个和2 162个基因的蛋白序列;比较基因组学分析发现,菌株KJ82与相似度最高的Bacillus altitudinis GQYP101菌株基因组之间的平均核酸一致性(Average nucleotide identity, ANI)值在97.59%~97.89%范围内,数字DNA-DNA杂交(Digital DNA-DNA hybridization, dDDH)值为81%。ANI和dDDH值均高于物种判断的临界值,基因组之间拥有极好的共线性和高度相似的基因组排布。通过antiSMASH预测发现,菌株KJ82基因组中共有11个次生代谢产物合成基因簇,其中有6个基因簇与已知合成基因簇相似度较低,4个基因簇功能未知。在该菌株基因组中发现了1个可能的水解酶和2个单加氧酶基因(分别位于Cluster 8、Cluster 4和Cluster 3上),前两个基因与已知合成基因簇之间的相似度分别为6%和50%,另一个仅能定位到基因簇的位置。本研究为该菌株在碱性条件下参与克百威降解的相关降解酶基因及其基因簇可能编码产生的新颖活性天然产物研究提供了科学依据。

     

    Abstract: A great deal of concern has been aroused among the scientific community about the extensive use of carbamate pesticides represented by carbofuran and their residues in soil. Strain KJ82 was isolated from the carbofuran degradation bacterial flora, which enriched in the saline alkali soil of the continuous cropping cotton field in Aksu area for more than 10 years. Now, the whole genome of this strain was sequenced by PacBio Sequel Ⅱthird-generation sequencing platform. Microbial assembly, HGAP4, Canu, Glimmer and other software were used to perform assembly, encoding gene prediction, gene function annotation, species collinear analysis and prediction of the strain KJ82 secondary metabolite synthesis gene cluster. The genome-wide analysis showed that the strain KJ82 genome was composed of one circular chromosome without plasmid. The total sequence length of the strain KJ82 genome was 3 754 440 bp, GC content of 41.41%, and 3 896 coding genes were annotated. There were twenty-four 16 S-23 S-5 S rRNAs, 81 tRNAs and 77 other RNAs, 9 CRISPR sequences, 4 genomic islands, and 1 prophage structure were predicted. The protein sequences of 3 005, 2 214, and 2 162 genes can be matched with annotation information in the COG, GO and KEGG/KOG databases, respectively. According to comparative genomics analysis, the ANI(Average nucleotide identity) value between the strain KJ82 and highest similarity strain Bacillus altitudinis GQYP101 was 97.59% to 97.89%, and the dDDH(Digital DNA-DNA hybridization) value was 81%. Therefore, all the ANI and dDDH values were higher than the cut-off point recommended for delineating species. Through antiSMASH prediction, it was found that there were 11 secondary metabolite synthesis gene clusters in the genome of strain KJ82, of which 6 gene clusters had low similarity with the known synthetic gene clusters, and 4 gene clusters had unknown functions, respectively. One possible hydrolase gene and two monooxygenase genes were found in the genome of this strain, which were located on Cluster 8, Cluster 4 and Cluster 3, respectively, and the similarity with known synthetic gene clusters was 6% and 50%, respectively, and a gene cluster functional location. This study provides a scientific basis for the study of the gene function of the strain involved in the degradation of carbofuran under alkaline conditions and the novel active natural products that may be encoded by its gene cluster.

     

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