Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat-13, Assam, India.
Silkworm Pathology Section, Central Sericultural Research and Training Institute, Central Silk Board, Ministry of Textile, Govt of India, Berhampore, West Bengal, 7421 01, India.
BMC Microbiol. 2023 Mar 31;23(1):91. doi: 10.1186/s12866-023-02821-0.
Bacillus thuringiensis (Bt) is a gram-positive ubiquitous saprophytic bacterium that produces proteins (Crystal protein, Vegetative insecticidal protein, and Secreted insecticidal protein) toxic to insects during its growth cycle. In the present study, the whole genome of a locally isolated B. thuringiensis strain BA04 was sequenced to explore the genetic makeup and to identify the genes responsible to produce insecticidal proteins including the virulence factors. The strain was isolated from the soil sample of the Kaziranga National Park, Assam, North-Eastern part of India (Latitude: 26°34'39.11''N and Longitude: 93°10'16.04''E).
The whole genome sequencing (WGS) of the BA04 strain revealed that it has a circular genome of size 6,113,005 bp with four numbers of plasmids. A total of 6,111 genes including two novel crystal protein-encoding genes (MH753362.1 and MH753363.1) were identified. The BLASTn analysis of MH753362.1 showed 84% similarities (maximum identity) with Cry1Ia (KJ710646.1) gene, whereas MH753363.1 exhibited 66% identity with Insecticidal Crystal Protein (ICP)-6 gene (KM053257.1). At the protein level, MH753362.1 and MH753363.1 shared 79% identity with Cry1Ia (AIW52613.1) and 40% identity with Insecticidal Crystal Protein (ICP)-6 (AJW76687.1) respectively. Three-dimensional structures of these two novel protein sequences revealed that MH753362.1 have 48% structural similarity with Cry8ea1 protein, whereas MH753363.1 showed only 20% structural similarity with Cry4Aa protein. Apart from these insecticidal genes, the strain was also found to contain virulence and virulence-associated factors including the antibiotic resistance genes and Clustered regularly interspaced short palindromic repeat (CRISPR) sequences.
This is the first report on the whole genome sequence of Bt strain BA04 isolated from Assam, a North-Eastern state of India. The WGS of strain BA04 unveils the presence of two novel types of insecticidal crystal protein-encoding genes which can be used for the development of insect-resistant transgenic crops. Additionally, the strain could be used for the formulations of effective biopesticides. The WGS provides the fastest and cheapest platform for a better understanding of the genetic makeup of a strain and helps to explore the role of virulence genes in pathogenicity against the insect host.
苏云金芽孢杆菌（Bt）是一种革兰氏阳性、无处不在的腐生细菌，在其生长周期中会产生对昆虫有毒的蛋白质（晶体蛋白、营养期杀虫蛋白和分泌型杀虫蛋白）。在本研究中，对一株从印度东北部的阿萨姆邦的卡齐兰加国家公园土壤样本中分离的本地 Bt 菌株 BA04 进行了全基因组测序，以探索其遗传构成，并鉴定产生杀虫蛋白的基因，包括毒力因子。
BA04 菌株的全基因组测序（WGS）显示，它具有大小为 6,113,005bp 的圆形基因组，带有四个质粒。总共鉴定出 6,111 个基因，包括两个新的晶体蛋白编码基因（MH753362.1 和 MH753363.1）。MH753362.1 的 BLASTn 分析显示，其与 Cry1Ia（KJ710646.1）基因具有 84%的相似性（最大同一性），而 MH753363.1 与杀虫晶体蛋白（ICP）-6 基因（KM053257.1）具有 66%的同一性。在蛋白质水平上，MH753362.1 和 MH753363.1 与 Cry1Ia（AIW52613.1）和 Insecticidal Crystal Protein（ICP）-6（AJW76687.1）分别具有 79%和 40%的同一性。这两个新蛋白序列的三维结构表明，MH753362.1 与 Cry8ea1 蛋白具有 48%的结构相似性，而 MH753363.1 与 Cry4Aa 蛋白仅具有 20%的结构相似性。除了这些杀虫基因外，该菌株还含有毒力和毒力相关因子，包括抗生素抗性基因和规律成簇间隔短回文重复序列（CRISPR）序列。
这是首次报道从印度东北部的阿萨姆邦分离出的 Bt 菌株 BA04 的全基因组序列。BA04 菌株的 WGS 揭示了两种新型杀虫晶体蛋白编码基因的存在，可用于开发抗虫转基因作物。此外，该菌株可用于有效生物农药的制剂。WGS 为更好地了解菌株的遗传构成提供了最快和最便宜的平台，并有助于探索毒力基因在对昆虫宿主的致病性中的作用。
