母细胞产生内含物的芽胞杆菌分析

Analysis of Bacillus spp.producing inclusion in mother cell

在苏云金芽胞杆菌(Bacillus thuringiensis,Bt)分离过程中发现有些芽胞杆菌产生与Bt相似的芽胞,但并不形成伴胞晶体,特别是发现它们在芽胞期的母细胞中含有丰富的内含物,对该类菌株的性质需要进一步明确。本研究选择6株该类型的菌株,对其种属、质粒、蛋白谱和杀虫活性等进行了初步分析。芽胞形态和质粒图谱分析结果显示,其与Bt菌株相似;肽指纹图谱分析发现选取的蛋白与蜡样芽胞杆菌(B.cereus)族细菌的蛋白匹配度最高;16SrDNA聚类研究表明,所分离的菌株的确与蜡样芽胞杆菌(B.cereus)族(包括Bc和Bt)同源性最高;从生物杀虫活性测定来看11-1菌株上清液对小菜蛾(Plutella xylostella)的校正死亡率达75.9%,而85-1和11-1菌株上清对亚洲玉米螟(Ostrinia furnacalis)的校正死亡率分别能达到100%和87.9%。本研究结果表明在Bt菌株的分离过程中,对于没有形成晶体但在芽胞形成时期还有内含物的菌株也应加以重视,这些菌株属于B.cereus族,具有潜在利用价值。

In the process of screening Bacillus thuringiensis （Bt）, strains which belonged to Bacillus spp. with spores similar to B. thuringiensis were found. Although the parasporal crystal did not appear after releasing spores, the inclusion in the mother cell could be observed markedly during sporulation, so the characterization of these strains should be clear. In this study, four aspects including species, plasmids, protein spectrum and insecticidal activity of six strains were analyzed. Both spore morphology and plasmids pattern of these Bacillus spp. strains were similar to those of B. thuringiensis. Additionally, Peptide Mass Fingerprinting results indicated that the selected proteins shared high similarity with those from bacteria of the B. cereus group containing Bc and Bt. According to the 16S rDNA phylogenetic tree, the six strains of Bacillus spp. belonged to B. cereus group. Through the statistics of bioassay, the corrected mortality of supernatant from 11-1 strains reached 75.9% for Plutella xylostella. As to Ostrinia furnacalis, the adjusted mortality of soluble constituents from 85-1 and 11-1 strains were 100% and 87.9%, respectively. These results suggested that the strains which could produce inclusion in the mother cell should not be ignored due to lacking parasporal crystal during screening Bt strains. In addition, the product of these strains without parasporal crystal might have high activity against insects too. These strains belonged to B. cereus group, and they were worth further investigation for their potential value.