| Bacillus thuringiensis and B. cereus are ubiquitous spore-forming bacteria, andbelong to B. cereus group because of their high level of phenotypic and geneticsimilarities. Due to the synergistic activity of Cry4A, Cry4B, Cry11A and Cyt1Aproduced during sporulation, B. thuringiensis subsp, israelensis (Bti) has high toxicitytowards mosquitos. P19 and P20 are two chaperones, which have been proved to playa key role in crystal assembling and stability.Using a pair of universal primers, 16S rRNA genes of 54 different strains of B.thuringiensis and B. cereus were amplified and sequenced. Sequences analysis revealsthat these 54 strains have as high as a 99% similarity in 16S rRNA gene level. Allthese 54 strains could be classified into six subgroups according to six differentregions on full-length 16S rRNA gene. Even if the regional differences are not evidentto distinguish B. thuringiensis from B. cereus, however the data of the 16S rRNA genesequences will serve to broaden the database for Bacillus, and provide someinformation for the classification of genus of Bacillus.Additionally, seven B. thuringiensis recombinants were constructed forstudying the interaction of chaperones with Cry11A and Cyt1A. The results indicatethat the expression of Cyt1A alone could result in the cytolysis of host bacterial cells,and both P20 and Cry11A could prevent bacterial cells from cytolysing caused byCyt1A protein. It was noticed that Cry11A could express in recombinant strain as crystals without any chaperones and the expression of P19 could enhance theproduction of Cry11A. However, no evident synergistic mosquiocidal acitivity of P19or P20 with Cyt1A and Cry11A has been observed. Besides, the interaction of Cyt1Aand Cry11A has preliminarily investigated in an alkaline condition. The resultsindicate that Cyt1A could be digested into 22 kD peptide. But the activated Cry11Acould bind with dissolved Cyt1A to protect disulfide bonds from digestion. So it isinferred that oligomeric Cyt1A could help Cry11A insert into the cell membrane toexhibit its pathogensis to mosquito larvaes. The data might provide furtherinformaiton for study the role of P19 and P20 proteins in the expression of crystaltoxins and their toxicity against target mosquitos. |
