The Adaptation Advantage Of The Spore-crystal Association In Bacillus Thuringiensis C15

Bacillus thuringiensis is a kind of Gram-positive bacteria,which could produce parasporal crystals that mainly composed of insecticidal crystal protein during its sporulation phase.Most of the crystal are usually produced near the pole of the mother cell,and separated from spore with the dissociation of mother cell.However,in a few cases,crystals are located inside exoporium and still associated with the spores after sporulation.This special phenotype is named as Spore-Crystal Association(SCA),and the crystals are called associated crystals.Currently,Bt is the largest usage amounts and the widest ranges biological pesticides.But in the process of using,the efficiency of insecticide will decrease because the toxin can be effect by varieties of adverse factors in environment.The crystals are located inside the exosporium in Bt of SCA,which adds a layer of natural biological barrier.Presumably,this phenotype can protect the crystals and improve the efficiency of insecticide for Bt.This study will elaborate the adaptation advange from biological significance,the protection to crystals and the role of Bt interacting with host on the basis of basic attributes to the SC A strain C15.Firstly,the identify of the correlative SCA basic properties of C15:1.The background of genetics:Using the second and third generation genome sequencing to C15,and we get the whole genome after assembling and spliting:The genome of C15 is comprised of a circular chromosome which composed by eight contigs and eight circular plasmids.And through the method of eliminating plasmids in high temperature to determine the plasmids of associated factors lociation on,but when we checked the 135 mutants by microscopy observation and PCR detection.There is no any obvious clues to assay the associated factors.2.The determination of associated crystals' compositions:Through the protein spectrum analysis and the deficiency of cry genes,we find that all the four cry genes(cry2lAa,cry2lAa-42.9%,cry21Ba-63.4%,cry2lBa-80%)in the genome of C15 are expressed and involved in the formation of crystals.2.The determination of spore structural proteins interacting with associated crystal protein:Through the Bacteria two-hybrid experiment,the associated crystal Cry21Aa in C15 has the similar results to Cry26Aa in YBT-020 when both of them interact with spore structural proteins.It illustrates that SC A is the result of associated crystal protein interacting with the spore structural proteins.On the basis of understanding to the properties of C15,it develops the study from the adaptability of the natural environment and the host:1.The biological significance of SCA to Bt:Through the biological activity determination of C15 and its free-crystal mutant strain BMB2050 to Caenorhabditis elegans,it show the higher activity of C15.This indicates that SCA can improve Bt's insecticidal activity.2.The advantage of natural environment adaptability to SCA-the protection to crystals:The crystals are more stable of SCA when exposed the SCA strain YBT-020 and its free-crystal mutant strain BMBJA in stress resistance experiments.It show that SCA has a certain protection to crystals.This provides a reliable guarantee to improve the insecticide of SCA strains.3.The advantage of host adaptability to SCA-cause the tendency of C.elegans:The C.elegans shows a preference to SCA strains through the chemotaxis and feeding frequency experiments of C.elegans.This also provides a reliable evidence for improving the toxicity of SCA strains.This study not only shows the advange of SCA to increase Bt's insecticidal activity in biology,but also discover the advange of the SCA strains to against the host.It also determines the protection of SCA to associated crystals,and explains the advange of developing biological pesticide capsule.