Characteristics Of Bacillus Thuringiensis Spore Germinatiom And Influencing Of Physicochemical Factors On Spore Germination

Spores usually form in vegetative cells of some bacilli and cocci,allowing them to tolerate extreme environmental conditions,such as heat,radiation,dryness,and toxic chemicals,mainly by their special structure and high content of Ca2+ and dipicolinic acid(DPA)in nucleus.Spore will germinate into vegetative cell in appropriate conditions.So it is important to study characteristics and physical or chemical factors in spore germination.That will be of great significance in restraining or preventing bacilli from medical or food sources.Bacillus thuringiensis is a biological pesticide widely used,and it has a close genetic relationship with some pathogenic bacteria.So the study of Bt's germination mechanism and influencing factors,will be help to understand how reagents kill spores to improve the effectiveness of biological pesticides.In this paper,a dynamic monitoring and analysis was carried out on the germination of Bt spores treated by ultraviolet radiation(UV),NaOH or HCl,through a method combined differential interference contrast(DIC)microscopy with Raman spectroscopy.The results showed:(1)Although Bt spores have strong resistance,UV still induced some changes in their protein secondary structure.UV has most significant effect on germinant receptor related proteins,followed on the proteins of DPA release channel,but has little effect on cortical hydrolase.(2)NaOH did not destroy the inner membrane of Bt spores,and not significantly changed protein secondary structure,but damaged some important proteins of spore gennination.Alkali were especially harm to cortex-lytic enzymes,next to DPA release channels and related proteins.After treated with 1.0 mol/L NaOH for 30 to 60 min,more than 75%of Bt spores could not form new colonies,but more than 50%of the spores could germinate again under the trigger of alanine.However,exogenous CaDPA could not trigger germination after alkali treatment.(3)The HCl concentration had greater effect on the spore than that of the treatment time.HCl could inactivate and damage the proteins associated with germination as following order:germination agent receptor protein,CaDPA release protein,and cortex hydrolysis proteins.At the same time,HCl also changed the spore permeability to release some of CaDPA.