Study On Bacillus Thuringiensis Spores And Parasporal Crystals Resisting Extreme Environment With The Assistance Of Ectoine

The parasporal crystal formed by Bacillus thuringiensis during growth has specific killing function against agricultural pests,we use B.thuringiensis to prepare microbial pesticides in agriculture.However reverse environment can lead to decrease germination rate of B.thuringiensis spores,ultraviolet rays cause parasporal crystals to fail.At present,the improvement of parasporal crystals activity under ultraviolet radiation has been reported,However,there is no report on the increase in germination rate of B.thuringiensis spores.Studies on the increase of B.thuringiensis spore germination rate have not been clearly reported.Therefore,it is necessary to find a substance which can resist the ultraviolet radiation of the parasporal crystal and increase the spore survival rate of the spore in the reverse environment.In this paper,the osmotic pressure-compensated solute Ectoine was used to protect the B.thuringiensis A54 spore and the parasporal crystals against the environment,In order to solve the problem that B.thuringiensis insecticide preparation is susceptible to adverse environmental effects and has a short duration of action.In this paper,the optimal fermentation conditions of strain B.thuringiensis A54 were optimized by response surface methodology,growth amount increased by 42.0%compared with before optimization.The strain B.thuringiensis A54 was identified by PCR to contain two genotypes,CrylAa and Cry2Ab.It was speculated that it had a killing effect on lepidopteran pests.RT-PCR experiments showed that the amount of synthesis of parasporal crystals began to increase after cell growth stopped.The germination rate of spores in a suitable environment was 95.1%by viable count method.As the UV radiation time increases,the water loss rate increases,and the temperature decreases,the spore germination rate gradually decreases.When the Ultraviolet radiation was 10 s,Spore germination rate increased by 2.5 times when 1200 mg/L Ectoine was added to the system;When the water loss rate was 40%,the germination rate of spores increased by 14.7%under 100 mg/L Ectoine;At a low temperature of 20℃,the germination rate of increased by 26.6%under 50 mg/L Ectoine.The results showed that Ectoine could increase the germination rate of spores in the extreme environment.Ultraviolet radiation is the most important cause of inactivation of parasporal crystals.This paper examined the protection of Ectoine to the parasporal crystals under UV radiation.After 20 min of UV irradiation,the spore crystals were not detected by alkali solubilization.When the concentration of Ectoine in the system was increased from 0 to 400 mg/L.,The protein content increased from 0 to 0.76 g/L The results showed that Ectoine has anti-retroviral protection against parasporal crystals.