The Mutating Effect of Microwave Irradiation on Spores and Crystal Protein Formation of Iraqi Bacillus thuringiensis kurstaki KS3

Alkhafaji, K.A., F.H. Nahar, S.A. Khlaywi, M.A. Abedallah, A.J. Feaath, A.A. Mezban. and S.A. Saleh. 2023. The Mutating Effect of Microwave Irradiation on Spores and Crystal Protein Formation of Iraqi Bacillus thuringiensis kurstaki KS3. Arab Journal of Plant Protection, 41(3): 285-291. https://doi.org/10.22268/AJPP-041.3.285291 Bacillus thuringiensis is the most important biological control agent that is used in fields and stores against insect pests of agricultural importance. This research was conducted to study the effect of microwave radiation on sporogenesis and crystal protein production by the Iraqi bacterium B. thuringiensis KS3 strain. The bacterium was enriched by Lauria bertani broth (LB) pH 7.0 for spore formation. Spore suspension was microwave irradiated at 1000 Watt for 5, 10 and 15 seconds. Spore inactivation rate for each time period of microwave treatment was calculated and the macroscopic differences were examined. Crystal protein and spore production were estimated for irradiated and nonirradiated bacterial cultures. Viable spores in the control treatment was 3×108 viable spores/ml, and decreased after 5, 10, and 15 s of microwave treatment to 3×107 , 2×106 and 2×104 viable spores/ml, respectively. The reduction of spore viability reached to 49.263% 15 seconds after treatment. The appearance of colonies on the top of nutrient agar (NA) were almost similar with the control, with no differences in color, margin and surface of treated colonies following the three time periods treatment. Colonies with dense color, smaller in size and with straight margin appeared on congo red culture for all treatments in contrast to the control. Microscopic examination showed that treated bacilli were similar regarding their shape, diameter and arrangement, however,smaller bacterial cell size following 15 s irradiation treatment was observed. Control culture after 72 h started to form spores, whereas after 24 h, irradiated spores for 5, 10 and 15 s formed 75, 90 and 90% viable spores, respectively. Crystal protein reached the highest concentration after 72 h in control culture, whereas it varied based on treatment period. The production of viable spores from microwave irradiated isolates increased about one logarithmic cycle compared with the control culture of B. thuringiensis KS3.The peak of the UV spectrum of Crystal protein extracts was recognized at 255-280 nm and the peak of the curve indicated the protein concentration at a given wavelength. Differences were recognized in the UV light wavelength range of 220-235 nm. Keywords: Sporogenesis, Physical effect, Delta toxin.