ABSTRACT
The infective juveniles [IJs] of five Heterorhabditis bacuriophora strains, entomopathogenic nematodes, demonstrated great variation in their pathogenicity to three full grown larvae of Galleria mellonella, Spodoptera littolaris and Agrotis ipsilon after 48 hr post infection. The infectivity could be arranged in a descending order as follows: EB7 > EG8 >EB6 > EA2 > EG7. The mean mortality% of G. mellonella was increased by increasing the length of exposure time to each nematode strain individually. The activity of acidic proteases was evaluated in the five H. bacteriophora strains and ranged from 27.3 to 112.9 units/10 [5] IJs with specific activity ranged from 13.2-76.3 units/mg protein. Highest insect mortality% was recorded in the strains of proteolytic activity > 55.0 units/10 [5] IJs [EB7 and EG8] except H. bacteriophora EG7. The least proteolytic activity was estimated in the least invasive strain, H. bacteriophora EA2. The relationship between pathogenicity and proteolytic activity is discussed. Acidic proteases zymogram revealed variation among strains with respect to the number and the relative mobility of the bands. Total protein and infectivity were tracked during storage of IJs of H. bacteriophora EB7. The consumption of protein indicated that proteins might be significant energy reserves. Acidic proteases have been purified from II. bacteriophora EB7. Three isoenzymes of acidic proteases, PI, PII, PIII, were resolved by ion exchange chromatography. The isoenzyme PII was further purified by chromatography on Sephacryl S-200 and specific activity increased to 441.7 units/mg protein which represents 22.5 folds purification