Résumé:
The aim of our study is to isolate, purify and characterize two entomopathogenic bacterial strains of the genus Bacillus from the soil of Adrar in the Algerian Sahara. The molecular characterization of the isolated strains was carried out by DNA isolation, PCR and sequencing of 16S rRNA gene, followed by a phylogenetic analysis. After that, the study of the bacteria toxicity on the fifth larvae stage of Locusta migratoria was conducted by assessing rates of mortality, LT50 and LC50. The phylogenetic analysis showed that the two strains (Strain-B1 and Strain -B2) were identified as Bacillus sp. (HE799656) and Bacillus sp. (HE805963), respectively, with a very high similarity (99%) with the strains Bacillus thuringiensis (NR_043403) and Bacillus weihenstephanensis (NR_024697). Besides, the results of toxicity tests showed that larvae of L. migratoria are influenced by the two isolated bacterial strains. This action is more pronounced with the Bacillus sp. strain-B1 (HE799656) compared to Bacillus sp. strain-B2 (HE805963). Examination of TL50 shows that these times vary depending on the bacteria and concentrations applied. Similarly, the LC50 are closely related with time and they also vary depending on the bacterial strain tested.
