Microbiological study and insecticidal potential of purified extract from Streptomyces sp. on the larvae of Galleria mellonella

In the present study, one Streptomyces species was isolated from a soil sample that was collected in Khafr El Shikh Governorate. Actinomycetes are prolific producers of antibiotics and important suppliers to the pharmaceutical industry. They can produce a wide range of secondary metabolites. The isolate was purified and characterized by morphological, physiological, biochemical methods and using Scanning electron microscope (SEM). The isolate was found to be Streptomyces catenula like microorganism and was therefore called Streptomyces catenula MY 12. The Streptomyces metabolite was extracted using ethyl acetate solvent. The purified extract was used to study the effect against 3rd instar larvae of the greater wax moth, Galleria mellonella. The study showed deleterious effects on growth and development of G. mellonella larvae. The results demonstrated that the mortality increased with increase in concentration. The extract prolonged the larval-pupal periods and reduced both pupation and percentage of adult emergence. The LC50 and LC90 values were calculated. The consumed food by unirradiated and irradiated 3rd instar larvae of G. mellonella in each concentration was studied. The larvae consumed much media in control treatment and fewer amounts in the higher concentration of the extract. The SEM revealed that different malformation or abnormalities were observed in larval cuticle and associated sensilla in the form of tear and ridged tergum cuticle. Also, broken and fallen or scarcity of trichodea sensilla. Undistinguished segments tear sternum and destroy plural membrane. The spiracles were completely closed, and prolegs crochets disappeared.

Automated summary

In this study, a Streptomyces species was isolated from a soil sample in Khafr El Shikh Governorate, and its effects on third instar larvae of Galleria mellonella were studied. The extract showed deleterious effects on the growth and development of the larvae, leading to morphological abnormalities.