Biological control of Culex pipiens mosquito by local bacterial isolates

Abstract

In this work, 62 bacterial and actinobacterial isolates were isolated from different soil samples and screened for their larvicidal activities against the 3 rd instar Culex pipiens larvae. Two potent isolates that showed high mortality rate were identified by16S rRNA gene sequencing as Bacillus subtilis (MH370499) and Streptomyces griseoruber (MH370498). Optimizing the environmental and nutritional conditions increased the mortality percentage of B. subtilis from 82.9% to 100% and S. griseoruber from 69% to be 100% LC 50 and LC 90 of B. subtilis were 13.68% and 28.29%, while for S. griseoruber were 5.79% and 18.53% respectively. The best solvent for active substance from B. subtilis extraction was ethyl acetate, while for S. griseoruber was hexane. The GC-MS analysis of S. griseoruber detected the presence of antilarval compounds ambrosin and triacontane. In addition, the larvicidal surfactin produced by B. subtilis was detected by haemolysis.

Larvicidal potential, toxicological assessment, and molecular docking studies of four Egyptian bacterial strains against Culex pipiens L. (Diptera: Culicidae)

“…During bacterial sporulation, B. thuringiensis creates a crystal protein (-endotoxin) capable of inducing gut cell lysis when ingested by susceptible insects 33 . Additionally, the extensive paralysis on the midgut epithelium layer might be the major reason for the mortal of C. pipiens , in addition to midgut deterioration, dropping the function of midgut and feeding refraining with various microorganisms 34 , Bacillus subtilis (MH370499) and Streptomyces griseoruber (MH370498) 12 . This deterioration is due to microbial peptides and carbohydrates that increase the pH level (Alkaly) in the insect gut, leading the insects to lose the ability to grow and reproduction 35 .…”

“…using staining protocols, the sectioned larvae and control samples were stained with eosin and hematoxylin, respectively. Using a microscope (Labomed), the mid-guts of control and treated larvae were examined and captured 12 .…”

Larvicidal potential and molecular docking analysis of metabolites from new Egyptian bacterial strains as effective biological control agents against Culex pipiens (L: Diptera)

“…During bacterial sporulation, B. thuringiensis creates a crystal protein (-endotoxin) capable of inducing gut cell lysis when ingested by susceptible insects 33 . Additionally, the extensive paralysis on the midgut epithelium layer might be the major reason for the mortal of C. pipiens, in addition to midgut deterioration, dropping the function of midgut and feeding refraining with various microorganisms 34 , Bacillus subtilis (MH370499) and Streptomyces griseoruber (MH370498) 12 . This deterioration is due to microbial peptides and carbohydrates that increase the pH level (Alkaly) in the insect gut, leading the insects to lose the ability to grow and reproduction 35 .…”