Magda A El-Bendary, Hala M Rifaat and Abeer A Keera
Keywords: Culex pipiens, larvicidal, secondary metabolites, Streptomyces.
Abstract: Eight isolates of actinomycetes were isolated from sand samples of underground spring at Giza Governorate, Egypt. The extracellular secondary metabolites of one isolate (Act-1) showed larvicidal activity against Culex pipiens. The morphological, physiological and chemotaxonomical characteristics of this isolate revealed that it belongs to Streptomyces sp. However, according to the 16S rDNA sequencing analysis, it was identified as Streptomyces microflavus. Twenty five ml of peptone-beef extract-yeast extract-glucose medium under static condition showed the best conditions for the production of secondary metabolites from Act-1 against mosquito larva. Addition of NaCl, FeSO4 and CaCO3 to the medium increased the produced mosquitocidal metabolites twelve times more than the original. The LC50 value of Streptomyces microflavus metabolites was 77.3 ppm with 95% fiducial limits (62.6-95.7).
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