ISSN: 0973-7510

E-ISSN: 2581-690X

Research Article | Open Access
Abdallah Rafeek1, Abd El-Latif Hesham2 , Aly A. Abd-Ella3, Ghada Abd-Elmonsef Mahmoud4 and A.E. Elfarash1
1Department of Genetics, Faculty of Agriculture, Assiut University, 71526 Assiut, Egypt.
2Department of Genetics, Faculty of Agriculture, Beni-Suef University, Beni-Suef 62511, Egypt.
3Plant Protection Department, Faculty of Agriculture, Assiut University, 71526 Assiut, Egypt.
4Botany and Microbiology Department, Faculty of Science, Assiut University, P.O. 71516, Assiut, Egypt.
Article Number: 8039 | © The Author(s). 2023
J Pure Appl Microbiol. 2023;17(1):143-154.
Received: 18 August 2022 | Accepted: 12 December 2022 | Published online: 16 January 2023
Issue online: March 2023

This study aims to evaluate the toxicity and genetic improvement of Bacillus thuringiensis isolates. Isolates were obtained from soil, insect and water samples from different regions of Assiut, Egypt for biological control of mosquito larvae. B. thuringiensis colonies were identified based on morphological and then by PCR which detect the Cry toxic genes in the isolates. Bioassays were performed to evaluate the toxicity of different strains of B. thuringiensis against mosquito larvae such as (Culex spp). In general, 36 B. thuringiensis isolates were obtained (31 from soil, 4 from insects, and 1 from water). And they were all toxic to mosquito larvae with different mortality percentages from 7 to 97% after 48 hours. Isolate Am2 recorded the highest mortality percentage 97% and Mn3 lowest mortality percentage 7%. PCR revealed that Am2 isolate which caused the highest mortality encodes three different types of Cry toxins, Cyt1AA, Cry1Ac and Cry2Aa. This isolate Am2 was examined by scanning electron microscopy to observe the shape of the Cry proteins. The results showed that the Am2 isolate contained of spherical and cuboidal toxic proteins. Then UV-mutagenesis was performed on the Am2 isolate to improve its toxicity. Out of 30 obtained UV-mutants, only one mutant showed improvement in the mortality of mosquito larvae since it caused a mortality rate of 100%. The results of the present study revealed the larvicidal efficacy of B. thuringiensis (Am2) isolate found in the soil of Assiut, could be used in biological control program of mosquito larvae.


B. thuringiensis, Cry Genes, Cyt Genes, UV- mutagenesis, Scanning Electron Microscope

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© The Author(s) 2023. Open Access. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License which permits unrestricted use, sharing, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.