Isolation and distribution of mosquito-larvicidal cry genes in Bacillus thuringiensis strains native to Saudi Arabia
- Author:
El-kersh, T.A.
;
Al-akeel, R.A.
;
Al-sheikh, Y.A.
;
Alharbi, S.A.
- Publication Type:Journal Article
- From:Tropical Biomedicine
2014;31(4):616-632
- CountryMalaysia
- Language:English
-
Abstract:
A total of 157 environmental samples were collected from 11 ecological regions
across Saudi Arabia to isolate native Bacillus thuringiensis (Bt) strains. Bt isolates (n=103)
were recovered by the 50% (v/v) ethanol treatment method with Bt index range of 0.01 to 0.4.
Most of Bt isolates showed spherical crystals (54%), while, irregular, bi-pyramidal, and sporeattached
crystal constituted 27, 16 and 3% respectively. PCR analysis with eight general and
specific dipteran primers of Cry and Cyt genes, revealed positive amplification for cry4 &
cyt1, and cry4A, cry4B and cyt2, and cry 10 and cry 11 genes in 28%, 26%, 22%, and 25% of
tested strains respectively; whereas cry2 gene was not detected except with the reference
Bt kurstaki HD-1 strain. Bioassays against Aedes caspuis and Culex pipiens larvae indicated
that 11 strains displayed better larvicidal activity compared with Bacillus thuringiensis H14
(Bti) reference (LC50 0.6 μg/ml) strain against Ae. caspuis, but only two strains (620A &
633R1, LC50 of 0.09 μg/ml & 0.064 μg/ml) that gave significant enhancement. Additionally,
one strain (633R1) showed LC50 similar to that of Bti H14 (LC50 0.064 μg/ml) against Cx.
pipiens. With the exception of cyt primers, sequenced DNA of all positive primers amplicons
revealed 95 to 99% identity in GenBank with Bacillus thuringiensis subsp. israelensis plasmid
pBtoxis and also correlated with its SDS-PAGE expressed protein profiles analysis. It is hoped
that our wild bio-insecticide Bt strains can be explored in future in the control of mosquitovector
borne diseases in Saudi Arabia.
- Full text:W020150528451331709037.pdf
