title: Isolation and distribution of mosquito-larvicidal cry genes in Bacillus thuringiensis strains native to Saudi Arabia.
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 spore-attached 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 mosquito-vector borne diseases in Saudi Arabia.
authors.affiliation: Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Saud University, Riyadh 11433, P.O. Box 10219.
authors.forename: T A
authors.initials: TA
authors.lastname: El-kersh
authors.affiliation: Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Saud University, Riyadh 11433, P.O. Box 10219.
authors.forename: R A
authors.initials: RA
authors.lastname: Al-akeel
authors.affiliation: Department of Clinical Laboratory Sciences, College of Applied Medical Sciences, King Saud University, Riyadh 11433, P.O. Box 10219.
authors.forename: Y A
authors.initials: YA
authors.lastname: Al-sheikh
authors.affiliation: Yanbu General Hospital, Yanbu City, Ministry of Health, Saudi Arabia.
authors.forename: S A
authors.initials: SA
authors.lastname: Alharbi
mesh_terms: D000330:Aedes / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics / Q000302:isolation & purification*; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000494:pharmacology*; D001681:Biological Assay; D003465:Culex / Q000187:drug effects* / Q000502:physiology; D004269:DNA, Bacterial / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D004731:Endotoxins / Q000235:genetics* / Q000302:isolation & purification / Q000494:pharmacology*; D004783:Environmental Microbiology; D005798:Genes, Bacterial; D006460:Hemolysin Proteins / Q000235:genetics* / Q000302:isolation & purification / Q000494:pharmacology*; D007306:Insecticides / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D012529:Saudi Arabia; D017422:Sequence Analysis, DNA; D016019:Survival Analysis
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004731:Endotoxins; D006460:Hemolysin Proteins; D007306:Insecticides; C030956:insecticidal crystal protein, Bacillus Thuringiensis