Screening and identification of a Bacillus thuringiensis strain S1/4 with large and efficient insecticidal activities.
The bacterium Bacillus thuringiensis was recognized for its entomopathogenic activities related to Cry and Cyt proteins forming the δ-endotoxins and some extracellular activities like the vegetative insecticidal proteins (VIP) and Cry1I. These activities may act specifically against diverse organisms and some of them typically characterize each strain. Here, we screened a set of 212 B. thuringiensis strains to search the higher insecticidal activities. These strains had bipyramidal and cubic crystal morphologies and 30% of them showed PCR amplification of vip3 internal region, from which five isolates (S1/4, S17, S122, S123, and S144) showed plasmid profile variability. These five strains contained the cry1I, cry1Aa and/or cry1Ac, cry1Ab and cry2 genes, and S1/4 harbored in addition the cry1C, vip1, and vip2 genes. They produced from 25 to 46 µg δ-endotoxin per 10(7) spores. Their δ-endotoxins displayed distinct lethal concentrations 50% against either Spodoptera littoralis or Ephestia kuehniella larvae with the lowest one for S1/4, which was also active against Tuta absoluta. Fortunately, the analysis of the culture supernatants revealed that S1/4 had the higher toxicity towards these lepidopteron but it did not show any toxicity against the Tribolium castaneum coleopteran larvae; additionally, S1/4 displayed an antibacterial activity. S1/4 is a good candidate for agricultural pest control, as it is more efficient than the reference strain HD1.
Biopesticides Team (LPAP), Centre of Biotechnology of Sfax, University of Sfax, Sfax, Tunisia.
Sameh
S
Sellami
Taheni
T
Zghal
Maroua
M
Cherif
Imen
I
Zalila-Kolsi
Samir
S
Jaoua
Kaïs
K
Jamoussi
D000818:Animals; D001413:Bacillus thuringiensis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001517:Coleoptera / Q000187:drug effects; D004731:Endotoxins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D007306:Insecticides; D007814:Larva / Q000187:drug effects; D007915:Lepidoptera / Q000187:drug effects; D010572:Pest Control, Biological / Q000379:methods; D010957:Plasmids / Q000235:genetics; D018411:Spodoptera / Q000187:drug effects
D001426:Bacterial Proteins; D004731:Endotoxins; D007306:Insecticides