Screening and identification of a Bacillus thuringiensis strain S1/4 with large and efficient insecticidal activities

Abstract

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.

Pathogenicity of indigenous soil isolate of Bacillus thuringiensis to Helicoverpa armigera Hübner 1809 (Lepidoptera: Noctuidae)

“…2). Obtained results are in agreement with those of Huang et al (2005) and Sellami et al (2013) who revealed a significant loss of body weight in the third-instar larvae of Ostrinia nubilalis, Spodoptera littoralis, and Ephestia kuehniella after 3 to 4 days post exposure to Bt Cry1Ac andVip3 toxins.…”

Molecular characterisation of Bacillus thuringiensis strain MEB4 highly toxic to the Mediterranean flour moth Ephestia kuehniella Zeller (Lepidoptera: Pyralidae)

“…Interestingly, the MEB4 strain was noted to induce the highest mortality rates against this lepidopteran larval insect, exhibiting an LC 50 value of 103,08 ± 36 µg g −1 , particularly when compared to the reference BNS3 strain (LC 50 of 120,432 ± 40,666 µg g −1 ). The detected insecticidal activity of the three strains (BLB140, BLB240 and MEB4) towards E. kuehniella could presumably be attributed to the mixture of Cry1 and Cry2 proteins as previously reported by Saadaoui et al and Sellami et al Furthermore, the differences observed in the insecticidal activities of the BLB140 and the MEB4 and BLB240 strains could be ascribed to the fact that Cry2 proteins were present only in the two latter strains, along with Cry1 toxins, and/or to a higher activity of their Cry1 proteins.…”

Investigation of lead(II) uptake by Bacillus thuringiensis 016

“…It is considered as the most widely used microbial biopesticide (Sellami et al 2013) with insecticidal crystal proteins (ICPs), which are highly specific to target insect and innocuous to humans, plant and animals (Bravo et al 2007;Soberon et al 2009). Moreover, many Bt stains also have been reported to possess the potential of removal organic pollutants and heavy metal from water and soil environments (Brar et al 2009;Dave and Dave 2009;Kebria et al 2009;Muneer et al 2009;Zhuang et al 2011;Huang et al 2014).…”