Variations in the mosquito larvicidal activities of toxins from <i>Bacillus thuringiensis</i> ssp. <i>israelensis</i>

Otieno-Ayayo, Z. Ngalo; Zaritsky, Arieh; Wirth, Margaret C.; Manasherob, Robert; Khasdan, Vadim; Cahan, Rivka; Ben‐Dov, Eitan

doi:10.1111/j.1462-2920.2008.01696.x

Cited by 37 publications

(40 citation statements)

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“…No data are given on the mosquitocidal activity of HS18-1 although weak activity against Aedes aegypti was found for the recombinant Cry4Cb1 and Cry30Ga toxins. Although we have yet to fully characterize all the toxins present in the Bt S2160-1 strain, or to establish whether there may be synergistic interactions between them as observed for Bti (Chilcott and Ellar, 1988;Otieno-Ayayo et al, 2008), we suggest that this strain has potential as an alternative to Bti for mosquito control. Fig.…”

Section: Discussionmentioning

confidence: 89%

Characterization of a new highly mosquitocidal isolate of Bacillus thuringiensis – An alternative to Bti?

Zhang

Crickmore

George

et al. 2012

Journal of Invertebrate Pathology

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Section: Discussionmentioning

confidence: 89%

Characterization of a new highly mosquitocidal isolate of Bacillus thuringiensis – An alternative to Bti?

Zhang

Crickmore

George

et al. 2012

Journal of Invertebrate Pathology

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“…Therefore, they synergize with and overcome resistance to mosquito larvicidal Cry proteins by functioning as a Cry membrane bound receptor. At high concentrations, due to their high affinity to lipids, these toxins can act as detergents by rupturing the cell membrane [6, 7, 14]. Additionally, the chitinase chi gene has been associated with enhanced mosquitocidal activity of Bt strains suggesting further synergism with the cyt and cry genes [7].…”

Section: Introductionmentioning

confidence: 99%

Isolation and characterization of native Bacillus thuringiensis strains from Saudi Arabia with enhanced larvicidal toxicity against the mosquito vector Anopheles gambiae (s.l.)

et al. 2016

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BackgroundWorldwide, mosquito vectors are transmitting several etiological agents of important human diseases, including malaria, causing millions of deaths every year. In Saudi Arabia, as elsewhere, vector-control is based mostly on chemical insecticides which may be toxic and cause environmental deprivation. Here, to support the development of bio-pesticide alternatives, a study was conducted to identify native Bacillus thuringiensis (Bt) isolates with improved toxicity against the malaria vector, Anopheles gambiae (s.l.).MethodsSixty-eight Bt isolates were obtained from 300 soil and other samples collected from 16 sites across Saudi Arabia. Bt identification was based on morphological characteristics of colonies, shape of parasporal crystals and biochemical profiles. After characterization of their mosquitocidal activity, larvicidal strains were described through 16S ribosomal DNA gene sequencing, cry, cyt and chi genes PCR-amplification profiles, and SDS-PAGE protein analyses.ResultsSpherical Bt crystals were predominant amongst the 68 isolates (34%), while irregular, bi-pyramidal and spore-attached crystals were found in 32, 13 and 21% of strains, respectively. LC50 and LC90 bioassays showed that 23/68 isolates were larvicidal, with distinct biochemical activity profiles compared to non-larvicidal Bt strains. Eight larvicidal strains showed larvicidal activity up to 3.4-fold higher (LC50 range: 3.90–7.40 μg/ml) than the reference Bti-H14 strain (LC50 = 13.33 μg/ml). Of these, 6 strains had cry and cyt gene profiles similar to Bti-H14 (cry4Aa, cry4Ba, cry10, cry11, cyt1Aa, cyt1Ab, cyt2Aa). The seventh strain (Bt63) displaying the highest larvicidal activity (LC50 = 3.90 μg/ml) missed the cry4Aa and cyt1Ab genes and had SDS-PAGE protein profiles and spore/crystal sizes distinct from Bti-H14. The eight strain (Bt55) with LC50 of 4.11μg/ml had cry and cyt gene profiles similar to Bti-H14 but gave a chi gene PCR product size of 2027bp. No strains harbouring cry2, cry17 + 27, cry24 + 40, cry25, cry29, cry30, or cyt2Ba were detected.ConclusionThis study represents the first report of several Saudi indigenous Bt strains with significantly higher larvicidal efficacy against An. gambiae than the reference Bti-H14 strain. The very high toxicity of the Bt63 strain, combined with distinct cry and cyt genes and SDS-PAGE-protein profiles makes it a promising candidate for future applications in mosquito bio-control.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1922-6) contains supplementary material, which is available to authorized users.

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“…strain PCC 7120) that express one or a combination of genes for mosquito larvicidal proteins from Bacillus thuringiensis subsp. israelensis (26). …”

Section: Discussionmentioning

confidence: 99%

“…strain PCC 7120 and demonstrated that Int catalyzes site-specific excision whether its substrate is located on a plasmid or on the chromosome. This system can thus be used as a novel model for simple and efficient genome manipulations in cyanobacteria, in particular, the removal of genes conferring antibiotic resistance, which are unacceptable for applied purposes in transgenic organisms (26).…”

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Site-Specific Recombination in the Cyanobacterium Anabaena sp. Strain PCC 7120 Catalyzed by the Integrase of Coliphage HK022

et al. 2009

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The integrase (Int) of the -like coliphage HK022 catalyzes the site-specific integration and excision of the phage DNA into and from the chromosome of its host, Escherichia coli. Int recognizes two different pairs of recombining sites attP ؋ attB and attL ؋ attR for integration and excision, respectively. This system was adapted to the cyanobacterium Anabaena sp. strain PCC 7120 as a potential tool for site-specific gene manipulations in the cyanobacterium. Two plasmids were consecutively cointroduced by conjugation into Anabaena cells, one plasmid that expresses HK022 Int recombinase and the other plasmid that carries the excision substrate P glnA -attL-T1/T2-attR-lacZ, where T1/T2 are the strong transcription terminators of rrnB, to prevent expression of the lacZ reporter under the constitutive promoter P glnA . The Int-catalyzed site-specific recombination reaction was monitored by the expression of lacZ emanating as a result of T1/T2 excision. Int catalyzed the site-specific excision reaction in Anabaena cells when its substrate was located either on the plasmid or on the chromosome with no need to supply an accessory protein, such as integration host factor and excisionase (Xis), which are indispensable for this reaction in its host, E. coli.The site-specific recombination mechanism of the temperate coliphage HK022 is similar, if not identical, to that of phage . To lysogenize its Escherichia coli host, circular phage DNA recombines via a site-specific recombination reaction between the nonidentical attP and attB sites of the phage and host genomes, respectively. This reaction results in the integrated prophage that is flanked by the recombinant attL and attR sites, which are the sites for phage excision. The phage-encoded site-specific integrase (Int), which belongs to the Tyr recombinase family, catalyzes phage integration and excision. Both reactions require the presence of the host-encoded DNA-bending heterodimeric accessory protein integration host factor (IHF); excision requires in addition the phage-encoded excisionase (Xis), whose activity can be partially replaced by the host-encoded FIS (factor for inversion stimulation). The bacterial attB consists of a 21-base-pair (bp) core sequence (BOBЈ) that is composed of 7 central bp, defined as the overlap O, which is identical in all four att sites and serves as the site of DNA exchange. O is flanked by two 7-bp inverted repeats (B and BЈ) that serve as weak binding sites for Int. The phage attP site is composed of a similar core (COCЈ) that is flanked by two long arms (P and PЈ of 142 and 85 bp, respectively) carrying tight binding sites for Int and for the accessory proteins (IHF, Xis, and FIS). The accessory proteins, bound to their sites on the arms of attP, regulate and facilitate arm-bound Int monomers access to the core, the site of the reaction. Subsequently, this proteo-DNA complex (the intasome) captures attB to execute the recombination. Each of the recombinant sites attL (BOPЈ) and attR (POBЈ) that flank the integrated prophage is composed of...

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Variations in the mosquito larvicidal activities of toxins from Bacillus thuringiensis ssp. israelensis

Cited by 37 publications

References 80 publications

Characterization of a new highly mosquitocidal isolate of Bacillus thuringiensis – An alternative to Bti?

Characterization of a new highly mosquitocidal isolate of Bacillus thuringiensis – An alternative to Bti?

Isolation and characterization of native Bacillus thuringiensis strains from Saudi Arabia with enhanced larvicidal toxicity against the mosquito vector Anopheles gambiae (s.l.)

Site-Specific Recombination in the Cyanobacterium Anabaena sp. Strain PCC 7120 Catalyzed by the Integrase of Coliphage HK022

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