Biochemistry and mode of action of the Bacillus sphaericus toxins

Davidson, Elizabeth W.

doi:10.1590/s0074-02761995000100018

Cited by 14 publications

(8 citation statements)

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“…The detailed mode of action of Bt and Bs toxins is still unknown. A number of studies (BAUMANN et al 1985, KNOWLES and ELLAR 1987, CHARLES 1987, SINGH and GILL 1988, DAVIDSON 1988, BROADWELL et al 1990, DE BARJAC 1990, OEI et al 1992, DAVIDSON 1995, CHARLES et al 1996and 1997, REGIS et al 2001, MANCEVA et al 2004and SMITH et al 2005 revealed that the action of the crystal toxin on susceptible larvae involved the following series of steps:…”

Section: Mode Of Action Of Bt and Bsmentioning

confidence: 99%

Bacillus thuringiensis andBacillus sphaericus biopesticides production

El-Bendary

2006

J. Basic Microbiol.

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The long residual action and toxicity of the chemical insecticides have brought about serious environmental problems such as the emergence and spread of insecticide resistance in many species of vectors, mammalian toxicity, and accumulation of pesticide residues in the food chain. All these problems have highlighted the need for alternative biological control agents. Entomo-pathogenic Bacillus thuringiensis (Bt) and Bacillus sphaericus (Bs) are two safe biological control agents. They have attracted considerable interest as possible replacements for the chemical insecticides. Although microbial insecticides based on Bt and Bs are available for use, their high cost makes large-scale application impracticable in developing countries. This review focuses on the economic production of these two microorganisms by submerged fermentation and solid state fermentation using agro-industrial by-products and other wastes.

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Section: Mode Of Action Of Bt and Bsmentioning

confidence: 99%

Bacillus thuringiensis andBacillus sphaericus biopesticides production

El-Bendary

2006

J. Basic Microbiol.

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“…Although both are highly toxic to mosquito larvae, there are fundamental differences in their toxin composition, mode of action, and relative risk for selecting insecticide resistance. The toxicity of B. sphaericus is due primarily to a binary toxin (Bin) that binds to a speciÞc receptor on the midgut microvilli of susceptible mosquitoes (Davidson 1995, Charles et al 1996, Darboux et al 2001). In addition to high toxicity, larvicides based on B. sphaericus have residual toxicity against Culex species in polluted water, a signiÞcant advantage.…”

mentioning

confidence: 99%

Synergy between Toxins ofBacillus thuringiensissubsp.israelensisandBacillus sphaericus

et al. 2004

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Synergistic interactions among the multiple endotoxins of Bacillus thuringiensis subsp. israelensis de Barjac play an important role in its high toxicity to mosquito larvae and the absence of insecticide resistance in populations treated with this bacterium. A lack of toxin complexity and synergism are the apparent causes of resistance to Bacillus sphaericus Neide in particular Culex field populations. To identify endotoxin combinations of the two Bacillus species that might improve insecticidal activity and manage mosquito resistance to B. sphaericus, we tested their toxins alone and in combination. Most combinations of B. sphaericus and B. t. subsp. israelensis toxins were synergistic and enhanced toxicity relative to B. sphaericus, particularly against Culex quinquefasciatus Say larvae resistant to B. sphaericus and Aedes aegypti (L.), a species poorly susceptible to B. sphaericus. Toxicity also improved against susceptible Cx. quinquefasciatus. For example, when the CytlAa toxin from B. t. subsp. israelensis was added to Bin and Cry toxins, or when native B. t. subsp. israelensis was combined with B. sphaericus, synergism values as high as 883-fold were observed and combinations were 4-59,000-fold more active than B. sphaericus. These data, and previous studies using cytolytic toxins, validate proposed strategies for improving bacterial larvicides by combining B. sphaericus with B. t. subsp. israelensis or by engineering recombinant bacteria that express endotoxins from both strains. These combinations increase both endotoxin complexity and synergistic interactions and thereby enhance activity and help avoid insecticide resistance.

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“…The pathogenicity of B. sphaericus strains has been attributed mainly to the production of a binary toxin consisting of 51‐ and 42‐kDa proteins (Davidson 1985). All highly insecticidal B. sphaericus strains contain the binary toxin, while the presence of a 100‐kDa protein has been reported in some weakly insecticidal strains (Priest 1992; Davidson 1995). It is generally accepted that the 42‐ and 51‐kDa toxins are produced as parasporal crystalline inclusions (Kalfon et al .…”

Section: Introductionmentioning

confidence: 99%

Production of asporogenous mutants of Bacillus sphaericus 2362 in continuous culture

Idachaba

Rogers

2001

Lett Appl Microbiol

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Aims: To report the production of asporogenous mutants (Spo ) ) of Bacillus sphaericus 2362 in continuous culture. Methods and Results: Microbial culture samples were taken at 0.05 h )1 dilution rate and plated out on nutrient agar plates. Translucent colonies were obtained with vegetative morphology under phase contrast microscope. Heat resistance evaluations at different temperature settings showed that the Spo ) mutants had lower heat resistance than the Spo + wild type. Western blots analyses carried out on both wild type and the mutants indicated the presence of binary protein toxins of 42 and 51 kDa in both. Bioassays carried out on the wild type and the Spo ± mutants against mosquitoes showed the mutants to be 100-fold less toxic in comparison to the wild type. Conclusions: Existence and production of asporogenous mutants of Bacillus sphaericus 2362 in continuous culture at low dilution rates is demonstrated by this study. The organism's ability to produce toxins appears to be signi®cantly reduced by the mutational process. Signi®cance and Impact of the Study: The production of asporogenous mutants had not been reported previously among strains of Bacillus sphaericus. The present report on the toxigenic capability of asporogenous mutants also raises the possibility of using continuous culture to signi®cantly improve the productivity of toxin production in future.

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Biochemistry and mode of action of the Bacillus sphaericus toxins

Cited by 14 publications

References 0 publications

Bacillus thuringiensis andBacillus sphaericus biopesticides production

Bacillus thuringiensis andBacillus sphaericus biopesticides production

Synergy between Toxins ofBacillus thuringiensissubsp.israelensisandBacillus sphaericus

Production of asporogenous mutants of Bacillus sphaericus 2362 in continuous culture

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