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Zhiming Yuan - One of the best experts on this subject based on the ideXlab platform.
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the lspc3 41i restriction modification system is the major determinant for genetic manipulations of lysinibacillus Sphaericus c3 41
BMC Microbiology, 2017Co-Authors: Ni Zhao, Zhiming YuanAbstract:Abstract Background Lysinibacillus Sphaericus has been widely used in integrated mosquito control program and it is one of the minority bacterial species unable to metabolize carbohydrates. In consideration of the high genetic conservation at genomic level and difficulty of genetic horizontal transfer, it is hypothesized that effective restriction-modification (R-M) systems existed in mosquitocidal L. Sphaericus . Results In this study, six type II R-M systems including LspC3–41I were predicted in L. Sphaericus C3–41 genome. It was found that the cell free extracts (CFE) from this strain shown similar restriction and methylation activity on exogenous Bacillus / Escherichia coli shuttle vector pBU4 as the H aeIII, which is an isoschizomer of BspRI. The Bsph_0498 (encoding the predicted LspC3–41IR) knockout mutant Δ0498 and the complement strain RC0498 were constructed. It was found that the unmethylated pBU4 can be digested by the CFE of C3–41 and RC0498, but not by that of Δ0498. Furthermore, the exogenous plasmid pBU4 can be transformed at very high efficacy into Δ0498, low efficacy into RC0498, but no transformation into C3–41, indicating that LspC3–41I might be a major determinant for the genetic restriction barrier of strain C3–41 . Besides, lspC3–41IR and lspC3–41IM genes are detected in other two strains besides C3–41 of the tested 16 L. Sphaericus strains, which all belonging to serotype H5 and MLST sequence type (ST) 1. Furthermore, the three strains are not horizontal transferred, and this restriction could be overcome by in vitro methylation either by the host CFE or by commercial methytransferase M. Hae III. The results provide an insight to further study the genetic restriction, modification and evolution of mosquitocidal L. Sphaericus, also a theoretical basis and a method for the genetic manipulations of L. Sphaericus. Conclusions LspC3–41I is identified as the major determinant for the restriction barrier of L. Sphaericus C3–41 . Only three strains of the tested 16 L. Sphaericus strains, which all belonging to serotype H5 and ST1 by MLST scheme, contain LspC3–41I system. Two different methods can be used to overcome the restriction barrier of the three isolates to get transformants efficiently: 1) to methylate plasmid DNA prior to the electroporation; and 2) to delete the major restriction endonuclease encoding gene lspC3–41IR .
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The LspC3–41I restriction-modification system is the major determinant for genetic manipulations of Lysinibacillus Sphaericus C3–41
BMC, 2017Co-Authors: Ni Zhao, Zhiming YuanAbstract:Abstract Background Lysinibacillus Sphaericus has been widely used in integrated mosquito control program and it is one of the minority bacterial species unable to metabolize carbohydrates. In consideration of the high genetic conservation at genomic level and difficulty of genetic horizontal transfer, it is hypothesized that effective restriction-modification (R-M) systems existed in mosquitocidal L. Sphaericus. Results In this study, six type II R-M systems including LspC3–41I were predicted in L. Sphaericus C3–41 genome. It was found that the cell free extracts (CFE) from this strain shown similar restriction and methylation activity on exogenous Bacillus/Escherichia coli shuttle vector pBU4 as the HaeIII, which is an isoschizomer of BspRI. The Bsph_0498 (encoding the predicted LspC3–41IR) knockout mutant Δ0498 and the complement strain RC0498 were constructed. It was found that the unmethylated pBU4 can be digested by the CFE of C3–41 and RC0498, but not by that of Δ0498. Furthermore, the exogenous plasmid pBU4 can be transformed at very high efficacy into Δ0498, low efficacy into RC0498, but no transformation into C3–41, indicating that LspC3–41I might be a major determinant for the genetic restriction barrier of strain C3–41. Besides, lspC3–41IR and lspC3–41IM genes are detected in other two strains besides C3–41 of the tested 16 L. Sphaericus strains, which all belonging to serotype H5 and MLST sequence type (ST) 1. Furthermore, the three strains are not horizontal transferred, and this restriction could be overcome by in vitro methylation either by the host CFE or by commercial methytransferase M. HaeIII. The results provide an insight to further study the genetic restriction, modification and evolution of mosquitocidal L. Sphaericus, also a theoretical basis and a method for the genetic manipulations of L. Sphaericus. Conclusions LspC3–41I is identified as the major determinant for the restriction barrier of L. Sphaericus C3–41. Only three strains of the tested 16 L. Sphaericus strains, which all belonging to serotype H5 and ST1 by MLST scheme, contain LspC3–41I system. Two different methods can be used to overcome the restriction barrier of the three isolates to get transformants efficiently: 1) to methylate plasmid DNA prior to the electroporation; and 2) to delete the major restriction endonuclease encoding gene lspC3–41IR
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complete genome sequence of the mosquitocidal bacterium bacillus Sphaericus c3 41 and comparison with those of closely related bacillus species
Journal of Bacteriology, 2008Co-Authors: Wei Fan, Bei Han, Haizhou Liu, Dasheng Zheng, Wei Dong, Jianping Yan, Meiying Gao, Colin Berry, Zhiming YuanAbstract:Bacillus Sphaericus strain C3-41 is an aerobic, mesophilic, spore-forming bacterium that has been used with great success in mosquito control programs worldwide. Genome sequencing revealed that the complete genome of this entomopathogenic bacterium is composed of a chromosomal replicon of 4,639,821 bp and a plasmid replicon of 177,642 bp, containing 4,786 and 186 potential protein-coding sequences, respectively. Comparison of the genome with other published sequences indicated that the B. Sphaericus C3-41 chromosome is most similar to that of Bacillus sp. strain NRRL B-14905, a marine species that, like B. Sphaericus, is unable to metabolize polysaccharides. The lack of key enzymes and sugar transport systems in the two bacteria appears to be the main reason for this inability, and the abundance of proteolytic enzymes and transport systems may endow these bacteria with exclusive metabolic pathways for a wide variety of organic compounds and amino acids. The genes shared between B. Sphaericus C3-41 and Bacillus sp. strain NRRL B-14905, including mobile genetic elements, membrane-associated proteins, and transport systems, demonstrated that these two species are a biologically and phylogenetically divergent group. Knowledge of the genome sequence of B. Sphaericus C3-41 thus increases our understanding of the bacilli and may also offer prospects for future genetic improvement of this important biological control agent.
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improving the insecticidal activity against resistant culex quinquefasciatus mosquitoes by expression of chitinase gene chiac in bacillus Sphaericus
Applied and Environmental Microbiology, 2007Co-Authors: Yajun Cai, Bei Han, Jianpin Yan, Zhiming YuanAbstract:Expression of a chitinase gene, chiAC, from Bacillus thuringiensis in B. Sphaericus 2297 using the binary toxin promoter yielded a recombinant strain that was 4,297-fold more toxic than strain 2297 against resistant Culex quinquefasciatus. These results show that this chitinase can synergize the toxicity of the binary toxin against mosquitoes and thus may be useful in managing mosquito resistance to B. Sphaericus.
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molecular characterization of a glucokinase with broad hexose specificity from bacillus Sphaericus strain c3 41
Applied and Environmental Microbiology, 2007Co-Authors: Bei Han, Haizhou Liu, Yajun Cai, Dasheng Zheng, Zhiming YuanAbstract:Bacillus Sphaericus cannot metabolize sugar since it lacks several of the enzymes necessary for glycolysis. Our results confirmed the presence of a glucokinase-encoding gene, glcK, and a phosphofructokinase-encoding gene, pfk, on the bacterial chromosome and expression of glucokinase during vegetative growth of B. Sphaericus strains. However, no phosphoglucose isomerase gene (pgi) or phosphoglucose isomerase enzyme activity was detected in these strains. Furthermore, one glcK open reading frame was cloned from B. Sphaericus strain C3-41 and then expressed in Escherichia coli. Biochemical analysis revealed that this gene encoded a protein with a molecular mass of 33 kDa and that the purified recombinant glucokinase had Km values of 0.52 and 0.31 mM for ATP and glucose, respectively. It has been proved that this ATP-dependent glucokinase can also phosphorylate fructose and mannose, and sequence alignment of the glcK gene indicated that it belongs to the ROK protein family. It is postulated that the absence of the phosphoglucose isomerase-encoding gene pgi in B. Sphaericus might be one of the reasons for the inability of this bacterium to metabolize carbohydrates. Our findings provide additional data that further elucidate the specific metabolic pathway and could be used for genetic improvement of B. Sphaericus.
William E. Walton - One of the best experts on this subject based on the ideXlab platform.
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mosquito larvicidal activity of aloe vera family liliaceae leaf extract and bacillus Sphaericus against chikungunya vector aedes aegypti
Saudi Journal of Biological Sciences, 2012Co-Authors: Jayapal Subramaniam, Kadarkarai Murugan, Kalimuthu Kovendan, Palanisamy Mahesh Kumar, William E. WaltonAbstract:The bio-efficacy of Aloe vera leaf extract and bacterial insecticide, Bacillus Sphaericus larvicidal activity was assessed against the first to fourth instars larvae of Aedes aegypti, under the laboratory conditions. The plant material was shade dried at room temperature and powdered coarsely. A. vera and B. Sphaericus show varied degrees of larvicidal activity against various instars larvae of A. aegypti. The LC50 of A. vera against the first to fourth instars larvae were 162.74, 201.43, 253.30 and 300.05 ppm and the LC90 442.98, 518.86, 563.18 and 612.96 ppm, respectively. B. Sphaericus against the first to fourth instars larvae the LC50 values were 68.21, 79.13, 93.48, and 107.05 ppm and the LC90 values 149.15, 164.67, 183.84, and 201.09 ppm, respectively. However, the combined treatment of A. vera + B. Sphaericus (1:2) material shows highest larvicidal activity of the LC50 values 54.80, 63.11, 74.66 and 95.10 ppm; The LC90 values of 145.29, 160.14, 179.74 and 209.98 ppm, against A. aegypti in all the tested concentrations than the individuals and clearly established that there is a substantial amount of synergist act. The present investigation clearly exhibits that both A. vera and B. Sphaericus materials could serve as a potential larvicidal agent. Since, A. aegypti is a container breeder vector mosquito this user and eco-friendly and low-cost vector control strategy could be a viable solution to the existing dengue disease burden. Therefore, this study provides first report on the mosquito larvicidal activity the combined effect of A. vera leaf extract and B. Sphaericus against as target species of A. aegypti.
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synergy between toxins of bacillus thuringiensis subsp israelensis and bacillus Sphaericus
Journal of Medical Entomology, 2004Co-Authors: Margaret C. Wirth, Brian A. Federici, Joshua A Jiannino, William E. WaltonAbstract: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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cyt1a from bacillus thuringiensis restores toxicity of bacillus Sphaericus against resistant culex quinquefasciatus diptera culicidae
Journal of Medical Entomology, 2000Co-Authors: Margaret C. Wirth, William E. Walton, Brian A. FedericiAbstract:The 2362 strain of Bacillus Sphaericus, which produces a binary toxin highly active against Culex mosquitoes, has been developed recently as a commercial larvicide. It is being used currently in operational mosquito control programs in several countries including Brazil, France, India, and the United States. Laboratory studies have shown that mosquitoes can develop resistance to B. Sphaericus, and low levels of resistance have already been reported in field populations in Brazil, France, and India. To develop tools for resistance management, the Cyt1A protein of Bacillus thuringiensis subsp. israelensis De Barjac was evaluated for its ability to suppress resistance to B. Sphaericus in a highly resistant population of Culex quinquefasciatus Say. A combination of B. Sphaericus 2362 in a 10:1 ratio with a strain of B. thuringiensis subsp. israelensis that only produces Cyt1A reduced resistance by >30,000-fold. Resistance was suppressed completely when B. Sphaericus was combined with purified Cyt1A crystals in a 10:1 ratio. Synergism was observed between the Cyt1A toxin and B. Sphaericus against the resistant mosquito population and accounted for the marked reduction in resistance. However, no synergism was observed between the toxins against a nonresistant mosquito population. These results indicate that Cyt1A could be useful for managing resistance to B. Sphaericus 2362 in Culex populations, and also provide additional evidence that Cyt1A may synergize toxicity by enhancing the binding to and insertion of toxins into the mosquito microvillar membrane.
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Cyt1A from Bacillus thuringiensis synergizes activity of Bacillus Sphaericus against Aedes aegypti (Diptera: Culicidae)
Applied and environmental microbiology, 2000Co-Authors: Margaret C. Wirth, Brian A. Federici, William E. WaltonAbstract:Bacillus Sphaericus is a mosquitocidal bacterium recently developed as a commercial larvicide that is used worldwide to control pestiferous and vector mosquitoes. Whereas B. Sphaericus is highly active against larvae of Culex and Anopheles mosquitoes, it is virtually nontoxic to Aedes aegypti, an important vector species. In the present study, we evaluated the capacity of the cytolytic protein Cyt1A from Bacillus thuringiensis subsp. israelensis to enhance the toxicity of B. Sphaericus toward A. aegypti. Various combinations of these two materials were evaluated, and all were highly toxic. A ratio of 10:1 of B. Sphaericus to Cyt1A was 3,600-fold more toxic to A. aegypti than B. Sphaericus alone. Statistical analysis showed this high activity was due to synergism between the Cyt1A toxin and B. Sphaericus. These results suggest that Cyt1A could be useful in expanding the host range of B. Sphaericus.
M S Foda - One of the best experts on this subject based on the ideXlab platform.
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Economic production of Lysinibacillus Sphaericus under solid state fermentation
Biocontrol Science and Technology, 2015Co-Authors: M S Foda, Magdi A. Amin, Noha A. Gawdat, Magda A. El-bendaryAbstract:A highly active mosquitocidal Lysinibacillus Sphaericus namely Ls 9B24 was isolated from soil of Alexandria governorate in Egypt. It was more active than the standard strain, L. Sphaericus 2362. The sporulation and toxin formation of both cultures grown on different leguminous seeds and by-products under solid state fermentation (SSF) were studied. Among the tested substrates, 6% cotton seed meal enhanced sporulation and the mosquitocidal activity of L. Sphaericus 2362, while 6% fodder yeast enhanced sporulation and the mosquitocidal activity of Ls 9B24. The optimum SSF growth conditions for maximum mosquitocidal activity by both cultures were using coarse wheat bran as a carrier material, 50% initial moisture content, 4–64 × 106 colony forming units (CFU)/g solid medium inoculum and 6 days’ incubation period at 30°C. Addition of 0.5% yeast extract enhanced toxicity about 2.2 and 1.8 fold for L. Sphaericus 2362 and Ls 9B24, respectively.
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Amino acids requirements for growth and toxin production by Lysinibacillus Sphaericus
BioTechnology: An Indian Journal, 2015Co-Authors: M S Foda, Magdi A. Amin, Osama M. El-tayeb, Noha A. Gawdat, Magda A. El-bendaryAbstract:Growth and mosquitocidal activity of Lysinibacillus Sphaericus 9B24 was studied in defined medium supplemented with amino acids. It was found that L-glutamate, L-arginine, and L-proline enhanced the sporulation and mosquitocidal activity of the tested culture against Culex pipiens larvae. Different concentrations of these three amino acids were tested for sporulation and toxin formation by Lysinibacillus Sphaericus 9B24 in comparisonwith Lysinibacillus Sphaericus 2362.Optimumconcentrations were 0.5-0.75%for L-arginine and 0.75%for L-glutamate and L-proline.All tested mixtures of these amino acids enhanced the sporulation and mosquitocidal toxicity of both cultures. L-arginine- L-proline - L-glutamate mixture at their optimum concentrations was the most mosquitocidal enhancer for Lysinibacillus Sphaericus 2362 (LC50 1.5 × 10-5) however, mixture of L-proline- L-glutamate was the optimum for Lysinibacillus Sphaericus 9B24 (LC50 1.66 × 10-5). Itwas concluded that thewasteswhich contain high quantities of L-arginine, L-proline and L-glutamate could be used as media for cost effective production of Lysinibacillus Sphaericus.
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High Efficiency Production of Mosquitocidal Toxin by a novel Bacillus Sphaericus isolate from Egyptian Soils on Local Agroindustrial Byproducts
2010Co-Authors: M S Foda, Maysa E MoharamAbstract:Eighty six cultures were isolated from soil of dif ferent Egyptian Governorates including Quina, El- Menofeya, El-Gharbia, El-Sharkia, El-Behera and Kafr EL-Sheikh Governorates. Investigations on the mosquitocidal Egyptian isolates have revealed that isolate No.1 have the ability to form more toxin th an the international reference strain Bacillus Sphaericus 2362(Bs 2362).The selected isolate No.1 exhibited a lower L C 50 and LC 90 values than the International strain B.s 2362 upon bioassay against second instars' larvae of Culex pipiens. The Egyptian isolate No.1was identified morphologically and biochemically as Bacillus Sphaericus. Physiological factors affecting growth and toxin formation in B. Sphaericus No 1 in comparison to B.s 2362 were carried out. THE organism grown on modified Nutrient broth medium yielded the highest larval toxicity against the secon d instars' of Culex pipiens for both Bacillus Sphaericus isolate No 1 and the international strain Bacillus Sphaericus. The Optimum air : medium ratio were 9:1 and 4:1 of the flask volume for 4 and 3 days incubation periods us ing 2%and 3% sizes of inocula for B. Sphaericus 2362 and the Egyptian isolate B. Sphaericus No.1, respectively. Sodium acetate was the suitable carbon source for the isol ate B. Sphaericus No.1, while B.s 2362 was capable to utilize both sodium acetate and sodium succinate as carbon sources.The Egyptian isolate B. Sphaericus No.1exhibited the highest mosquitocidal activity upon growth on kidn ey beans seeds and sesame meal as nutrient substrat es at 3% final concentration, while B.s 2362 exhibited the highest mosquitocidal activity by utilizing soy beans, lentils and sesame meal as complete media for growth and mosquitocidal toxin production.
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efficient mosquitocidal toxin production by bacillus Sphaericus using cheese whey permeate under both submerged and solid state fermentations
Journal of Invertebrate Pathology, 2008Co-Authors: Magda A Elbendary, Maysa E Moharam, M S FodaAbstract:Abstract Whey permeate (WP) was used efficiently for production of mosquitocidal toxin by Bacillus Sphaericus 2362 (B. Sphaericus 2362) and the Egyptian isolate, B. Sphaericus 14N1 (B. Sphaericus 14N1) under both submerged and solid state fermentation conditions. Under submerged fermentation, high mosquitocidal activity was produced by B. Sphaericus 2362 and B. Sphaericus 14N1 at 50–100% and 25–70% WP, respectively. Initial pH of WP was a critical factor for toxin production by both tested organisms. The highest toxicity was obtained at initial pH 7. Egyptian isolate, B. Sphaericus 14N1 was tested for growth and toxin production under solid state fermentation conditions (SSF) by using WP as moistening agent instead of distilled water. The optimum conditions for production of B. Sphaericus 14N1 on wheat bran-WP medium were 10 g wheat bran/250 ml flask moistened with 10–70% WP at 50% moisture content, inoculum size ranged between 17.2 × 107 and 34.4 × 107 and 6 days incubation under static conditions at 30 °C. Preliminary pilot-scale production of B. Sphaericus 14N1 under SSF conditions in trays proved that wheat bran-WP medium was efficient and economic for industrial production of mosquitocidal toxin by B. Sphaericus.
Margaret C. Wirth - One of the best experts on this subject based on the ideXlab platform.
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synergy between toxins of bacillus thuringiensis subsp israelensis and bacillus Sphaericus
Journal of Medical Entomology, 2004Co-Authors: Margaret C. Wirth, Brian A. Federici, Joshua A Jiannino, William E. WaltonAbstract: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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cyt1a from bacillus thuringiensis restores toxicity of bacillus Sphaericus against resistant culex quinquefasciatus diptera culicidae
Journal of Medical Entomology, 2000Co-Authors: Margaret C. Wirth, William E. Walton, Brian A. FedericiAbstract:The 2362 strain of Bacillus Sphaericus, which produces a binary toxin highly active against Culex mosquitoes, has been developed recently as a commercial larvicide. It is being used currently in operational mosquito control programs in several countries including Brazil, France, India, and the United States. Laboratory studies have shown that mosquitoes can develop resistance to B. Sphaericus, and low levels of resistance have already been reported in field populations in Brazil, France, and India. To develop tools for resistance management, the Cyt1A protein of Bacillus thuringiensis subsp. israelensis De Barjac was evaluated for its ability to suppress resistance to B. Sphaericus in a highly resistant population of Culex quinquefasciatus Say. A combination of B. Sphaericus 2362 in a 10:1 ratio with a strain of B. thuringiensis subsp. israelensis that only produces Cyt1A reduced resistance by >30,000-fold. Resistance was suppressed completely when B. Sphaericus was combined with purified Cyt1A crystals in a 10:1 ratio. Synergism was observed between the Cyt1A toxin and B. Sphaericus against the resistant mosquito population and accounted for the marked reduction in resistance. However, no synergism was observed between the toxins against a nonresistant mosquito population. These results indicate that Cyt1A could be useful for managing resistance to B. Sphaericus 2362 in Culex populations, and also provide additional evidence that Cyt1A may synergize toxicity by enhancing the binding to and insertion of toxins into the mosquito microvillar membrane.
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Cyt1A from Bacillus thuringiensis synergizes activity of Bacillus Sphaericus against Aedes aegypti (Diptera: Culicidae)
Applied and environmental microbiology, 2000Co-Authors: Margaret C. Wirth, Brian A. Federici, William E. WaltonAbstract:Bacillus Sphaericus is a mosquitocidal bacterium recently developed as a commercial larvicide that is used worldwide to control pestiferous and vector mosquitoes. Whereas B. Sphaericus is highly active against larvae of Culex and Anopheles mosquitoes, it is virtually nontoxic to Aedes aegypti, an important vector species. In the present study, we evaluated the capacity of the cytolytic protein Cyt1A from Bacillus thuringiensis subsp. israelensis to enhance the toxicity of B. Sphaericus toward A. aegypti. Various combinations of these two materials were evaluated, and all were highly toxic. A ratio of 10:1 of B. Sphaericus to Cyt1A was 3,600-fold more toxic to A. aegypti than B. Sphaericus alone. Statistical analysis showed this high activity was due to synergism between the Cyt1A toxin and B. Sphaericus. These results suggest that Cyt1A could be useful in expanding the host range of B. Sphaericus.
Brian A. Federici - One of the best experts on this subject based on the ideXlab platform.
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Properties and applied use of the mosquitocidal bacterium, Bacillus Sphaericus
Journal of Asia-Pacific entomology, 2010Co-Authors: Hyun-woo Park, Dennis K. Bideshi, Brian A. FedericiAbstract:Abstract Strains of Bacillus Sphaericus exhibit varying levels of virulence against mosquito larvae. The most potent strain, B. Sphaericus 2362, which is the active ingredient in the commercial product VectoLex ® , together with another well-known larvicide Bacillus thuringiensis subsp. israelensis , is used to control vector and nuisance mosquito larvae in many regions of the world. Although not all strains of B. Sphaericus are mosquitocidal, lethal strains produce one or two combinations of three different types of toxins. These are (1) the binary toxin (Bin) composed of two proteins of 42 kDa (BinA) and 51 kDa (BinB), which are synthesized during sporulation and co-crystallize, (2) the soluble mosquitocidal toxins (Mtx1, Mtx2 and Mtx3) produced during vegetative growth, and (3) the two-component crystal toxin (Cry48Aa1/Cry49Aa1). Non-mosquitocidal toxins are also produced by certain strains of B. Sphaericus , for example sphaericolysin, a novel insecticidal protein toxic to cockroaches. Larvicides based on B. Sphaericus -based have the advantage of longer persistence in treated habitats compared to B. thuringiensis subsp. israelensis . However, resistance is a much greater threat, and has already emerged at significant levels in field populations in China and Thailand treated with B. Sphaericus . This likely occurred because toxicity depends principally on Bin rather than various combinations of crystal (Cry) and cytolytic (Cyt) toxins present in B. thuringiensis subsp. israelensis . Here we review both the general characteristics of B. Sphaericus , particularly as they relate to larvicidal isolates, and strategies or considerations for engineering more potent strains of this bacterium that contain built-in mechanisms that delay or overcome resistance to Bin in natural mosquito populations.
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synergy between toxins of bacillus thuringiensis subsp israelensis and bacillus Sphaericus
Journal of Medical Entomology, 2004Co-Authors: Margaret C. Wirth, Brian A. Federici, Joshua A Jiannino, William E. WaltonAbstract: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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cyt1a from bacillus thuringiensis restores toxicity of bacillus Sphaericus against resistant culex quinquefasciatus diptera culicidae
Journal of Medical Entomology, 2000Co-Authors: Margaret C. Wirth, William E. Walton, Brian A. FedericiAbstract:The 2362 strain of Bacillus Sphaericus, which produces a binary toxin highly active against Culex mosquitoes, has been developed recently as a commercial larvicide. It is being used currently in operational mosquito control programs in several countries including Brazil, France, India, and the United States. Laboratory studies have shown that mosquitoes can develop resistance to B. Sphaericus, and low levels of resistance have already been reported in field populations in Brazil, France, and India. To develop tools for resistance management, the Cyt1A protein of Bacillus thuringiensis subsp. israelensis De Barjac was evaluated for its ability to suppress resistance to B. Sphaericus in a highly resistant population of Culex quinquefasciatus Say. A combination of B. Sphaericus 2362 in a 10:1 ratio with a strain of B. thuringiensis subsp. israelensis that only produces Cyt1A reduced resistance by >30,000-fold. Resistance was suppressed completely when B. Sphaericus was combined with purified Cyt1A crystals in a 10:1 ratio. Synergism was observed between the Cyt1A toxin and B. Sphaericus against the resistant mosquito population and accounted for the marked reduction in resistance. However, no synergism was observed between the toxins against a nonresistant mosquito population. These results indicate that Cyt1A could be useful for managing resistance to B. Sphaericus 2362 in Culex populations, and also provide additional evidence that Cyt1A may synergize toxicity by enhancing the binding to and insertion of toxins into the mosquito microvillar membrane.
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Cyt1A from Bacillus thuringiensis synergizes activity of Bacillus Sphaericus against Aedes aegypti (Diptera: Culicidae)
Applied and environmental microbiology, 2000Co-Authors: Margaret C. Wirth, Brian A. Federici, William E. WaltonAbstract:Bacillus Sphaericus is a mosquitocidal bacterium recently developed as a commercial larvicide that is used worldwide to control pestiferous and vector mosquitoes. Whereas B. Sphaericus is highly active against larvae of Culex and Anopheles mosquitoes, it is virtually nontoxic to Aedes aegypti, an important vector species. In the present study, we evaluated the capacity of the cytolytic protein Cyt1A from Bacillus thuringiensis subsp. israelensis to enhance the toxicity of B. Sphaericus toward A. aegypti. Various combinations of these two materials were evaluated, and all were highly toxic. A ratio of 10:1 of B. Sphaericus to Cyt1A was 3,600-fold more toxic to A. aegypti than B. Sphaericus alone. Statistical analysis showed this high activity was due to synergism between the Cyt1A toxin and B. Sphaericus. These results suggest that Cyt1A could be useful in expanding the host range of B. Sphaericus.
