scholarly journals Decreased Toxicity of Bacillus thuringiensis subsp. israelensis to Mosquito Larvae after Contact with Leaf Litter

2012 ◽  
Vol 78 (15) ◽  
pp. 5189-5195 ◽  
Author(s):  
Guillaume Tetreau ◽  
Renaud Stalinski ◽  
Dylann Kersusan ◽  
Sylvie Veyrenc ◽  
Jean-Philippe David ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Leaf Litter ◽  
Mosquito Larvae ◽  
Important Food ◽  
Cry Toxins ◽  
Content Type ◽  
Breeding Sites ◽  
Mosquito Breeding ◽  
Important Food Source ◽  
Crystal Toxins

ABSTRACTBacillus thuringiensissubsp.israelensisis a bacterium producing crystals containing Cry and Cyt proteins, which are toxic for mosquito larvae. Nothing is known about the interaction between crystal toxins and decaying leaf litter, which is a major component of several mosquito breeding sites and represents an important food source. In the present work, we investigated the behavior ofB. thuringiensissubsp.israelensistoxic crystals sprayed on leaf litter. In the presence of leaf litter, a 60% decrease in the amount of Cyt toxin detectable by immunology (enzyme-linked immunosorbent assays [ELISAs]) was observed, while the respective proportions of Cry toxins were not affected. The toxicity of Cry toxins towardAedes aegyptilarvae was not affected by leaf litter, while the synergistic effect of Cyt toxins on allB. thuringiensissubsp.israelensisCry toxins was decreased by about 20% when mixed with leaf litter. The toxicity of two commercialB. thuringiensissubsp.israelensisstrains (VectoBac WG and VectoBac 12AS) and a laboratory-producedB. thuringiensissubsp.israelensisstrain decreased by about 70% when mixed with leaf litter. Taken together, these results suggest that Cyt toxins interact with leaf litter, resulting in a decreased toxicity ofB. thuringiensissubsp.israelensisin litter-rich environments and thereby dramatically reducing the efficiency of mosquitocidal treatments.

scholarly journals Fate of Bacillus thuringiensis subsp. israelensis in the Field: Evidence for Spore Recycling and Differential Persistence of Toxins in Leaf Litter

2012 ◽  
Vol 78 (23) ◽  
pp. 8362-8367 ◽  
Author(s):  
Guillaume Tetreau ◽  
Mattia Alessi ◽  
Sylvie Veyrenc ◽  
Sophie Périgon ◽  
Jean-Philippe David ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Leaf Litter ◽  
Mosquito Control ◽  
Crystal Form ◽  
High Concentration ◽  
Content Type ◽  
Breeding Sites ◽  
Commercial Mixture ◽  
Field Evidence ◽  
Larval Toxicity

ABSTRACTBacillus thuringiensissubsp.israelensisis a bioinsecticide increasingly used worldwide for mosquito control. Despite its apparent low level of persistence in the field due to the rapid loss of its insecticidal activity, an increasing number of studies suggested that the recycling ofB. thuringiensissubsp.israelensiscan occur under specific, unknown conditions. Decaying leaf litters sampled in mosquito breeding sites in the French Rhône-Alpes region several months after a treatment were shown to exhibit a high level of larval toxicity and contained large amounts of spores. In the present article, we show that the high concentration of toxins found in these litters is consistent with spore recycling in the field, which gave rise to the production of new crystal toxins. Furthermore, in these toxic leaf litter samples, Cry4Aa and Cry4Ba toxins became the major toxins instead of Cyt1Aa in the commercial mixture. In a microcosm experiment performed in the laboratory, we also demonstrated that the toxins, when added in their crystal form to nontoxic leaf litter, exhibited patterns of differential persistence consistent with the proportions of toxins observed in the field-collected toxic leaf litter samples (Cry4 > Cry11 > Cyt). These results give strong evidence thatB. thuringiensissubsp.israelensisrecycled in specific breeding sites containing leaf litters, and one would be justified in asking whether mosquitoes can become resistant when exposed to field-persistentB. thuringiensissubsp.israelensisfor several generations.

scholarly journals An Intramolecular Salt Bridge in Bacillus thuringiensis Cry4Ba Toxin Is Involved in the Stability of Helix α-3, Which Is Needed for Oligomerization and Insecticidal Activity

2017 ◽  
Vol 83 (20) ◽  
Author(s):  
Sabino Pacheco ◽  
Isabel Gómez ◽  
Jorge Sánchez ◽  
Blanca-Ines García-Gómez ◽  
Mario Soberón ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Double Point ◽  
Single Point ◽  
Three Dimensional ◽  
Point Mutations ◽  
Salt Bridge ◽  
Dimensional Structure ◽  
Cry Toxins ◽  
Content Type ◽  
Domain I

ABSTRACT Bacillus thuringiensis three-domain Cry toxins kill insects by forming pores in the apical membrane of larval midgut cells. Oligomerization of the toxin is an important step for pore formation. Domain I helix α-3 participates in toxin oligomerization. Here we identify an intramolecular salt bridge within helix α-3 of Cry4Ba (D111-K115) that is conserved in many members of the family of three-domain Cry toxins. Single point mutations such as D111K or K115D resulted in proteins severely affected in toxicity. These mutants were also altered in oligomerization, and the mutant K115D was more sensitive to protease digestion. The double point mutant with reversed charges, D111K-K115D, recovered both oligomerization and toxicity, suggesting that this salt bridge is highly important for conservation of the structure of helix α-3 and necessary to promote the correct oligomerization of the toxin. IMPORTANCE Domain I has been shown to be involved in oligomerization through helix α-3 in different Cry toxins, and mutations affecting oligomerization also elicit changes in toxicity. The three-dimensional structure of the Cry4Ba toxin reveals an intramolecular salt bridge in helix α-3 of domain I. Mutations that disrupt this salt bridge resulted in changes in Cry4Ba oligomerization and toxicity, while a double point reciprocal mutation that restored the salt bridge resulted in recovery of toxin oligomerization and toxicity. These data highlight the role of oligomer formation as a key step in Cry4Ba toxicity.

Algae in mosquito breeding sites and the effectiveness of the mosquito larvicide Bacillus thuringiensis H-14

1993 ◽  
Vol 9 (2) ◽  
pp. 156-159 ◽  
Author(s):  
A. Abdel-Hameed ◽  
J. Kiviranta ◽  
K. Sivonen ◽  
S. Niemel� ◽  
G. Carlberg
Keyword(s):  
Bacillus Thuringiensis ◽  
Breeding Sites ◽  
Mosquito Breeding

Larvicidal properties of decomposed leaf litter in the subalpine mosquito breeding sites

2002 ◽  
Vol 21 (1) ◽  
pp. 62-66 ◽  
Author(s):  
Jean-Philippe David ◽  
Delphine Rey ◽  
Andre Cuany ◽  
Jean-Marc Bride ◽  
Jean-Claude Meyran
Keyword(s):  
Leaf Litter ◽  
Breeding Sites ◽  
Mosquito Breeding

scholarly journals Cry64Ba and Cry64Ca, Two ETX/MTX2-TypeBacillus thuringiensisInsecticidal Proteins Active against Hemipteran Pests

2017 ◽  
Vol 84 (3) ◽  
Author(s):  
Yonglei Liu ◽  
Yinglong Wang ◽  
Changlong Shu ◽  
Kejian Lin ◽  
Fuping Song ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Specific Binding ◽  
Genetically Modified Crops ◽  
Membrane Vesicles ◽  
Laodelphax Striatellus ◽  
Sogatella Furcifera ◽  
Cry Toxins ◽  
Content Type ◽  
Bt Toxin ◽  
Rice Planthoppers

ABSTRACTGenetically modified crops that express insecticidalBacillus thuringiensis(Bt) proteins have become a primary approach for control of lepidopteran (moth) and coleopteran (beetle) pests that feed by chewing the plants. However, the sap-sucking insects (Hemiptera) are not particularly susceptible to Bt toxins. In this study, we describe two Cry toxins (Cry64Ba and Cry64Ca) from Bt strain 1012 that showed toxicity against two important hemipteran rice pests,Laodelphax striatellusandSogatella furcifera. Both of these proteins contain an ETX/MTX2 domain and share common sequence features with the β-pore-forming toxins. Coexpression ofcry64Baandcry64Cagenes in the acrystalliferous Bt strain HD73−resulted in high insecticidal activity against both hemipteran pests. No toxicity was observed on other pests such asOstrinia furnacalis,Plutella xylostella, orColaphellus bowringi. Also, no hemolytic activity or toxicity against cancer cells was detected. Binding assays showed specific binding of the Cry64Ba/Cry64Ca toxin complex to brush border membrane vesicles isolated fromL. striatellus. Cry64Ba and Cry64Ca are Bt Cry toxins highly effective against hemipteran pests and could provide a novel strategy for the environmentally friendly biological control of rice planthoppers in transgenic plants.IMPORTANCEIn Asia, rice is an important staple food, whose production is threatened by rice planthoppers. To date, no effectiveBacillus thuringiensis(Bt) protein has been shown to have activity against rice planthoppers. We cloned two Bt toxin genes from Bt strain 1012 that showed toxicity against small brown planthoppers (Laodelphax striatellus) and white-backed planthoppers (Sogatella furcifera). To our knowledge, the proteins encoded by thecry64Baandcry64Cagenes are the most efficient insecticidal Bt Cry proteins with activity against hemipteran insects reported so far. Cry64Ba and Cry64Ca showed no toxicity against some lepidopteran or coleopteran pests. These two proteins should be able to be used for integrated hemipteran pest management.

scholarly journals Insect Hsp90 Chaperone Assists Bacillus thuringiensis Cry Toxicity by Enhancing Protoxin Binding to the Receptor and by Protecting Protoxin from Gut Protease Degradation

mBio ◽  
2019 ◽  
Vol 10 (6) ◽  
Author(s):  
Blanca I. García-Gómez ◽  
Sayra N. Cano ◽  
Erika E. Zagal ◽  
Edgar Dantán-Gonzalez ◽  
Alejandra Bravo ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Receptor Binding ◽  
Insecticidal Activity ◽  
Insect Pests ◽  
Biotechnological Applications ◽  
Cry Proteins ◽  
Cry Toxins ◽  
Content Type ◽  
Hsp90 Chaperone ◽  
Protease Degradation

ABSTRACT Bacillus thuringiensis Cry proteins are pore-forming insecticidal toxins with specificity against different crop pests and insect vectors of human diseases. Previous work suggested that the insect host Hsp90 chaperone could be involved in Cry toxin action. Here, we show that the interaction of Cry toxins with insect Hsp90 constitutes a positive loop to enhance the performance of these toxins. Plutella xylostella Hsp90 (PxHsp90) greatly enhanced Cry1Ab or Cry1Ac toxicity when fed together to P. xylostella larvae and also in the less susceptible Spodoptera frugiperda larvae. PxHsp90 bound Cry1Ab and Cry1Ac protoxins in an ATP- and chaperone activity-dependent interaction. The chaperone Hsp90 participates in the correct folding of proteins and may suppress mutations of some client proteins, and we show here that PxHsp90 recovered the toxicity of the Cry1AbG439D protoxin affected in receptor binding, in contrast to the Cry1AbR99E or Cry1AbE129K mutant, affected in oligomerization or membrane insertion, respectively, which showed a slight toxicity improvement. Specifically, PxHsp90 enhanced the binding of Cry1AbG439D protoxin to the cadherin receptor. Furthermore, PxHsp90 protected Cry1A protoxins from degradation by insect midgut proteases. Our data show that PxHsp90 assists Cry1A proteins by enhancing their binding to the receptor and by protecting Cry protoxin from gut protease degradation. Finally, we show that the insect cochaperone protein PxHsp70 also increases the toxicity of Cry1Ac in P. xylostella larvae, in contrast to a bacterial GroEL chaperone, which had a marginal effect, indicating that the use of insect chaperones along with Cry toxins could have important biotechnological applications for the improvement of Cry insecticidal activity, resulting in effective control of insect pests. IMPORTANCE Bacillus thuringiensis took advantage of important insect cellular proteins, such as chaperones, involved in maintaining protein homeostasis, to enhance its insecticidal activity. This constitutes a positive loop where the concentrations of Hsp90 and Hsp70 in the gut lumen are likely to increase as midgut cells burst due to Cry1A pore formation action. Hsp90 protects Cry1A protoxin from degradation and enhances receptor binding, resulting in increased toxicity. The effect of insect chaperones on Cry toxicity could have important biotechnological applications to enhance the toxicity of Cry proteins to insect pests, especially those that show low susceptibility to these toxins.

scholarly journals Assessing Mosquito Breeding Sites and Abundance Using An Unmanned Aircraft

2019 ◽  
Vol 35 (3) ◽  
pp. 228-232 ◽  
Author(s):  
Eric J. Haas-Stapleton ◽  
Miguel C. Barretto ◽  
Erika B. Castillo ◽  
Ryan J. Clausnitzer ◽  
Robert L. Ferdan
Keyword(s):  
Surface Water ◽  
San Francisco ◽  
Tidal Marsh ◽  
Video Camera ◽  
Unmanned Aircraft ◽  
Mosquito Larvae ◽  
Breeding Sites ◽  
Mosquito Breeding ◽  
Artificial Intelligence Algorithm ◽  
Aircraft System

ABSTRACT An unmanned aircraft system (UAS; i.e., drone) with an attached multispectral camera was used to quantify accumulated surface water on a 0.54-km2 tidal marsh that abuts San Francisco Bay, CA, USA. The results of the survey showed unequal accumulation of surface water and provided information for focused inspections of potential mosquito breeding areas and identified areas where existing ditches needed improvement for increasing water circulation in the marsh to reduce mosquito breeding. The UAS was also outfitted with a high-magnification zoom video camera and piloted at varying heights to measure the video camera's ability to visualize immature mosquitoes in 2 small containers of contrasting colors during simulation tests in a marsh habitat. Immature mosquitoes could be seen clearly in white or black containers at heights up to 14 and 8 m, respectively. An artificial intelligence algorithm identified mosquito larvae and pupae in videos of the white tray with 94.1% and 52.8% accuracy, respectively. Together, our studies show that an UAS equipped with multispectral and zoom cameras provides a means for vector control agencies to rapidly and quantitatively assess the landscape for the presence of surface water and mosquito larvae.

scholarly journals Survei Jentik Nyamuk Anopheles di Desa Maukeli Kecamatan Mauponggo

2020 ◽  
Vol 2 (1) ◽  
pp. 10-17
Author(s):  
Helen Ndiki ◽  
Apris A. Adu ◽  
Ribka Limbu
Keyword(s):  
Salt Water ◽  
Protozoan Parasite ◽  
Average Density ◽  
Rice Fields ◽  
Anopheles Mosquito ◽  
Mosquito Larvae ◽  
Breeding Sites ◽  
Mosquito Breeding ◽  
Descriptive Survey ◽  
River Mouths

Malaria is an infectious disease caused by the parasitic plasmodium protozoan parasite. This disease is transmitted through female Anopheles sp mosquito bites. Anopheles mosquito breeding sites can be in the form of fresh water or salt water, ponds that are overgrown with aquatic plants or those that do not plant, rice fields, river mouths where the flow is not swift and small pools filled with rainwater. Maukeli Village is a village that has a lot of rice fields. The purpose of this study was to determine the density of Anopheles mosquito larvae at various breeding places in Maukeli Village, Mauponggo District in 2018. This type of research design was a descriptive survey with a population of all Anopheles sp. existing in the breeding places and breeding places of mosquito larvae Anopheles sp. The samples in this study were all Anopheles mosquito larvae from the results of abduction at breeding places in Maukeli Village. Sampling was carried out accidentally (ie Anopheles mosquito larvae which happened to be available or available to be sampled. The results showed that there were 4 breeding places, namely paddy fields with average density of Anopheles mosquito larvae (12 tail/ cut), river mouths with average density of Anopheles mosquito larvae (8 tail/ cud), pools with average density of mosquito larvae Anopheles (3 tail/ cud) and the lagoon with average density of Anopheles mosquito larvae (5 tail/ cud) while permanent breeding sites are river mouths and temporary breeding sites, such as river mouths, pools and lagoon.  

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