scholarly journals An Overview on the Crystal Toxins from <i>Bacillus thuringiensis</i>

2013 ◽  
Vol 03 (05) ◽  
pp. 462-472 ◽  
Author(s):  
Veloorvalappil N. Jisha ◽  
Robinson B. Smitha ◽  
Sailas Benjamin
Keyword(s):  
Bacillus Thuringiensis ◽  
Crystal Toxins

Knockdown of cadherin genes decreases susceptibility of Chilo suppressalis larvae to Bacillus thuringiensis produced Crystal toxins

2020 ◽  
Vol 29 (3) ◽  
pp. 301-308
Author(s):  
H. Zhou ◽  
W. Hu ◽  
Q. Huang ◽  
M. Abouzaid ◽  
H. Jin ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Chilo Suppressalis ◽  
Crystal Toxins

scholarly journals Bacillus thuringiensis Spores and Vegetative Bacteria: Infection Capacity and Role of the Virulence Regulon PlcR Following Intrahaemocoel Injection of Galleria mellonella

Insects ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 129 ◽  
Author(s):  
Christophe Buisson ◽  
Michel Gohar ◽  
Eugénie Huillet ◽  
Christina Nielsen-LeRoux
Keyword(s):  
Bacillus Thuringiensis ◽  
Galleria Mellonella ◽  
Lethal Dose ◽  
Intestinal Barrier ◽  
Oral Route ◽  
Infection Model ◽  
Wild Type ◽  
Response Curves ◽  
Vegetative Cells ◽  
Crystal Toxins

Bacillus thuringiensis is an invertebrate pathogen that produces insecticidal crystal toxins acting on the intestinal barrier. In the Galleria mellonella larvae infection model, toxins from the PlcR virulence regulon contribute to pathogenicity by the oral route. While B. thuringiensis is principally an oral pathogen, bacteria may also reach the insect haemocoel following injury of the cuticle. Here, we address the question of spore virulence as compared to vegetative cells when the wild-type Bt407cry- strain and its isogenic ∆plcR mutant are inoculated directly into G. mellonella haemocoel. Mortality dose-response curves were constructed at 25 and 37 °C using spores or vegetative cell inocula, and the 50% lethal dose (LD50) in all infection conditions was determined after 48 h of infection. Our findings show that (i) the LD50 is lower for spores than for vegetative cells for both strains, while the temperature has no significant influence, and (ii) the ∆plcR mutant is four to six times less virulent than the wild-type strain in all infection conditions. Our results suggest that the environmental resistant spores are the most infecting form in haemocoel and that the PlcR virulence regulon plays an important role in toxicity when reaching the haemocoel from the cuticle and not only following ingestion.

scholarly journals Differential Effects of pH on the Pore-Forming Properties of Bacillus thuringiensis Insecticidal Crystal Toxins

2001 ◽  
Vol 67 (10) ◽  
pp. 4488-4494 ◽  
Author(s):  
Le Binh Tran ◽  
Vincent Vachon ◽  
Jean-Louis Schwartz ◽  
Raynald Laprade
Keyword(s):  
Bacillus Thuringiensis ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Insect Midgut ◽  
Tetramethylammonium Chloride ◽  
Effects Of Ph ◽  
Alkaline Conditions ◽  
Crystal Toxins ◽  
Ph Range ◽  
Reduced Activity

ABSTRACT The effect of pH on the pore-forming ability of two Bacillus thuringiensis toxins, Cry1Ac and Cry1C, was examined with midgut brush border membrane vesicles isolated from the tobacco hornworm,Manduca sexta, and a light-scattering assay. In the presence of Cry1Ac, membrane permeability remained high over the entire pH range tested (6.5 to 10.5) for KCl and tetramethylammonium chloride, but was much lower at pH 6.5 than at higher pHs for potassium gluconate, sucrose, and raffinose. On the other hand, the Cry1C-induced permeability to all substrates tested was much higher at pH 6.5, 7.5, and 8.5 than at pH 9.5 and 10.5. These results indicate that the pores formed by Cry1Ac are significantly smaller at pH 6.5 than under alkaline conditions, whereas the pore-forming ability of Cry1C decreases sharply above pH 8.5. The reduced activity of Cry1C at high pH correlates well with the fact that its toxicity for M. sexta is considerably weaker than that of Cry1Aa, Cry1Ab, and Cry1Ac. However, Cry1E, despite having a toxicity comparable to that of Cry1C, formed channels as efficiently as the Cry1A toxins at pH 10.5. These results strongly suggest that although pH can influence toxin activity, additional factors also modulate toxin potency in the insect midgut.

Parasporal Crystal Toxins in Bacillus thuringiensis

2021 ◽  
pp. 125-148
Author(s):  
Carmen Sieiro ◽  
Ángeles Pichardo-Gallardo ◽  
Lara Areal-Hermida ◽  
Raquel Almuiña-González ◽  
Tomás G. Villa
Keyword(s):  
Bacillus Thuringiensis ◽  
Parasporal Crystal ◽  
Crystal Toxins

scholarly journals FlhA Influences Bacillus thuringiensis PlcR-Regulated Gene Transcription, Protein Production, and Virulence

2005 ◽  
Vol 71 (12) ◽  
pp. 8903-8910 ◽  
Author(s):  
Laurent Bouillaut ◽  
Nalini Ramarao ◽  
Christophe Buisson ◽  
Nathalie Gilois ◽  
Michel Gohar ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Virulence Factors ◽  
Gene Transcription ◽  
Galleria Mellonella ◽  
Flagellar Apparatus ◽  
Flagellar Proteins ◽  
Crystal Toxins ◽  
Opportunistic Human Pathogen ◽  
Hemolysin Bl ◽  
Lower Production

ABSTRACT Bacillus thuringiensis and Bacillus cereus are closely related. B. thuringiensis is well known for its entomopathogenic properties, principally due to the synthesis of plasmid-encoded crystal toxins. B. cereus appears to be an emerging opportunistic human pathogen. B. thuringiensis and B. cereus produce many putative virulence factors which are positively controlled by the pleiotropic transcriptional regulator PlcR. The inactivation of plcR decreases but does not abolish virulence, indicating that additional factors like flagella may contribute to pathogenicity. Therefore, we further analyzed a mutant (B. thuringiensis 407 Cry− ΔflhA) previously described as being defective in flagellar apparatus assembly and in motility as well as in the production of hemolysin BL and phospholipases. A large picture of secreted proteins was obtained by two-dimensional electrophoresis analysis, which revealed that flagellar proteins are not secreted and that production of several virulence-associated factors is reduced in the flhA mutant. Moreover, we quantified the effect of FlhA on plcA and hblC gene transcription. The results show that the flhA mutation results in a significant reduction of plcA and hblC transcription. These results indicate that the transcription of several PlcR-regulated virulence factors is coordinated with the flagellar apparatus. Consistently, the flhA mutant also shows a strong decrease in cytotoxicity towards HeLa cells and in virulence against Galleria mellonella larvae following oral and intrahemocoelic inoculation. The decrease in virulence may be due to both a lack of flagella and a lower production of secreted factors. Hence, FlhA appears to be an essential virulence factor with a pleiotropic role.

Lepidopteran-specific crystal toxins from Bacillus thuringiensis form cation- and anion-selective channels in planar lipid bilayers

1993 ◽  
Vol 132 (1) ◽  
Author(s):  
Jean-Louis Schwartz ◽  
Line Garneau ◽  
Diane Savaria ◽  
Luke Masson ◽  
Roland Brousseau ◽  
...  
Keyword(s):  
Bacillus Thuringiensis ◽  
Lipid Bilayers ◽  
Planar Lipid Bilayers ◽  
Crystal Toxins
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