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PubMed1990

[Presence of flagellar antigenic subfactors in serotype 1 of Bacillus thuringiensis].

The strain G was isolated from a dead army worm (Leucania separata Walker) in corn field, at Hebei. It has the typical morphological characteristics of Bacillus thuringiensis. The serological analysis showed that the flagellar suspensions of the strain G was agglutinated only by the antisera against the H1 antigen and not by the antisera against the other 22 known H-antigens. The agglutination titre was 1:6,400. The flagellar suspension of the serotype 1, subsp. thuringiensis, was agglutinated by the antiserum against the strain G, with a titre of 1:12,800. However, the cross-saturation of antisera showed that there were different fractions in the H1 antigen. The H antiserum against subsp. thuringiensis still agglutinated with subsp. thuringiensis, having a titre of 1:6,400, even if it was fully saturated by strain G. When it was saturated by subsp. thuringiensis the H antiserum of strain G did not agglutinate by himself. Therefore, the H1 antigen (subsp. thuringiensis) must be divided into subfactors H1alb and strain G antigen is H1a. On the basis of this study, we propose the strain G represents the serotype H1a under the name of Bacillus thuringiensis subsp. hebeiensis.

Animals↗
PubMed1989

Phosphatidylinositol-specific phospholipase C of Bacillus thuringiensis as a probe for the distribution of phosphatidylinositol in hepatocyte membranes.

Phosphatidylinositol-specific phospholipase C (PI-PLC) produced by Bacillus thuringiensis has been used as a probe for the distribution of phosphatidylinositol in hepatocyte membranes. Approx. 50% of this phospholipid was hydrolysed in microsomal vesicles (endoplasmic reticulum) with no significant hydrolysis of the remaining membrane phospholipids. Latency of mannose-6-phosphatase was retained during treatment indicating that the vesicles remained impermeable. Stripping of the ribosomes did not increase hydrolysis of phosphatidylinositol; however, when the vesicles were opened using dilute sodium carbonate, hydrolysis increased to greater than 90%. Hydrolysis of phosphatidylinositol of Golgi membranes was 35% and of plasma membranes was 50%. After treatment with PI-PLC, radiolabelled secretory proteins were retained in Golgi membranes and trapped lactate dehydrogenase was retained in plasma-membrane preparations indicating that the vesicles remained closed. Hydrolysis of phosphatidylinositol increased to greater than 90% when the membranes were opened by treatment with dilute sodium carbonate. These observations indicate that PI-PLC of Bacillus thuringiensis is a suitable probe for the distribution of phosphatidylinositol in membranes, and that in liver membranes this phospholipid occurs on each side of the bilayer, a topography consistent with its diverse roles.

Animals↗
PubMed1990

Effects of Bacillus thuringiensis delta-endotoxin on the permeability of brush border membrane vesicles from tobacco hornworm (Manduca sexta) midgut.

1. The effect of two recombinant Bacillus thuringiensis delta-endotoxins on brush border membrane vesicles of Manduca sexta midgut was investigated using an in vitro assay system, based on ion-amino acid cotransport. 2. A CryIA(b)-toxin provoked an increase in the permeability of the vesicles. 3. A CryIB-toxin, not toxic to M. sexta larvae in vivo, had no effect in our assay. 4. In contrast to earlier reports, the increase in permeability was found to be neither selective for K+ nor specifically inhibited by Ca2+ or Ba2+. 5. Our data support the hypothesis that B. thuringiensis delta-endotoxins create non-specific pores.

Alanine↗
PubMed2004

Microcalorimetric investigation on the growth model and the protein yield of Bacillus thuringiensis.

A novel microcalorimetric technique based on the bacterial heat output was applied to evaluate the special growth model, the protein expression and the generation time of Bacillus thuringiensis for the first time. The thermogenic curves of the aerobic metabolism of B. thuringiensis strains YBT-833, YBT-1520 and YBT-833-2-1 were determined by using an LKB-2277 BioActivity Monitor. The analysis of the thermogenic curves indicated both the mutant strain and the wild-type strains followed the same linear growth model during sporulation. The metabolism heat output revealed heat output was correlated to the yield of the insecticidal crystal proteins (ICPs) very well, the more protein product, and the less heat output. Based on the data acquired, we proposed that this method could be a useful tool in monitoring the fermentation of B. thuringiensis.

Bacillus thuringiensis↗
PubMed1989

Release of PI-anchoring enzymes and other effects of phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis on TN-368 cells from a moth ovary.

Release of PI-anchoring enzymes and other effects of phosphatidylinositol-specific phospholipase C from Bacillus thuringiensis on TN-368 cells from a moth ovary. Toxicon 27, 637-645, 1989.--The effect of phosphatidylinositol-specific phospholipase C(PIPLC) from Bacillus thuringiensis was investigated on TN-368 cells, derived from the ovary of a moth, Trichoplusia ni. Quantitative analysis of lipids showed that phosphatidylinositol (PI) was contained as one of the major phospholipids in TN-368 cells, whereas sphingomyelin and cholesterol were minor lipid components. When TN-368 cells were treated with PIPLC, significant amounts of alkaline phosphatase, 5'-nucleotidase and beta-glucosidase were released from these cells. Thus, these enzymes were shown to be PI-anchoring proteins in the plasma membrane of these cells. In the presence of 4.2 units of PIPLC, the cell growth of TN-368 was inhibited by 50%. In contrast with normal cells, the cells cultured in the presence of PIPLC became swollen and globular, losing their protoplasmic extensions. Also, there was degeneration of the interior of TN-368 cells cultivated in the presence of PIPLC. Mitochondria became swollen with a decrease in number of granules while the crista turned transparent. Also, an increase in lysosomes was observed and vacuoles seemingly derived from smooth endoplasmic reticula appeared.

Animals↗
PubMed2005

Low persistence of Bacillus thuringiensis serovar israelensis spores in four mosquito biotopes of a salt marsh in southern France.

We studied the persistence of Bacillus thuringiensis serovar israelensis (Bti) in a typical breeding site of the mosquito Ochlerotatus caspius in a particularly sensitive salt marsh ecosystem following two Bti-based larvicidal applications (Vectobac 12AS, 1.95 L/ha). The treated area was composed of four larval biotopes that differed in terms of the most representative plant species (Sarcocornia fruticosa, Bolboschoenus maritimus, Phragmites australis, and Juncus maritimus) and the physical and chemical characteristics of the soil. We sampled water, soil, and plants at various times before and after the applications (from spring to autumn, 2001) and quantified the spores of B. thuringiensis (Bt) and Bacillus species. The B. cereus group accounted for between 0% and 20% of all Bacillus spp. before application depending on the larval biotope. No Bti were found before application. The variation in the quantity of bacilli during the mosquito breeding season depended more on the larval biotope than on the season or the larvicidal application. More bacilli were found in soil (10(4)-10(6) spores/g) than on plant samples (10(2)-10(4) spores/g). The abundance in water (10(5) to 10(7) spores/L) appeared to be correlated to the water level of the breeding site. The number of Bti spores increased just after application, after declining; no spores were detected in soil or water 3 months after application. However, low numbers of Bti spores were present on foliage from three of the four studied plant strata. In conclusion, the larvicidal application has very little impact on Bacillus spp. flora after one breeding season (two applications).

Animals↗
PubMed2001

Cyt1Aa from Bacillus thuringiensis subsp. israelensis is toxic to the diamondback moth, Plutella xylostella, and synergizes the activity of Cry1Ac towards a resistant strain.

The Bacillus thuringiensis subsp. israelensis cytolytic protein Cyt1Aa was found to be toxic to an insecticide-susceptible laboratory population of Plutella xylostella. Cry1Ac-resistant populations of P. xylostella showed various degrees of resistance to Cyt1Aa. Cyt1Aa/Cry1Ac mixtures showed a marked level of synergism in the Cry1Ac-resistant populations.

Animals↗
PubMed2000

Bacillus thuringiensis crystal delta-endotoxin: role of proteases in the conversion of protoxin to toxin.

The conversion of delta-endoprotoxins of Bacillus thuringiensis to active toxins is mediated by trypsin, insect gut (exogenous) and bacterial (endogenous) proteases. The biochemical aspects of exogenous and endogenous proteases involved in the conversion of protoxin to toxin are reviewed. Perhaps, these proteases also play a role in influencing the host range of toxin and in the development of resistance to toxin.

Animals↗
PubMed2000

Characterization study of the sporulation kinetics of Bacillus thuringiensis.

A wild-type and an rDNA strain of Bacillus thuringiensis were cultured in a net-draft-tube modified 20-L airlift bioreactor. A comparison of the sporulation patterns suggests that the early sporulation strain has a lower final spore count. Results from off-gas analysis suggests that the CO(2) profile could be an alternative indication to spore counts for the examination of fermentation performance or even the mortality in bioassay of the cultivation product. The difference in mortality tests exhibited by the microorganism was attributed to different patterns of sporulation as well as different levels of gene control inside the cell itself. The sporulation kinetics of B. thuringiensis was simulated by a simple modified Hill equation, where the initial glucose concentration could affect the timing of the onset of sporulation. The equation matches well with the experimental sporulation data for B. thuringiensis in both wild-type and rDNA strains.

Bacillus thuringiensis↗
PubMed2001

Ion channels induced in planar lipid bilayers by the Bacillus thuringiensis toxin Cry1Aa in the presence of gypsy moth (Lymantria dispar) brush border membrane.

The apical brush border membrane, the main target site of Bacillus thuringiensis toxins, was isolated from gypsy moth (Lymantria dispar) larval midguts and fused to artificial planar lipid bilayer membranes. Under asymmetrical N-methyl-d-glucamine-HCl conditions (450 mm cis/150 mm trans, pH 9.0), which significantly reduce endogenous channel activity, trypsin-activated Cry1Aa, a B. thuringiensis insecticidal protein active against the gypsy moth in vivo, induced a large increase in bilayer membrane conductance at much lower concentrations (1.1-2.15 nm) than in receptor-free bilayer membranes. At least 5 main single-channel transitions with conductances ranging from 85 to 420 pS were resolved. These Cry1Aa channels share similar ionic selectivity with P(Cl)/P(NMDG) permeability ratios ranging from 4 to 8. They show no evidence of current rectification. Analysis of the macroscopic current flowing through the composite bilayer suggested voltage-dependence of several channels. In comparison, the conductance of the pores formed by 100-500 nm Cry1Aa in receptor-free bilayer membranes was significantly smaller (about 8-fold) and their P(Cl)/P(NMDG) permeability ratios were also reduced (2- to 4-fold). This study provides a detailed demonstration that the target insect midgut brush border membrane material promotes considerably pore formation by a B. thuringiensis Cry toxin and that this interaction results in altered channel properties.

Animals↗
PubMed2005

Broadening the insecticidal spectrum of Lepidoptera-specific Bacillus thuringiensis strains by chromosomal integration of cry3A.

A TnpI-TnpIA-mediated and thermosensitive recombination system was developed to construct genetically modified Bacillus thuringiensis strains encoding a crystal protein particularly active against Coleopteran species. Based on B. thuringiensis transposon Tn4430, an integrative vector, pBMB-R14E, was constructed, by which the cry3A delta-endotoxin gene highly toxic to Lepidoptera was delivered into a wildtype B. thuringiensis subsp. kurstaki strain YBT1520. The cry3A gene was integrated into the chromosome of the host strain. Then the integrative vector was eliminated by moving recombinant cultures to 46 degrees C. Two recombinant B. thuringiensis strains, BMB1520-S and BMB1520-T, were obtained. In recombinant strains, the cry3A gene was stably expressed in measurable amounts and did not reduce the expression of endogenous crystal protein genes. Bioassay results showed that BMB1520-S and BMB1520-T, in addition to the activity against lepidopteran Plutella xylostella third-instar larvae present in the parental strains, exhibited a high level of activity against coleopteran Rhyllodecta vulgatissima third-instar larvae, absent from the parental strains.

Animals↗
PubMed2005

Novel antibacterial proteins from entomocidal crystals of Bacillus thuringiensis ssp. israelensis.

Proteins with molecular masses of 36 and 34 kDa (Bti36 and Bti34) were isolated from entomocidal crystals formed by Bacillus thuringiensis ssp. israelensis cells. The samples of Bti36 contained the admixture of a protein with a molecular mass of 33 kDa (Bti33), apparently a product of proteolysis of Bti36. These 3 proteins are significantly different in N-terminal sequences from known delta-endotoxins of B. thuringiensis and show antibacterial activity toward Micrococcus luteus. The combination of Bti36 and Bti33 also suppresses the growth of some other microorganisms including Streptomyces chrysomallus. The effects of the mixture of Bti36 and Bti33 on the M. luteus cell surface and on the surface of S. chrysomallus cells and exospores are similar, but they are different from the effect of endotoxin Cry11A on micrococcal cells.

Aedes↗
PubMed1995

Germination of Bacillus thuringiensis spores in bacteriophagous nematodes (Nematoda: Rhabditida).

During screening of Bacillus thuringiensis isolates for nematicidal activity it was observed that spores of B. thuringiensis germinated in the intestine of bacteriophagous nematodes in the presence of antibiotics. This phenomenon was studied more closely by scanning electron microscopy. The nematodes were fed with bacterial spore-crystal mixtures in axenic culture medium supplemented with tetracyclin and chloramphenicol. Germination of spores was rare but was more frequently observed in Panagrellus redivivus than in other nematode species investigated. Germination of spores in the nematode intestine resulted in the colonization of the entire nematode within 24 hr. Crude nematode tissue preparations supported germination and subsequent growth of B. thuringiensis spores and vegetative cells. The mechanism for the loss of antibiotic activity in the nematode intestine is unknown. Since B. thuringiensis requires a nutrient-rich environment for reproduction, e.g., a cadaver, bacteriophagous nematodes may serve as suitable hosts for B. thuringiensis.

Animals↗
PubMed1991

Cytotoxicity of a cloned Bacillus thuringiensis subsp. israelensis CryIVB toxin to an Aedes aegypti cell line.

A cloned CryIVB toxin was purified from a cured strain of Bacillus thuringiensis (BT) containing the cryIVB gene on the recombinant plasmid Cam135. Solubilized protoxin was treated with Aedes gut extract or trypsin for varying times and tested for toxicity in vitro on three dipteran and one lepidopteran cell line. Treatment with the Aedes extract but not trypsin, produced an active toxin which lysed only Aedes aegypti cells out of those tested. This activation was time-dependent reaching a maximum after 6 h. Both the Aedes extract-treated and trypsin-treated toxin killed A. aegypti larvae, but this toxicity declined rapidly with increasing time of exposure to the proteolytic preparations.

Aedes↗
PubMed1999

Two types of entomocidal crystals of Bacillus thuringiensis ssp. finitimus have the same set of unique delta-endotoxins.

The strain B-1166 differs from the other strains of Bacillus thuringiensis ssp. finitimus because it has two crystal types with different localization in the sporulating cell, i.e., inside and outside of exosporium membrane. Two dissociants of the strain were obtained containing only one of the crystal types. The initial strain produces at least three various delta-endotoxins (Fin2, Fin3, and Fin5) differing from all other known entomocidal proteins; Fin2 and Fin3 are similar to each other but differ from Fin5. Both crystal types contain the same endotoxins (Fin2, Fin3, and Fin5). In the B-1166 strain the site of crystal deposition is not determined by their protein composition.

Amino Acid Sequence↗
PubMed1995

Irreversible binding kinetics of Bacillus thuringiensis CryIA delta-endotoxins to gypsy moth brush border membrane vesicles is directly correlated to toxicity.

To examine the binding of Bacillus thuringiensis delta-endotoxins, CryIAa, CryIAb, and CryIAc, to Lymantria dispar (gypsy moth) brush border membrane vesicles (BBMV), saturation kinetic analyses were conducted according to a two-step interaction scheme [formula: see text] for delta-endotoxin binding to BBMV, rather than the one-step reversible binding presented in prior reports. The order of toxicity of the delta-endotoxins, as measured by the dose required for a 50% inhibition of weight gain (ID50), was CryIAa (77.3 ng) > CryIAb (157 ng) > CryIAc (187 ng). While both the maximum extent of binding, Bmax, and the half-maximum insertion rate concentration, K1/2, was observed to be indirectly related to toxicity, the rate constant of irreversible binding, k2, was found to be directly correlated to toxicity.

Animals↗
PubMed1993

Full expression of the cryIIIA toxin gene of Bacillus thuringiensis requires a distant upstream DNA sequence affecting transcription.

The cryIIIA gene encoding a coleopteran-specific toxin is poorly expressed in Bacillus thuringiensis when cloned in a low-copy-number plasmid. This weak expression is observed when the gene is cloned only with its promoter and its putative terminator. cryIIIA gene expression was analyzed by using deletion derivatives of a larger DNA fragment carrying the toxin gene and additional adjacent sequences. The results indicate that a 1-kb DNA fragment located 400 bp upstream of the promoter strongly enhances CryIIIA production in B. thuringiensis sporulating cells. Similar results were obtained when the low-copy-number plasmid pHT304 carrying transcriptional fusions between upstream regions of cryIIIA and the lacZ gene was used. Analysis of the start sites, the sizes, and the amounts of cryIIIA-specific mRNAs shows that the enhancement occurs at the transcriptional level by increasing the number of cryIIIA-specific transcripts from the onset of sporulation to about 6 h after the onset of sporulation. The nucleotide sequence of the 1-kb activating fragment and of the 700 bp containing the promoter region and the 5' end of cryIIIA were determined. No potential protein-coding sequences were found upstream of the promoter. The major characteristic of the 1-kb activating fragment is the presence of a 220-bp A + T-rich region.

Bacillus thuringiensis↗
PubMedDate not supplied

Bacillus thuringiensis cry3Ca1 protein is toxic to the Colorado potato beetle, Leptinotarsa decemlineata (Say).

We expressed the wild-type cry3Aa3 and cry3Ca1 Bacillus thuringiensis genes, which code for insecticidal proteins, in an Escherichia coli expression system. Highly purified preparations of the soluble delta-endotoxins were used to perform comparative bioassays with third-instar larvae of the Colorado potato beetle (CPB). Acute mortality data showed that Cry3Ca1 (LD(50) = 320.1 ng) was 2-fold more toxic than Cry3Aa3 (LD(50) = 672.9 ng). We also compared the chronic effects of sublethal doses of these toxins by measuring the consumption of untreated foliage and monitoring survival and development for 6 days after intoxication. No significant additional mortality was recorded, but we found that surviving larvae fed Cry3Ca1 consumed foliage at a slower rate than the larvae fed Cry3Aa3, suggesting more damage to their digestive epithelium. This study, the first assessment of the toxicity of cry3Ca1 in third-instar CPB, suggests cry3Ca1 will prove useful for the control of this important insect pest.

Animals↗