Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Bacillus thuringiensis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 739 records · Page 41Linked to original sources
PubMed2000

[Ribonuclease from Bacillus thuringiensis var. subtoxicus. Gene structure and biosynthesis regulation].

The gene for extracellular guanyl-specific ribonuclease of Bacillus thuringiensis var. subtoxicus (RNase Bth), a close homologue of the B. intermedius RNase (binase), was completely sequenced. Analysis of nucleotide sequences in the regions adjoining RNase genes revealed an identical organization of the chromosomal loci of RNase Bth and binase. Growth characteristics of the Bacillus thuringiensis var. subtoxicus strain and its synthesis of RNase were studied. It was shown that the exogenous inorganic phosphate inhibits the biosynthesis of RNase. At the same time, actinomycin D in low doses stimulates the enzyme synthesis. Comparative analysis of the influence of inorganic phosphate and actinomycin D on the biosynthesis of RNAse Bth and binase suggests a possibility of coincidence of regulatory pathways of synthesis of these enzymes.

Amino Acid Sequence↗
PubMed1999

Binding of Bacillus thuringiensis Cry1Ac toxin to Manduca sexta aminopeptidase-N receptor is not directly related to toxicity.

Bacillus thuringiensis Cry1Ac delta-endotoxin specifically binds a 115-kDa aminopeptidase-N purified from Manduca sexta midgut. Cry1Ac domain III mutations were constructed around a putative sugar-binding pocket and binding to purified aminopeptidase-N and brush border membrane vesicles (BBMV) was compared to toxicity. Q509A, R511A, Y513A, and 509-511 (QNR-AAA) eliminated aminopeptidase-N binding and reduced binding to BBMV. However, toxicity decreased no more than two-fold, indicating activity is not directly correlated with aminopeptidase-N binding. Analysis of toxin binding to aminopeptidase-N in M. sexta is therefore insufficient for predicting toxicity. Mutants retained binding, however, to another BBMV site, suggesting alternative receptors may compensate in vivo.

Acetylgalactosamine↗
PubMed1997

Spo0A represses transcription of the cry toxin genes in Bacillus thuringiensis.

The DNA regions upstream from the genes encoding polypeptides of Bacillus thuringiensis subsp. israelensis larvicidal crystals (cry4A, cry4B, cry11A) contain sequences with similarities to the spo0A box of Bacillus subtilis (or '0A' box) and the promoter recognized by the sigma H-associated RNA polymerase of B. subtilis. Expression of cry-lacZ transcriptional fusions was analysed in various B. thuringiensis genetic backgrounds. The early transcription of the toxin genes was not sporulation-dependent, whereas the late-stage expression at t4-6 was sigma E-dependent. Primer extension analysis confirmed that the cry4- and cry11-type toxin genes were weakly transcribed during the transition phase; expression analysis of a cry11A'-lacZ transcriptional fusion in B. subtilis sporulation mutants confirmed the involvement of the sigma H-RNA polymerase. Primer extension analysis showed that in B. thuringiensis subsp. israelensis, the cry4A and cry11A gene transcription observed at the end of the growth stage was turned off at the beginning of the sporulation phase. The DNA region located upstream from the cry11A gene promoter including the putative '0A' box was deleted. This led to a derepression of the expression of the cry11A operon. These results suggest that the cry4A, cry4B and cry11A toxin genes of B. thuringiensis subsp. Israelensis are transcribed during the transition phase by the RNA polymerase associated with the sigma H factor and are subject to Spo0A repression.

Bacillus subtilis↗
PubMed1990

Isolation of the second Bacillus thuringiensis RNA polymerase that transcribes from a crystal protein gene promoter.

A crystal protein gene of Bacillus thuringiensis subsp. kurstaki HD-1-Dipel is transcribed in vivo from two overlapping promoters that are activated at different times during sporulation. We reported earlier (K. L. Brown and H. R. Whiteley, Proc. Natl. Acad. Sci. USA 85:4166-4170, 1988) that an RNA polymerase containing a sigma subunit with an apparent Mr of 35,000 can transcribe in vitro from the promoter utilized from early to midsporulation. We now report the isolation of an RNA polymerase containing a sigma subunit with an Mr of ca. 28,000; this polymerase activates transcription in vitro from the promoter used from mid- to late sporulation. This form of RNA polymerase also directs transcription in vitro from promoters preceding two other crystal protein genes and a gene coding for a spore coat protein. On the basis of a comparison of the four promoters, we propose the following consensus sequence for the -10 region recognized by RNA polymerase containing the Mr-28,000 sigma subunit: 5'-TNATANNaTGag-3'. No consensus sequence could be derived for the -35 region. When the N-terminal amino acid sequence of the sigma 28 polypeptide was aligned with the amino acid sequences of known sigma subunits, significant homology was found with the N terminus of the mature form of the sigma K subunit of RNA polymerase isolated from sporulating cells of Bacillus subtilis.

Amino Acid Sequence↗
PubMedDate not supplied

[Expression of a partially modified delta-endotoxin gene from Bacillus thuringiensis var. tenebrionis in transgenic potato plants].

A modified gene (Bt77) of delta-endotoxin from Bacillus thuringiensis var. tenebrionis was constructed and cloned into pMON505. This binary transformation vector was introduced into Agrobacterium tumefaciens strains containing different helper disarmed Ti-plasmids, LBA4404, A281, and CBE21. These Agrobacterium strains were used to transform potato stem segments (S. tuberosum, cv Desiree, Resy, Temp, Granat). Regenerants were selected on kanamycin-containing media. The presence of the Bt77 sequence in plant genomic DNA was confirmed by PCR analysis. Bt gene expression was studied in regenerated plants. Western blot analysis revealed that transgenic plants produced the Bt protein in the range of 0.005-0.02% of total protein. Total protection against insect damage of leaf tissue from these plants was observed in laboratory bioassays with of Colorado beetle larvae. Transgenic plants showed incomplete protection from CB larvae.

Agrobacterium tumefaciens↗
PubMed2002

Regulation of crystal protein biosynthesis by Bacillus thuringiensis: I. Effects of mineral elements and pH.

Crystal protein synthesis by a local isolate of Bacillus thuringiensis was monitored and compared in association with growth and sporulation in media differing in mineral element content. Mg and Cu were the most important metals for the biosynthesis of 135 kDa and 65 kDa toxin components in that the former was essential and the latter was greatly stimulatory at 10(-6) to 10(-7) M concentration. Also the inclusion of Mn favored toxin production at concentrations ranging from 3 x 10(-4) to 10(-5) M. The omission of Zn and Ca had no effect on toxin formation. Crystal protein synthesis and sporulation did not generally seem to be co-regulated by the minerals as these processes responded differently to mineral levels. There was no evidence for suppression of biosynthesis by inorganic phosphate over a range of 3 to 100 mM. Crystal protein production was more efficient in buffered medium, especially when the initial pH was adjusted to 6.5.

Bacillus thuringiensis↗
PubMed1989

Delineation of the toxin coding fragments and an insect-specificity region of a dual toxicity Bacillus thuringiensis crystal protein gene.

A series of deletion mutants have been constructed from the dual toxicity Bacillus thuringiensis aizawai IC1 (Bta IC1) crystal protein gene. The mutant toxin genes were expressed in Escherichia coli, their protein products purified and the authenticity of these mutant proteins confirmed immunologically. Analysis of the toxicity spectra of these mutants revealed that lepidopteran toxicity is located on the N-terminal region of the toxin between residues Ile30-Glu595. 3' deletion of a further 37 residues from Glu595 of the lepidopteran-specific toxin abolished lepidopteran toxicity but the resulting protein consisting of residues Ile30-Gly558 was still fully toxic to dipteran larvae and cells. Another mutant crystal protein gene truncated to encode residues between Ile30-Gly563 was toxic only to diptera. These data indicate that the determinants of lepidopteran specificity in the Bta IC1 toxin are located between residues Gly558-Glu595 and that the N-terminal portion of the toxin between Ile30-Gly558 is sufficient to express dipteran toxicity.

Amino Acid Sequence↗
PubMed1993

Effects on toxicity of eliminating a cleavage site in a predicted interhelical loop in Bacillus thuringiensis CryIVB delta-endotoxin.

When activated by treatment with mosquito (Aedes aegypti) gut extract, the Bacillus thuringiensis CryIVB delta-endotoxin lysed A. aegypti cells in vitro. SDS-PAGE and N-terminal sequence determination showed that in addition to removal of the C-terminal half of the molecule, the activated toxin had undergone proteolytic cleavage at two internal regions producing 47-48-kDa and 16-18-kDa polypeptides. Aligning the CryIVB protein sequence with the crystallographic structure of the CryIIIA toxin suggested that one set of cleavages occurred in a region before the start of the N-terminal helical bundle and the second cleavage site occurred in a predicted loop between helices 5 and 6 in the bundle at arginine-203. To investigate the suggestion by Li et al. that interhelical proteolysis is important in the cytolytic mechanism of these toxins, arginine-203 was substituted by alanine. The mutated toxin now resisted proteolysis at this position and showed a marked decrease in cytolysis in vitro but an increase in larvicidal activity.

Aedes↗
PubMed1995

The insecticidal CryIB crystal protein of Bacillus thuringiensis ssp. thuringiensis has dual specificity to coleopteran and lepidopteran larvae.

The crystals found in sporulation extracts of Bacillus thuringiensis (Berliner) contain proteins that are highly toxic to insects. Different crystal proteins exhibit distinct specificities for restricted groups of insects. An uncharacterized strain of B. thuringiensis (BtS2), derived from China, was found to carry several crystal protein genes and to be toxic to a wide variety of insects, including some coleopterans. Surprisingly, the coleopteran toxicity was traced to a CryIB-class protein. The previously cloned CryIB protein from B. thuringiensis ssp. thuringiensis strain HD-290-I, which was believed to be lepidopteran-specific, was also found to be toxic to at least two species of coleopteran larvae under certain conditions. In contrast to CryIB toxicity toward lepidopterans, the coleopteran activity of CryIB is enhanced by solubilization and by truncation with trypsin prior to administration. The magnitude of this effect varies with the host species and is reversed for the one lepidopteran tested. These results suggest that, for at least some insects, the apparent host specificity of CryIB may depend both on differences in midgut environment and on differences in toxin-receptor interaction. The results of insect toxicity experiments with a series of deletion mutants allowed definition of a CryIB protein fragment of ca. 65 kDa as the smallest peptide that retains bioactivity against both lepidopteran and coleopteran larvae. Deletions smaller than this resulted in the production of a protein that was nontoxic to both lepidopteran and coleopteran larvae.

Amino Acid Sequence↗
PubMed1993

Is an amphiphilic region responsible for the haemolytic activity of Bacillus thuringiensis toxin?

The amino acid sequence of the 27 kDa protein responsible for the haemolytic activity of Bacillus thuringiensis subsp. israelensis toxin has been analysed by secondary structure prediction, helical wheel/net diagrams and molecular mechanics calculations. We found that segment 116-126 presumably forms a strongly amphiphilic alpha-helix. This is supported by the findings that the synthesized segment 116-126 (a) has a significant alpha-helical content in water, and (b) displays an in vitro haemolytic activity comparable to that of bee venom peptide melittin. As segment 116-126 is present in the haemolyzing, but not present in the non-haemolyzing proteins from B. thuringiensis toxins, we suggest that this segment is responsible for the lytic potential of the B. thuringiensis subsp. israelensis protein.

Amino Acid Sequence↗
PubMed1994

Characterization of larvicidal toxin protein from Bacillus thuringiensis serovar japonensis strain Buibui specific for scarabaeid beetles.

The delta-endo toxin proteins from Bacillus thuringiensis which kill the larvae of various scarabaeid beetles such as Anomala cuprea, A. rufocuprea and Popillia japonica were purified by DEAE ion exchange chromatography. A protein with a molecular size of 130 kDa was purified. During the purification a minor peak was also detected which was estimated to be 67 kDa by SDS-PAGE. Both 130 and 67 kDa proteins showed larvicidal activity against A. cuprea. The lethal concentration of the 130 kDa protein which killed 50% of the larvae tested (LC50) against A. cuprea was 2 micrograms g-1 compost. A comparison by SDS-PAGE of the V8 protease digestion pattern of the 130 and 67 kDa larvicidal proteins showed that proteolytic resistant core peptides of approximately 60 kDa molecular size were resulted. The N-terminus amino acid sequence of the 130 and 67 kDa proteins was determined to be NH2-XXPNNQNEYEIIDAL and NH2-XSRNPGTFI, respectively, which is not identical to the sequence of CryIA, CryIB, CryIC and CryIII proteins.

Amino Acid Sequence↗
PubMed2002

Evaluation of the natural refuge function for Helicoverpa arnigera (Lepidoptera: Noctuidae) within Bacillus thuringiensis transgenic cotton growing areas in north China.

The density of Helicoverpa armigera (Hübner) populations on Bacillus thuringiensis Berliner (Bt) transgenic cotton, corn, peanut, and soybean; differences in its development on Bt cotton and common (nontransgenic) cotton; and the potential for mating among populations from Bt cotton fields and other crop fields were investigated in the suburbs of Xinxiang City (Henan Province) and Langfang City (Hebei Province) in the southern and northern parts of north China, respectively. Although development of H. armigera on Bt cotton was much slower than on common cotton, there was a still high probability of mating between populations from Bt cotton and other sources due to the scattered emergence pattern of H. armigera adults, and overlap of the second and third generations. In a cotton and corn growing region, early and late planted corn provided suitable refugia for the third and fourth generations of H. armigera, but not for the second generation. In a cotton and soybean/ peanut mix system, noncotton crops provided a natural refugia from the second- to fourth-generation H. armigera, but function of the refuge would closely depend on the proportion of Bt cotton. Consequently, it may be necessary to compensate the original mixed cropping patterns in different areas for delaying resistance development of H. armigera to Bt cotton.

Animals↗
PubMed2004

Bt-R1a extracellular cadherin repeat 12 mediates Bacillus thuringiensis Cry1Ab binding and cytotoxicity.

The cadherin protein Bt-R(1a) is a receptor for Bacillus thuringiensis Cry1A toxins in Manduca sexta. Cry1Ab toxin is reported to bind specific epitopes located in extracellular cadherin repeat (CR) 7 and CR11 on Bt-R(1) (Gomez, B., Miranda-Rios, J., Riudino-Pinera, E., Oltean, D. I., Gill, S. S., Bravo, A., and Soberon, M. (2002) J. Biol. Chem. 277, 30137-30143; Dorsch, J. A., Candas, M., Griko, N., Maaty, W., Midboe, E., Vadlamudi, R., and Bulla, L. (2002) Insect Biochem. Mol. Biol. 32, 1025-1036). We transiently expressed CR domains of Bt-R(1a) in Drosophila melanogaster Schneider 2 (S2) cells as fusion peptides between a signal peptide and a terminal region that included membrane-proximal, membrane-spanning, and cytoplasmic domains. A domain consisting of CR11 and 12 was the minimal (125)I-Cry1Ab binding region detected under denaturing conditions. Only CR12 was essential for Cry1Ab binding and cytotoxicity to S2 cells when tested under native conditions. Under these conditions expressed CR12 bound (125)I-Cry1Ab with high affinity (K(com) = 2.9 nm). Flow cytometry assays showed that expression of CR12 conferred susceptibility to Cry1Ab in S2 cells. Derivatives of Bt-R(1a) with separate deletions of CR7, 11, and 12 were expressed in S2 cells. Only deletion of CR12 caused loss of Cry1Ab binding and cytotoxicity. These results demonstrate that CR12 is the essential Cry1Ab binding component on Bt-R(1) that mediates Cry1Ab-induced cytotoxicity.

Animals↗
PubMed2004

Oligomerization triggers binding of a Bacillus thuringiensis Cry1Ab pore-forming toxin to aminopeptidase N receptor leading to insertion into membrane microdomains.

Bacillus thuringiensis Cry1A toxins, in contrast to other pore-forming toxins, bind two putative receptor molecules, aminopeptidase N (APN) and cadherin-like proteins. Here we show that Cry1Ab toxin binding to these two receptors depends on the toxins' oligomeric structure. Toxin monomeric structure binds to Bt-R1, a cadherin-like protein, that induces proteolytic processing and oligomerization of the toxin (Gomez, I., Sanchez, J., Miranda, R., Bravo A., Soberon, M., FEBS Lett. (2002) 513, 242-246), while the oligomeric structure binds APN, which drives the toxin into the detergent-resistant membrane (DRM) microdomains causing pore formation. Cleavage of APN by phospholipase C prevented the location of Cry1Ab oligomer and Bt-R1 in the DRM microdomains and also attenuates toxin insertion into membranes despite the presence of Bt-R1. Immunoprecipitation experiments demonstrated that initial Cry1Ab toxin binding to Bt-R1 is followed by binding to APN. Also, immunoprecipitation of Cry1Ab toxin-binding proteins using pure oligomeric or monomeric structures showed that APN was more efficiently detected in samples immunoprecipitated with the oligomeric structure, while Bt-R1 was preferentially detected in samples immunoprecipitated with the monomeric Cry1Ab. These data agrees with the 200-fold higher apparent affinity of the oligomer than that of the monomer to an APN enriched protein extract. Our data suggest that the two receptors interact sequentially with different structural species of the toxin leading to its efficient membrane insertion.

Animals↗
PubMed2000

Biocontrol of the sugarcane borer Eldana saccharina by expression of the Bacillus thuringiensis cry1Ac7 and Serratia marcescens chiA genes in sugarcane-associated bacteria.

The cry1Ac7 gene of Bacillus thuringiensis strain 234, showing activity against the sugarcane borer Eldana saccharina, was cloned under the control of the tac promoter. The fusion was introduced into the broad-host-range plasmid pKT240 and the integration vector pJFF350 and without the tac promoter into the broad-host-range plasmids pML122 and pKmM0. These plasmids were introduced into a Pseudomonas fluorescens strain isolated from the phylloplane of sugarcane and the endophytic bacterium Herbaspirillum seropedicae found in sugarcane. The ptac-cry1Ac7 construct was introduced into the chromosome of P. fluorescens using the integration vector pJFF350 carrying the artificial interposon Omegon-Km. Western blot analysis showed that the expression levels of the integrated cry1Ac7 gene were much higher under the control of the tac promoter than under the control of its endogenous promoter. It was also determined that multicopy expression in P. fluorescens and H. seropedicae of ptac-cry1Ac7 carried on pKT240 caused plasmid instability with no detectable protein expression. In H. seropedicae, more Cry1Ac7 toxin was produced when the gene was cloned under the control of the Nm(r) promoter on pML122 than in the opposite orientation and bioassays showed that the former resulted in higher mortality of E. saccharina larvae than the latter. P. fluorescens 14::ptac-tox resulted in higher mortality of larvae than did P. fluorescens 14::tox. An increased toxic effect was observed when P. fluorescens 14::ptac-tox was combined with P. fluorescens carrying the Serratia marcescens chitinase gene chiA, under the control of the tac promoter, integrated into the chromosome.

Animals↗
PubMed2006

Cadherin-based resistance to Bacillus thuringiensis cotton in hybrid strains of pink bollworm: fitness costs and incomplete resistance.

Recessive resistance to Bacillus thuringiensis (Bt) cotton, Gossypium hirsutum L., in laboratory-selected strains of pink bollworm, Pectinophora gossypiella (Saunders), is associated with three resistance alleles (r1, r2, and r3) of a cadherin gene. Previous experiments based on measurement of fitness components in Bt-resistant and Bt-susceptible strains revealed that fitness costs and incomplete resistance are associated with resistance. Here, we used two hybrid strains of pink bollworm, each containing a mixture of susceptible and resistant individuals, and polymerase chain reaction (PCR) amplifications to test the association between cadherin genotype and fitness components for individuals sharing a common genetic background. All survivors on Bt cotton had two r alleles, confirming that recessive cadherin alleles are tightly linked with resistance to Bt cotton. On non-Bt cotton, significantly greater developmental time for rr than ss larvae indicated a recessive fitness cost, but costs did not affect survival or pupal weight. Incomplete resistance was manifested as longer developmental time, lower survival, and smaller pupal weight in rr individuals developing on Bt cotton compared with non-Bt cotton. As in previous experiments, no significant variation in performance on Bt cotton was detected among rr genotypes. However, a meta-analysis of data from seven experiments revealed that survival on Bt cotton relative to non-Bt cotton was lower in r2r3 and higher in r1r2 compared with the other rr genotypes. Assessment of fitness components associated with cadherin genotypes in hybrid strains of pink bollworm confirms that recessive resistance to Bt cotton is associated with recessive fitness costs and incomplete resistance.

Animals↗
PubMed2002

Expression of the mel gene from Pseudomonas maltophilia in Bacillus thuringiensis.

AIMS: The objective of this work was to express a novel mel gene, responsible for melanin formation, in Bacillus thuringiensis. METHODS AND RESULTS: A novel mel gene from Pseudomonas maltophilia was sub-cloned into B. thuringiensis using a shuttle vector plasmid and electroporation. Results revealed that the mel gene was expressed under the control of the CryIIIA promoter in B. thuringiensis and conferred u.v. protection on the recipient strain. CONCLUSIONS: The novel mel gene from Ps. maltophilia expressed in B. thuringiensis conferred u.v. protection on the recipient strain. SIGNIFICANCE AND IMPACT OF THE STUDY: Products containing B. thuringiensis for pest control are sensitive to u.v. degradation. As melanin has the ability to act as a u.v. absorber, a recombinant B. thuringiensis strain producing melanin provides a new stability for B. thuringiensis preparations.

Bacillus thuringiensis↗