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PubMed1998

SASP (small, acid-soluble spore proteins) and spore properties in Bacillus thuringiensis israelensis and Bacillus sphaericus.

Entomopathogenic bacilli B. thuringiensis israelensis (Bti) and B. sphaericus (Bf) exhibit low survival on field application. It was previously shown that their spores are very sensitive to different stress effectors (heat, UV light) and especially to osmotic variations. Since SASP (Small, Acid-Soluble Spore Proteins), alpha/beta and gamma type, are involved in spore tolerance to heat, UV light, peroxide, and salt, they were analyzed in Bti and Bf. The molecular weight, migration pattern and amino acid composition of different SASP were determined and compared with other bacilli, in particular to B. subtilis. A relation between spore osmotolerance, SASP content, and amino acid composition was shown. In addition, the absence of gamma SASP in Bti and Bf is discussed.

Bacillus↗

PubMed2002

Cry1A toxins of Bacillus thuringiensis bind specifically to a region adjacent to the membrane-proximal extracellular domain of BT-R(1) in Manduca sexta: involvement of a cadherin in the entomopathogenicity of Bacillus thuringiensis.

Many subspecies of the soil bacterium Bacillus thuringiensis produce various parasporal crystal proteins, also known as Cry toxins, that exhibit insecticidal activity upon binding to specific receptors in the midgut of susceptible insects. One such receptor, BT-R(1) (210 kDa), is a cadherin located in the midgut epithelium of the tobacco hornworm, Manduca sexta. It has a high binding affinity (K(d) approximately 1nM) for the Cry1A toxins of B. thuringiensis. Truncation analysis of BT-R(1) revealed that the only fragment capable of binding the Cry1A toxins of B. thuringiensis was a contiguous 169-amino acid sequence adjacent to the membrane-proximal extracellular domain. The purified toxin-binding fragment acted as an antagonist to Cry1Ab toxin by blocking the binding of toxin to the tobacco hornworm midgut and inhibiting insecticidal action. Exogenous Cry1Ab toxin bound to intact COS-7 cells expressing BT-R(1) cDNA, subsequently killing the cells. Recruitment of BT-R(1) by B. thuringiensis indicates that the bacterium interacts with a specific cell adhesion molecule during its pathogenesis. Apparently, Cry toxins, like other bacterial toxins, attack epithelial barriers by targeting cell adhesion molecules within susceptible insect hosts.

Amino Acid Sequence↗

PubMed1990

Relative potency of Bacillus thuringiensis var. israelensis and Bacillus sphaericus 2362 for Mansonia titillans and Mansonia dyari.

Bacillus thuringiensis var. israelensis (B.t.i.), HD-968-S-1983, and a primary powder of Bacillus sphaericus 2362 were assayed against Mansonia titillans and Ma. dyari. The susceptibility of the 2 species to the individual bacterial toxins was similar. The B.t.i. LC50 values were 50.5 micrograms/liter for Ma. dyari and 54.7 micrograms/liter for Ma. titillans; the B. sphaericus LC50 values were 339.0 micrograms/liter and 347.2 micrograms/liter, respectively. The log dose-probit mortality lines were parallel for both target species. The potency of B. sphaericus relative to B.t.i. was 0.15 for Ma. dyari and 0.16 for Ma. titillans.

Animals↗

PubMed2000

Coexpression of cyt1Aa of Bacillus thuringiensis subsp. israelensis with Bacillus sphaericus binary toxin gene in acrystalliferous strain of B. thuringiensis.

The cyt1Aa gene of Bacillus thuringiensis subsp. israelensis and binary toxin gene of Bacillus sphaericus C3-41 were introduced into an acrystalliferous strain of B. thuringiensis independently and in combination by using shuttle vector pBU4. SDS-PAGE and Western blot analysis proved that cyt1Aa and binary toxin genes coexpressed during the sporulation of the recombinant. Transformant strain expressing the Cyt1Aa and binary toxin proteins in combination was more toxic to susceptible and resistant Culex pipiens quinquefasciatus than the transformants expressing Cyt1Aa protein or binary toxin proteins independently. It was suggested that large amount of production of Cyt1Aa protein and binary toxin proteins possibly interacted synergistically, thereby increasing its mosquitocidal toxicity significantly.

Animals↗

PubMed1998

Expression of a Bacillus thuringiensis delta-endotoxin gene by Bacillus pumilus.

The delta-endotoxin genes from Bacillus thuringiensis were introduced into a rhizosphere-inhabiting Bacillus pumilus isolate to create a delta-endotoxin expression and delivery system for subterranean feeding insects such as the larvae of pale western cutworm (Agrotis orthogonia Morrison (Lepidoptera: Noctuidae)). Preliminary experiments indicated that Bacillus thuringiensis subsp. kurstaki cultures were toxic to pale western cutworm larvae. Three different cry genes from Bacillus thuringiensis subsp. kurstaki were cloned into high and low copy number vectors and mated into Bacillus pumilus RB8. When carried on high copy number vectors, cry genes appeared to inhibit sporulation and delta-endotoxin production in Bacillus pumilus RB8 cultures, since microscopic examination of these cultures revealed that < 0.1% of the cells of late stationary phase cultures had sporulated and produced parasporal inclusions. On low copy number vectors, the cry genes did not inhibit sporulation; however, production of delta-endotoxins was undetectable. Using a heat shock regime for enrichment of sporogenous crystalliferous variants, a Bacillus pumilus isolate, carrying cryIA(c) on a high copy number plasmid, was obtained in which high level delta-endotoxin production occurred concomitant with sporulation. Synthesis of functional delta-endotoxin by this strain was confirmed by Western blot analysis and bioassay with pale western cutworm larvae. These results show that rhizosphere-inhabiting bacilli are indeed a potential route for introduction of delta-endotoxins to the root environment for biocontrol purposes.

Animals↗

PubMed2005

GIL16, a new gram-positive tectiviral phage related to the Bacillus thuringiensis GIL01 and the Bacillus cereus pBClin15 elements.

One of the most notable characteristics of Tectiviridae resides in their double-layer coats: the double-stranded DNA is located within a flexible lipoprotein vesicle covered by a rigid protein capsid. Despite their apparent rarity, tectiviruses have an extremely wide distribution compared to other phage groups. Members of this family have been found to infect gram-negative (PRD1 and relatives) as well as gram-positive (Bam35, GIL01, AP50, and phiNS11) hosts. Several reports have shown that tectiviruses infecting gram-negative bacteria are closely related, whereas no information is currently available on the genetic relationship among those infecting gram-positive bacteria. The present study reports the sequence of GIL16, a new isolate originating from Bacillus thuringiensis, and a genetic comparison of this isolate with the tectiviral bacteriophages Bam35 and GIL01, which originated from B. thuringiensis serovars Alesti and Israelensis, respectively. In contrast to PRD1 and its relatives, these are temperate bacteriophages existing as autonomous linear prophages within the host cell. Mutations in a particular motif in both the GIL01 and GIL16 phages are also shown to correlate with a switch to the lytic cycle. Interestingly, both bacterial viruses displayed narrow, yet slightly different, host spectrums. We also explore the hypothesis that pBClin15, a linear plasmid hosted by the Bacillus cereus reference strain ATCC 14579, is also a prophage. Sequencing of its inverted repeats at both extremities and a comparison with GIL01 and GIL16 emphasize its relationship to the Tectiviridae.

Bacillus cereus↗

PubMed1993

Field trials of Bacillus thuringiensis H-14 and Bacillus sphaericus (strain 2362) formulations against Anopheles arabiensis in the central highlands of Madagascar.

Malaria is highly endemic and unstable in the central Highlands plateau of Madagascar. The infection is seasonally transmitted by Anopheles funestus and An. arabiensis. The latter species is abundant especially in rice-growing areas. The field efficacies of commercial formulations of Bacillus thuringiensis H-14 and B. sphaericus (strain 2362) were assessed against An. arabiensis in 5 types of larval habitats. The granular formulation of B. thuringiensis (Vectobac GR) provided very good control in small ponds and rainwater ditches. In ricefields complete larval control was achieved with Vectobac GR and the flowable concentrate (Vectobac 12AS) at 2.5 kg/ha and 0.6 liter/ha, respectively. The granular formulation of B. sphaericus (ABG 6185) showed activity similar to that of Vectobac GR in small pools and ricefields. ABG 6185 was less effective in rainwater ditches where it gave satisfactory control at rates not lower than 6 kg/ha.

Animals↗

PubMed1990

Molecular cloning of the 130-kilodalton mosquitocidal delta-endotoxin gene of Bacillus thuringiensis subsp. israelensis in Bacillus sphaericus.

A 3.7-kilobase (kb) XbaI fragment harboring the cryIVB gene (L. Thorne, F. Garduno, T. Thompson, D. Decker, M. A. Zounes, M. Wild, A. M. Walfield, and T. J. Pollock, J. Bacteriol. 166:801-811, 1986) which encoded a 130-kilodalton (kDa) mosquitocidal toxin from a 110-kb plasmid of Bacillus thuringiensis subsp. israelensis 4Q2-72 was cloned into pUC12 and transformed into Escherichia coli. The clone with a recombinant plasmid (designated pBT8) was toxic to Aedes aegypti larvae. The fragment (3.7 kb) was ligated into pBC16 (tetracycline resistant [Tcr]) and transformed by the method of protoplast transformation into Bacillus sphaericus 1593 and 2362, which were highly toxic to Anopheles and Culex mosquito larvae but less toxic to Aedes larvae. After cell regeneration on regeneration medium, the Tcr plasmids from transformants (pBTC1) of both strains of B. sphaericus were prepared and analyzed. The 3.7-kb XbaI fragment from the B. thuringiensis subsp. israelensis plasmid was shown to be present by agarose gel electrophoresis and Southern blot hybridization. In addition, B. sphaericus transformants produced a 130-kDa mosquitocidal toxin which was detected by Western (immuno-) blot analysis with antibody prepared against B. thuringiensis subsp. israelensis 130-kDa mosquitocidal toxin. The 50% lethal concentrations of the transformants of strains 1593 and 2362 against A. aegypti larvae were 2.7 X 10(2) and 5.7 X 10(2) cells per ml, respectively. This level of toxicity was comparable to the 50% lethal concentration of B. thuringiensis subsp. israelensis but much higher than that of B. sphaericus 1593 and 2362 (4.7 X 10(4) cells per ml) against A. aegypti larvae.(ABSTRACT TRUNCATED AT 250 WORDS)

Aedes↗

PubMed2005

Characterization of Cry34/Cry35 binary insecticidal proteins from diverse Bacillus thuringiensis strain collections.

Bacillus thuringiensis crystal proteins of the Cry34 and Cry35 classes function as binary toxins showing activity on the western corn rootworm, Diabrotica virgifera virgifera LeConte. We surveyed 6,499 B. thuringiensis isolates by hybridization for sequences related to cry35A genes, identifying 78 strains. Proteins of the appropriate molecular mass (ca. 44 kDa) for Cry35 were observed in 42 of the strains. Full-length, or nearly full-length, sequences of 34 cry34 genes and 16 cry35 genes were also obtained from cloning, PCR analysis, and DNA sequencing. These included representatives of all known Cry34A, Cry34B, Cry35A, and Cry35B classes, as well as a novel Cry34A/Cry35A-like pair. Bioassay analysis indicated that cry35-hybridizing strains not producing a ca. 14-kDa protein, indicative of Cry34, were not active on corn rootworms, and that the previously identified Cry34A/Cry35A pairs were more active than the Cry34B/Cry35B pairs. The cry35-hybridizing B. thuringiensis strains were found in locales and materials typical for other B. thuringiensis strains. Comparison of the sequences with the geographic origins of the strains showed that identical, or nearly identical, sequences were found in strains from both Australasia and the Americas. Sequence similarity searches revealed that Cry34 proteins are similar to predicted proteins in Photorhabdus luminescens and Dictyostelium discoidium, and that Cry35Ab1 contains a segment similar to beta-trefoil domains that may be a binding motif. The binary Cry34/Cry35 B. thuringiensis crystal proteins thus appear closely related to each other, are environmentally ubiquitous, and share sequence similarities consistent with activity through membrane disruption in target organisms.

Amino Acid Sequence↗

PubMed1999

Subspecies-dependent regulation of Bacillus thuringiensis protoxin genes.

Bacillus thuringiensis accumulates, primarily during sporulation, large quantities of insecticidal protoxins which are deposited as crystalline, intracellular inclusions. Most subspecies contain several plasmid-encoded cry genes, each of which has a unique specificity. The overall toxicity profile of a subspecies depends not only on the array of cry genes present but also on the relative expression of the genes. In general, transcription depends on sporulation-specific sigma factors, but little is known about regulation of expression of the individual genes. In order to determine whether expression of a particular cry gene varies in different subspecies, lacZ fusions to the cry promoters of two protoxin genes (cry1 class) were constructed. Protoxin accumulation and mRNA contents were also measured by performing immunoblotting and Northern analyses, respectively. The expression of a cry1Ab-lacZ fusion, but not the expression of a cry1C-lacZ fusion, was three to four times lower in B. thuringiensis subsp. aizawai strains than in B. thuringiensis subsp. kurstaki or B. thuringiensis subsp. tolworthi. Also, the Cry1Ab antigen and steady-state mRNA contents of B. thuringiensis subsp. aizawai were lower. The regulation of the genes must involve regions upstream of the promoters which are unique to each cry gene since (i) mutations in the upstream region of the cry1Ab gene resulted in enhanced expression in B. thuringiensis subsp. aizawai and (ii) no differences were found when the lacZ fusions contained the cry1Ab promoters but no upstream sequences. The capacity to regulate each of the protoxin genes must be a factor in the overall protoxin composition of a subspecies and thus its toxicity profile.

Antigens, Bacterial↗

PubMed1991

Isolation and characterization of a novel insecticidal crystal protein gene from Bacillus thuringiensis subsp. aizawai.

Bacillus thuringiensis subsp. aizawai EG6346, a novel grain dust isolate, was analyzed by Southern blot hybridization for its insecticidal crystal protein (ICP) gene profile. Strain EG6346 lacks previously characterized cryIA ICP genes yet does possess novel cryI-related gene sequences. A recombinant genomic plasmid library was constructed for strain EG6346 in Escherichia coli. One recombinant plasmid, pEG640, isolated from the library contained a novel ICP gene on a 5.7-kb Sau3A insert. The sequence of this gene, designated cryIF, was related to, but distinct from, the published sequences for other cryI genes. A second novel cryI-related sequence was also located on pEG640, approximately 500 bp downstream from cryIF. Introduction of cryIF into a Cry- B. thuringiensis recipient strain via electroporation enabled sufficient production of CryIF protein for quantitative bioassay analyses of insecticidal specificity. The CryIF crystal protein was selectively toxic to a subset of lepidopteran insects tested, including the larvae of Ostrinia nubilalis and Spodoptera exigua.

Amino Acid Sequence↗

PubMed2002

Expression of the full-length and 3'-spliced cry1Ab gene in the 135-kDa crystal protein minus derivative of Bacillus thuringiensis subsp. kyushuensis.

Bacillus thuringiensis produces a 130-135-kDa insecticidal protein in the form of bipyramidal crystal which is toxic to lepidopteran larvae. Part of the C-terminal region of the native Cry1Ab was replaced by a heterologous sequence of Cry11Aa C-terminus to get a 3'-spliced cry1Ab gene. The full-length cry1Ab and 3'-spliced cry1Ab, which were both cloned into the E. coli-B. thuringiensis shuttle expression vector pHZB1, were expressed in a 135-kDa crystal protein minus derivative of B. thuringiensis subsp. kyushuensis (4U1-Cry(-135)). The crystal shape of Cry1Ab proteins from both recombinants was regularly bipyramidal, while the crystal size of the intact Cry1Ab was approximately fivefold larger than the 3'-spliced Cry1Ab. In addition, these two kinds of Cry1Ab proteins had similar toxicity against Argyrogramma agnata larvae.

Amino Acid Sequence↗

PubMed1991

Cloning and analysis of delta-endotoxin genes from Bacillus thuringiensis subsp. alesti.

Bacillus thuringiensis subsp. alesti produced only CryIA(b)-type protoxins, and three cryIA(b) genes were cloned. One was cryptic because of an alteration near the 5' end, and the other two were very similar to each other. The protoxin encoded by one of the latter genes differed from other CryIA(b) protoxins in its greater stability and relative toxicity for two members of the order Lepidoptera.

Amino Acid Sequence↗

PubMed1997

Proteinase-mediated insect resistance to Bacillus thuringiensis toxins.

Two Bacillus thuringiensis (Bt)-resistant strains of the Indianmeal moth, Plodia interpunctella, lack a major gut proteinase that activates Bt protoxins. The absence of this enzyme is genetically linked to larval survival on Bt-treated diets. When considered with previous data supporting the existence of receptor-mediated insect resistance to Bt, these results provide evidence that insect adaptation to these toxins occurs through multiple physiological mechanisms, which complicate efforts to prevent or manage resistance to Bt toxins in insect control programs.

Animals↗

PubMed1988

Differential specificity of two insecticidal toxins from Bacillus thuringiensis var. aizawai.

Bacillus thuringiensis var. aizawai HD-249 produces more than one protein of 130-135 kD in its insecticidal crystal delta-endotoxin. We describe an indirect method of assessing the relative contribution to toxicity of two of these protoxins using monospecific antibodies directed against their active proteolytic products. Our results show that one toxin is active against Spodoptera frugiperda but not Choristoneura fumiferana cells in vitro, while the other lyses C. fumiferana but not S. frugiperda cells. There is no indication of synergism between these toxins in vitro.

Antigen-Antibody Complex↗

PubMed2005

Using worms to better understand how Bacillus thuringiensis kills insects.

Bacillus thuringiensis is widely used as a biological pesticide to control insects that either cause damage to crops or transmit disease. That it can also target the model organism Caenorhabditis elegans has not only provided exciting new insights into how the toxins produced by the bacterium target their victims but also how target insects counter the attack. Modern approaches such as reverse genetics and microarray technology have revealed novel receptors for the toxins and possible signal transduction pathways induced within the host following intoxication. This article will discuss how these findings fit in with current models and how they might influence future studies.

Animals↗

PubMedDate not supplied

[Sensitivity of dissociation variants of Micrococcus luteus to the action of delta-endotoxins of Bacillus thuringiensis].

Endotoxins of Bacillus thuringiensis subsp. tenebrionis produced an antibiotic effect on three out of the four species of micrococci tested, showing an activity of 10-23 units/mg, comparable with that of bacitracin. The R variants of Micrococcus luteus were more than twice as resistant to the action of delta-endotoxins as cells of the S and M types. Enhanced growth of the tested microorganisms at concentrations of antibiotics large enough to inhibit the growth of the S and M variants, but insufficient to suppress the R-variant, was shown to be determined by the intense development of the latter variant.

Anti-Bacterial Agents↗

PubMed1992

A broad-spectrum cytolytic toxin from Bacillus thuringiensis var. kyushuensis.

Bacillus thuringiensis (Bt) var. kyushuensis synthesizes a mosquitocidal crystalline inclusion containing several proteins ranging from 140 to 14 kDa. We have identified a 25 kDa protein protoxin in this inclusion which is not cytolytic, but when activated proteolytically to 23-22 kDa products is cytolytic to mosquito, lepidopteran and mammalian cells, can release entrapped glucose from liposomes and forms cation-selective channels in a planar lipid bilayer. This broad-spectrum cytolytic toxin is related antigenically to the 23 kDa toxin from Bt var. darmstadiensis strain 73-E10-2, but not to the 25 kDa CytA toxin of Bt var. israelensis. The cytolytic activity of these Bt var. kyushuensis toxins, like that of the latter two toxins, can be neutralized by incubation with liposomes containing phospholipids.

Aedes↗