Showing papers on "Bacillus thuringiensis published in 1998"

Insecticidal Toxins from the Bacterium Photorhabdus luminescens

Abstract: Transgenic plants expressing Bacillus thuringiensis (Bt) toxins are currently being deployed for insect control. In response to concerns about Bt resistance, we investigated a toxin secreted by a different bacterium Photorhabdus luminescens, which lives in the gut of entomophagous nematodes. In insects infected by the nematode, the bacteria are released into the insect hemocoel; the insect dies and the nematodes and bacteria replicate in the cadaver. The toxin consists of a series of four native complexes encoded by toxin complex loci tca, tcb, tcc, and tcd. Both tca and tcd encode complexes with high oral toxicity to Manduca sexta and therefore they represent potential alternatives to Bt for transgenic deployment.

Two-toxin strategies for management of insecticidal transgenic crops: can pyramiding succeed where pesticide mixtures have not?

Abstract: Transgenic insectresistant crops that express toxins from Bacillus thuringiensis (Bt) offer significant advantages to pest management, but are at risk of losing these advantages to the evolution of...

Characterization of cry Genes in a Mexican Bacillus thuringiensis Strain Collection

Abstract: Mexico is located in a transition zone between the Nearctic and Neotropical biogeographical regions and contains a rich and unique biodiversity. A total of 496 Bacillus thuringiensis strains were isolated from 503 soil samples collected from the five macroregions of the country. The characterization of the strain collection provided useful information on the ecological patterns of distribution of B. thuringiensis and opportunities for the selection of strains to develop novel bioinsecticidal products. The analysis of the strains was based on multiplex PCR with novel general and specific primers that could detect the cry1, cry3, cry5, cry7, cry8, cry9, cry11, cry12, cry13, cry14, cry21, and cyt genes. The proteins belonging to the Cry1 and Cry9 groups are toxic for lepidopteran insects. The Cry3, Cry7, and Cry8 proteins are active against coleopteran insects. The Cry5, Cry12, Cry13, and Cry14 proteins are nematocidal. The Cry11, Cry21, and Cyt proteins are toxic for dipteran insects. Six pairs of general primers are used in this method. Strains for which unique PCR product profiles were obtained with the general primers were further characterized by additional PCRs with specific primers. Strains containing cry1 genes were the most abundant in our collection (49.5%). Thirty-three different cry1-type profiles were identified. B. thuringiensis strains harboring cry3 genes represented 21.5% of the strains, and 7.9% of the strains contained cry11 and cyt genes. cry7, cry8, and cry9 genes were found in 0.6, 2.4, and 2.6% of the strains, respectively. No strains carrying cry5, cry12, cry13, cry14, or cry21 genes were found. Finally, 14% of the strains did not give any PCR product and did not react with any polyclonal antisera. Our results indicate the presence of strains that may harbor potentially novel Cry proteins as well as strains with combinations of less frequently observed cry genes.

Effects of transgenic Bacillus thuringiensis corn-fed prey on mortality and development time of immature Chrysoperla cornea (Neuroptera: Chrysopidae)

Abstract: Laboratory feeding experiments using transgenic Bacillus thuringiensis variety kurstaki (Berliner) corn plants have been carried out to study the effects of B. thuringiensis -fed herbivores (i.e., prey), on the predator Chrysoperla carnea Stephens. Host plants were a transgenic B. thuringiensis -expressing (CrylAb) corn hybrid and the corresponding untransformed, B. thuringiensis -free corn hybrid. Two different prey species were used in the experiments, the European corn borer, Ostrinia nubilalis (Hubner) (lepidopterous target pest), and Spodoptera littoralis (Boisduval) (lepidopterous nontarget pest for B. thuringiensis ). The objectives were to quantify the effects of B. thuringiensis -fed prey on chrysopid immature development and to determine whether observed effects were caused by sick, suboptimal prey (indirect effects) or associated with B. thuringiensis -related causes (direct effects). Mean total immature mortality for chrysopid larvae raised on B. thuringiensis -fed prey was 62% compared with 37% when raised on B. thuringiensis -free prey. There was no significant difference in mortality between chrysopid larvae reared on B. thuringiensis -fed O. nubilalis or B. thuringiensis -fed S. littoralis . Similarly, no significant difference in mortality was detected when chrysopid larvae were raised on B. thuringiensis -free O. nubilalis or B. thuringiensis -free S. littoralis . Development time of chrysopid larvae was prolonged when B. thuringiensis -fed O. nubilalis was given to the predators but not for B. thuringiensis -fed S. littoralis . Although some unnoticed adverse effects in S. littoralis may have occurred because of the B. thuringiensis corn, our results suggest that the reduced fitness of chrysopid larvae was associated with B. thuringiensis . The prolonged development time of chrysopid larvae raised on B. thuringiensis -fed O. nubilalis was probably because of a combined effect of B. thuringiensis exposure and nutritional deficiency caused by sick prey.

Agrobacterium-transformed rice plants expressing synthetic cryIA(b) and cryIA(c) genes are highly toxic to striped stem borer and yellow stem borer

Abstract: Over 2,600 transgenic rice plants in nine strains were regenerated from >500 independently selected hygromycin-resistant calli after Agrobacterium-mediated transformation. The plants were transformed with fully modified (plant codon optimized) versions of two synthetic cryIA(b) and cryIA(c) coding sequences from Bacillus thuringiensis as well as the hph and gus genes, coding for hygromycin phosphotransferase and β-glucuronidase, respectively. These sequences were placed under control of the maize ubiquitin promoter, the CaMV35S promoter, and the Brassica Bp10 gene promoter to achieve high and tissue-specific expression of the lepidopteran-specific δ-endotoxins. The integration, expression, and inheritance of these genes were demonstrated in R0 and R1 generations by Southern, Northern, and Western analyses and by other techniques. Accumulation of high levels (up to 3% of soluble proteins) of CryIA(b) and CryIA(c) proteins was detected in R0 plants. Bioassays with R1 transgenic plants indicated that the transgenic plants were highly toxic to two major rice insect pests, striped stem borer (Chilo suppressalis) and yellow stem borer (Scirpophaga incertulas), with mortalities of 97–100% within 5 days after infestation, thus offering a potential for effective insect resistance in transgenic rice plants.

Persistence of the insecticidal toxin from Bacillus thuringiensis subsp. kurstaki in soil

Abstract: The accumulation and persistence of the insecticidal toxins from Bacillus thuringiensis may result in environmental hazards, such as toxicity to nontarget species and the selection of toxin-resistant target species. Toxins from B. thuringiensis subsp. kurstaki were added to three soils [Kitchawan soil (which contains kaolinite but not montmorillonite) unamended or amended with montmorillonite or kaolinite (as an internal control); Mopala soil, which contains montmorillonite and kaolinite; and San Alejo soil, which does not contain montmorillonite but contains kaolinite], and the persistence of the toxins was determined by insect bioassays using the larvae of the tobacco hornworm (Manduca sexta). Toxicity varied with the type of soil: the Kitchawan soil, either unamended or amended with kaolinite, remained toxic to the larvae for more than 6 months, maintaining a lethal concentration at which 50% of the larvae were killed (LC50) of 61 to 111 ng 100 μl−1 of soil suspension throughout 195 d of incubation. The Kitchawan soil amended with montmorillonite and the Mopala and San Alejo soils showed reduced insecticidal activity after only 35 d (LC50 from 104 to 192 ng 100 μl−1). The pH of soils in which insecticidal activity was reduced was higher (5.8 to 7.3) than that of soils in which insecticidal activity was retained (4.9 to 5.1). As microbial activity is greater at higher pH values, more of the toxins may have been degraded by microbes in soils with the higher pH values. This hypothesis was confirmed by the greater loss in insecticidal activity during 234 d when the pH of the Kitchawan soil, unamended or amended to 6% (vol vol−1) with kaolinite, was increased from 4.9 to ca. 7.0 by the addition of CaCO3.

Constitutive and tissue-specific differential expression of the cryIA(b) gene in transgenic rice plants conferring resistance to rice insect pest

Abstract: The truncated chimeric Bt gene, cryIA(b) of Bacillus thuringiensis, driven by two constitutive promoters, 35S from CaMV and Actin-1 from rice, and two tissue-specific promoters, pith tissue and pepcarboxylase (PEPC) for green tissue from maize, was introduced into several varieties of rice (indica and japonica) by microprojectile bombardment and protoplast systems. A total of 1800 putative transgenic Bt rice plants could be produced. Southern analysis revealed that more than 100 independently transformed plants could be confirmed for integration of the cryIA(b) gene. High levels of CryIA(b) proteins were obtained in the green tissue (leaves and stem) of many plants using the PEPC promoter. There was little difference in Bt protein level in leaves and stems from transgenic plants with the 35 S or Actin-1 promoter. Out of 800 Southern-positive plants that were bioassayed, 81 transgenic plants showed 100% mortality of insect larvae of the yellow stem borer (Scirpophaga incertulas). The transgene, cryIA(b), driven by different promoters showed a wide range of expression (low to high) of Bt proteins stably inherited in a number of rice varieties with enhanced yellow stem borer resistance. This first report of transgenic indica Bt rice plants with the PEPC or pith promoter either alone or in combination should provide a better strategy for providing rice plants with protection against insect pest resistance, minimizing the expression of the CryIA(b) protein in seeds and other tissues.

Insecticidal activity and biodegradation of the toxin from bacillus thuringiensis subsp. kurstaki bound to humic acids from soil

Abstract: The equilibrium adsorption and binding of the active toxin from Bacillus thuringiensis subsp kurstaki , toxic to lepidopteran larvae, to humic acids extracted from two forest and two cultivated soils, as well as the insecticidal activity and the biodegradation of the bound toxin, were studied From 75 to 85% of the toxin added was rapidly adsorbed to the humic acids at equilibrium, and adsorption to a constant amount of humic acids increased with the concentration of the toxin until a plateau was reached Differences in total acidity and in the content of phenolic groups of the humic acids appeared to be primarily responsible for differences in the amounts of toxin bound (45–80% of the adsorbed toxin) after extensive washing with distilled water The content of carboxyl groups and the degree of polymerization (E4/E6) did not appear to influence significantly the differential binding Bound humic acid–toxin complexes were toxic to larvae of the tobacco hornworm ( Manduca sexta ) The lethal concentration necessary to kill 50% of the larvae (LC 50 ) of the bound toxin was comparable with that of the free toxin, indicating that the binding of the toxin to humic acids did not affect its insecticidal activity The bound toxin did not support the growth of a mixed microbial culture from soil, although the free toxin was rapidly utilized as a carbon and energy source for growth, indicating that binding of the toxin to humic acids reduced its biodegradability The result of these studies indicate that the toxins from B thuringiensis introduced in transgenic plants and microbes could persist, accumulate, and remain insecticidal in soil as a result of binding to humic acids, as well as on clays, as previously described This persistence could pose a hazard to non-target organisms and enhance the selection of toxin-resistant target species

Involvement of chitinases of Bacillus thuringiensis during pathogenesis in insects

Abstract: Bacillus thuringiensis subsp. israelensis IPS78 and B. thuringiensis subsp. aizawai HD133 both secreted exochitinase activity when grown in a medium containing chitin. Allosamidin, a specific chitinase inhibitor, inhibited activity from both strains, with IC50 values of about 50 μM with colloidal chitin as substrate and between 1 and 10 μM with 4-methylumbelliferyl-diacetylchitobioside and 4-methylumbelliferyl-triacetylchitotrioside as substrates. The involvement of these chitinolytic activities during pathogenesis in insects has been investigated with B. thuringiensis subsp. israelensis IPS78 against larvae of the midge Culicoides nubeculosus, and with B. thuringiensis subsp. aizawai HD133 against caterpillars of the cotton leafworm Spodoptera littoralis. Presence of 100 μM allosamidin increased the LD50 by factors of 1.3 and 1.4, respectively, demonstrating a role for bacterial chitinases in the attack on the insects. Presence of chitinase A from Serratia marcescens considerably decreased the values for LD50' confirming previous observations with different systems of the potentiation of entomopathogenesis of B. thuringiensis by exogenous chitinases. The most likely action of the endogenous chitinases of B. thuringiensis is to weaken the insects' peritrophic membranes, allowing more ready access of the bacterial toxins to the gut epithelia. Addition of exogenous chitinases will then increase this effect. Complementary cross-infection experiments, strain HD133 against midge larvae and strain IPS78 against caterpillars, were performed to investigate the pathogen/host specificities of the effects. Results showed that much higher concentrations of bacteria were required to achieve even low mortalities, and addition of chitinase A gave no increase in death rate.

Bacillus thuringiensis subsp. konkukian (serotype H34) superinfection: case report and experimental evidence of pathogenicity in immunosuppressed mice.

Abstract: We present a case of severe war wounds infected by Bacillus thuringiensis serotype H34 and describe the experimental protocol used to demonstrate its ability to infect mice after cutaneous inoculation. This case is interesting because B. thuringiensis is considered to be a contaminant in laboratories and receives inadequate attention.

Insect resistance to Bacillus thuringiensis: uniform or diverse?

Abstract: Resistance to the insecticidal proteins produced by the soil bacterium Bacillus thuringiensis (Bt) has been documented in more than a dozen species of insect. Nearly all of these cases have been produced primarily by selection in the laboratory, but one pest, the diamondback moth (Plutella xylostella), has evolved resistance in open-field populations. Insect resistance to Bt has immediate and widespread significance because of increasing reliance on Bt toxins in genetically engineered crops and conventional sprays. Furthermore, intense interest in Bt provides an opportunity to examine the extent to which evolutionary pathways to resistance vary among and within species of insect. One mode of resistance to Bt is characterized by more than 500-fold resistance to at least one Cry1A toxin, recessive inheritance, little or no cross-resistance to Cry1C, and reduced binding of at least one Cry1A toxin. Analysis of resistance to Bt in the diamondback moth and two other species of moth suggests that although this particular mode of resistance may be the most common, it is not the only means by which insects can attain resistance to Bt.

Genetic diversity of Bacillus cereus B-thuringiensis isolates from natural sources

Abstract: The genetic diversity and relationships among 154 Bacillus cereus/B. thuringiensis isolates recovered from soil samples from five geographic areas in Norway were investigated with multilocus enzyme electrophoresis (MEE). Cluster analysis revealed two major groups (designated cluster I and cluster II) separated at genetic distance greater than 0.55. Cluster I included 62 electrophoretic types (ETs) originating from all five locations, whereas, in cluster II, all but one isolate were from the same location. The isolates were also serotyped with B. thuringiensis flagellar antisera, and 28 distinct serotypes were identified. In general, serotyping did not show correlation to the genetic diversity of the isolates. The presence of IS231- and IS240-like transposable elements was detected in 14% of the strains of cluster II only. Parasporal crystals were observed in three strains; ten other strains were toxic to Trichoplusia ni. We conclude that B. cereus/B. thuringiensis from soil exhibit a high degree of recombination.

A holistic approach for determining the entomopathogenic potential of Bacillus thuringiensis strains

Abstract: The cry gene content of Bacillus thuringiensis subsp. aizawai HD-133 was analyzed by a combination of high-pressure liquid chromatography (HPLC) and exclusive PCR. A total of six cry genes were detected in genomic DNA purified from HD-133, four from the cry1 family (cry1Aa, cry1Ab, cry1C, and cry1D) as well as a gene each from the cry2 (cry2B) and the cry1I families. To directly determine which genes were expressed and crystallized in the purified parasporal inclusions, solubilized and trypsinized HD-133 crystals were subjected to chromatographic separation by HPLC. Only three proteins, Cry1Ab, Cry1C, and Cry1D, were found, in a 60/37/3 ratio. Dot blot analysis of total mRNA purified from HD-133 showed that both the cry2B and cry1I genes, but not the cry1Aa gene, were transcribed. Cloning and sequencing of the cry1Aa gene revealed an inserted DNA sequence within the cry coding sequence, resulting in a disrupted reading frame. Taken together, our results show that combining crystal protein analysis with a genetic approach is a highly complementary and powerful way to assess the potential of B. thuringiensis isolates for new insecticidal genes and specificities. Furthermore, based on the number of cryptic genes found in HD-133, the total cry gene content of B. thuringiensis strains may be higher than previously thought.

Cloning, Sequencing, and Expression of the Bombyx mori Receptor for Bacillus thuringiensis Insecticidal CryIA(a) Toxin

Abstract: Bacillus thuringiensis strains produce insect-specific Bt toxins. Bt CryIA(a) toxin binds to a 175-kDa glycoprotein (BtR175) on the microvillus membranes of columnar cells in the Bombyx mori midgut and causes lysis of the cells. BtR175 was purified, and its cDNA was cloned. The cDNA encodes a newly identified 193.3-kDa preproprotein form of BtR175 that includes nine extracellular cadherin repeats, a 23.5-kDa membrane-proximal domain, a membrane-spanning region, and a 13.6-kDa cytoplasmic domain. Spodoptera frugiperda cells transfected with a recombinant baculovirus DNA carrying the cDNA produced a 175-kDa protein that reacted with anti-BtR antibodies and the Bt CryIA(a) toxin.

Effective control of yellow stem borer and rice leaf folder in transgenic rice indica varieties Basmati 370 and M 7 using the novel δ-endotoxin cry2A Bacillus thuringiensis gene

Abstract: Transgenic rice indica varieties Basmati 370 and M 7 expressing the novel cry2A (Bt) insecticidal gene were generated by particle bombardment. Molecular and biochemical analyses in R0 and R1 populations confirmed stable integration and expression of this novel Bt transgene. We estimated that the gene product was expressed up to 5% of total leaf protein. Insect feeding bioassays demonstrated that the Cry2A protein was effective against the yellow stem borer and the rice leaf folder, two major rice pests in the Indian Subcontinent. This is the first report of the control of major rice pests using this specific Bt gene. The cry2A gene can now be used in combination with other insecticidal genes for pyramiding resistance against insect pests. This will delay, or perhaps in combination with integrated pest management practices, prevent evolution of insect populations resistant to single insecticidal genes.

Identification of Bombyx mori midgut receptor for Bacillus thuringiensis insecticidal CryIA(a) toxin.

Abstract: As part of a study of the mechanism by which Bacillus thuringiensis insecticidal crystal protein acts, a Bombyx mori receptor to the CryIA(a) toxin specific for lepidopterans was examined. Histological examination showed that the toxin acted on the brush-border membrane of the midgut columnar cells and broke its infolding structure, causing cell lysis. The membrane vesicles were purified, and a 175-kDa protein binding the toxin was found that accounted for some 0.015% of membrane proteins. The protein, designated BtR175, was a glycoprotein that reacted with concanavalin A. Anti-BtR antibodies inhibited the binding of toxin to membrane vesicles in vitro and decreased the effect of the toxin to silkworms in vivo. BtR175, although found in the gut, was not found in fat bodies, integument, or silk glands. These results indicated that BtR175 was the receptor protein for the insecticidal toxin. Proteins (137 and 107 kDa) binding the CryIA(a) toxin also were found in the gut membranes of Tenebrio moritor larvae, a coleopteran not sensitive to the toxin. The specificity of the toxin could not be explained only in term of the existence of its binding protein.

Characterization of plasmid pAW63, a second self-transmissible plasmid in Bacillus thuringiensis subsp. kurstaki HD73

Abstract: Bacillus thuringiensis subspecies kurstaki HD73, toxic for lepidopteran larvae, contains two large self-transmissible plasmids of approximately 75 kb, pHT73 and pAW63 The conjugative plasmid pHT73 has been studied extensively and has been shown to harbour the toxin gene cry1Ac, the transposon Tn4430 and several insertion sequences In this study it was demonstrated that the minor plasmid pAW63 is also self-transmissible and about 10-30 times more efficient in mobilizing plasmid pBC16 To facilitate direct selection for pAW63 transfer, the plasmid was tagged with the tetracycline resistance transposon Tn5401 and in intraspecies matings it was found that after 2 h, all recipients had acquired a copy of the plasmid Mating experiments demonstrated that pAW63 could be transferred to Bacillus thuringiensis subsp israelensis, Bacillus cereus, Bacillus licheniformis, Bacillus subtilis and Bacillus sphaericus, and that the conjugative functions were expressed in these hosts Hybridization studies showed that the replicons of pAW63 and pHT73 were distinct from one another Sequences homologous to transposon Tn4430 and several insertion sequences were, however, shown to reside on both plasmids

Optimization of Cry3A Yields in Bacillus thuringiensis by Use of Sporulation-Dependent Promoters in Combination with the STAB-SD mRNA Sequence

Abstract: The insecticidal activity of Bacillus thuringiensis strains toxic to coleopterous insects is due to Cry3 proteins assembled into small rectangular crystals. Toxin synthesis in these strains is dependent primarily upon a promoter that is active in the stationary phase and a STAB-SD sequence that stabilizes the cry3 transcript-ribosome complex. Here we show that significantly higher yields of Cry3A can be obtained by using dual sporulation-dependent cyt1Aa promoters to drive the expression of cry3Aa when the STAB-SD sequence is included in the construct. The Cry3A yield per unit of culture medium obtained with this expression system was 12.7-fold greater than that produced by DSM 2803, the wild-type strain of B. thuringiensis from which Cry3Aa was originally described, and 1.4-fold greater than that produced by NB176, a mutant of the same strain containing two or three copies of cry3Aa, which is the active ingredient of the commercial product Novodor, used for control of beetle pests. The toxicities of Cry3A produced with this construct or the wild-type strain were similar when assayed against larvae of the cottonwood leaf beetle, Chrysomela scripta. The volume of Cry3A crystals produced with cyt1Aa promoters and the STAB-SD sequence was 1.3-fold that of typical bipyramidal Cry1 crystals toxic to lepidopterous insects. The dual-promoter/STAB-SD system offers an additional method for potentially improving the efficacy of insecticides based on B. thuringiensis.

Insect-resistant transgenic brinjal plants.

Abstract: A synthetic cry1Ab gene coding for an insecticidal crystal protein (ICP) of Bacillus thuringiensis (Bt) was transferred to brinjal (eggplant) by cocultivating cotyledonary explants with Agrobacterium tumefaciens. Transformant plants resistant to kanamycin were regenerated. Hybridization experiments demonstrated gene integration and mRNA expression. Double-antibody sandwich ELISA analysis revealed Bt toxin protein expression in the transgenic plants. The expression resulted in a significant insecticidal activity of transgenic brinjal fruits against the larvae of fruit borer (Leucinodes orbonalis). The results also demonstrated that a synthetic gene based on monocot codon usage can be expressed in dicotyledonous plants for insect control.

Using an F2 Screen to Search for Resistance Alleles to Bacillus thuringiensis Toxin in European Corn Borer (Lepidoptera: Crambidae)

Abstract: We present an application of an F2 screening method for recovering and estimating the frequencies of rare alleles that confer insect resistance to a transgenic corn variety producing Bacillus thuringiensis Berliner crystal protein toxin ( Bt corn). Based on a sample of 91 female Ostrinia nubilalis (Hubner) we show with 95% confidence that the frequency of B. thuringiensis resistance alleles from a wild Minnesota population is <0.013. This is an upper limit to the estimated allele frequency and does not provide clear evidence that 1 of the assumptions of the refuge plus high-dose strategy will or will not be met. With additional sampling, a more precise estimate of resistance allele frequency could be obtained that would clearly support or refute 1 of the assumptions of the refuge plus high-dose strategy. Variable costs of the screening method were 19.70per female line, but these could be reduced by improved collecting, rearing, and handling methods.

Bacillus thuringiensis Insecticidal Proteins: Molecular Mode of Action

Abstract: Growing interest in biorational pesticides has placed the Bacillus thuringiensis insecticidal crystal proteins at the forefront of pesticides for plant genetic engineering. The development of improvement pesticides, both in enhanced activity and broader host range, depends on an understanding of its mechanism of action. This review presents a complete overview of the bacterium and the group of insecticidal proteins known as Cry proteins or delta-endotoxins. The molecular mode of action is described in detail, including the mapping of receptor binding sites by site-directed mutagenesis, the known receptors, and the ion-channel activity of the toxins.

Cyt1Aa Protein of Bacillus thuringiensis Is Toxic to the Cottonwood Leaf Beetle, Chrysomela scripta, and Suppresses High Levels of Resistance to Cry3Aa

Abstract: The insecticidal activity of Bacillus thuringiensis is due primarily to Cry and Cyt proteins. Cry proteins are typically toxic to lepidopterous, coleopterous, or dipterous insects, whereas the known toxicity of Cyt proteins is limited to dipterans. We report here that a Cyt protein, Cyt1Aa, is also highly toxic to the cottonwood leaf beetle, Chrysomela scripta, with a median lethal concentration of 2.5 ng/mm2 of leaf surface for second-instar larvae. Additionally, we show that Cyt1Aa suppresses resistance to Cry3Aa greater than 5,000-fold in C. scripta, a level only partially overcome by Cry1Ba due to cross-resistance. Studies of the histopathology of C. scripta larvae treated with Cyt1Aa revealed disruption and sloughing of midgut epithelial cells, indicating that its mechanism of action against C. scripta is similar to that observed in mosquito and blackfly larvae. These novel properties suggest that Cyt proteins may have an even broader spectrum of activity against insects and, owing to their different mechanism of action in comparison to Cry proteins, might be useful in managing resistance to Cry3 and possibly other Cry toxins used in microbial insecticides and transgenic plants.

Survival, Development, and Oviposition of Resistant Diamondback Moth (Lepidoptera: Plutellidae) on Transgenic Canola Producing a Bacillus thuringiensis Toxin

Abstract: We measured responses of diamondback moth, plutella xylostella L., to transgenic and nontransgenic canola, Brassica napus L. Transgenic canola expressed a crylAc gene of Bacillus thurngiensis Berliner resulting in 238 ± 29 ng of Cry lAc protein per milligram of total extractable protein in leaves. We tested 2 Hawaiian strains of diamondback moth: NO-QA was resistant to CrylAc and LAB-PS was susceptible. Larval and pupal durations, pupal weights, and adult emergence of the 2 strains were similar on nontransgenic canola, but differed significantly on transgenic canola. Transgenic canola killed all larvae tested from the susceptible strain. In contrast, for the resistant strain, no differences occurred between transgenic and nontransgenic canola in larval survival and head capsule width at day 5, percentage pupation, pupal weight, percentage adult emergence, and extent of defoliation. For both the susceptible and resistant strains of diamondback moth, no differences were detected between transgenic and nontransgenic canola in feeding initiation or oviposition preference. The lack of discrimination between transgenic and nontransgenic canola by neonates and ovipositing females indicates that host choice behavior is independent from susceptibility to CrylAc. Development of resistant diamondback moth on transgenic canola without any adverse effects provides an example of a pest that has completely overcome high levels of a B. thuringiensis toxin expressed by a genetically engineered plant.

Discrimination among Bacillus cereus, B. mycoides and B. thuringiensis and some other species of the genus Bacillus by Fourier transform infrared spectroscopy

Abstract: Fourier transform infrared spectroscopy (FTIR) in conjunction with canonical variate analysis was found to be effective in discriminating among spectra of 9 representative strains of Bacillus spp., including B. cereus, B. mycoides and B. thuringiensis. The method was also able to discriminate according to species among spectra of 14 other non-type strains of B. cereus, 12 of B. mycoides and 12 of B. thuringiensis with a success rate of >95%, even without using a prior classification of the groups by species. FTIR spectroscopy can be used for the rapid and accurate differentiation of species in the genus Bacillus that are of importance to the food and dairy industry.