Bacillus thuringiensis Toxins: An Overview of Their Biocidal Activity (original) (raw)
Related papers
The Insecticidal Proteins of Bacillus thuringiensis
Advances in Applied Microbiology Volume 42, 1996
I. Introduction 11. Classification of Bt Toxins 111. Structure of Bt Toxin Proteins and Genes IV. Screening for New Bt Toxin Proteins and Genes V. Mechanism of Action VI. Bt as a Biological Insecticide A. Construction of Novel Bt Strains by Conjugation B. Construction of Recombinant Bt Strains C. Construction of Transgenic Microbes D. Baculoviruses as Bt Vectors E. Insect-Tolerant Transgenic Crop Plants A. Rotations B. Mixtures of Toxins C. Refuges D. Toxin Doses E.
Purification and characterization of Bacillus thuringiensis vegetative insecticidal toxin protein(s)
Significance and Impact of the Study: Insecticidal activity of Bacillus thuringiensis subsp. aegypti was determined, and its vegetative insecticidal protein was subjected to FPLC for protein purification. This work contributes to improve understanding the different toxins secreted during vegetative growth of Bt. Moreover, the N-terminal amino acid sequences of 88-kDa protein was only 92% identical to that of vip3A, and for 44 kDa was 92% identical with Cry35a, suggesting that we might have identified a new genes. Finally, we have proven these proteins to be novel insecticidal agents that may complement the use of known insecticidal proteins derived from Bacillus.
Current Microbiology, 2003
Little is known about the occurrence and linkage between secreted insecticidal virulence factors in natural populations of Bacillus thuringiensis (Bt). We carried out a survey of 392 Bt strains isolated from various samples originating from 31 countries. The toxicity profile of the culture supernatants of these strains was determined individually against Anthonomus grandis (Coleoptera) and Spodoptera littoralis (Lepidoptera). We analyzed -exotoxin I production and searched for the genes encoding Vip1-2, Vip3, and Cry1I toxins in 125 of these strains. Our results showed that these insecticidal toxins were widespread in Bt but that their distribution was nonrandom, with significant linkage observed between vip3 and cry1I and between vip1-2 and -exotoxin I. Strains producing significant amounts of -exotoxin I were more frequently isolated from invertebrate samples than from dust, water, soil, or plant samples.
Bacillus thuringiensis subsp. israelensis and Its Dipteran-Specific Toxins
Toxins, 2014
Bacillus thuringiensis subsp. israelensis (Bti) is the first Bacillus thuringiensis to be found and used as an effective biological control agent against larvae of many mosquito and black fly species around the world. Its larvicidal activity resides in four major (of 134, 128, 72 and 27 kDa) and at least two minor (of 78 and 29 kDa) polypeptides encoded respectively by cry4Aa, cry4Ba, cry11Aa, cyt1Aa, cry10Aa and cyt2Ba, all mapped on the 128 kb plasmid known as pBtoxis. These six δ-endotoxins form a complex parasporal crystalline body with remarkably high, specific and different toxicities to Aedes, Culex and Anopheles larvae. Cry toxins are composed of three domains (perforating domain I and receptor binding II and III) and create cation-selective channels, whereas Cyts are composed of one domain that acts as well as a detergent-like membrane perforator. Despite the low toxicities of Cyt1Aa and Cyt2Ba alone against exposed larvae, they are highly synergistic with the Cry toxins and hence their combinations prevent emergence of resistance in the targets. The lack of significant levels of resistance in field mosquito populations treated for decades with Bti-bioinsecticide suggests that this bacterium will be an effective biocontrol agent for years to come.
The Cytocidal Spectrum of Bacillus thuringiensis Toxins: From Insects to Human Cancer Cells
Toxins
Bacillus thuringiensis (Bt) is a ubiquitous bacterium in soils, insect cadavers, phylloplane, water, and stored grain, that produces several proteins, each one toxic to different biological targets such as insects, nematodes, mites, protozoa, and mammalian cells. Most Bt toxins identify their particular target through the recognition of specific cell membrane receptors. Cry proteins are the best-known toxins from Bt and a great amount of research has been published. Cry are cytotoxic to insect larvae that affect important crops recognizing specific cell membrane receptors such as cadherin, aminopeptidase-N, and alkaline phosphatase. Furthermore, some Cry toxins such as Cry4A, Cry4B, and Cry11A act synergistically with Cyt toxins against dipteran larvae vectors of human disease. Research developed with Cry proteins revealed that these toxins also could kill human cancer cells through the interaction with specific receptors. Parasporins are a small group of patented toxins that may or...
Molecular Approaches to Improve the Insecticidal Activity of Bacillus thuringiensis Cry Toxins
Toxins, 2014
Bacillus thuringiensis (Bt) is a gram-positive spore-forming soil bacterium that is distributed worldwide. Originally recognized as a pathogen of the silkworm, several strains were found on epizootic events in insect pests. In the 1960s, Bt began to be successfully used to control insect pests in agriculture, particularly because of its specificity, which reflects directly on their lack of cytotoxicity to human health, non-target organisms and the environment. Since the introduction of transgenic plants expressing Bt genes in the mid-1980s, numerous methodologies have been used to search for and improve toxins derived from native Bt strains. These improvements directly influence the increase in productivity and the decreased use of chemical insecticides on OPEN ACCESS Toxins 2014, 6 2394 Bt-crops. Recently, DNA shuffling and in silico evaluations are emerging as promising tools for the development and exploration of mutant Bt toxins with enhanced activity against target insect pests. In this report, we describe natural and in vitro evolution of Cry toxins, as well as their relevance in the mechanism of action for insect control. Moreover, the use of DNA shuffling to improve two Bt toxins will be discussed together with in silico analyses of the generated mutations to evaluate their potential effect on protein structure and cytotoxicity.
Promising active bioinsecticides produced by Bacillus thuringiensis strain BLB427
World Journal of Advanced Research and Reviews
Bacillus thuringiensis is gaining worldwide importance in the control of pests in agriculture and public health. Characterization of new isolated strains with original, higher and broader spectrum of activity is an ever developing field. Parasporal inclusions from BLB427, a new B. thuringiensis strain isolated from Tunisian soil, contained 2 major Cry proteins having molecular weights of about 130-135 kDa and 65-70 kDa corresponding to cry1-type and cry2-type genes, respectively. These toxins exhibited high toxicities to Ephestia kuehniella and Spodoptera littoralis larvae, with LC50 values of about 81.91 µg/cm 2 (+/-15.30) and 79.70 µg/cm 2 (+/-36.73), respectively. BLB427 supernatant showed a promising activity against Lepidopteran pests due to the presence of vip3-type gene in this strain. The high toxicity of BLB427 supernatant compared to that of BUPM95, used as control, was due in part to the high copy number of vip3 gene of BLB427 compared to that of vip3Aa16 of BUPM95, as demonstrated by Real-time PCR. This gene was cloned, sequenced and the comparison with the most known vip3 genes in databases, demonstrated that vip3(427) gene and the corresponding protein showed differences that can influence the efficiency of the Vip3(427) toxin against Lepidoptera. After overexpression of Vip3(427) protein in Esherichia coli and its purification using His-Trap column, the toxin showed a promising toxicity against the lepidopteran pest S. littoralis with extremely damages in the larvae midgut traduced by the vacuolization of the apical cells, the damage of microvilli and the disruption of epithelial cells. The results described in the present study proved that B. thuringiensis BLB427 strain could be of a great interest for lepidopteran biocontrol by using its -endotoxins and/or Vip3 toxins in bioinsecticides formulations.
Gene, 1986
Cloning and expression of the lepidopteran toxin produced by ~aciZ~~s t~uringie~sis var. t~uri~gie~sis in Escherichia coli (Recombinant DNA; plasmid size determination; pACYC; restriction analysis; colony hybridization, bioassay) SUMMARY The BaciZlus thuringiensis var. thuringiensis strain 3A produces a proteinaceous parasporal crystal toxic to larvae of a variety of lepidopteran pests including Spodoptera littoralis (Egyptian cotton leaf worm), Heliothis zeae, H. virescens and Boarmia selenaria. By cloning of individual plasmids of B. thuringiensis in Escherichia coli, we localized a gene coding for the delta-endotoxin on the B. thuringiensis plasmid of about 17 kb designated pTN4. Following partial digestion of the B. th~r~ngiensjs plasmid pTN4 and cloning into the E. co/i pACYC 184 plasmid three clones were isolated in which toxin production was detected. One of these hybrid plasmids pTNG43 carried a 1.7-kb insert that hybridized to the 14-kb BumHI DNA fragments of B. thuringiensis var. thuringiensis strains 3A and berliner 1715. This BamHI DNA fragment of strain bet-finer 17 15 has been shown to contain the gene that codes for the toxic protein of the crystal . No homologous sequences have been found between pTNG33 and the DNA of B. thu~ngie~is var. e~tomocidMs strain 24, which exhibited insecticidal activity against S. littoralis similar to that of strain 3A.