What plasmid is required for Crystal toxin production in Bacillus thuringiensis variety israelensis?
A large transmissible plasmid is required for crystal toxin production in Bacillus thuringiensis variety israelensis. Plasmid. 1984;11:28–38. doi: 10.1016/0147-619X(84)90004-0. [PubMed] [CrossRef] [Google Scholar]
What is the function of Bt toxin?
Bt thus synthesizes a vast number of protein toxins with activity against a wide range of organisms in nature, including not only a broad range of insect orders but also nematodes, a human-pathogenic protozoan, animal and human parasites plus different human-cancer cell lines [5,9,11,26,30,113].
What is BT δ-endotoxins (Cry and Cyt)?
Summarized view showing the known host spectrum of Bt δ-endotoxins (Cry and Cyt) [9,26]. Cry1A-C (separated by hyphen) indicates a group of C3y1A, Cry1B and Cry1C toxins. Cry1B, I (separated by colon) indicates different Cry1B and Cry1I toxins. Semicolons separate groups or individual toxins. Cyt toxins are in red.
Where do cry1a toxins of Bacillus thuringiensis bind?
"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". Insect Biochemistry and Molecular Biology. 32 (9): 1025–36. doi: 10.1016/S0965-1748 (02)00040-1.
What is the name of the cytolytic toxins in Bt?
What is Bt bacterium?
What are the secreted proteins in Bt?
What is the largest group of insecticidal proteins produced by species of Bacillus?
What is a Bt?
Why are Bt crystals important?
What is the mode of action of cry toxins?
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About this website
What is the name of the gene that encodes the Bt endotoxin?
The insecticidal toxins (Cry toxins) of Bt, oftentimes referred to as δ-endotoxins after Heimpel,52 are somewhat specific to certain insects. The family of genes coding for these toxins is the cry gene family.
Which toxin is produced by Bacillus thuringiensis?
Abstract. Bacillus thuringiensis bacteria produce different insecticidal proteins known as Cry and Cyt toxins. Among them the Cyt toxins represent a special and interesting group of proteins. Cyt toxins are able to affect insect midgut cells but also are able to increase the insecticidal damage of certain Cry toxins.
How is Bt toxin produced?
Bt toxins are produced by soil bacteria Bacillus thuringiensis [3]. In their native form, a subgroup of Bt toxins, classified as Cry toxins, are mostly regarded as safe for human health and the environment because of their mode of action, that requires a basic pH and some specific receptors and enzymes [4].
Where do cry gene product is converted into active toxin?
It is proposed that Cry toxins bind to specific protein receptors in the microvilli of the mosquito midgut cells.
What is true about Bt toxin?
Bt toxin kills certain insects such as lepidopterans (tobacco budworm, armyworm), coleopterans (beetles) and dipterans (flies, mosquitoes). But, actually, the Bt toxin protein exists as inactive protoxins.
Which of the following is incorrect with respect to Bt toxin?
Bt toxin does not kill the bacteria themselves because toxin proteins occur in inactive form called protoxin.
Why is the gene coding for Bt toxin called Cry?
Detailed Solution Bacillus thuringiensis, produces crystals (Cry) protein. This Cry protein is a toxin to Larvae of certain insects. Each Cry protein is toxic to a different group of insects. The gene encoding cry protein is called the "cry gene".
How does Bt gene work Bt gene?
Bt has to be eaten to cause mortality. The Bt toxin dissolve in the high pH insect gut and become active. The toxins then attack the gut cells of the insect, punching holes in the lining. The Bt spores spills out of the gut and germinate in the insect causing death within a couple days.
What is Bt and how is it produced?
Bt Crops are transgenic crops that produce the same toxin as the bacterium Bacillus thuringiensis in the plant cell, thereby, protecting the crops from pests. The bacterium secretes specific proteins known as “cry proteins” that are toxic to insects. A few of the Bt crops include cotton, brinjal, corn, etc.
What is the Bt toxin gene for CRY protein?
thuringiensis cry genes is due to the expression of bacterial prokaryotic genes in higher plants or in any other eukaryotic organism. Fully modified genes can express up to 100-fold higher level of insecticidal toxin compared to those levels obtained when typical bacterial gene is expressed.
In which of the following plant Bt toxin gene is expressed?
Bt toxin gene has been closed from the bacteria and expressed in plants to provide resistance to insects without the need for insecticides. Examples are Bt cotton, Bt corn, rice, tomato, potato and soybean, etc.
On which group is Bt toxin effective?
These toxins have been successfully used as bioinsecticides against caterpillars, beetles, and flies, including mosquitoes and blackflies. Bt also synthesizes insecticidal proteins during the vegetative growth phase, which are subsequently secreted into the growth medium.
What is Bacillus thuringiensis for?
B.t. is a naturally occurring bacteria that is commonly found in soil and food. B.t. has been used safely for over 30 years to control insects in the United States, Canada, and other parts in the world. B.t. operates through a well-known protein mechanism that causes toxicity in caterpillars (i.e. insect larvae).
In which plants Bt toxin is used?
Bt toxin can be applied to crops, including potatoes, corn, and cotton, as a spray or, less commonly, in granular form. Bt proteins can also be introduced into the crops themselves through genetic engineering.
Is Bt toxin harmful to humans?
Bt is a bacterium that is not toxic to humans or other mammals but is toxic to certain insects when ingested. Bt works as an insecticide by producing a crystal-shaped protein (Cry toxin) that specifically kills certain insects.
What is the Bt toxin gene for CRY protein?
thuringiensis cry genes is due to the expression of bacterial prokaryotic genes in higher plants or in any other eukaryotic organism. Fully modified genes can express up to 100-fold higher level of insecticidal toxin compared to those levels obtained when typical bacterial gene is expressed.
How do toxins from Bacillus thuringiensis kill insects? An evolutionary ...
Three-domain Cry toxins from the bacterium Bacillus thuringiensis (Bt) are increasingly used in agriculture to replace chemical insecticides in pest control. Most chemical insecticides kill pest insects swiftly, but are also toxic to beneficial insects and other species in the agroecosystem. Cry tox …
Toxicity of Bacillus thuringiensis-Derived Pesticidal Proteins Cry1Ab ...
2.1. Bt Strain-Derived Toxins with Activity against Asian Citrus Psyllid (ACP) To identify Bt strain-derived toxins that have toxicity against ACP, toxin mixtures derived from each of 18 Bt strains and two recombinant Bt Cry toxins were screened in ACP bioassays using toxin preparations that had been solubilized and trypsin activated to expose ACP to activated toxins (Table 1).
What is the name of the cytolytic toxins in Bt?
Bt strains synthesize Crystal (Cry) and cytolytic (Cyt) toxins, (also known as δ-endotoxins), at the onset of sporulation and during the stationary growth phase as parasporal crystalline inclusions (Figure 1). Once ingested by insects, these crystals are solubilized in the midgut, the toxins are then proteolytically activated by midgut proteases and bind to specific receptors located in the insect cell membrane [5,7], leading to cell disruption and insect death.
What is Bt bacterium?
Bacillus thuringiensis(Bt) is a Gram positive, spore-forming bacterium that synthesizes parasporal crystalline inclusions containing Cry and Cyt proteins, some of which are toxic against a wide range of insect orders, nematodes and human-cancer cells . These toxins have been successfully used as bioinsecticides against caterpillars, beetles, and flies, including mosquitoes and blackflies. Bt also synthesizes insecticidal proteins during the vegetative growth phase, which are subsequently secreted into the growth medium. These proteins are commonly known as vegetative insecticidal proteins (Vips) and hold insecticidal activity against lepidopteran, coleopteran and some homopteran pests. A less well characterized secretory protein with no amino acid similarity to Vip proteins has shown insecticidal activity against coleopteran pests and is termed Sip (secreted insecticidal protein). Bin-like and ETX_MTX2-family proteins (Pfam PF03318), which share amino acid similarities with mosquitocidal binary (Bin) and Mtx2 toxins, respectively, from Lysinibacillus sphaericus, are also produced by some Bt strains. In addition, vast numbers of Bt isolates naturally present in the soil and the phylloplane also synthesize crystal proteins whose biological activity is still unknown. In this review, we provide an updated overview of the known active Bt toxins to date and discuss their activities.
What are the secreted proteins in Bt?
The secreted insecticidal proteins constitute two classes that were designated as vegetative insecticidal proteins (Vip) [8,13,14] and secreted insecticidal protein (Sip) [15]. Currently, the Bt Toxin Nomenclature Committee [8] has identified and classified Vip proteins into four different families namely Vip1, Vip2, Vip3 and a novel family of Vip proteins, recently identified and classified as Vip4 by the Bt Toxin Nomenclature Committee [8]. Bt secretable proteins like Vip1, Vip2 and Sip, contain conserved signal peptide sequences that are commonly cleaved before or after the secretion process is completed [13,14,15,21,74]. Vip1 and Vip2 constitute a binary toxin with high insecticidal activity against some coleopteran pests [14] and the sap-sucking insect pest Aphis gossypii(Hemiptera) [75]. In contrast, Vip3 proteins are single-chain (not binary) toxins with insecticidal activity against a wide variety of lepidopteran species [13].
What is the largest group of insecticidal proteins produced by species of Bacillus?
Currently, the Cry proteins constitute the largest group of insecticidal proteins produced by species of Bacillus. To date, the Bt Toxin Nomenclature Committee [8] has classified 73 different types (Cry1 to Cry73) of Cry proteins, including three-domain and ETX_MTX2 family proteins from Bt and Ls, with individual toxins showing well documented toxicity against lepidopterans, coleopterans, hemipterans, dipterans, nematodes (human and animal parasites, and free living; Rhabditida) some snails [1,5,9,18,21,25,26,27,28] and/or human-cancer cells of various origins [11,12] (Figure 3).
What is a Bt?
Bacillus thuringiensis(Bt) is a ubiquitous Gram-positive, rod-shaped and sporulating bacterium that has been isolated worldwide from a great diversity of ecosystems including soil, water, dead insects, dust from silos, leaves from deciduous trees, diverse conifers, and insectivorous mammals, as well as from human tissues with severe necrosis [1,2,3,4]. Bt strains produce a wide variety of insecticidal proteins active against larvae of very diverse insect orders as well as, in some cases, against species from other phyla. This has led Bt-based products to become the best selling biological insecticides to date [4,5] since the genes encoding insecticidal proteins have been successfully used in novel insecticidal formulations and in the construction of transgenic crops [6].
Why are Bt crystals important?
Bt crystal and secreted soluble toxins are highly specific for their hosts and have gained worldwide importance as an alternative to chemical insecticides. The usefulness of these insecticidal proteins has also motivated the search for new Bt isolates from the most diverse habitats in order to identify and characterize new insecticidal proteins with different specificities. Some of these isolates exhibit novel and unexpected toxic activities against organisms other than insects, suggesting a pluripotential nature of some toxins.
What is the mode of action of cry toxins?
Three different models have been proposed to explain the mode of action of three-domain Cry toxins: the “classical” model, the sequential binding model and the signaling pathway model [46]. The “classical” model basically proposes that the toxin lyses the midgut epithelial cells of susceptible insects throughout the following steps: (a) crystal inclusion ingestion and dissolution in the alkaline midgut lumen; (b) protoxin (native protein) proteolytic activation that turns the native Cry protein into smaller protease-resistant toxic polypeptides; (c) binding of toxin fragments to specific receptors on the surface of midgut epithelial cells; and (d) formation of non-selective pores permeable to inorganic ions, amino acids and sugars [46,47]. Such pores produce the lysis of epithelial cells and hence midgut disarrangements, leading to insect death. Additionally, spores may colonize, germinate, and replicate in the hemolymph, eventually killing larvae by septicemia [1,2,5]. Although this scheme has been accepted for many years, some details still remain poorly understood (e.g., pore structure and mechanism of pore assembly) [46]. The sequential binding model suggests that Cry toxins, once activated by intestinal proteases, bind to cadherin-like proteins (transmembrane glycoproteins that function as toxin receptors) and undergo a conformational change that favors proteolytic removal of the α-1 helix from domain I and formation of an oligomeric pre-pore structure. Later, binding to a secondary receptor, such as an aminopeptidase, facilitates the insertion of the pre-pore structure into the membrane, leading to cell and insect death [7,39]. In contrast, the signaling-pathway model suggests that the toxic activity is mediated by the specific binding to cadherin receptors, leading to undescribed Mg2+-dependent and adenylyl cyclase/protein kinase A signaling pathway that produces necrotic cell death [48]. Vachon et al.(2012) have recently reviewed experimental evidence supporting both the sequential binding and the pathway-signaling models [46]. These authors concluded that both models, and more importantly the sequential binding model, are supported by little reliable experimental evidence and that the present available information supports the “classical” model postulating that Cry toxins act by forming pores, although most events leading to their formation and receptor binding remain still poorly understood [48]. While cadherins and amino peptidases frequently emerge as candidates in Cry toxin binding [49], a number of other potential receptors have been proposed including alpha amylases and alpha glycosidases [50,51], prohibitin [52] and alkaline phosphatases [53,54]. The precise role of multiple putative receptors identified for individual toxins is, as yet, unclear.
What is beta exotoxin?
Beta-exotoxin is a nucleotide analogue produced by the entomopathogenic bacterium Bacillus thuringiensis. We have defined two new HPLC procedures for quantification of this exotoxin in culture supernatants of B. thuringiensis grown in poor or rich medium. The sample is prepared either by precipitation in solvent or by solid-phase extraction. Solvent precipitation is achieved treating the sample with acetone and acetonitrile. Solid-phase extraction is performed with a C18 and an anion-exchange cartridge. Reversed-phase HPLC with gradient elution of the prepared samples gives a limit of quantitation of 2 microg/ml for samples prepared by solvent precipitation and of 0.3 microg/ml for samples prepared by solid-phase extraction.
What is Bt bacterium?
Bacillus thuringiensis (Bt) is a Gram positive, spore-forming bacterium that synthesizes parasporal crystalline inclusions containing Cry and Cyt proteins, some of which are toxic against a wide range of insect orders, nematodes and human-cancer cells . These toxins have been successfully used as bioinsecticides against caterpillars, beetles, and flies, including mosquitoes and blackflies. Bt also synthesizes insecticidal proteins during the vegetative growth phase, which are subsequently secreted into the growth medium. These proteins are commonly known as vegetative insecticidal proteins (Vips) and hold insecticidal activity against lepidopteran, coleopteran and some homopteran pests. A less well characterized secretory protein with no amino acid similarity to Vip proteins has shown insecticidal activity against coleopteran pests and is termed Sip (secreted insecticidal protein). Bin-like and ETX_MTX2-family proteins (Pfam PF03318), which share amino acid similarities with mosquitocidal binary (Bin) and Mtx2 toxins, respectively, from Lysinibacillus sphaericus, are also produced by some Bt strains. In addition, vast numbers of Bt isolates naturally present in the soil and the phylloplane also synthesize crystal proteins whose biological activity is still unknown. In this review, we provide an updated overview of the known active Bt toxins to date and discuss their activities.
What is Bt in soil?
Bacillus thuringiensis (Bt) is a Gram-positive soil bacteria that infects invertebrates, predominantly of Arthropoda phylum. Due to its immense host range Bt has become a leading producer of biopesticides applied both in biotechnology and agriculture. Cytotoxic effect of Bt, as well as its host specificity, are commonly attributed either to proteinaceous crystal parasporal toxins (Cry and Cyt) produced by bacteria in a stationary phase or to soluble toxins of Vip and Sip families secreted by vegetative cells. At the same time, numerous non-toxin virulence factors of Bt have been discovered, including metalloproteases, chitinases, aminopolyol antibiotics and nucleotide-mimicking moieties. These agents act at each stage of the B. thuringiensis invasion and contribute to cytotoxic properties of Bt strains enhancing toxin activity, ensuring host immune response evasion and participating in extracellular matrix degeneration. In this review we attempt to classify Bt virulence factors unrelated to major groups of protein toxins and discuss their putative role in the establishment of Bt specificity to various groups of insects.
Is Bacillus thuringiensis toxic?
Most toxins produce by this microorganism are highly specific, therefore the use of it in biological control is considered environmentally safe and so this bacteria is extensively used in the production of biological insecticides and genetically modified plants. However, the thuringiensin is considered toxic to almost all life forms, including humans, due to its ability to inhibit the biosynthesis of RNA polymerase, an enzyme essential to the transfer of genetic information in almost all organisms. This way, the release of new strains of Bt with insecticidal properties for the biological control of pests must pass by verification of the absence of production of exotoxin, so that non-target organisms are not affected and the use of Bt in this field remains safe. Thus, this revision will discussed the knowledge about features, structure, genetic determinants, biosynthesis, mechanism of action, insecticide spectrum, security assessment and procedures for identification of thuringiensin in Bt strains.
What is the name of the cytolytic toxins in Bt?
Bt strains synthesize Crystal (Cry) and cytolytic (Cyt) toxins, (also known as δ-endotoxins), at the onset of sporulation and during the stationary growth phase as parasporal crystalline inclusions (Figure 1). Once ingested by insects, these crystals are solubilized in the midgut, the toxins are then proteolytically activated by midgut proteases and bind to specific receptors located in the insect cell membrane [5,7], leading to cell disruption and insect death.
What is Bt bacterium?
Bacillus thuringiensis(Bt) is a Gram positive, spore-forming bacterium that synthesizes parasporal crystalline inclusions containing Cry and Cyt proteins, some of which are toxic against a wide range of insect orders, nematodes and human-cancer cells . These toxins have been successfully used as bioinsecticides against caterpillars, beetles, and flies, including mosquitoes and blackflies. Bt also synthesizes insecticidal proteins during the vegetative growth phase, which are subsequently secreted into the growth medium. These proteins are commonly known as vegetative insecticidal proteins (Vips) and hold insecticidal activity against lepidopteran, coleopteran and some homopteran pests. A less well characterized secretory protein with no amino acid similarity to Vip proteins has shown insecticidal activity against coleopteran pests and is termed Sip (secreted insecticidal protein). Bin-like and ETX_MTX2-family proteins (Pfam PF03318), which share amino acid similarities with mosquitocidal binary (Bin) and Mtx2 toxins, respectively, from Lysinibacillus sphaericus, are also produced by some Bt strains. In addition, vast numbers of Bt isolates naturally present in the soil and the phylloplane also synthesize crystal proteins whose biological activity is still unknown. In this review, we provide an updated overview of the known active Bt toxins to date and discuss their activities.
What are the secreted proteins in Bt?
The secreted insecticidal proteins constitute two classes that were designated as vegetative insecticidal proteins (Vip) [8,13,14] and secreted insecticidal protein (Sip) [15]. Currently, the Bt Toxin Nomenclature Committee [8] has identified and classified Vip proteins into four different families namely Vip1, Vip2, Vip3 and a novel family of Vip proteins, recently identified and classified as Vip4 by the Bt Toxin Nomenclature Committee [8]. Bt secretable proteins like Vip1, Vip2 and Sip, contain conserved signal peptide sequences that are commonly cleaved before or after the secretion process is completed [13,14,15,21,74]. Vip1 and Vip2 constitute a binary toxin with high insecticidal activity against some coleopteran pests [14] and the sap-sucking insect pest Aphis gossypii(Hemiptera) [75]. In contrast, Vip3 proteins are single-chain (not binary) toxins with insecticidal activity against a wide variety of lepidopteran species [13].
What is the largest group of insecticidal proteins produced by species of Bacillus?
Currently, the Cry proteins constitute the largest group of insecticidal proteins produced by species of Bacillus. To date, the Bt Toxin Nomenclature Committee [8] has classified 73 different types (Cry1 to Cry73) of Cry proteins, including three-domain and ETX_MTX2 family proteins from Bt and Ls, with individual toxins showing well documented toxicity against lepidopterans, coleopterans, hemipterans, dipterans, nematodes (human and animal parasites, and free living; Rhabditida) some snails [1,5,9,18,21,25,26,27,28] and/or human-cancer cells of various origins [11,12] (Figure 3).
What is a Bt?
Bacillus thuringiensis(Bt) is a ubiquitous Gram-positive, rod-shaped and sporulating bacterium that has been isolated worldwide from a great diversity of ecosystems including soil, water, dead insects, dust from silos, leaves from deciduous trees, diverse conifers, and insectivorous mammals, as well as from human tissues with severe necrosis [1,2,3,4]. Bt strains produce a wide variety of insecticidal proteins active against larvae of very diverse insect orders as well as, in some cases, against species from other phyla. This has led Bt-based products to become the best selling biological insecticides to date [4,5] since the genes encoding insecticidal proteins have been successfully used in novel insecticidal formulations and in the construction of transgenic crops [6].
Why are Bt crystals important?
Bt crystal and secreted soluble toxins are highly specific for their hosts and have gained worldwide importance as an alternative to chemical insecticides. The usefulness of these insecticidal proteins has also motivated the search for new Bt isolates from the most diverse habitats in order to identify and characterize new insecticidal proteins with different specificities. Some of these isolates exhibit novel and unexpected toxic activities against organisms other than insects, suggesting a pluripotential nature of some toxins.
What is the mode of action of cry toxins?
Three different models have been proposed to explain the mode of action of three-domain Cry toxins: the “classical” model, the sequential binding model and the signaling pathway model [46]. The “classical” model basically proposes that the toxin lyses the midgut epithelial cells of susceptible insects throughout the following steps: (a) crystal inclusion ingestion and dissolution in the alkaline midgut lumen; (b) protoxin (native protein) proteolytic activation that turns the native Cry protein into smaller protease-resistant toxic polypeptides; (c) binding of toxin fragments to specific receptors on the surface of midgut epithelial cells; and (d) formation of non-selective pores permeable to inorganic ions, amino acids and sugars [46,47]. Such pores produce the lysis of epithelial cells and hence midgut disarrangements, leading to insect death. Additionally, spores may colonize, germinate, and replicate in the hemolymph, eventually killing larvae by septicemia [1,2,5]. Although this scheme has been accepted for many years, some details still remain poorly understood (e.g., pore structure and mechanism of pore assembly) [46]. The sequential binding model suggests that Cry toxins, once activated by intestinal proteases, bind to cadherin-like proteins (transmembrane glycoproteins that function as toxin receptors) and undergo a conformational change that favors proteolytic removal of the α-1 helix from domain I and formation of an oligomeric pre-pore structure. Later, binding to a secondary receptor, such as an aminopeptidase, facilitates the insertion of the pre-pore structure into the membrane, leading to cell and insect death [7,39]. In contrast, the signaling-pathway model suggests that the toxic activity is mediated by the specific binding to cadherin receptors, leading to undescribed Mg2+-dependent and adenylyl cyclase/protein kinase A signaling pathway that produces necrotic cell death [48]. Vachon et al.(2012) have recently reviewed experimental evidence supporting both the sequential binding and the pathway-signaling models [46]. These authors concluded that both models, and more importantly the sequential binding model, are supported by little reliable experimental evidence and that the present available information supports the “classical” model postulating that Cry toxins act by forming pores, although most events leading to their formation and receptor binding remain still poorly understood [48]. While cadherins and amino peptidases frequently emerge as candidates in Cry toxin binding [49], a number of other potential receptors have been proposed including alpha amylases and alpha glycosidases [50,51], prohibitin [52] and alkaline phosphatases [53,54]. The precise role of multiple putative receptors identified for individual toxins is, as yet, unclear.