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Bacillus thuringiensis is a gram-positive, soil-dwelling bacterium, the most commonly used biological pesticide worldwide. B. thuringiensis also occurs naturally in the gut of caterpillars of various types of moths and butterflies, as well on leaf surfaces, aquatic environments, animal feces, insect-rich environments, flour mills and grain-storage facilities. It has also been observed to parasitize moths such as Cadra calidella—in laboratory experiments working with C. calidella, many of the moths were diseased due to this parasite.
Genetically modified maize (corn) is a genetically modified crop. Specific maize strains have been genetically engineered to express agriculturally-desirable traits, including resistance to pests and to herbicides. Maize strains with both traits are now in use in multiple countries. GM maize has also caused controversy with respect to possible health effects, impact on other insects and impact on other plants via gene flow. One strain, called Starlink, was approved only for animal feed in the US but was found in food, leading to a series of recalls starting in 2000.
Agricultural biotechnology, also known as agritech, is an area of agricultural science involving the use of scientific tools and techniques, including genetic engineering, molecular markers, molecular diagnostics, vaccines, and tissue culture, to modify living organisms: plants, animals, and microorganisms. Crop biotechnology is one aspect of agricultural biotechnology which has been greatly developed upon in recent times. Desired trait are exported from a particular species of Crop to an entirely different species. These transgene crops possess desirable characteristics in terms of flavor, color of flowers, growth rate, size of harvested products and resistance to diseases and pests.
Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Acaricides, which kill mites and ticks, are not strictly insecticides, but are usually classified together with insecticides. The major use of Insecticides is agriculture, but they are also used in home and garden, industrial buildings, vector control and control of insect parasites of animals and humans. Insecticides are claimed to be a major factor behind the increase in the 20th-century's agricultural productivity. Nearly all insecticides have the potential to significantly alter ecosystems; many are toxic to humans and/or animals; some become concentrated as they spread along the food chain.
Pesticide resistance describes the decreased susceptibility of a pest population to a pesticide that was previously effective at controlling the pest. Pest species evolve pesticide resistance via natural selection: the most resistant specimens survive and pass on their acquired heritable changes traits to their offspring. If a pest has resistance then that will reduce the pesticide's efficacy – efficacy and resistance are inversely related.
Bacillus thuringiensis serotype israelensis (Bti) is a group of bacteria used as biological control agents for larvae stages of certain dipterans. Bti produces toxins which are effective in killing various species of mosquitoes, fungus gnats, and blackflies, while having almost no effect on other organisms. The major advantage of B. thuringiensis products is that they are thought to affect few non-target species. However, even though Bti may have minimal direct effects on non-target organisms, it may potentially be associated with knock-on effects on food webs and other ecosystem properties, including biodiversity and ecosystem functioning.
The Western corn rootworm, Diabrotica virgifera virgifera, is one of the most devastating corn rootworm species in North America, especially in the midwestern corn-growing areas such as Iowa. A related species, the Northern corn rootworm, D. barberi, co-inhabits in much of the range and is fairly similar in biology.
Bt cotton is a genetically modified pest resistant plant cotton variety that produces an insecticide to combat bollworm.
Signal recognition particle (SRP) receptor, also called the docking protein, is a dimer composed of 2 different subunits that are associated exclusively with the rough ER in mammalian cells. Its main function is to identify the SRP units. SRP is a molecule that helps the ribosome-mRNA-polypeptide complexes to settle down on the membrane of the endoplasmic reticulum.
Pore-forming proteins are usually produced by bacteria, and include a number of protein exotoxins but may also be produced by other organisms such as apple snails that produce perivitellin-2 or earthworms, who produce lysenin. They are frequently cytotoxic, as they create unregulated pores in the membrane of targeted cells.
MON 863 is a genetically engineered variety of maize produced by Monsanto. It is genetically altered to express a modified version of Cry3Bb1, a delta endotoxin which originates from Bacillus thuringiensis. This protects the plant from corn rootworm. Unlike MON 810, Bt 11, and Bt 176 which each produce a modified Cry1Ab, MON 863 instead produces a modified Cry3Bb1 toxin and contains nptII, a marker gene for antibiotic resistance.
Lysinibacillus sphaericus is a Gram-positive, mesophilic, rod-shaped bacterium commonly found on soil. It can form resistant endospores that are tolerant to high temperatures, chemicals and ultraviolet light and can remain viable for long periods of time. It is of particular interest to the World Health Organization due to the larvicide effect of some strains against two mosquito genera, more effective than Bacillus thuringiensis, frequently used as a biological pest control. L. sphaericus cells in a vegetative state are also effective against Aedes aegypti larvae, an important vector of yellow fever and dengue viruses.
Delta endotoxins (δ-endotoxins) are a family of pore-forming toxins produced by Bacillus thuringiensis species of bacteria. They are useful for their insecticidal action and are the primary toxin produced by the genetically modified (GM) Bt maize/corn and other GM crops. During spore formation the bacteria produce crystals of such proteins that are also known as parasporal bodies, next to the endospores; as a result some members are known as a parasporin. The Cyt (cytolytic) toxin group is another group of delta-endotoxins formed in the cytoplasm. VIP toxins are formed at other stages of the life cycle.
Scorpion toxins are proteins found in the venom of scorpions. Their toxic effect may be mammal- or insect-specific and acts by binding with varying degrees of specificity to members of the Voltage-gated ion channel superfamily; specifically, voltage-gated sodium channels, voltage-gated potassium channels, and Transient Receptor Potential (TRP) channels. The result of this action is to activate or inhibit the action of these channels in the nervous and cardiac organ systems. For instance, α-scorpion toxins MeuNaTxα-12 and MeuNaTxα-13 from Mesobuthus eupeus are neurotoxins that target voltage-gated Na+ channels (Navs), inhibiting fast inactivation. In vivo assays of MeuNaTxα-12 and MeuNaTxα-13 effects on mammalian and insect Navs show differential potency. These recombinants exhibit their preferential affinity for mammalian and insect Na+ channels at the α-like toxins' active site, site 3, in order to inactivate the cell membrane depolarization faster[6]. The varying sensitivity of different Navs to MeuNaTxα-12 and MeuNaTxα-13 may be dependent on the substitution of a conserved Valine residue for a Phenylalanine residue at position 1630 of the LD4:S3-S4 subunit or due to various changes in residues in the LD4:S5-S6 subunit of the Navs. Ultimately, these actions can serve the purpose of warding off predators by causing pain or to subdue predators.
Bacillus anthracis is a gram-positive and rod-shaped bacterium that causes anthrax, a deadly disease to livestock and, occasionally, to humans. It is the only permanent (obligate) pathogen within the genus Bacillus. Its infection is a type of zoonosis, as it is transmitted from animals to humans. It was discovered by a German physician Robert Koch in 1876, and became the first bacterium to be experimentally shown as a pathogen. The discovery was also the first scientific evidence for the germ theory of diseases.
The AB toxins are two-component protein complexes secreted by a number of pathogenic bacteria, though there is a pore-forming AB toxin found in the eggs of a snail. They can be classified as Type III toxins because they interfere with internal cell function. They are named AB toxins due to their components: the "A" component is usually the "active" portion, and the "B" component is usually the "binding" portion. The "A" subunit possesses enzyme activity, and is transferred to the host cell following a conformational change in the membrane-bound transport "B" subunit. These proteins consist of two independent polypeptides, which correspond to the A/B subunit moieties. The enzyme component (A) enters the cell through endosomes produced by the oligomeric binding/translocation protein (B), and prevents actin polymerisation through ADP-ribosylation of monomeric G-actin.
The MON 810 corn is a genetically modified maize used around the world. It is a Zea mays line known as YieldGard from the company Monsanto. This plant is a genetically modified organism (GMO) designed to combat crop loss due to insects. There is an inserted gene in the DNA of MON 810 which allows the plant to make a protein that harms insects that try to eat it. The inserted gene is from the Bacillus thuringiensis which produces the Bt protein that is poisonous to insects in the order Lepidoptera, including the European corn borer.
Cry1Ac protoxin is a crystal protein produced by the gram-positive bacterium, Bacillus thuringiensis (Bt) during sporulation. Cry1Ac is one of the delta endotoxins produced by this bacterium which act as insecticides. Because of this, the genes for these have been introduced into commercially important crops by genetic engineering in order to confer pest resistance on those plants.
Bacillus thuringiensis subsp. kurstaki (Btk) is a group of bacteria used as biological control agents against lepidopterans. Btk, along with other B. thuringiensis products, is one of the most widely used biological pesticides due to its high specificity; it is effective against lepidopterans, and it has little to no effect on nontarget species. During sporulation, Btk produces a crystal protein that is lethal to lepidopteran larvae. Once ingested by the insect, the dissolution of the crystal allows the protoxin to be released. The toxin is then activated by the insect gut juice, and it begins to break down the gut.
Cry6Aa is a toxic crystal protein generated by the bacterial family Bacillus thuringiensis during sporulation. This protein is a member of the alpha pore forming toxins family, which gives it insecticidal qualities advantageous in agricultural pest control. Each Cry protein has some level of target specificity; Cry6Aa has specific toxic action against coleopteran insects and nematodes. The corresponding B. thuringiensis gene, cry6aa, is located on bacterial plasmids. Along with several other Cry protein genes, cry6aa can be genetically recombined in Bt corn and Bt cotton so the plants produce specific toxins. Insects are developing resistance to the most commonly inserted proteins like Cry1Ac. Since Cry6Aa proteins function differently than other Cry proteins, they are combined with other proteins to decrease the development of pest resistance. Recent studies suggest this protein functions better in combination with other virulence factors such as other Cry proteins and metalloproteinases.>
References
- 1 2 Moellenbeck DJ, Peters ML, Bing JW, Rouse JR, Higgins LS, Sims L, et al. (July 2001). "Insecticidal proteins from Bacillus thuringiensis protect corn from corn rootworms". Nature Biotechnology. 19 (7): 668–72. doi:10.1038/90282. PMID 11433280. S2CID 18133775.
- 1 2 Li H, Olson M, Lin G, Hey T, Tan SY, Narva KE (2013-01-04). "Bacillus thuringiensis Cry34Ab1/Cry35Ab1 interactions with western corn rootworm midgut membrane binding sites". PLOS ONE. 8 (1): e53079. Bibcode:2013PLoSO...853079L. doi: 10.1371/journal.pone.0053079 . PMC 3537739 . PMID 23308139.
- ↑ Palma L, Muñoz D, Berry C, Murillo J, Caballero P (December 2014). "Bacillus thuringiensis toxins: an overview of their biocidal activity". Toxins. 6 (12): 3296–325. doi: 10.3390/toxins6123296 . PMC 4280536 . PMID 25514092.
- 1 2 3 Kelker MS, Berry C, Evans SL, Pai R, McCaskill DG, Wang NX, et al. (2014-11-12). "Structural and biophysical characterization of Bacillus thuringiensis insecticidal proteins Cry34Ab1 and Cry35Ab1". PLOS ONE. 9 (11): e112555. Bibcode:2014PLoSO...9k2555K. doi: 10.1371/journal.pone.0112555 . PMC 4229197 . PMID 25390338.
