68038-71-1

Basic information

• Product Name: Bacillus thuringiensis
• Synonyms: BACILLUS THURINGIENSIS;Bactospeine(distributor,Biochem Products Ltd);Condor,Cutlass(Roussel-Uclaf Group);BACILLUS THURINGENSIS;BIOTROL4K;Bacilex;THURICIDE-HP;DIPEL
• CAS NO: 68038-71-1
• Molecular Formula: C22H32N5O16P
• Molecular Weight: 0
• EINECS: 1806241-263-5
• Product Categories: INSECTICIDE
• Mol File: 68038-71-1.mol
• Article Data: 0

Chemical Properties

• Boiling Point: 100°C
• Appearance: powder
• Density: 09 mg/ml
• CAS DataBase Reference: Bacillus thuringiensis(CAS DataBase Reference)
• NIST Chemistry Reference: Bacillus thuringiensis(68038-71-1)
• EPA Substance Registry System: Bacillus thuringiensis(68038-71-1)

Safety Data

• Hazardous Substances Data: 68038-71-1(Hazardous Substances Data)

Usage

Description

Bacillus thuringiensis, also known as Bt, is a naturally occurring rod-shaped, spore-forming, aerobic, gram-positive micro-organism (bacterium) that can be found in soils, on leaves/needles, and in other common environmental situations throughout most areas of the world. When the bacteria produces spores, it also produces unique crystalline proteins that are toxic to certain insects but not to human beings, birds, or other animals. Bt is differentiated from other spore-forming bacilli by the presence of a parasporal body, a high-molecular-mass protein crystal with insecticidal properties.

Uses

Used in Agriculture:
Bacillus thuringiensis is used as a bioinsecticide for controlling disease-vector insect and crop pest populations. Its insecticidal protein genes have been incorporated into several major crops, making it an effective control strategy for pests such as lepidopteran defoliators, which are pests of coniferous forests mainly in Canada and the United States.
Used in Public Health:
Bacillus thuringiensis subsp. israelensis (Bti) is highly active against larvae of disease-vector mosquitoes like Aedes aegypti (vector of dengue fever), Aedes albopictus (vector of chikungunya), Simulium damnosum (vector of onchocerciasis), and certain Anopheles species (vectors of malaria). Bti formulations have been evaluated by the World Health Organization Pesticide Evaluation Scheme (WHOPES) and recommended as mosquito larvicides, including their use against mosquito larvae that develop in drinking-water containers.
The successful application of Bt is highly dependent on proper timing, weather conditions, and dosage of spray applications, which combine to determine the probability of larvae ingesting a lethal dose. However, the widespread use of Bt crops has led to concerns about their potential effects on the environment and human health.

History

Bacillus thuringiensis (Bt) is a bacterium that was first identified by S. Ishiwata in 1901 in Japanese silkworms presenting flacherie, or flaccid disease. It was later scientifically described and named by E. Berliner in Thüringen, Germany (Knowles 1994) . Berliner noted that the bacterium was producing insecticidal crystal (Cry) proteins, which were causing cell death in the digestive tract. These proteins have been used in insecticidal sprays and dusts to control pest insects since the 1930s. However, today they are most widely utilized as a transgene inserted into crop plants. These transgenic plants (Bt crops) are able to express the bacterial toxin-genes to defend themselves against herbivory. The use of these crops has been effective in controlling pest populations and increasing crop yield and quality. Bt crops were first commercialized in 1996 and, in 2013 187.5 million acres of Bt transgenic crops were planted worldwide (James et al. 2014).

Biological Functions

These early experiments showed that Bt toxins needed to be activated in the gut, and it was soon discovered that the critical factors were an alkaline environment and the presence of specific proteases, which cleaved the innocuous protoxin into its active form. Once activated by proteolysis, each toxin binds to receptors in the brush border membrane and causes pores to open, disrupting them ovement of solutes across the gut epithelium and causing the influx of water. The toxins were shown to be orally lethal to caterpillars in pure form, and the pro-toxins could be converted into active toxinsin vitro, using specific pro-teases under alkaline conditions. The requirement for alkaline conditions, specific proteases and specific receptors explains why Bt is harmless to mammals (which have anacidic gut and lack the corresponding receptors) and why each toxin has a narrow host range. Nine common pests of rice, cotton and maize that are controlled by Bt crops

Health Hazard

The insecticidal action of B.t. is attributed to protein crystals produced by the bacte- rium. Exposures of test animals to B.t. using several routes did not produce any acute toxicity in birds, dogs, guinea pigs, mice, or rats. Also laboratory rats when injected with B.t.k., showed no toxic or virus-like effects. No oral toxicity was found in rats, mice, or Japanese quail fed protein crystals from B.t. var. israelensis. Studies indicated that after rats ate B.t., the microorganism remained in the digestive system until it was eliminated from the body. Rabbits exposed to B.t. showed mild skin irritation and rats showed low inhalation toxicity to B.t. In fact, chronic toxicity studies in dogs, guinea pigs, rats, and other species of test animals showed no evidence of adverse health effects. The toxicity of B.t. is insect specii c. Researches have provided valuable data and identii ed B.t. subspecies that differ in toxicity to different insects. Examples of B.t. subspecies and the insects they affect are aizawai (moths), kurstaki (moths), israelen- sis (mosquitoes and l ies), and tenebrionis (beetles). Also, phytotoxicity studies (plant researches) showed B.t. genes in some crops (B.t. crops) to combat insects of corn crops, cotton, and potatoes. B.t. must be eaten by insects to be effective and works by interfer- ing with digestion. Insects are most sensitive to B.t. when they are larvae, an immature life stage. Insects that eat B.t., die from hunger or infection. It does not cause disease outbreaks in insect populations. B.t. may produce toxic chemicals that are released from the organism

Safety Profile

Low toxicity by ingestion and skincontact. When heated to decomposition it emits acridsmoke and irritating vapors.

Environmental Fate

Bt Cry and Cyt toxins belong to a class of bacterial toxins known as pore-forming toxins (PFT) that are secreted as watersoluble proteins undergoing conformational changes in order to insert into, or to translocate across, cell membranes of their host. The primary action of Cry toxins is to lyse midgut epithelial cells in the target insect by forming pores in the apical microvilli membrane of the cells. Bt is ineffective against adult insects and must be eaten by feeding larvae in order to be toxic. When ingested by insect larvae, sporulated-Bt crystalline inclusions dissolve in the alkaline environment of insect gut, and the solubilized inactive protoxins are converted into protease resistant active Cry and Cyt toxins. Toxin activation involves N-terminal, Cterminal, and intra-molecular cleavage. The activated Cry toxins are composed of three functional domains, a seven ahelices bundle that is involved in membrane insertion (domain I), and two b-sheet domains (domains II and III) involved in receptor interactions. Once activated, Cry toxins bind to specific receptors on the brush border membrane of the midgut epithelium columnar cells before inserting into the membrane. Toxin insertion leads to the formation of lytic pores in microvilli of apical membranes. Subsequently cell lysis and disruption of the midgut epithelium release the cell content providing the spores with a germinating medium leading to a severe septicemia and insect death.

Toxicity evaluation

Bt is moderately persistent in soil with a half-life of ca. 4 months. Bt subsp. israelensis is often applied directly to water for the control of mosquitoes and blackflies. It has been demonstrated that the sedimentation of Bti is facilitated by adsorption onto particulate material. Bti can persist as long as 5 months in cold water, and adsorption to particulate matter in water facilitates persistence. Bt is relatively short-lived on foliage due to rapid photodegradation. Its half-life under normal sunlight conditions is 3.8 h. In general, Bt loses 50% of its insecticide activity in 1-3 days after spraying. However, high toxicity toward mosquito larvae has been found in decaying leaf litter collected in several natural mosquito breeding sites in forested areas. From the toxic fraction of the leaf litter, B. cereus-like bacteria were isolated and further characterized as Bt subsp. israelensis using PCR (polymerase chain reaction) amplification of specific toxin genes. The anthropogenic origin of Bti was demonstrated by amplified fragment length polymorphism (AFLP) profile comparisons. Nevertheless, persistence of acute toxicity several months after Bti spraying remains exceptional, as this was only observed once in only one out of eight sampling sites. In this particular site, Bti spores and toxins may be protected from degradation by the vegetal matrix.