Quimica

Bacillus thuringiensis (or Bt) is a Gram-positive, soil-dwelling bacterium, commonly used as a biological pesticide; alternatively, the Cry toxin may be extracted and used as a pesticide. B.thuringiensis also occurs naturally in the gut of caterpillars of various types of moths and butterflies, as well as on the dark surfaces of plants.[1]
During sporulation, many Bt strains produce crystalproteins (proteinaceous inclusions), called δ-endotoxins, that have insecticidal action. This has led to their use as insecticides, and more recently to genetically modified crops using Bt genes. Thereare, however, many crystal-producing Bt strains that do not have insecticidal properties.[2]
Spores and crystalline insecticidal proteins produced by B. thuringiensis have been used to control insectpests since the 1920s.[11] They are now used as specific insecticides under trade names such as Dipel and Thuricide. Because of their specificity, these pesticides are regarded as environmentallyfriendly, with little or no effect on humans, wildlife, pollinators, and most other beneficial insects
B. thuringiensis-based insecticides are often applied as liquid sprays on crop plants, where theinsecticide must be ingested to be effective. The solubilized toxins are thought to form pores in the midgut epithelium of susceptible larvae. Recent research has suggested the midgut bacteria ofsusceptible larvae are required for B. thuringiensis insecticidal activity
Bt crops (in corn and cotton) were planted on 281,500 km² in 2006 (165,600 km² of Bt corn and 115900 km² of Bt cotton). This wasequivalent to 11.1% and 33.6%, respectively, of global plantings of corn and cotton in 2006.[18] Claims of major benefits to farmers, including poor farmers in developing countries, have been made byadvocates of the technology, and have been challenged by opponents.
Because B. thuringiensis is gram-positive, it has a thick cell wall that is comprised of peptidoglycan (amino acid polypeptide and...