The Biotechnology of Bacillus Thuringiensis

Abstract

One of the challenges in the application of biotechnology to pest control is the identification of agents found in nature which can be used effectively. Biotechnology offers the potential of developing pesticides based on such agents which will provide environmentally sound and economically feasible insect control alternatives. Such an agent, the insect pathogen Bacillus thuringiensis, is the subject of intense investigations in several laboratories. Insecticides which use the entomocidal properties of B. thuringiensis are currently produced and sold worldwide; new products are currently in the development stage. Herein, the biology and genetics of B. thuringiensis and the problems associated with current products are critically reviewed with respect to biotechnology. Moreover, the economic and regulatory implications of technologically advanced products are evaluated.

Characterization study of the sporulation kinetics ofBacillus thuringiensis

“…The insecticidal activity of B. thuringiensis is the most important feature of this organism. The activity is due to its ability to produce the entomocidal parasporal crystalline toxin, also known as ␦-endotoxin or Cry protein, which is insecticidal to larval forms of Lepidoptera, Diptera, and Coleoptera during the sporulation cycle (Andrews et al, 1987). Shortly after digestion by the insect larvae, the crystalline proteins are solubilized and activated in the midgut of insects by proteolysis.…”

Characterization of the parasporal inclusion of Bacillus thuringiensis subsp. kyushuensis

“…Proteinaceous parasporal crystals, toxic predominantly to lepidopterous larvae, are produced by Bacillus thuringiensis during sporulation (1). However, a few subspecies, such as B. thuringiensis subsp.…”

“…However, a few subspecies, such as B. thuringiensis subsp. israelensis, produce crystals that are highly toxic to the larvae of mosquitoes and blackflies (1). The effectiveness of such subspecies against medically important insect pests has led to the search for other strains with similar host ranges.…”

“…The crystals of this strain, like those of B. thuringiensis subsp. israelensis, appear irregularly shaped when examined by phase-contrast microscopy (1,13 B. thuringiensis subsp. israelensis crystals were purified as previously described (3).…”

Bt Crops: Past and Future

“…Currently, more than 400 Bt toxin genes have been cloned and sequenced, including 218 Cry and 28 Vip toxin holotypes (Crickmore et al 2011). Thorough characterization of the mechanisms directing Bt toxin gene expression (Agaisse and Lereclus 1995), and the small number of genetic loci implicated in controlling this process, greatly facilitated genetic manipulations for efficient expression in heterologous systems (Andrews et al 1987). A diverse range of microorganisms were initially transformed with Bt toxin genes including alternative Bacillus spp.…”