Bacillus thuringiensis: mechanism of action, resistance, and new applications: a review

Abstract

Since the first report by Ishiwata in 1902 of a Bombyx mori infection, followed by the description by Berliner, Bacillus thuringiensis (Bt) has become the main microorganism used in biological control. The application of Bt to combat invertebrates of human interest gained momentum with the growing demand for food free of chemical pesticides and with the implementation of agriculture methods that were less damaging to the environment. However, the mechanisms of action of these products have not been fully elucidated. There are two proposed models: the first is that Bt causes an osmotic imbalance in response to the formation of pores in a cell membrane, and the second is that it causes an opening of ion channels that activate the process of cell death. There are various ways in which Bt resistance can develop: changes in the receptors that do not recognize the Cry toxin, the synthesis of membrane transporters that eliminate the peptides from the cytosol and the development of regulatory mechanisms that disrupt the production of toxin receptors. Besides the potential for formulation of biopesticides and the use in developing genetically modified cultivars, recent studies with Bt have discussed promising applications in other branches of science. Chitinase, an enzyme that degrades chitin, increases the efficiency of Bt insecticides, and there has been of increasing interest in the industry, given that its substrate is extremely abundant in nature. Another promising field is the potential for Bt proteins to act against cancer cells. Parasporins, toxins of Bt that do not have an entomopathogenic effect, have a cytotoxic effect on the cells changed by some cancers. This demonstrates the potential of the microorganism and new opportunities opening for future applications.

Somatic Embryogenesis in Coffea spp.

“…There are two proposed models for its mechanism of action. First, an osmotic imbalance produced by the pores in the cell membrane or second, an opening of ion channels producing the cell death (Melo et al 2016).…”

Transgenic Bt cotton inhibited arbuscular mycorrhizal fungus differentiation and colonization

“…Many researches have conducted studies on the action model of Bt toxin cytotoxicity to invertebrates (Carroll and Ellar 1993, Vachon et al 2012, Melo et al 2016). The present study does not identify the mechanism of the inhibitive effect of Bt cotton on AM fungi.…”

Surviving Between Hosts: Sporulation and Transmission

“…Two models have been proposed for Cry-mediated death. Formation of pores in cell membranes causes an osmotic imbalance and/or the opening of ion channels activates the process of cell death (24). B. thuringiensis infection in insects includes three successive steps, virulence, necrotrophism, and sporulation, which are controlled by quorum sensing systems and multiple regulators.…”