Toxic Potential ofBacillus thuringiensis: An Overview

Abstract

The toxins of Bacillus thuringiensis (Bt) have shown great potential in the control of harmful insects affecting human health and agriculture, used as the main biological agent for the formulation of bioinsecticides due to its specificity to target different insects' orders. This has led Bt-based products to become the best-selling biological insecticides in the world since the genes encoding insecticidal proteins have been successfully used in novel insecticidal formulation, genetically engineered (GE) crops, and development of transgenic rice that produce insecticidal toxins derived from Bacillus thuringiensis. It has been proven that insecticidal activity of Bt protein crystals can prolong their toxicity in shelf life or field under specific conditions, and this can improve the use of special strains and formulations to control insect vectors of diseases. Bt toxins have shown well-documented toxicity against lepidopterans, coleopterans, hemipterans, dipterans, nematodes, Rhabditida and human cancer cells of various origins. These crystal toxins may be responsible for other novel biological properties suggesting a pluripotential nature with different specificities.

Encapsulation Strategies forBacillus thuringiensis: From Now to the Future

“…Most of the effects are due to exposure to adverse temperature and continuous sunlight, which reduce the effectiveness of these products. 40 Several studies have demonstrated the negative effects on Bt performance after UV exposure, mainly leading to the loss of spore viability and toxin integrity and, consequently, to low insecticidal activity. 48 It is in this context that studies with the development of formulations have expanded, especially those analyzing encapsulation techniques.…”

“…As described above, microbial agents, such as Bt, are susceptible to degradation when applied to the plant canopy. Most of the effects are due to exposure to adverse temperature and continuous sunlight, which reduce the effectiveness of these products . Several studies have demonstrated the negative effects on Bt performance after UV exposure, mainly leading to the loss of spore viability and toxin integrity and, consequently, to low insecticidal activity. − …”

“…38 The main disadvantages of Bt-based formulations are as follows: (i) short host contact times, (ii) difficulty in reaching insects that attack the roots and internal parts of the plant, (iii) low persistence in the field, mainly as a result of the action of the temperature and UV radiation, and (iv) low compatibility with other types of management involving chemical control. 39,40 Although the potential of Bt as a biological pest control agent has been explored for a long period of time, research with this organism still continues, to identify new approaches for its use. These studies are mainly related to obtain new forms of application, increase persistence, and improve virulence of the microorganism.…”

“…The main disadvantages of Bt-based formulations are as follows: (i) short host contact times, (ii) difficulty in reaching insects that attack the roots and internal parts of the plant, (iii) low persistence in the field, mainly as a result of the action of the temperature and UV radiation, and (iv) low compatibility with other types of management involving chemical control. , …”

Role of Microbial Biopesticides as an Alternative to Insecticides in Integrated Pest Management of Cotton Pests

“…Therefore, it is difficult for the pathogen to attack those insects that feed inside the plant [32]. B. thuringiensis toxins have shown well-documented toxicity against various insects, including Lepidoptera, Diptera, Hemiptera, Coleoptera, and nematodes [35][36][37][38][39][40]. In cotton, B. thuringiensis has been widely reported as a biopesticide to control various insect pests [27,41,42].…”