Modern Toolboxes for Crop Protection

**183**

**Chapter 12**

**Abstract**

*and Luis Galán-Wong*

with different specificities.

**1. Introduction**

were found [1].

Toxic Potential of *Bacillus* 

*thuringiensis*: An Overview

*David Fernández-Chapa, Jesica Ramírez-Villalobos* 

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

**Keywords:** *Bacillus thuringiensis*, Cry toxins, bioinsecticide, resistance, Dulmage

In the modern era, *Bt* was isolated for the first time in Japan by the bacteriologist Ishiwata Shigetane in 1901, and it was considered the microorganism responsible for the disease of the silkworm sotto *Bombyx mori*. The author named it *Bacillus sotto*, which means soft and flaccid, in reference to the appearance of the infected larvae. He noted that young bacterial cultures were not pathogenic to larval insects; in contrast old cultures that suffered sporulation were highly toxic. However, the first valid description was until 1911, when the German scientist, Ernst Berliner, isolated it from diseased larvae of the flower moth *Anagasta kuehniella*. He named it *Bacillus thuringiensis*, which derives from Thuringia, the German town where moths

*Bacillus thuringiensis* is a ubiquitous gram-positive, rod-shaped soil bacterium, that has been isolated worldwide from a great diversity of ecosystems including soil, water, dead insects, dust from silos, leaves from deciduous trees, diverse conifers, and insectivorous mammals [2–4], known by its ability to produce crystalline inclusions during sporulation (Cry toxins) which contain insecticidal proteins called
