Bacillus thuringiensis and insects: a century of intimate history

Within the vast Bacillus cereus group, two bacterial species have stood out for over a century: Bacillus anthracis for its pathogenicity to mammals, and Bacillus thuringiensis for its remarkable and economically exploitable activity against invertebrates. One hundred years of extensive research around the world have unraveled the sophisticated mechanisms that make B. thuringiensis a formidable weapon designed to kill insects, exploiting them as an ecological niche for its proliferation. Evolution has led to the selection of a great diversity of highly specific toxins targeting a wide range of insects and nematodes. Bacteria have developed transcriptional, post-transcriptional, and post-translational mechanisms that enable the massive production of these toxins as crystalline inclusions. Virulence and adaptation factors, together with regulation systems, have also been selected to enable the bacterium to make the most of the ecological niche provided by insects. In addition to their interest in the bacterium, the biological tools and processes developed by B. thuringiensis can be exploited by mankind to create insect-resistant plants, overproduce proteins, crystallize them, and gain a better understanding of the microbial world. All the research carried out on B. thuringiensis over the last century has made this bacterium a remarkable study model and biotechnological resource, revealing all the subtlety and power of the mechanisms that a microorganism has been able to acquire in the course of its evolution.