10.4 Bacillus thuringiensis (Bt): Brief History, Ecology,
and Biology
The discovery of B. thuringiensis dates back to over a century ago, in 1901, which
had been isolated by a Japanese biologist, Shigetane Ishiwata, from the diseased
larvae of Bombyx mori (Lep.: Bombycidae) (Ishiwata 1901) and named B. sotto.
Afterward, in 1911, Bt was isolated from the flour moth, Ephestia kuehniella (Lep.:
Pyralidae) infected larvae in the Thuringia region of Germany, described and
denominated B. thuringiensis by Ernest Berliner (Berliner 1915). In 1928, Bt
crystals for the first time were used to control the European corn borer, Ostrinia
nubilalis Hüber (Lep.: Crambidae). Sporine was the first commercial Bt-based
product produced in France in 1938 and used to control the flour moth. The
identification and characterization of Bt toxins led to a revolution in genetically
modified crops expressing cry genes and subsequently the introduction of transgenic
plant resistant to different insect pests (Lambert and Peferoen 1992; Letourneau et al.
2003). Since 1996, the cultivation of Bt crops has been expanded worldwide (Kleter
et al. 2007). Since the discovery of Bt, intensive research has been conducted to
study profoundly different aspects of this bacterium. Amongst these, a long history
of studies has been performed in Iran to isolate, characterize and mass-produce local
Iranian Bt strains.
B. thuringiensis is a ubiquitous bacterium widely distributed in diverse environments and can be isolated from soil, water, plant surface, insect feces, dust, and
storage products (Federici et al. 2006). When the food is sufficient for its growth, the
spores germinate, begin the growth stage and reproduce through duplicate reproduction. The bacteria continue to proliferate while food sources are sufficient to
sustain vegetative growth. Under adverse conditions, Bt sporulates and produces one
or more insecticidal crystal proteins (de Maagd et al. 2003).
The endogenous crystalline inclusions produced during the sporulation phase,
also called δ-endotoxins, are predominantly comprised of one or more Crystal (Cry)
and Cytolytic (Cyt) proteins. These proteins have a specific insecticidal activity to
certain groups of insects mostly within Lepidoptera, Diptera and Coleoptera, but also
from other orders; Hymenoptera, Hemiptera, Orthoptera and Mallophaga. Beyond
the insect worlds, Bt toxins are also found to be toxic to mites, nematodes, protozoa
and human cancer cells (Schnepf et al. 1998; van Frankenhuyzen 2009; Ohba et al.
2009). The insecticidal activity of Bt strains also relies on the other toxins and
virulence factors such as β-exotoxin, Vip (vegetative insecticidal protein), Sip
(secreted insecticidal protein) and enzymes (phospholipase, protease, chitinase,
AHL-degrading enzyme) (Regev et al. 1996; Jurat-Fuentes and Jackson 2012; Salehi
Jouzani et al. 2017).
10 Progress on the Bacterium Bacillus thuringiensis and Its. . .
405
and Biology
The discovery of B. thuringiensis dates back to over a century ago, in 1901, which
had been isolated by a Japanese biologist, Shigetane Ishiwata, from the diseased
larvae of Bombyx mori (Lep.: Bombycidae) (Ishiwata 1901) and named B. sotto.
Afterward, in 1911, Bt was isolated from the flour moth, Ephestia kuehniella (Lep.:
Pyralidae) infected larvae in the Thuringia region of Germany, described and
denominated B. thuringiensis by Ernest Berliner (Berliner 1915). In 1928, Bt
crystals for the first time were used to control the European corn borer, Ostrinia
nubilalis Hüber (Lep.: Crambidae). Sporine was the first commercial Bt-based
product produced in France in 1938 and used to control the flour moth. The
identification and characterization of Bt toxins led to a revolution in genetically
modified crops expressing cry genes and subsequently the introduction of transgenic
plant resistant to different insect pests (Lambert and Peferoen 1992; Letourneau et al.
2003). Since 1996, the cultivation of Bt crops has been expanded worldwide (Kleter
et al. 2007). Since the discovery of Bt, intensive research has been conducted to
study profoundly different aspects of this bacterium. Amongst these, a long history
of studies has been performed in Iran to isolate, characterize and mass-produce local
Iranian Bt strains.
B. thuringiensis is a ubiquitous bacterium widely distributed in diverse environments and can be isolated from soil, water, plant surface, insect feces, dust, and
storage products (Federici et al. 2006). When the food is sufficient for its growth, the
spores germinate, begin the growth stage and reproduce through duplicate reproduction. The bacteria continue to proliferate while food sources are sufficient to
sustain vegetative growth. Under adverse conditions, Bt sporulates and produces one
or more insecticidal crystal proteins (de Maagd et al. 2003).
The endogenous crystalline inclusions produced during the sporulation phase,
also called δ-endotoxins, are predominantly comprised of one or more Crystal (Cry)
and Cytolytic (Cyt) proteins. These proteins have a specific insecticidal activity to
certain groups of insects mostly within Lepidoptera, Diptera and Coleoptera, but also
from other orders; Hymenoptera, Hemiptera, Orthoptera and Mallophaga. Beyond
the insect worlds, Bt toxins are also found to be toxic to mites, nematodes, protozoa
and human cancer cells (Schnepf et al. 1998; van Frankenhuyzen 2009; Ohba et al.
2009). The insecticidal activity of Bt strains also relies on the other toxins and
virulence factors such as β-exotoxin, Vip (vegetative insecticidal protein), Sip
(secreted insecticidal protein) and enzymes (phospholipase, protease, chitinase,
AHL-degrading enzyme) (Regev et al. 1996; Jurat-Fuentes and Jackson 2012; Salehi
Jouzani et al. 2017).
10 Progress on the Bacterium Bacillus thuringiensis and Its. . .
405