FoodBacillus thuringiensis (Bt) is an important tool beginning from the start of 20th century till now. Bacillus thuringiensis (Bt) was a splendid discovery made in about 1900s by a Japanese scientist named Ishiwata from diseased effected silk moths. The bacterium noted as Bacillus soto was not taken much attention and gradually was separated by German scientist Berliner in 1909 from diseased Mediterranean flour moth. Use of Bt for pathological management of insect pests was forecasted by Berliner on considering the disease producing ability of bacterial spores in flour moth, so his effort and predictions must be appreciated in the present long run use of Bt in the present scenario. In 1920, Bt was used for the control of European corn borer. Very first industrial product of Bt was manufactured in France with the brand name of Sporéine in 1938. In 1950, it became evident that the insect killing characters of Bt are actually due to its crystals formed in sporulation process.

Until now, there was a remarkable range for the discoveries of Bt serotypes and recorded up to 45. Formerly, it was regarded that Bt is injurious to only lepidopteron pests (moths and butterflies) but in 1977 a discovery of Bt strain, Bacillus thuringiensis subsp. israelensis from pond by Goldberg and Margalit also revealed Bt toxicity to diptrans (mosquitoes and blackflies mainly). Similarly, in 1983, another discovery by Krieg et al. made possible the control of coleopteran insect pests (e.g. Colorado potato beeltel) in the form of Bt strain, Bacillus thuringiensis subsp. tenebrionis.

A number of Bt characteristics including easy rearing in culture media, spores viability for years and germinating ability has made it ideal for commercial propagation of insect control device. Crystal protein genes of Bt has extra importance in pest control. Following is a precise presentation of these genes.

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BACILLUS THURINGIENSIS CRYSTAL PROTEIN GENES

Name Old name Access no. Size (Da) Activity
Cry1Aa1 Cry1A(a) M11250 133500 Lepidoptera
Cry1Ab1 Cry1A(b) M13898 130615 Lepidoptera
Cry1Ac1 Cry1A(c) M11068 131000 Lepidoptera
Cry1Ad1 Cry1A(d) M73250 131000 Lepidoptera
         
Cry1Ae1 Cry1A(e) M65252 131000 Lepidoptera
         
Cry1Ba1 Cry1B X06711 136500 Lep./Coleop.
         
Cry1Bb1 ET5 L32020 136500 Lepidoptera
         
Cry1Bc1 Cry 1B(c) Z46442 138000 Lepidoptera
Cry1Ca1 Cry1C X07518 132000 Lepidoptera
Cry1Cb1 Cry1C(b) M97880 130500 Lepidoptera
Cry1Da1 Cry1D X54160 129500 Lepidoptera
Cry1Db1 PrtB Z2251 1 129000 Unknown
Cry1Ea1 Cry1E X53985 133236 Lepidoptera
Cry1Eb1 Cry1E(b) M73253 130500 Lepidoptera
         
Cry1Fa1 Cry1F M63897 130500 Lepidoptera
         
CryFb1 PrtD Z22512 131000 Unknown
Cry1Ga1 PrtA Z22510 129 500 Unknown
Cry1Ha1 PrtC Z22513 130000 Unknown
Cry1la1 CryV X62821 81200 Lep./Coleop.

 

Production of such plants resistant to insect pests and expressing the gene of resistance from seed level to the complete plant was one of the earlier biotechnologist and plant breeders’ effort. Initially Bt was introduced in tomato and tobacco plants with the assistance of Agrobacterium tumefaciens. Cotton varieties were also developed by constructing their base on Bt. Bt cotton, still marketed with a huge profit earning, have rendered control for chewing insects mainly bollworms of notorious status as Helicoverpa armigera, Pectinophora gossypiella and Earias spp. Hence, saving about 35-70% boll loss against these insect pests.

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Three-dimensional structure of activated Cry3Aa toxin. Schematic diagram showing the three domains of the protein.

In the same fashion, including Bt vegetables, Bt corn has also made to save the loss majorly due to European corn borers which may moves up to US$800–900 million annually. Investigations are being carried out for further developments in this regard.

Bacillus thuringiensis has a better potential to cope with the challenge of food security and to have more food for more population demands. This step is successfully being undertaken and occupied by the employment of transgenic plant varieties inclusive Bt. But there is a virtual and sometimes actual threat is debated regarding the action and effect of Bt on higher animals including humans. The danger or threat is that “what will be happen if the effect of Bt will be same on man as on insects?” and also “the use of bacteria based food and then its presence in human body subsequently may cause the resistance against antibiotics in  man dwelling bacterial pathogens leading to improper or no cure of bacterial diseases in man”.

Such questions and debates are worthy to mention and important to comprehend and investigate. In case of first danger, there is no chance of its occurrence in higher animals including man due to acidic pH of food canal. Bt endotoxins are activated mainly in alkaline pH existed in the gut of insects (for moths and butterflies range of pH is 9 to 12 and activation pH for Bt crystals if >9.5) and not human beings. There is more chance and probabilities of occurrence of latter threat of antibiotic resistance but it can be avoided by using Bt in the form of spray rather than incorporating it in food materials in plants which may directly incorporated in human bodies.

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In short, Bt (Bacillus thuringiensis) has an eminent position in food provisions on sustained basis directly or indirectly. There is a dire need to further exploit its potential and hidden capabilities for food securing purpose in order to make every person a happy, healthy and hunger free.

This article is collectively authored by Muhammad Wajid Javed, Muhammad Hamid Javed, Dr. Jam Nazeer Ahmad, Dr. Samina Jam Nazeer Ahmad and  Samia Sabir.

 

EditorialArticlesbacillus,food,future,Security,significance,standpoint,thuringiensisBacillus thuringiensis (Bt) is an important tool beginning from the start of 20th century till now. Bacillus thuringiensis (Bt) was a splendid discovery made in about 1900s by a Japanese scientist named Ishiwata from diseased effected silk moths. The bacterium noted as Bacillus soto was not taken much attention...Pakistan's Only Newspaper on Science and Technology