Bacillus thuringiensis

Spores and bipyramidal crystals of Bacillus thuringiensis morrisoni strain T08025

Spores and bipyramidal crystals of Bacillus thuringiensis morrisoni strain T08025

Scientific classification
| Kingdom:  | Eubacteria

|

Phylum:  | Firmicutes

Class:  | Bacilli

Order:  | Bacillales

Family:  | Bacillaceae

Genus:  | Bacillus

Species:  | thuringiensis

Binomial name
Bacillus thuringiensis
Berliner 1915

WikiDoc Resources for Bacillus thuringiensis

Articles

Most recent articles on Bacillus thuringiensis

Most cited articles on Bacillus thuringiensis

Review articles on Bacillus thuringiensis

Articles on Bacillus thuringiensis in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on Bacillus thuringiensis

Images of Bacillus thuringiensis

Photos of Bacillus thuringiensis

Podcasts & MP3s on Bacillus thuringiensis

Videos on Bacillus thuringiensis

Evidence Based Medicine

Cochrane Collaboration on Bacillus thuringiensis

Bandolier on Bacillus thuringiensis

TRIP on Bacillus thuringiensis

Clinical Trials

Ongoing Trials on Bacillus thuringiensis at Clinical Trials.gov

Trial results on Bacillus thuringiensis

Clinical Trials on Bacillus thuringiensis at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on Bacillus thuringiensis

NICE Guidance on Bacillus thuringiensis

NHS PRODIGY Guidance

FDA on Bacillus thuringiensis

CDC on Bacillus thuringiensis

Books

Books on Bacillus thuringiensis

News

Bacillus thuringiensis in the news

Be alerted to news on Bacillus thuringiensis

News trends on Bacillus thuringiensis

Commentary

Blogs on Bacillus thuringiensis

Definitions

Definitions of Bacillus thuringiensis

Patient Resources / Community

Patient resources on Bacillus thuringiensis

Discussion groups on Bacillus thuringiensis

Patient Handouts on Bacillus thuringiensis

Directions to Hospitals Treating Bacillus thuringiensis

Risk calculators and risk factors for Bacillus thuringiensis

Healthcare Provider Resources

Symptoms of Bacillus thuringiensis

Causes & Risk Factors for Bacillus thuringiensis

Diagnostic studies for Bacillus thuringiensis

Treatment of Bacillus thuringiensis

Continuing Medical Education (CME)

CME Programs on Bacillus thuringiensis

International

Bacillus thuringiensis en Espanol

Bacillus thuringiensis en Francais

Business

Bacillus thuringiensis in the Marketplace

Patents on Bacillus thuringiensis

Experimental / Informatics

List of terms related to Bacillus thuringiensis

Bacillus thuringiensis is a Gram-positive, soil dwelling bacterium of the genus Bacillus. Additionally, B. thuringiensis also occurs naturally in the caterpillars of some moths and butterflies, as well as on the surface of plants.[1]

B. thuringiensis was discovered 1901 in Japan by Ishiwata and 1911 in Germany by Ernst Berliner, who discovered a disease called Schlaffsucht in flour moth caterpillars. B. thuringiensis is closely related to B. cereus, a soil bacterium, and B. anthracis, the cause of anthrax: the three organisms differ mainly in their plasmids. Like other members of the genus, all three are aerobes capable of producing endospores.[1]

Upon sporulation, B. thuringiensis forms crystals of proteinaceous insecticidal δ-endotoxins (Cry toxins: Bacillus thuringiensis Toxin Nomenclature) which are encoded by cry genes. Cry toxins have specific activities against species of the orders Lepidoptera (Moths and Butterflies), Diptera (Flies and Mosquitoes) and Coleoptera (Beetles). Thus, B. thuringiensis serves as an important reservoir of Cry toxins and cry genes for production of biological insecticides and insect-resistant genetically modified crops.

## Contents

* 1 Use in pest control
* 2 Genetic engineering for pest control
* 2.1 Usage
* 2.2 Advantages
* 2.3 Safety
* 2.4 Problems
* 2.5 Fighting resistance
* 3 References
* 4 See also
* 5 External links

## Use in pest control

[edit | edit source]

Spores and crystalline insecticidal proteins produced by B. thuringiensis are used as specific insecticides under trade names such as Dipel and Thuricide. Because of their specificity, these pesticides are regarded as environmentally friendly, with little or no effect on humans, wildlife, pollinators, and most other beneficial insects. The Belgian company Plant Genetic Systems was the first company (in 1985) to develop genetically engineered (tobacco) plants with insect tolerance by expressing cry genes from B. thuringiensis.[2][3]

B. thurigiensis-based insecticides are often applied as liquid sprays on crop plants, where the insecticide must be ingested to be effective. It is thought that the solubilized toxins form pores in the midgut epithelium of susceptible larvae. Recent research has suggested that the midgut bacteria of susceptible larvae are required for B. thuringiensis insecticidal activity.[4]

Bacillus thuringiensis serovar israelensis, a strain of B. thuringiensis is widely used as a larvicide against mosquito larvae, where it is also considered an environmentally friendly method of mosquito control.

## Genetic engineering for pest control

[edit | edit source]

File:Bt plants.pngBt-toxins present in peanut leaves (bottom image) protect it from extensive damage caused by European corn borer larvae (top image).[5] Kenyans examining insect-resistant transgenic Bt corn.

### Usage

[edit | edit source]

In 2000 more than 115,000 square kilometers of Bt transgenic crops were grown, constituting 19% of the worlds GM crops. There is potential for Bt GM crops to take up 33% of the insecticide market. The current use of transgenic Bt crops reduces the number of chemical insecticide treatments by more than 7.7 million acres (31,000 km²) per year.

### Advantages

[edit | edit source]

There are several advantages in expressing Bt toxins in transgenic Bt crops: i). The level of toxin expression can be very high thus delivering sufficient dosage to the pest, ii). The toxin expression is contained within the plant system and hence only those insects that feed on the crop perish, iii). The toxin expression can be modulated by using tissue-specific promoters, iv). The resistance is inherited in a stable and Mendelian fashion and v). The toxin gene can be integrated in the chloroplast genome and thus the possibility of gene transfer via pollen is eliminated.

### Safety

[edit | edit source]

Bt crops appear to be safe for the farmers and for consumers. The toxin is insect specific and poses no known danger to humans, although the technology is too new for long-term studies to be available.[citation needed] Bt toxin is not inactivated by sun (as normal) and is present for a long time in the soil (see documentary). A recent study funded by the European arm of Greenpeace, while inconclusive, has shown the possibility of a slight but statistically meaningful risk of liver damage in rats.[6]

### Problems

[edit | edit source]

The expression of the Bt gene can vary. For instance, if the temperature is not ideal this stress can lower the toxin production and make the plant more susceptible. More importantly, reduced late-season expression of toxin has been documented, possibly resulting from DNA methylation of the promoter.[7]

Due to the constant exposure to the toxin an evolutionary pressure is created for resistant pests. Already, the Diamondback moth population is known to have adapted so that it now has a resistance to Bt in spray form.[8] There is also a hypothetical risk that for example, transgenic maize will crossbreed with wild grass variants, and that the Bt-gene will end up in a natural environment, retaining its toxicity. An event like this would have ecological implications, as well as increasing the risk of Bt resistance arising in the general herbivore population.

As of 2007, a new phenomenon called Colony Collapse Disorder (CCD) is affecting bee hives all over North America. While its causes are still unknown, its link to the use of Bt resistant transgenic crops is causing concern among scientists.[9] A research group called Mid-Atlantic Apiculture Research and Extension Consortium published a report on 2007-03-27 that found no evidence that pollen from Bt crops is adversely affecting bees. However, the study only investigated short term exposure. Studies on long term exposure still need to be investigated to determine if it causes changes in bee behaviour.[10]

### Fighting resistance

[edit | edit source]

One method of reducing resistance is the creation of Non-Bt crop refuges to allow some non-resistant insects to survive and maintain a susceptible population. The refuge approach is required by legislation in some regions including the US and Europe. The aim is to encourage a large population of pests so that any genes for resistance are greatly diluted. This technique is based on the assumption that resistance genes will be recessive. It appears so far to be a successful method of delaying widespread resistance to Bt toxins.[11] Alternately, creating a mosaic GM crop expressing many different Bt toxins would have a greater chance of eliminating the entire pest population and thus eliminating resistance alleles.[12] To date, no  planned extinction of an insect pest has been successful.[13][14]

## References

[edit | edit source]

1. ↑ 1.0 1.1 Madigan, Michael; Martinko, John (editors) (2005). Brock Biology of Microorganisms (11th ed. ed.). Prentice Hall. ISBN 0-13-144329-1.CS1 maint: Multiple names: authors list (link) CS1 maint: Extra text: authors list (link) CS1 maint: Extra text (link)
2. ↑ Höfte H, de Greve H, Seurinck J, Jansens S, Mahillon J, Ampe C, Vandekerckhove J, Vanderbruggen H, van Montagu M, Zabeau M (1986). "Structural and functional analysis of a cloned delta endotoxin of Bacillus thuringiensis berliner 1715". Eur J Biochem. 161 (2): 273–80. PMID 3023091.CS1 maint: Multiple names: authors list (link)
3. ↑ Vaeck M, Reynaerts A, Hofte A, Jansens S, De Beuckeleer M, Dean C, Zabeau M, Van Montagu M, Leemans J (1987). "Transgenic plants protected from insect attack". Nature. 328: 33&ndash, 37.CS1 maint: Multiple names: authors list (link)
4. ↑ Broderick N, Raffa K, Handelsman J (2006). "Midgut bacteria required for Bacillus thuringiensis insecticidal activity". Proc Natl Acad Sci U S A. 103 (41): 15196–9. PMID 17005725.CS1 maint: Multiple names: authors list (link)
5. ↑ Jan Suszkiw (November 1999.). "Tifton, Georgia: A Peanut Pest Showdown". Agricultural Research magazine. Retrieved 2007-05-23. Check date values in: `|date=` (help)
6. ↑ Séralini, et al: New analysis of a rat feeding study with a genetically modified maize reveals signs of hepatorenal toxicty, Archives of Environmental Contamination and Toxicology, Springer Science, Published online 13 March 2007.
7. ↑ VDong, H. Z. and Li, W. J. (2007) Variability of Endotoxin Expression in Bt Transgenic Cotton. Journal of Agronomy & Crop Science; 193:21-29.
8. ↑ "Organic Mystery," Scientific American, December, 2006, p. 33, quote by Bruce Tabashnik of the University of Arizona. [1]
9. ↑ Latsch, Gunther. Are GM Crops Killing Bees?. Spiegel International. March 22, 2007. [2]
10. ↑ Dively, G.P. Summary of Research on the Non-Target Effects of Bt Corn Pollen on Honeybees. March 27, 2007. [3]
11. ↑ Bt Cotton Script \- Australian Broadcasting Corporation's Science Show
12. ↑ Atkinson, H. Lecture: Engineering Resistance to Insects. Unknown parameter `|Publisher=` ignored (`|publisher=` suggested) (help)
13. ↑ Judson, Olivia. A Bug's Death. New York Times. July 23, 2007. [4]
14. ↑ The Science Show. Controlling pests in cotton crops. May 13, 2006. [5]

## See also

[edit | edit source]

* Western corn rootworm

## External links

[edit | edit source]

* Bacillus thuringiensis General Fact Sheet - National Pesticide Information Center
* Bacillus thuringiensis Technical Fact Sheet - National Pesticide Information Center
* Breakdown of the Bt toxin and effects on the environment Research projects and results

* Bacillus thuringiensis Genome Projects (from Genomes OnLine Database)

de:Bacillus thuringiensis it:Bacillus thuringiensis nl:Bacillus thuringiensis uk:Bacillus thuringiensis

Template:WikiDoc Sources