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| binomial_authority = Berliner 1915
| binomial_authority = Berliner 1915
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'''''Bacillus thuringiensis''''' (or '''Bt''') is a [[Gram-positive]], soil-dwelling [[bacterium]], commonly used as a [[biological pesticide]]; alternatively, the Cry toxin may be extracted and used as a pesticide. ''B. thuringiensis'' also occurs naturally in the gut of [[caterpillar]]s of various types of [[moth]]s and [[butterfly|butterflies]], as well on leaf surfaces, aquatic environments, animal feces, insect rich environments, flour mills and grain storage facilities.<ref name=Brock>{{cite book | author = Madigan M, Martinko J (editors) | title = Brock Biology of Microorganisms | edition = 11th | publisher = Prentice Hall | year = 2005 | (ISBN=0131443291}}</ref><ref>Nicolette du Rand. Isolation of Entomopathogenic Gram Positive Spore Forming Bacteria Effective Against Coleoptera. Submitted in fulfillment of the requirements for the degree of Doctor of Philosophy. University of KwaZulu-Natal, Pietermaritzburg, South Africa. July 2009 [http://researchspace.ukzn.ac.za/xmlui/bitstream/handle/10413/1235/Du%20Rand_N_2009_Thesis.pdf?sequence=1]</ref>
'''''Bacillus thuringiensis''''' (or '''Bt''') is a [[Gram-positive]], soil-dwelling [[bacterium]], commonly used as a [[biological pesticide]]; alternatively, the Cry toxin may be extracted and used as a pesticide. ''B. thuringiensis'' also occurs naturally in the gut of [[caterpillar]]s of various types of [[moth]]s and [[butterfly|butterflies]], as well on leaf surfaces, aquatic environments, animal feces, insect rich environments, flour mills and grain storage facilities.<ref name=Brock>{{cite book |editor1-last=Madigan |editor1-first=Michael T. |editor2-last=Martinko |editor2-first=John M. |title=Brock Biology of Microorganisms |edition=11th |publisher=Prentice Hall |year=2005 |isbn=978-0-13-144329-7}}{{pn}}</ref><ref>{{cite book |first=Nicolette |last=du Rand |title=Isolation of Entomopathogenic Gram Positive Spore Forming Bacteria Effective Against Coleoptera |type=PhD Thesis |publisher=University of KwaZulu-Natal |location=Pietermaritzburg, South Africa |month=July |year=2009 |id={{hdl|10413/1235}}}}{{pn}}</ref>


During [[sporulation]], many Bt strains produce crystal proteins (proteinaceous inclusions), called [[δ-endotoxins]], that have [[insecticidal]] action. This has led to their use as insecticides, and more recently to [[genetically modified crops]] using Bt genes. Many crystal-producing Bt [[strain (biology)|strains]], though, do not have insecticidal properties.<ref>{{cite pmid|18051264}}</ref>
During [[sporulation]], many Bt strains produce crystal proteins (proteinaceous inclusions), called [[δ-endotoxins]], that have [[insecticidal]] action. This has led to their use as insecticides, and more recently to [[genetically modified crops]] using Bt genes. Many crystal-producing Bt [[strain (biology)|strains]], though, do not have insecticidal properties.<ref>{{cite journal |pmid=18051264}}</ref>


==Discovery and mechanism of insecticidal action==
==Discovery and mechanism of insecticidal action==
''B. thuringiensis'' was first discovered in 1901 by Japanese [[biologist]] Ishiwata Shigetane.<ref>Roh JY, et al. (2007) [http://www.ncbi.nlm.nih.gov/pubmed/18051264 Bacillus thuringiensis as a specific, safe, and effective tool for insect pest control]. J Microbiol Biotechnol. 17(4):547-59.</ref> In 1911, ''B. thuringiensis'' was rediscovered in Germany by Ernst Berliner, who isolated it as the cause of a disease called ''Schlaffsucht'' in flour moth caterpillars. In 1976, Robert A. Zakharyan reported the presence of a plasmid in a strain of ''B. thuringiensis'' and suggested the plasmid's involvement in endospore and crystal formation.<ref>Zakharyan R.A ''et. el.'' (1979). "Plasmid DNA from Bacillus thuringiensis". Microbiologiya 48 (2): 226–229. ISSN 0026-3656.</ref><ref>Thomas Clement Cheng,(1984) Pathogens of invertebrates: application in biological control and transmission mechanisms, ''Society for Invertebrate Pathology Meeting'' Volume 7 page 159 [http://books.google.com/books?cd=1&id=TugDAQAAIAAJ&dq=Zakharyan+thuringiensis&q=Zakharyan#search_anchor]</ref> ''B. thuringiensis'' is closely related to ''[[Bacillus cereus|B.cereus]]'', a soil bacterium, and ''[[Bacillus anthracis|B.anthracis]]'', the cause of [[Anthrax disease|anthrax]]: the three organisms differ mainly in their [[plasmid]]s. Like other members of the genus, all three are [[aerobe]]s capable of producing [[endospore]]s.<ref name=Brock/> Upon sporulation, ''B. thuringiensis'' forms crystals of [[proteinaceous]] insecticidal [[δ-endotoxin]]s (called crystal proteins or Cry proteins), which are encoded by ''cry'' genes.<ref>{{cite web |author=Circkmore N |url=http://www.lifesci.sussex.ac.uk/home/Neil_Crickmore/Bt/index.html |title=Bacillus thuringiensis toxin nomenclature |work= |accessdate=2008-11-23| archiveurl= http://web.archive.org/web/20081009193337/http://www.lifesci.sussex.ac.uk/home/Neil_Crickmore/Bt/index.html| archivedate= 9 October 2008 <!--DASHBot-->| deadurl= no}}</ref> In most strains of ''B. thuringiensis'', the ''cry'' genes are located on a [[plasmid]] (in other words, ''cry'' is not a chromosomal gene in most strains).<ref name=Stahly>{{cite journal | author = Stahly D.P | title=Biochemical Genetics of the Bacterial Insect-Control Agent Bacillus thuringiensis: Basic Principles and Prospects Engineering. |year =1984 |journal=Biotechnol. Genet. Eng. Rev. | volume=84 |pages=341–63| volume=2|issn=0264-8725}}</ref><ref name=Clayton1992>{{cite journal|author=Clayton C. Beegle and Takhashi Yamamoto | year=1992 | title= INVITATION PAPER ( C. P. ALEXANDER FUND) : History of Bacillus thuringiensis berliner research and development | journal = Canadian Entomologist | volume=124|issue=4 | pages =587–616|doi=10.4039/Ent124587-4}}</ref><ref name=Xu2006>{{cite journal|author=XU Jian, LIU Qin, YIN Xiang-dong and ZHU Shu-de |year=2006|title=A review of recent development of Bacillus thuringiensis ICP genetically engineered microbes | journal =Entomological Journal of East China | issue=1 | pages=53–58 | volume =15}}</ref>
''B. thuringiensis'' was first discovered in 1901 by Japanese [[biologist]] Ishiwata Shigetane.<ref>{{cite journal |pmid=18051264}}</ref> In 1911, ''B. thuringiensis'' was rediscovered in Germany by Ernst Berliner, who isolated it as the cause of a disease called ''Schlaffsucht'' in flour moth caterpillars. In 1976, Robert A. Zakharyan reported the presence of a plasmid in a strain of ''B. thuringiensis'' and suggested the plasmid's involvement in endospore and crystal formation.<ref>{{cite journal |author=Zakharyan R.A ''et. el.'' |year=1979 |title=Plasmid DNA from Bacillus thuringiensis |journal=Microbiologiya |volume=48 |issue=2 |pages=226–9 |issn=0026-3656}}</ref><ref>{{cite book |editor1-first=Thomas Clement |editor1-last=Cheng |year=1984 |title=Pathogens of invertebrates: application in biological control and transmission mechanisms |isbn=978-0-306-41700-9 |page=159}}</ref> ''B. thuringiensis'' is closely related to ''[[Bacillus cereus|B.cereus]]'', a soil bacterium, and ''[[Bacillus anthracis|B.anthracis]]'', the cause of [[Anthrax disease|anthrax]]: the three organisms differ mainly in their [[plasmid]]s. Like other members of the genus, all three are [[aerobe]]s capable of producing [[endospore]]s.<ref name=Brock/> Upon sporulation, ''B. thuringiensis'' forms crystals of [[proteinaceous]] insecticidal [[δ-endotoxin]]s (called crystal proteins or Cry proteins), which are encoded by ''cry'' genes.<ref>{{cite web |author=Circkmore N |url=http://www.lifesci.sussex.ac.uk/home/Neil_Crickmore/Bt/index.html |title=Bacillus thuringiensis toxin nomenclature |work= |accessdate=2008-11-23| archiveurl= http://web.archive.org/web/20081009193337/http://www.lifesci.sussex.ac.uk/home/Neil_Crickmore/Bt/index.html| archivedate= 9 October 2008 <!--DASHBot-->| deadurl= no}}</ref> In most strains of ''B. thuringiensis'', the ''cry'' genes are located on a [[plasmid]] (in other words, ''cry'' is not a chromosomal gene in most strains).<ref name=Stahly>{{cite journal |pmid=6443645}}</ref><ref name=Clayton1992>{{cite journal |doi=10.4039/Ent124587-4}}</ref><ref name=Xu2006>{{cite journal|author=XU Jian, LIU Qin, YIN Xiang-dong and ZHU Shu-de |year=2006|title=A review of recent development of Bacillus thuringiensis ICP genetically engineered microbes | journal =Entomological Journal of East China | issue=1 | pages=53–58 | volume =15}}</ref>


Cry toxins have specific activities against insect species of the orders [[Lepidoptera]] (moths and butterflies), [[Diptera]] (flies and mosquitoes), [[Coleoptera]] (beetles), [[Hymenoptera]] ([[wasp]]s, [[bee]]s, [[ant]]s and [[sawfly|sawflies]]) and [[nematode]]s. Thus, ''B. thuringiensis'' serves as an important reservoir of Cry toxins for production of biological insecticides and insect-resistant [[Genetically modified food|genetically modified crops]]. When insects ingest toxin crystals, the alkaline pH of their digestive tract denatures the insoluble crystals, making them soluble and thus amenable to being cut with [[proteases]] found in the insect gut, which liberate the cry toxin from the crystal.<ref name="Stahly"/> The Cry toxin is then inserted into the insect gut cell membrane, forming a pore. The pore results in cell lysis and eventual death of the insect.<ref>{{cite web |author=Babu M, Geetha M | url=http://www.mrc-lmb.cam.ac.uk/genomes/madanm/articles/dnashuff.htm |title=DNA shuffling of Cry proteins |accessdate=2008-11-23}}</ref><ref name=Dean1984>Dean D.H. ( October 1984)."Biochemical Genetics of the Bacterial Isect-Control Agent Bacillus thuringiensis:Basic Principles and Prospects for Genetic Engineering". Biotechnology and Genetic Engineering Reviews-vol.2,341-363.</ref> Research published in 2006 has suggested the midgut bacteria of susceptible larvae are required for ''B. thuringiensis'' insecticidal activity.<ref name=Broderick_2006>{{cite journal |author=Broderick NA, Raffa KF, Handelsman J |title=Midgut bacteria required for Bacillus thuringiensis insecticidal activity |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=103 |issue=41 |pages=15196–9 |year=2006 |month=October |pmid=17005725 |pmc=1622799 |doi=10.1073/pnas.0604865103 |url=http://www.pnas.org/cgi/pmidlookup?view=long&pmid=17005725|bibcode = 2006PNAS..10315196B }}</ref>
Cry toxins have specific activities against insect species of the orders [[Lepidoptera]] (moths and butterflies), [[Diptera]] (flies and mosquitoes), [[Coleoptera]] (beetles), [[Hymenoptera]] ([[wasp]]s, [[bee]]s, [[ant]]s and [[sawfly|sawflies]]) and [[nematode]]s. Thus, ''B. thuringiensis'' serves as an important reservoir of Cry toxins for production of biological insecticides and insect-resistant [[Genetically modified food|genetically modified crops]]. When insects ingest toxin crystals, the alkaline pH of their digestive tract denatures the insoluble crystals, making them soluble and thus amenable to being cut with [[proteases]] found in the insect gut, which liberate the cry toxin from the crystal.<ref name="Stahly"/> The Cry toxin is then inserted into the insect gut cell membrane, forming a pore. The pore results in cell lysis and eventual death of the insect.<ref>{{cite web |author=Babu M, Geetha M | url=http://www.mrc-lmb.cam.ac.uk/genomes/madanm/articles/dnashuff.htm |title=DNA shuffling of Cry proteins |accessdate=2008-11-23}}</ref><ref name=Dean1984>{{cite journal |pmid=6443645}}</ref> Research published in 2006 has suggested the midgut bacteria of susceptible larvae are required for ''B. thuringiensis'' insecticidal activity.<ref name=Broderick_2006>{{cite journal |doi=10.1073/pnas.0604865103}}</ref>


In 2000, a novel functional group of Cry protein, designated parasporin, was discovered from non-insecticidal ''B. thuringiensis'' isolates.<ref>Mizuki E et al (2000) [http://cvi.asm.org/content/7/4/625.full?view=long&pmid=10882663 Parasporin, a Human Leukemic Cell-Recognizing Parasporal Protein of Bacillus thuringiensis] Clin Vaccine Immunol 7(4):625-634</ref> The proteins of parasporin group are defined as "''Bacillus thuringiensis'' and related bacterial parasporal proteins that are non-hemolytic but capable of preferentially killing cancer cells". As of January 2013, parasporins comprise six subfamilies (PS1 to PS6).<ref>[http://parasporin.fitc.pref.fukuoka.jp/ Official Website of the Committee of Parasporin Classification and Nomenclature] Accessed Jan 4, 2013</ref>
In 2000, a novel functional group of Cry protein, designated parasporin, was discovered from non-insecticidal ''B. thuringiensis'' isolates.<ref>{{cite journal |doi=10.1128/CDLI.7.4.625-634.2000}}</ref> The proteins of parasporin group are defined as "''Bacillus thuringiensis'' and related bacterial parasporal proteins that are non-hemolytic but capable of preferentially killing cancer cells". As of January 2013, parasporins comprise six subfamilies (PS1 to PS6).<ref>[http://parasporin.fitc.pref.fukuoka.jp/ Official Website of the Committee of Parasporin Classification and Nomenclature] Accessed Jan 4, 2013</ref>


==Use of spores and proteins in pest control==
==Use of spores and proteins in pest control==
Spores and crystalline insecticidal proteins produced by ''B. thuringiensis'' have been used to control insect pests since the 1920s and are often applied as liquid sprays.<ref name="review">{{cite journal|last=Lemaux|first=Peggy|date=February 19, 2008|title=Genetically Engineered Plants and Foods: A Scientist's Analysis of the Issues (Part I)|journal=Annual Review of Plant Biology|volume=59|pages=771–812|url=http://arjournals.annualreviews.org/doi/abs/10.1146/annurev.arplant.58.032806.103840|accessdate=9 May 2009|doi=10.1146/annurev.arplant.58.032806.103840|pmid=18284373}}</ref> They are now used as specific [[insecticide]]s under trade names such as Dipel and Thuricide. Because of their specificity, these [[pesticide]]s are regarded as [[environmentally friendly]], with little or no effect on [[human]]s, [[wildlife]], [[pollinator]]s, and most other [[beneficial insect]]s and are used in [[Organic farming]].<ref>Staff (19 February 2003) [http://biology.ucsd.edu/news/article_021903.html Bt Toxins, Used By Organic Farmers As An Environmentally Safe Insecticide, Found To Kill Parasitic Roundworms] UC San Diego, Division of Biological Sciences, Retrieved 26 July 2012</ref>
Spores and crystalline insecticidal proteins produced by ''B. thuringiensis'' have been used to control insect pests since the 1920s and are often applied as liquid sprays.<ref name="review">{{cite journal |doi=10.1146/annurev.arplant.58.032806.103840}}</ref> They are now used as specific [[insecticide]]s under trade names such as Dipel and Thuricide. Because of their specificity, these [[pesticide]]s are regarded as [[environmentally friendly]], with little or no effect on [[human]]s, [[wildlife]], [[pollinator]]s, and most other [[beneficial insect]]s and are used in [[Organic farming]].<ref>Staff (19 February 2003) [http://biology.ucsd.edu/news/article_021903.html Bt Toxins, Used By Organic Farmers As An Environmentally Safe Insecticide, Found To Kill Parasitic Roundworms] UC San Diego, Division of Biological Sciences, Retrieved 26 July 2012</ref>


[[Bacillus thuringiensis israelensis|''Bacillus thuringiensis'' serovar ''israelensis'']], a strain of ''B. thuringiensis'' is widely used as a [[larvicide]] against [[mosquito]] [[larva]]e, where it is also considered an environmentally friendly method of [[mosquito control]].<ref>Poopathi S and Abidha S (2010) [http://www.academicjournals.org/jpap/PDF/Pdf2010/Nov/Poopathi%20and%20Abidha.pdf Review: Mosquitocidal bacterial toxins (Bacillus sphaericus and Bacillus thuringiensis serovar israelensis): Mode of action, cytopathological effects and mechanism of resistance] Journal of Physiology and Pathophysiology 1(3):22-38, November 2010</ref>
[[Bacillus thuringiensis israelensis|''Bacillus thuringiensis'' serovar ''israelensis'']], a strain of ''B. thuringiensis'' is widely used as a [[larvicide]] against [[mosquito]] [[larva]]e, where it is also considered an environmentally friendly method of [[mosquito control]].<ref>{{cite journal |first1=Subbiah |last1=Poopathi |first2=S. |last2=Abidha |year=2010 |url=http://www.academicjournals.org/jpap/abstracts/abstracts/abstracts2010/Nov/Poopathi%20and%20Abidha.htm |title=Mosquitocidal bacterial toxins (''Bacillus sphaericus'' and ''B. thuringiensis'' serovar ''israelensis''): Mode of action, cytopathological effects and mechanism of resistance |journal=Journal of Physiology and Pathophysiology |volume=1 |issue=3 |pages=22-38}}</ref>


Formulations of Bt that are approved for organic farming in the US are listed at the website of the Organic Materials Review Institute (OMRI)<ref>http://www.omri.org/simple-opl-search/results/BACILLUS%20THURINGIENSIS BT formulations at OMRI]</ref> and several university extension websites offer advice on how to use Bt spore or protein preparations in organic farming.<ref>Caldwell B et al. October 2005 [http://web.pppmb.cals.cornell.edu/resourceguide/mfs/02bacillus_thuringiensis.php MATERIAL NAME: BACILLUS THURINGIENSIS (BT)] Resource Guide for Organic Insect and Disease Management. ISBN 0-9676507-2-0</ref><ref> W.S. Cranshaw for Colorado State University Extension Service. Updated November 02, 2012. [http://www.ext.colostate.edu/pubs/insect/05556.html Bacillus thuringiensis Fact Sheet]</ref>
Formulations of Bt that are approved for organic farming in the US are listed at the website of the Organic Materials Review Institute (OMRI)<ref>http://www.omri.org/simple-opl-search/results/BACILLUS%20THURINGIENSIS BT formulations at OMRI]</ref> and several university extension websites offer advice on how to use Bt spore or protein preparations in organic farming.<ref>Caldwell B et al. October 2005 [http://web.pppmb.cals.cornell.edu/resourceguide/mfs/02bacillus_thuringiensis.php MATERIAL NAME: BACILLUS THURINGIENSIS (BT)] Resource Guide for Organic Insect and Disease Management. ISBN 0-9676507-2-0</ref><ref> W.S. Cranshaw for Colorado State University Extension Service. Updated November 02, 2012. [http://www.ext.colostate.edu/pubs/insect/05556.html Bacillus thuringiensis Fact Sheet]</ref>


==Use of Bt genes in genetic engineering of plants for pest control==
==Use of Bt genes in genetic engineering of plants for pest control==
The [[Belgium|Belgian]] company [[Plant Genetic Systems]] (now part of [[Bayer CropScience]]) was the first company (in 1985) to develop genetically engineered ([[tobacco]]) plants with insect tolerance by expressing ''cry'' genes from ''B. thuringiensis''.<ref name=Hofte_1986>{{cite journal |author=Höfte H, de Greve H, Seurinck J |title=Structural and functional analysis of a cloned delta endotoxin of Bacillus thuringiensis berliner 1715 |journal=Eur. J. Biochem. |volume=161 |issue=2 |pages=273–80 |year=1986 |month=December |pmid=3023091 |doi= 10.1111/j.1432-1033.1986.tb10443.x|url=http://www.blackwell-synergy.com/openurl?genre=article&sid=nlm:pubmed&issn=0014-2956&date=1986&volume=161&issue=2&spage=273}}</ref><ref name=Vaeck>{{cite journal | author = Vaeck M, Reynaerts A, Hofte A| title = Transgenic plants protected from insect attack | journal = Nature | year = 1987 | volume = 328 | issue = 6125 | pages = 33–7 | doi = 10.1038/328033a0 |url=http://www.nature.com/nature/journal/v328/n6125/abs/328033a0.html | bibcode=1987Natur.328...33V}}</ref>
The [[Belgium|Belgian]] company [[Plant Genetic Systems]] (now part of [[Bayer CropScience]]) was the first company (in 1985) to develop genetically engineered ([[tobacco]]) plants with insect tolerance by expressing ''cry'' genes from ''B. thuringiensis''.<ref name=Hofte_1986>{{cite journal |doi=10.1111/j.1432-1033.1986.tb10443.x}}</ref><ref name=Vaeck>{{cite journal |doi=10.1038/328033a0}}</ref>
[[Image:Bt plants.png|thumb|Bt toxins present in [[peanut]] leaves (bottom image) protect it from extensive damage caused by [[Lesser Cornstalk Borer]] [[larva]]e (top image).<ref>{{cite web |author= Jan Suszkiw|url=http://ars.usda.gov/is/ar/archive/nov99/pest1199.htm |title=Tifton, Georgia: A Peanut Pest Showdown |accessdate=2008-11-23 |work= Agricultural Research magazine|month=November | year=1999.| archiveurl= http://web.archive.org/web/20081012182444/http://www.ars.usda.gov/is/AR/archive/nov99/pest1199.htm| archivedate= 12 October 2008 <!--DASHBot-->| deadurl= no}}</ref>]]
[[Image:Bt plants.png|thumb|Bt toxins present in [[peanut]] leaves (bottom image) protect it from extensive damage caused by [[Lesser Cornstalk Borer]] [[larva]]e (top image).<ref>{{cite web |author= Jan Suszkiw|url=http://ars.usda.gov/is/ar/archive/nov99/pest1199.htm |title=Tifton, Georgia: A Peanut Pest Showdown |accessdate=2008-11-23 |work= Agricultural Research magazine|month=November | year=1999.| archiveurl= http://web.archive.org/web/20081012182444/http://www.ars.usda.gov/is/AR/archive/nov99/pest1199.htm| archivedate= 12 October 2008 <!--DASHBot-->| deadurl= no}}</ref>]]


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===Insect resistance===
===Insect resistance===
In November 2009, [[Monsanto]] scientists found the [[pink bollworm]] had become resistant to the first generation Bt cotton in parts of [[Gujarat]], India - that generation expresses one Bt gene, ''Cry1Ac''. This was the first instance of Bt resistance confirmed by Monsanto anywhere in the world.<ref name=MonsantoWebCotton>[http://www.monsanto.com/newsviews/Pages/india-pink-bollworm.aspx Cotton in India]</ref><ref>Pallava Bagla. (2010) Hardy Cotton-Munching Pests Are Latest Blow to GM Crops Science 327(5972): 1439[http://www.sciencemag.org/content/327/5972/1439.summary]</ref> Monsanto immediately responded by introducing a second generation cotton with multiple Bt proteins, which was rapidly adopted.<ref name=MonsantoWebCotton /> Bollworm resistance to first generation Bt cotton was also identified in the Australia, China, Spain and the United States.<ref>Tabashnik BE et al (2008) Insect resistance to Bt crops: evidence versus theory Nature Biotechnology 26: 199 - 202[http://www.nature.com/nbt/journal/v26/n2/abs/nbt1382.html]</ref>
In November 2009, [[Monsanto]] scientists found the [[pink bollworm]] had become resistant to the first generation Bt cotton in parts of [[Gujarat]], India - that generation expresses one Bt gene, ''Cry1Ac''. This was the first instance of Bt resistance confirmed by Monsanto anywhere in the world.<ref name=MonsantoWebCotton>[http://www.monsanto.com/newsviews/Pages/india-pink-bollworm.aspx Cotton in India]</ref><ref>{{cite journal |doi=10.1126/science.327.5972.1439}}</ref> Monsanto immediately responded by introducing a second generation cotton with multiple Bt proteins, which was rapidly adopted.<ref name=MonsantoWebCotton /> Bollworm resistance to first generation Bt cotton was also identified in the Australia, China, Spain and the United States.<ref>{{cite journal |doi=10.1038/nbt1382}}</ref>


===Secondary pests===
===Secondary pests===
Several studies have documented surges in "sucking pests" (which are not affected by Bt toxins) within a few years of adoption of Bt cotton. In China, the main problem has been with [[mirids]],<ref>Lu Y et al (2010) Mirid Bug Outbreaks in Multiple Crops Correlated with Wide-Scale Adoption of Bt Cotton in China. Science 328(5982):1151-4[http://www.ncbi.nlm.nih.gov/pubmed?term=20466880]</ref><ref>Susan Lang, Cornell Chronicle [http://www.news.cornell.edu/stories/July06/Bt.cotton.China.ssl.html "Profits die for Bt cotton in China"] Retrieved on 2009-4-6</ref> which have in some cases "completely eroded all benefits from Bt cotton cultivation”.<ref>Wang, S et al (2008) Bt-cotton and secondary pests. International Journal of Biotechnology 10: 113–121[http://www.inderscience.com/info/inarticle.php?artid=18348]</ref> A 2009 study in China concluded that the increase in sucking pests depended on local temperature and rainfall conditions and increased in half the villages studied. The increase in insecticide use for the control of these secondary insects was far smaller than the reduction in total insecticide use due to Bt cotton adoption.<ref>Wang ZJ et al (2009) "Bt Cotton in China: Are Secondary Insect Infestations Offsetting the Benefits in Farmer Fields?" Agricultural Sciences in China 8(1):83–90[http://www.sciencedirect.com/science/article/pii/S1671292709600122]</ref> Another study published in 2011 was based on a survey of 1,000 randomly selected farm households in five provinces in China and found that the reduction in pesticide use in Bt cotton cultivars is significantly lower than that reported in research elsewhere, consistent with the hypothesis suggested by recent studies that more pesticide sprayings are needed over time to control emerging secondary pests, such as aphids, spider mites, and lygus bugs.<ref>Zhao JH, et al (2011) Benefits of Bt cotton counterbalanced by secondary pests? Perceptions of ecological change in China. Environ Monit Assess. 173(1-4):985-94[http://www.ncbi.nlm.nih.gov/pubmed/20437270]; Erratum published 2012 Aug 5.[http://www.ncbi.nlm.nih.gov/pubmed/22864609]</ref>
Several studies have documented surges in "sucking pests" (which are not affected by Bt toxins) within a few years of adoption of Bt cotton. In China, the main problem has been with [[mirids]],<ref>{{cite journal |pmid=20466880}}</ref><ref>Susan Lang, Cornell Chronicle [http://www.news.cornell.edu/stories/July06/Bt.cotton.China.ssl.html "Profits die for Bt cotton in China"] Retrieved on 2009-4-6</ref> which have in some cases "completely eroded all benefits from Bt cotton cultivation”.<ref>{{cite journal |doi=10.1504/IJBT.2008.018348}}</ref> A 2009 study in China concluded that the increase in sucking pests depended on local temperature and rainfall conditions and increased in half the villages studied. The increase in insecticide use for the control of these secondary insects was far smaller than the reduction in total insecticide use due to Bt cotton adoption.<ref>{{cite journal |doi=10.1016/S1671-2927(09)60012-2}}</ref> Another study published in 2011 was based on a survey of 1,000 randomly selected farm households in five provinces in China and found that the reduction in pesticide use in Bt cotton cultivars is significantly lower than that reported in research elsewhere, consistent with the hypothesis suggested by recent studies that more pesticide sprayings are needed over time to control emerging secondary pests, such as aphids, spider mites, and lygus bugs.<ref>{{cite journal |pmid=20437270}}; Erratum published 2012 Aug 5: {{cite journal |pmid=22864609}}</ref>


Similar problems have been reported in India, with both [[mealy bugs]]<ref>Bhaskar Goswami, InfoChange
Similar problems have been reported in India, with both [[mealy bugs]]<ref>Bhaskar Goswami, InfoChange
[http://infochangeindia.org/200709026463/Other/Features/Making-a-meal-of-Bt-cotton.html "Making a meal of Bt cotton"] Retrieved on 2009-4-6</ref><ref>India Times
[http://infochangeindia.org/200709026463/Other/Features/Making-a-meal-of-Bt-cotton.html "Making a meal of Bt cotton"] Retrieved on 2009-4-6</ref><ref>India Times
[http://economictimes.indiatimes.com/News/Economy/Agriculture/Bug_makes_meal_of_Punjab_cotton_whither_Bt_magic/articleshow/msid-2330585,curpg-1.cms "Bug makes meal of Punjab cotton, whither Bt magic?"] Retrieved on 2009-4-6</ref> and aphids<ref>{{cite journal|journal=World Development |year=2010| volume=39| issue=3| pages= 387–398|doi=10.1016/j.worlddev.2010.09.008|title=Field versus Farm in Warangal: Bt Cotton, Higher Yields, and Larger Questions|author=Stone, G. D.}}</ref> although a survey of small Indian farms between 2002 and 2008 concluded that Bt cotton adoption has led to higher yields and lower pesticide use, decreasing over time.<ref>{{Cite doi|10.1016/j.agsy.2011.11.005}}</ref>
[http://economictimes.indiatimes.com/News/Economy/Agriculture/Bug_makes_meal_of_Punjab_cotton_whither_Bt_magic/articleshow/msid-2330585,curpg-1.cms "Bug makes meal of Punjab cotton, whither Bt magic?"] Retrieved on 2009-4-6</ref> and aphids<ref>{{cite journal |doi=10.1016/j.worlddev.2010.09.008}}</ref> although a survey of small Indian farms between 2002 and 2008 concluded that Bt cotton adoption has led to higher yields and lower pesticide use, decreasing over time.<ref>{{cite journal |doi=10.1016/j.agsy.2011.11.005}}</ref>


===Possible problems===
===Possible problems===
Line 56: Line 56:


====Lepidopteran toxicity====
====Lepidopteran toxicity====
The most publicised problem associated with Bt crops is the claim that pollen from Bt maize could kill the [[monarch butterfly]].<ref>{{cite journal |author=Losey JE, Rayor LS, Carter ME |title=Transgenic pollen harms monarch larvae |journal=Nature |volume=399 |issue=6733 |pages=214 |year=1999 |month=May |pmid=10353241 |doi=10.1038/20338|bibcode = 1999Natur.399..214L }}</ref> This report was puzzling<!-- why? lepidopterans feed on pollen selectively --> because the pollen from most maize hybrids contains much lower levels of Bt than the rest of the plant<ref>{{cite journal |author=Mendelsohn M, Kough J, Vaituzis Z, Matthews K |title=Are Bt crops safe? |journal=Nat. Biotechnol. |volume=21 |issue=9 |pages=1003–9 |year=2003 |month=September |pmid=12949561 |doi=10.1038/nbt0903-1003}}</ref> and led to multiple follow-up studies.
The most publicised problem associated with Bt crops is the claim that pollen from Bt maize could kill the [[monarch butterfly]].<ref>{{cite journal |doi=10.1038/20338}}</ref> This report was puzzling<!-- why? lepidopterans feed on pollen selectively --> because the pollen from most maize hybrids contains much lower levels of Bt than the rest of the plant<ref>{{cite journal |doi=10.1038/nbt0903-1003}}</ref> and led to multiple follow-up studies.


The initial study apparently was flawed by faulty pollen-collection procedure; researchers fed nontoxic pollen mixed with [[anther]] walls containing Bt toxin.<ref>{{cite journal |author=Hellmich RL, Siegfried BD, Sears MK |title=Monarch larvae sensitivity to Bacillus thuringiensis- purified proteins and pollen |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=98 |issue=21 |pages=11925–30 |year=2001 |month=October |pmid=11559841 |pmc=59744 |doi=10.1073/pnas.211297698 |url=http://www.pnas.org/cgi/pmidlookup?view=long&pmid=11559841|bibcode = 2001PNAS...9811925H }}</ref> The weight of the evidence is that Bt crops do not pose a risk to the monarch butterfly.<ref>{{cite web |url=http://www.ars.usda.gov/is/br/btcorn/ |title=Bt Corn and Monarch Butterflies |date=2004-03-29 |work=USDA Agricultural Research Service |accessdate=2008-11-23| archiveurl= http://web.archive.org/web/20081106062846/http://www.ars.usda.gov/is/br/btcorn/| archivedate= 6 November 2008 <!--DASHBot-->| deadurl= no}}</ref> Monarch butterflies have no innate relationship to maize crops in the wild, and are [[Monarch_butterfly#Host_plants|not believed to consume maize pollen]] (or pollen of related plants) in either life stage.
The initial study apparently was flawed by faulty pollen-collection procedure; researchers fed nontoxic pollen mixed with [[anther]] walls containing Bt toxin.<ref>{{cite journal |doi=10.1073/pnas.211297698}}</ref> The weight of the evidence is that Bt crops do not pose a risk to the monarch butterfly.<ref>{{cite web |url=http://www.ars.usda.gov/is/br/btcorn/ |title=Bt Corn and Monarch Butterflies |date=2004-03-29 |work=USDA Agricultural Research Service |accessdate=2008-11-23| archiveurl= http://web.archive.org/web/20081106062846/http://www.ars.usda.gov/is/br/btcorn/| archivedate= 6 November 2008 <!--DASHBot-->| deadurl= no}}</ref> Monarch butterflies have no innate relationship to maize crops in the wild, and are [[Monarch_butterfly#Host_plants|not believed to consume maize pollen]] (or pollen of related plants) in either life stage.


====Wild maize genetic mixing====
====Wild maize genetic mixing====
A study published in ''Nature'' in 2001 reported that Bt-containing maize genes were found in maize in its center of origin, Oaxaca, Mexico.<ref>Quist D, Chapela IH. (2001) "Transgenic DNA introgressed into traditional maize landraces in Oaxaca, Mexico." Nature. 14(6863):541-3.[http://www.ncbi.nlm.nih.gov/pubmed/11734853]</ref> In 2002 ''Nature'' "concluded that the evidence available is not sufficient to justify the publication of the original paper."<ref>Kaplinsky N, et al (2002) "Biodiversity (Communications arising): maize transgene results in Mexico are artefacts." Nature 416(6881):601-2; discussion 600, 602. Epub 2002 Apr 4.[http://www.ncbi.nlm.nih.gov/pubmed/11935145]</ref> A significant controversy happened over the paper and ''Nature''{{'}}s unprecedented notice.<ref name="pbs.org">http://www.pbs.org/now/science/genenature.html</ref><ref>http://www.organicconsumers.org/articles/article_17133.cfm</ref>
A study published in ''Nature'' in 2001 reported that Bt-containing maize genes were found in maize in its center of origin, Oaxaca, Mexico.<ref>{{cite journal |pmid=11734853}}</ref> In 2002 ''Nature'' "concluded that the evidence available is not sufficient to justify the publication of the original paper."<ref>{{cite journal |pmid=11935145}}</ref> A significant controversy happened over the paper and ''Nature''{{'}}s unprecedented notice.<ref name="pbs.org">http://www.pbs.org/now/science/genenature.html{{full}}</ref><ref>http://www.organicconsumers.org/articles/article_17133.cfm{{full}}</ref>


A subsequent large-scale study, in 2005, failed to find any evidence of genetic mixing in Oaxaca.<ref>Ortiz-García S, et al (2005) "Absence of detectable transgenes in local landraces of maize in Oaxaca, Mexico (2003-2004)." Proc Natl Acad Sci U S A. 2005 Aug 30;102(35):12338-43.[http://www.ncbi.nlm.nih.gov/pubmed?term=16093316]</ref> A 2007 study found that "transgenic proteins expressed in maize were found in two (0.96%) of 208 samples from farmers' fields, located in two (8%) of 25 sampled communities. Mexico imports a substantial amount of maize from the US, and due to formal and informal seed networks among rural farmers, there are many potential routes of entrance for transgenic maize into food and feed webs."<ref> Serratos-Hernández, JA et al (2007) "Transgenic proteins in maize in the Soil Conservation area of Federal District, Mexico" Frontiers in Ecology and the Environment 5: 247–252. [http://dx.doi.org/10.1890/1540-9295(2007)5%5B247:TPIMIT%5D2.0.CO;2]</ref> A study published in 2008 showed some small-scale (about 1%) introduction of transgenic sequences in sampled fields in Mexico; it did not find evidence for or against this introduced genetic material being inherited by the next generation of plants.<ref>Piñeyro-Nelson A, et al 2009, epub 2008) "Transgenes in Mexican maize: molecular evidence and methodological considerations for GMO detection in landrace populations." Mol Ecol. 18(4):750-61.[http://www.ncbi.nlm.nih.gov/pubmed/19143938]</ref><ref>http://www.nature.com/news/2008/081112/full/456149a.html</ref> That study was immediately criticized, with the reviewer writing that "Genetically any given plant should be either non-transgenic or transgenic, therefore for leaf tissue of a single transgenic plant, a GMO level close to 100% is expected. In their study, the authors chose to classify leaf samples as transgenic despite GMO levels of ∼0.1%. We contend that results such as these are incorrectly interpreted as positive and are more likely to be indicative of contamination in the laboratory."<ref>Schoel B, Fagan J. (2009) "Insufficient evidence for the discovery of transgenes in Mexican landraces." Mol Ecol. 2009 Oct;18(20):4143-4; discussion 4145-50. Epub 2009 Sep 28.[http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2009.04368.x/full]</ref>
A subsequent large-scale study, in 2005, failed to find any evidence of genetic mixing in Oaxaca.<ref>{{cite journal |pmid=16093316}}</ref> A 2007 study found that "transgenic proteins expressed in maize were found in two (0.96%) of 208 samples from farmers' fields, located in two (8%) of 25 sampled communities. Mexico imports a substantial amount of maize from the US, and due to formal and informal seed networks among rural farmers, there are many potential routes of entrance for transgenic maize into food and feed webs."<ref>{{cite journal |doi=10.1890/1540-9295(2007)5[247:TPIMIT]2.0.CO;2}}</ref> A study published in 2008 showed some small-scale (about 1%) introduction of transgenic sequences in sampled fields in Mexico; it did not find evidence for or against this introduced genetic material being inherited by the next generation of plants.<ref>{{cite journal |pmid=19143938}}</ref><ref>{{cite journal |doi=10.1038/456149a}}</ref> That study was immediately criticized, with the reviewer writing that "Genetically any given plant should be either non-transgenic or transgenic, therefore for leaf tissue of a single transgenic plant, a GMO level close to 100% is expected. In their study, the authors chose to classify leaf samples as transgenic despite GMO levels of ∼0.1%. We contend that results such as these are incorrectly interpreted as positive and are more likely to be indicative of contamination in the laboratory."<ref>{{cite journal |doi=10.1111/j.1365-294X.2009.04368.x}}</ref>


====Disproven link to colony collapse disorder====
====Disproven link to colony collapse disorder====
As of 2007, a new phenomenon called [[colony collapse disorder]] (CCD) began affecting [[Honey bee|bee]] hives all over North America. Initial speculation on possible causes ranged from new parasites to pesticide use<ref>{{cite web |url=http://www.ars.usda.gov/News/docs.htm?docid=15572 |title=ARS : Questions and Answers: Colony Collapse Disorder |work=ARS News |date=2008-05-29 | accessdate=2008-11-23| archiveurl= http://web.archive.org/web/20081105121119/http://www.ars.usda.gov/News/docs.htm?docid=15572| archivedate= 5 November 2008 <!--DASHBot-->| deadurl= no}}</ref> to the use of Bt transgenic crops.<ref>{{cite journal | author= Latsch G | title=Are GM Crops Killing Bees? | journal=Spiegel (International) | date=2007-03-22 | url=http://www.spiegel.de/international/world/0,1518,473166,00.html | accessdate=2008-11-23| archiveurl= http://web.archive.org/web/20081205014706/http://www.spiegel.de/international/world/0,1518,473166,00.html| archivedate= 5 December 2008 <!--DASHBot-->| deadurl= no}}</ref> The [[Mid-Atlantic Apiculture Research and Extension Consortium]] published a report in March 2007 that found no evidence that pollen from Bt crops is adversely affecting bees.<ref>{{Cite web |url=http://maarec.psu.edu/CCDPpt/NontargeteffectsofBt.pdf |title=SUMMARY OF RESEARCH ON THE NON-TARGET EFFECTS OF BT CORN POLLEN ON HONEYBEES |author=Galen P. Dively |date=2007-03-28 |accessdate=2010-01-12}}</ref> The actual cause of CCD remains unknown, and scientists believe that it may have multiple causes.<ref>http://news.bbc.co.uk/1/hi/sci/tech/7925397.stm 'No proof' of bee killer theory</ref>
As of 2007, a new phenomenon called [[colony collapse disorder]] (CCD) began affecting [[Honey bee|bee]] hives all over North America. Initial speculation on possible causes ranged from new parasites to pesticide use<ref>{{cite web |url=http://www.ars.usda.gov/News/docs.htm?docid=15572 |title=ARS : Questions and Answers: Colony Collapse Disorder |work=ARS News |date=2008-05-29 | accessdate=2008-11-23| archiveurl= http://web.archive.org/web/20081105121119/http://www.ars.usda.gov/News/docs.htm?docid=15572| archivedate= 5 November 2008 <!--DASHBot-->| deadurl= no}}</ref> to the use of Bt transgenic crops.<ref>{{cite journal | author= Latsch G | title=Are GM Crops Killing Bees? | journal=Spiegel (International) | date=2007-03-22 | url=http://www.spiegel.de/international/world/0,1518,473166,00.html | accessdate=2008-11-23| archiveurl= http://web.archive.org/web/20081205014706/http://www.spiegel.de/international/world/0,1518,473166,00.html| archivedate= 5 December 2008 <!--DASHBot-->| deadurl= no}}</ref> The [[Mid-Atlantic Apiculture Research and Extension Consortium]] published a report in March 2007 that found no evidence that pollen from Bt crops is adversely affecting bees.<ref>{{cite journal |doi=10.1051/apido:2007022}}</ref> The actual cause of CCD remains unknown, and scientists believe that it may have multiple causes.<ref>http://news.bbc.co.uk/1/hi/sci/tech/7925397.stm 'No proof' of bee killer theory</ref>


==See also==
==See also==
Line 78: Line 78:
==Further reading==
==Further reading==
{{expand article|date=February 2012}}
{{expand article|date=February 2012}}
*{{cite doi|10.1016/S0168-9525(01)02237-5}}
*{{cite journal |doi=10.1016/S0168-9525(01)02237-5}}
*{{cite doi|10.1016/j.toxicon.2006.11.022}}
*{{cite journal |doi=10.1016/j.toxicon.2006.11.022}}
*{{cite doi|10.1128/MMBR.00034-06}}
*{{cite journal |doi=10.1128/MMBR.00034-06}}
*{{cite pmid|20069826}}
*{{cite journal |pmid=20069826}}


==External links==
==External links==

Revision as of 18:33, 27 February 2013

Bacillus thuringiensis
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:
B. thuringiensis
Binomial name
Bacillus thuringiensis
Berliner 1915

Bacillus thuringiensis (or Bt) is a Gram-positive, soil-dwelling bacterium, commonly used as a biological pesticide; alternatively, the Cry toxin may be extracted and used as a pesticide. B. thuringiensis also occurs naturally in the gut of caterpillars of various types of moths and butterflies, as well on leaf surfaces, aquatic environments, animal feces, insect rich environments, flour mills and grain storage facilities.[1][2]

During sporulation, many Bt strains produce crystal proteins (proteinaceous inclusions), called δ-endotoxins, that have insecticidal action. This has led to their use as insecticides, and more recently to genetically modified crops using Bt genes. Many crystal-producing Bt strains, though, do not have insecticidal properties.[3]

Discovery and mechanism of insecticidal action

B. thuringiensis was first discovered in 1901 by Japanese biologist Ishiwata Shigetane.[4] In 1911, B. thuringiensis was rediscovered in Germany by Ernst Berliner, who isolated it as the cause of a disease called Schlaffsucht in flour moth caterpillars. In 1976, Robert A. Zakharyan reported the presence of a plasmid in a strain of B. thuringiensis and suggested the plasmid's involvement in endospore and crystal formation.[5][6] 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 (called crystal proteins or Cry proteins), which are encoded by cry genes.[7] In most strains of B. thuringiensis, the cry genes are located on a plasmid (in other words, cry is not a chromosomal gene in most strains).[8][9][10]

Cry toxins have specific activities against insect species of the orders Lepidoptera (moths and butterflies), Diptera (flies and mosquitoes), Coleoptera (beetles), Hymenoptera (wasps, bees, ants and sawflies) and nematodes. Thus, B. thuringiensis serves as an important reservoir of Cry toxins for production of biological insecticides and insect-resistant genetically modified crops. When insects ingest toxin crystals, the alkaline pH of their digestive tract denatures the insoluble crystals, making them soluble and thus amenable to being cut with proteases found in the insect gut, which liberate the cry toxin from the crystal.[8] The Cry toxin is then inserted into the insect gut cell membrane, forming a pore. The pore results in cell lysis and eventual death of the insect.[11][12] Research published in 2006 has suggested the midgut bacteria of susceptible larvae are required for B. thuringiensis insecticidal activity.[13]

In 2000, a novel functional group of Cry protein, designated parasporin, was discovered from non-insecticidal B. thuringiensis isolates.[14] The proteins of parasporin group are defined as "Bacillus thuringiensis and related bacterial parasporal proteins that are non-hemolytic but capable of preferentially killing cancer cells". As of January 2013, parasporins comprise six subfamilies (PS1 to PS6).[15]

Use of spores and proteins in pest control

Spores and crystalline insecticidal proteins produced by B. thuringiensis have been used to control insect pests since the 1920s and are often applied as liquid sprays.[16] They are now 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 and are used in Organic farming.[17]

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.[18]

Formulations of Bt that are approved for organic farming in the US are listed at the website of the Organic Materials Review Institute (OMRI)[19] and several university extension websites offer advice on how to use Bt spore or protein preparations in organic farming.[20][21]

Use of Bt genes in genetic engineering of plants for pest control

The Belgian company Plant Genetic Systems (now part of Bayer CropScience) was the first company (in 1985) to develop genetically engineered (tobacco) plants with insect tolerance by expressing cry genes from B. thuringiensis.[22][23]

Bt toxins present in peanut leaves (bottom image) protect it from extensive damage caused by Lesser Cornstalk Borer larvae (top image).[24]

Usage

In 1995, potato plants producing Bt toxin were approved safe by the Environmental Protection Agency, making it the first pesticide-producing crop to be approved in the USA.[25] For current crops and their acreage under cultivation, see genetically modified crops.

Kenyans examining insect-resistant transgenic Bt corn

Insect resistance

In November 2009, Monsanto scientists found the pink bollworm had become resistant to the first generation Bt cotton in parts of Gujarat, India - that generation expresses one Bt gene, Cry1Ac. This was the first instance of Bt resistance confirmed by Monsanto anywhere in the world.[26][27] Monsanto immediately responded by introducing a second generation cotton with multiple Bt proteins, which was rapidly adopted.[26] Bollworm resistance to first generation Bt cotton was also identified in the Australia, China, Spain and the United States.[28]

Secondary pests

Several studies have documented surges in "sucking pests" (which are not affected by Bt toxins) within a few years of adoption of Bt cotton. In China, the main problem has been with mirids,[29][30] which have in some cases "completely eroded all benefits from Bt cotton cultivation”.[31] A 2009 study in China concluded that the increase in sucking pests depended on local temperature and rainfall conditions and increased in half the villages studied. The increase in insecticide use for the control of these secondary insects was far smaller than the reduction in total insecticide use due to Bt cotton adoption.[32] Another study published in 2011 was based on a survey of 1,000 randomly selected farm households in five provinces in China and found that the reduction in pesticide use in Bt cotton cultivars is significantly lower than that reported in research elsewhere, consistent with the hypothesis suggested by recent studies that more pesticide sprayings are needed over time to control emerging secondary pests, such as aphids, spider mites, and lygus bugs.[33]

Similar problems have been reported in India, with both mealy bugs[34][35] and aphids[36] although a survey of small Indian farms between 2002 and 2008 concluded that Bt cotton adoption has led to higher yields and lower pesticide use, decreasing over time.[37]

Possible problems

Further information: Genetically modified food controversies

Lepidopteran toxicity

The most publicised problem associated with Bt crops is the claim that pollen from Bt maize could kill the monarch butterfly.[38] This report was puzzling because the pollen from most maize hybrids contains much lower levels of Bt than the rest of the plant[39] and led to multiple follow-up studies.

The initial study apparently was flawed by faulty pollen-collection procedure; researchers fed nontoxic pollen mixed with anther walls containing Bt toxin.[40] The weight of the evidence is that Bt crops do not pose a risk to the monarch butterfly.[41] Monarch butterflies have no innate relationship to maize crops in the wild, and are not believed to consume maize pollen (or pollen of related plants) in either life stage.

Wild maize genetic mixing

A study published in Nature in 2001 reported that Bt-containing maize genes were found in maize in its center of origin, Oaxaca, Mexico.[42] In 2002 Nature "concluded that the evidence available is not sufficient to justify the publication of the original paper."[43] A significant controversy happened over the paper and Nature's unprecedented notice.[44][45]

A subsequent large-scale study, in 2005, failed to find any evidence of genetic mixing in Oaxaca.[46] A 2007 study found that "transgenic proteins expressed in maize were found in two (0.96%) of 208 samples from farmers' fields, located in two (8%) of 25 sampled communities. Mexico imports a substantial amount of maize from the US, and due to formal and informal seed networks among rural farmers, there are many potential routes of entrance for transgenic maize into food and feed webs."[47] A study published in 2008 showed some small-scale (about 1%) introduction of transgenic sequences in sampled fields in Mexico; it did not find evidence for or against this introduced genetic material being inherited by the next generation of plants.[48][49] That study was immediately criticized, with the reviewer writing that "Genetically any given plant should be either non-transgenic or transgenic, therefore for leaf tissue of a single transgenic plant, a GMO level close to 100% is expected. In their study, the authors chose to classify leaf samples as transgenic despite GMO levels of ∼0.1%. We contend that results such as these are incorrectly interpreted as positive and are more likely to be indicative of contamination in the laboratory."[50]

Disproven link to colony collapse disorder

As of 2007, a new phenomenon called colony collapse disorder (CCD) began affecting bee hives all over North America. Initial speculation on possible causes ranged from new parasites to pesticide use[51] to the use of Bt transgenic crops.[52] The Mid-Atlantic Apiculture Research and Extension Consortium published a report in March 2007 that found no evidence that pollen from Bt crops is adversely affecting bees.[53] The actual cause of CCD remains unknown, and scientists believe that it may have multiple causes.[54]

See also

References

  1. ^ a b Madigan, Michael T.; Martinko, John M., eds. (2005). Brock Biology of Microorganisms (11th ed.). Prentice Hall. ISBN 978-0-13-144329-7.[page needed]
  2. ^ du Rand, Nicolette (2009). Isolation of Entomopathogenic Gram Positive Spore Forming Bacteria Effective Against Coleoptera (PhD Thesis). Pietermaritzburg, South Africa: University of KwaZulu-Natal. hdl:10413/1235. {{cite book}}: Unknown parameter |month= ignored (help)[page needed]
  3. ^ . PMID 18051264. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  4. ^ . PMID 18051264. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  5. ^ Zakharyan R.A et. el. (1979). "Plasmid DNA from Bacillus thuringiensis". Microbiologiya. 48 (2): 226–9. ISSN 0026-3656.
  6. ^ Cheng, Thomas Clement, ed. (1984). Pathogens of invertebrates: application in biological control and transmission mechanisms. p. 159. ISBN 978-0-306-41700-9.
  7. ^ Circkmore N. "Bacillus thuringiensis toxin nomenclature". Archived from the original on 9 October 2008. Retrieved 2008-11-23. {{cite web}}: Unknown parameter |deadurl= ignored (|url-status= suggested) (help)
  8. ^ a b . PMID 6443645. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  9. ^ . doi:10.4039/Ent124587-4. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  10. ^ XU Jian, LIU Qin, YIN Xiang-dong and ZHU Shu-de (2006). "A review of recent development of Bacillus thuringiensis ICP genetically engineered microbes". Entomological Journal of East China. 15 (1): 53–58.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  11. ^ Babu M, Geetha M. "DNA shuffling of Cry proteins". Retrieved 2008-11-23.
  12. ^ . PMID 6443645. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  13. ^ . doi:10.1073/pnas.0604865103. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  14. ^ . doi:10.1128/CDLI.7.4.625-634.2000. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  15. ^ Official Website of the Committee of Parasporin Classification and Nomenclature Accessed Jan 4, 2013
  16. ^ . doi:10.1146/annurev.arplant.58.032806.103840. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  17. ^ Staff (19 February 2003) Bt Toxins, Used By Organic Farmers As An Environmentally Safe Insecticide, Found To Kill Parasitic Roundworms UC San Diego, Division of Biological Sciences, Retrieved 26 July 2012
  18. ^ Poopathi, Subbiah; Abidha, S. (2010). "Mosquitocidal bacterial toxins (Bacillus sphaericus and B. thuringiensis serovar israelensis): Mode of action, cytopathological effects and mechanism of resistance". Journal of Physiology and Pathophysiology. 1 (3): 22–38.
  19. ^ http://www.omri.org/simple-opl-search/results/BACILLUS%20THURINGIENSIS BT formulations at OMRI]
  20. ^ Caldwell B et al. October 2005 MATERIAL NAME: BACILLUS THURINGIENSIS (BT) Resource Guide for Organic Insect and Disease Management. ISBN 0-9676507-2-0
  21. ^ W.S. Cranshaw for Colorado State University Extension Service. Updated November 02, 2012. Bacillus thuringiensis Fact Sheet
  22. ^ . doi:10.1111/j.1432-1033.1986.tb10443.x. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  23. ^ . doi:10.1038/328033a0. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  24. ^ Jan Suszkiw (1999.). "Tifton, Georgia: A Peanut Pest Showdown". Agricultural Research magazine. Archived from the original on 12 October 2008. Retrieved 2008-11-23. {{cite web}}: Check date values in: |year= (help); Unknown parameter |deadurl= ignored (|url-status= suggested) (help); Unknown parameter |month= ignored (help)
  25. ^ Genetically Altered Potato Ok'd For Crops Lawrence Journal-World - 6 May 1995
  26. ^ a b Cotton in India
  27. ^ . doi:10.1126/science.327.5972.1439. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  28. ^ . doi:10.1038/nbt1382. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  29. ^ . PMID 20466880. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  30. ^ Susan Lang, Cornell Chronicle "Profits die for Bt cotton in China" Retrieved on 2009-4-6
  31. ^ . doi:10.1504/IJBT.2008.018348. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  32. ^ . doi:10.1016/S1671-2927(09)60012-2. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
  33. ^ . PMID 20437270. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help); Erratum published 2012 Aug 5: . PMID 22864609. {{cite journal}}: Cite journal requires |journal= (help); Missing or empty |title= (help)
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  35. ^ India Times "Bug makes meal of Punjab cotton, whither Bt magic?" Retrieved on 2009-4-6
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Further reading

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External links

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