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Commercial Production of Biopesticides with reference
to
Bacillus Thurigiensis
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What are biopesticide?
Biopesticides are certain types of pesticides derived from
such natural materials as animals, plants, bacteria, and
certain minerals. For example, canola oil and baking soda
have pesticidal applications and are consideredbiopesticides.
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Biopesticides fall into three majorclasses
1. Microbial pesticide - consist of a microorganism (e.g., a
bacterium, fungus, virus or protozoan's .
2. Plant-Incorporated-Protectants (PIPs)-pesticidal
substances that plants produce from genetic material
that has been added to the plant.
3. Biochemical pesticides-naturally occurring substances
that control pests by non-toxic mechanisms.
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What are the advantages of usingbiopesticides?
Biopesticides are usually inherently less toxic thanconventional pesticides.
Biopesticides generally affect only the target pestand closely related organisms, in contrast to broadspectrum, conventional pesticides that may affectorganisms as different as birds, insects, andmammals.
Biopesticides often are effective in very smallquantities and often decompose quickly, therebyresulting in lower exposures and largely avoiding the
pollution problems caused by conventional pesticides.
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BACILLUS THURIGIENSIS ASBIOPESTICIDE
The most widely used microbial pesticides are subspecies
and strains ofBacillus thuringiensis, or Bt. Each strain ofthis bacterium produces a different mix of proteins, and
specifically kills one or a few related species of insect
larvae.
some Bt's control moth larvae found on plants, other Bt's
are specific for larvae of flies and mosquitoes. The targetinsect species are determined by whether the particular Bt
produces a protein that can bind to a larval gut receptor,
thereby causing the insect larvae to starve.
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WHAT IS NATURAL BACILLUSTHURIGIENSIS?Gram Positive
Spore Forming Bacteria
During speculation produce
protein crystal (cry) called -endotoxins, that
have insecticidal action
In most strains ofB.thuringiensis, the crygenes arelocated on a plasmid (in other
words, cryis not achromosomal gene in most
strains).
http://en.wikipedia.org/wiki/%CE%94-endotoxinshttp://en.wikipedia.org/wiki/%CE%94-endotoxinshttp://en.wikipedia.org/wiki/%CE%94-endotoxinshttp://en.wikipedia.org/wiki/Insecticidalhttp://en.wikipedia.org/wiki/Plasmidhttp://en.wikipedia.org/wiki/Plasmidhttp://en.wikipedia.org/wiki/Insecticidalhttp://en.wikipedia.org/wiki/%CE%94-endotoxinshttp://en.wikipedia.org/wiki/%CE%94-endotoxinshttp://en.wikipedia.org/wiki/%CE%94-endotoxins7/31/2019 Presentation on Bt _final
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Cry toxins have specific activities against insect species of
the orders Lepidoptera (moths and butterflies), Diptera (fliesand
mosquitoes), Coleoptera (beetles), Hymenoptera (wasps, be
es, antsand sawflies) and nematodes.
Bthas to be eaten to cause mortality. The Bttoxindissolve in the high pH insect gut and become active. The
toxins then attack the gut cells of the insect, punching
holes in the lining. The Btspores spills out of the gut and
germinate in the insect causing death within a couple days.
Bacillus thurigiensis toxin
http://en.wikipedia.org/wiki/Lepidopterahttp://en.wikipedia.org/wiki/Dipterahttp://en.wikipedia.org/wiki/Coleopterahttp://en.wikipedia.org/wiki/Hymenopterahttp://en.wikipedia.org/wiki/Wasphttp://en.wikipedia.org/wiki/Beehttp://en.wikipedia.org/wiki/Beehttp://en.wikipedia.org/wiki/Anthttp://en.wikipedia.org/wiki/Sawflyhttp://en.wikipedia.org/wiki/Nematodehttp://en.wikipedia.org/wiki/Nematodehttp://en.wikipedia.org/wiki/Sawflyhttp://en.wikipedia.org/wiki/Anthttp://en.wikipedia.org/wiki/Beehttp://en.wikipedia.org/wiki/Beehttp://en.wikipedia.org/wiki/Wasphttp://en.wikipedia.org/wiki/Hymenopterahttp://en.wikipedia.org/wiki/Coleopterahttp://en.wikipedia.org/wiki/Dipterahttp://en.wikipedia.org/wiki/Lepidoptera7/31/2019 Presentation on Bt _final
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How BT Works?
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1. Insect eats Btcrystals andspores.
2. The toxin binds to specific
receptors in the gut and the
insects stops eating.
3. The crystals cause the gut
wall to break down, allowing
spores and normal gut bacteria
to enter the body.
4. The insect dies as spores and
gut bacteria proliferate in the
body.
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Application of BT Bt is used in agriculture as a liquid applied through overhead
irrigation systems or in a granular form for control of Europeancorn borer. The treatments funnel down the corn whorl to where
the feeding larvae occur.
Bt useful in applications where pesticide drift onto Gardens islikely to occur, such as treating trees and shrubs.
To control mosquito larvae, formulations containing
the israelensisstrain are placed into the standing water of
mosquito breeding sites.
Use of Bt (israelensis) for control of fungus gnat larvae involvesdrenching the soil.
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Insects Controlled by Bt
Cabbage worm (cabbage looper, imported cabbageworm, diamondback moth,etc.).
Tomato and tobacco hornworm
Vegetable insects
European corn borer (granular formulations have given good control of firstgeneration corn borers).
Alfalfa caterpillar, alfalfa webworm
Field and forage crop insects
Leafroller.
Achemon sphinx.
Fruit crop insects
Tent caterpillar.
Pine budworm
Western spruce budworm.
Fruit crop insects
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Israelensisstrains (Vectobac, Mosquito Dunks, Gnatrol,Bactimos, etc.)
Insects Controlled by Bt continue..
Mosquito.
Black fly.
Fungus gnat.
San diego/tenebrionisstrains (Trident, M-One, M-Trak, Foil,Novodor, etc.)
Colorado potato beetle.
Elm leaf beetle.
Cottonwood leaf beetle.
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Disadvantages
Bt is susceptible to degradation by sunlight
The highly specific activity of Bt insecticides might limit their
use on Crops where problems with several pests occur,
including nonsusceptible insects (aphids, grasshoppers, etc.).
Since Bt does not kill rapidly, users may incorrectly assume
that it is ineffective a day or two after treatment.
Bt-based products tend to have a shorter shelf life than other
insecticides.
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Advantages
The specific activity of Bt generally is considered highly
beneficial Perhaps the major advantage is that Bt isessentially nontoxic to people, pets and wildlife.
This high margin of safety recommends its use on food
Crops or in other sensitive sites where pesticide use can
cause adverse effects.
Perhaps the major advantage is that Bt is essentially
nontoxic to people, pets and wildlife.
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Since 1996, a wide range of crop plants have been geneticallyengineered to contain the delta-endotoxin gene from Bacillusthuringiensis.
These "Bt crops" are now available commercially in the USA. They
include "Bt corn", "Bt potato", "Bt cotton" and "Bt soybean". Such plants
have been genetically engineered to express part of the active Cry toxin in
their tissues, so they kill insects that feed on the crops.
In some respects, this is an important technological and practical
development, because it ensures that only those insects that attack the
crop will be exposed to Bt toxins - there is no risk to other types of insect.
However, there is also a "downside", because the target insects are
perpetually exposed to toxins and this creates a very strong selection
pressure for the development of resistance to the toxins. Various crop-
management strategies are being developed to try to minimise this risk.
Plants genetically engineered with the Btgene
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.
Biopesticide Production from Bacillusthuringiensis: An Environmentally
Friendly AlternativeNinfa M. Rosas Garca*
Received: October 29, 2008; Accepted: November 26, 2008; Revised:November 28, 2008
Laboratorio de Biotecnologa Ambiental. Centro de Biotecnologa
Genmica-IPN. Blvd. del Maestro s/n. Reynosa,Tamp. CP 88710 Mxico
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Introduction
The bacterium Bacillus thuringiensis was discovered by
Shigetane Ishiwata in 1901.
The bacterium was isolated from diseased larvae of
Anagasta kuehniella, and this finding led to theestablishmentofB. thuringiensis as microbial insecticide.
The first record of its application to control insects was in
Hungary at the end of 1920, and in Yugoslavia at the
beginning of 1930s, it was applied to control the European
corn borer.
During the following two decades, several field tests were
conducted to evaluate its effectiveness against lepidopterans,
both in Europe and in the United States.
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results favored the development of formulations against on
this pathogen. Subsequently, the first commercial product was
produced in 1938 by Libec I France.
serious environmental and health issues began to be
recognized by the presence of chemical residues in food,
water, and air during 1950.
To counteract this contamination, attention and efforts weredirected to the use of biological control agents including insect
pathogens.
As an entomopathogenic organism, B.thuringiensis fulfills allthese requirements.
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MODE OF ACTION
The C-terminal extension found in the long protoxins is
necessary for toxicity and is believed to play a role in theformation of the crystal within the bacterium.
During proteolytic activation, peptides from the N terminus and C
terminus are cleaved from the full protein.
During proteolytic activation, peptides from the N terminus and
C terminus are cleaved from the full protein.
Activated toxin binds to receptors located on the apical
microvillus membranes of epithelial midgut cells.
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For Cry1A toxins, at least four different binding sites have been
described in different lepidopteran insects:
1. a cadherin-like protein(CADR),2. a glycosylphosphatidyl-inositol (GPI)-anchored
aminopeptidase-N (APN),
3. a GPI-anchored alkaline
4. phosphatase (ALP) and a 270 kDa glycoconjugate .
After binding, toxin adopts a conformation allowing its insertion
into the cell membrane. Subsequently, oligomerization occurs,
and this oligomer forms a ion channel induced by an increase
in cationic permeability within the functional receptorscontained on the brush borders membranes
This causing disruption of membrane transport and cell lysis,
and leading to insect death
Photograph sho s lepidopteran lar ae s sceptible to B th ringiensis to ic
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Photograph shows lepidopteran larvae susceptible to B.thuringiensis toxicactivity.
A) Nine day-old, healthy larvae,
notexposed to B. thuringiensis
B) Nine-day old larvae exposed to
sublethal concentration ofB. thuringiensis.Larvae exhibit a smallersize due to theirpoor feeding.
C) Larvae exposed to lethalconcentrationofB. thuringiensis.
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BACILLUS THURINGIENSIS-BASEFORMULATIONS
The active ingredient in commercial formulations is the
sporecrystal complex.
It is more effective to use and cheaper to obtain than the
crystals alone, which are frequently used in experimental tests.
A great variety of ingredients have been employed to prepare
formulations, including liquid or solid carriers, surfactants,
coadjuvants, fluidity agents, adherents, dispersants,stabilizers, moisturizers, attractants, and protective agents
among others
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An interesting and recent example of these kind of inert
ingredients is the superabsorbent starch graft copolymer,
which combined with a B. thuringiensisstrain among manyother pesticides constitutes a novel formulation that could be
applied in an agricultural environment.
The biological activity of one particular bioinsecticide was
enhanced when the antibiotic zwittermycin was added. Thiscombination was also successful in pest control.
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Bacillus thuringiensis-based products are classifiedaccordingto their formulation.
first-generation products- All products containing a blend ofspores and crystals from a native strain.
Second generation products -based on spores and crystals
from a
B. thuringiensis strain bearing artificially introduced genescoding for delta-endotoxins from several strains, in order to
increase the activity spectrum against other insect pests.
Third generation products- Formulations containing deadrecombinant Pseudomonas fluorescens cells transformed withgenes coding for deltaendotoxins
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Types of Bacillus thuringiensisFormulations andTheir Applications for
Insect Pest Control
Form
ulatio
n Emulsions Encapsulations
Wettable powders
Granules
Powders
Briquettes
Appl
ication Agriculture and forestry
Agriculture and forestry
Gardens and agriculture
Agriculture and forestry
Forestry
Aquatic systems
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Most Common Commercial Bacillusthuringiensis-based Bioinsecticides
Company CommercialName
ActiveIngredient
Target Pest
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CHIMERIC CRYSTAL PROTEINS
In recent years, hybrid delta-endotoxins have arisen as
proteins with potential for enhanced toxic activity orimproved properties.
Recent advances in molecular methodologies have allowed
gene fusions and chimeric protein construction.
This construction can include alteration of amino acid
sequences, fusion of portions of two or more proteins
together into a single recombinant protein, or alteration of
the genetic sequences encoding for proteins withcommercial application.
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There is a great amount of scientific research on the
bacterium B. thuringiensis, involving aspects ranging fromitsmolecular biology to its activity in a bioinsecticide.
The development of formulations with biodegradable
ingredients is a favored approach for the reduction of chemicalinsecticide use, which can threaten the environment.
CURRENT & FUTURE DEVELOPMENTS
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REFERENCES[1] Aizawa K. Shigetane Ishiwata: His discovery of sottokin (Bacillus thuringiensis) in1901 and subsequent investigations in Japan. Proceedings of a CentennialSymposium CommemoratingIshiwatas Discovery of Bacillus thuringiensis. Japan2001.[2] Lord JC. From Metchnikoff to Monsanto and beyond: The path of microbial
control. J Invertebr Pathol 2005; 89 (1): 19-29.
[3] Cern JA. Productos comerciales nativos y recombinantes a base de Bacillusthuringiensis. Bioinsecticidas: Fundamentos yaplicaciones de Bacillus thuringiensis
en el control integrado deplagas. In: Caballero P, Ferr J. Eds, Phytoma-Espaa2001; 153-168.
[4] Aronson A, Beckman W, Dunn P. Bacillus thuringiensis andrelated insectpathogens. Microbiol Rev 1986; 50 (1): 1-24.
[5] Nester EW, Thomashow LS, Metz M, Gordon M. 100 years ofBacillusthuringiensis: A critical scientific assessment. AmericanAcademy of Microbiology.
Washington DC 2002.[6] King E. Control biolgico de insectos y caros plaga. Avances recientes en labiotecnologa en Bacillus thuringiensis. In: Galn-Wong LJ, Rodrguez-Padilla C,Luna-Olvera HA, Eds. Universidad Autnoma de Nuevo Len 1996; 13-19.
[7] Margalith Y, Ben-Dov E. Biological control by Bacillus thuringiensis subp.israelensis. Insect pest management, techniquesfor environmental protection. In:
Rechcigl JE, Rechcigl NA, Eds.Lewis Publishers 2000; 243-301.[8] Aizawa K. Selection and utilization ofBacillus thuringiensisstrains for microbial
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