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Biocontrol Potential Of Bacillus Thuringiensis Isolated From Soil Samples Against Larva Of Mosquito
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OTHER PATHOGENIC FACTORS OF BACILLUS THURINGIENSIS
At
the period of the active growth cycle, the strains of Bacillus
thuringiensis produce extracellular compounds; this compound might yield
to virulence. These extracellular compounds include proteases,
chitinases phospholipases, and vegetative conseticidal protein (Zhang et
al. 1993; Sohneff et al. 1998).
Bacillus thuringrensis also produces
antibiotics compounds having antifungal activity (stab et al. 1994).
However the crystal toxins are more effective then these extracellular
compounds and allow the development of the bacteria in dead insect
larvae.
Bacillus thuringiensis strains also produce a protease, which
is called inhibitor. This protein attacks and selectively destroys
cecropiris and attacisis which are antibacterial proteins in insects, as
a result of this, the defence response of the insect collapses. This
protease activity is specific, it attacks an open
hydrophobic region near C – terminus of the cecropin and it does not
attack the globular proteins (Duthambar & Steiner, 1984).
Other
important insecticidal proteins which are unrelated to crustal proteins
are vegetative insecticidal protein. These proteins are produce by some
strains of Bacillus thuringiensis during vegetative growth.
MORPHOLOGICAL PROPERTIES OF BACILLUS THURINGIENSIS
Colony
forms can help to distinguish Bacillus thuringiensis colonies from
other Bacillus species. The organism forms white, rough colonies, which
spread out and can expand over the plate very quickly. Bacillus
thuringiensis strains have unswallon and ellipsoidal spores that lie in
the subterminal position. The presence of parasporal crystals that are
adjacent to the spore in another cell is the best criteria to
distinguish Bacillus thuringiensis from other closely related Bacillus
species. The size number, of parasporal inclusion and morphology may
vary among Bacillus thuringiensis strains. However, four distinct
crystal morphologies are apparently the typical bipyramidal crystal,
related to crystal proteins (Aronson et al. 1976). Cuboidal usually
associated with bipyramidal crystal (Ohba&Aizawi 1986), amorphous
and composite crystals related to cry4 and cry proteins (federicet al.
1990), and flat, square crystal related to cry3 proteins (Hernstadet al.
1986, Lopezmeza & Ibarra, 1996)
The classification was
based in part on the possession of parasporal bodies. Bernard et
al.(1997) isolated 5303 Bacillus thuringiensis from 80 different
countries and 2793 of them were classified according to their crystal
shape.
Bacillus thuringiensis vary’s based on geographical or
environmental location. Each habitat may contain novel Bacillus
thuringiensis isolated that have more toxic effects on target insects.
Intensive screening programs have been identified Bacillus thuringiensis
strain from soil, plant surfaces and stored product dust samples.
Therefore many strain collections have been described in the literature,
such as Assian (Chak et al. 1994, Ben – Dov et al. 1997, 1999) and
Maxican (Bravo et al. 1998).
Therefore the aim of this study is to
isolate Bacillus thuringiensis from soil sample and to isolate Bacillus
thuringiensis against larva of mosquito or to determine Bacillus
thuringiensis against larva of mosquito.
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ABSRACT - [ Total Page(s): 1 ]A major challenge for achieving successful mosquito control is overcoming insecticide resistance. Bacillus thuringiensis which is one of the most effective biolarvacide for control of species of mosquitoes and monitoring of larval susceptibility is essential to avoid resistance development. Mosquito larvacidal activity of Bacillus thuringiensis was assessed by isolating them from ecologically different soil habitats in and around Enugu metropolis. The isolate organisms were confirmed as Bacillus ... Continue reading---
