Molecular Approaches for the Improvement of Bacillus thuringiensis Against Pests 185
This review has shown that all contributions are
focusing on the main biotechnological application
of Bt as bioinsecticide, although they are using dif-
ferent genetic techniques. However, all techniques
have advantages and disadvantages that make
them different from each other and true to the pur-
pose of each research as summarized in Table 6.
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Biotechnol Bioeng 92:1–7Table 6 Advantages and disadvantages of each genetic method for improvement of Bt strains. (Sansinenea et al. 2010 )
Method of genetic manipulation Advantages Disadvantages
Transduction Is an efficient means of gene transfer
yielding high levels of gene
expression
Not all strains are amenable to phage
transduction and the stability of the
introduced plasmids depends mainly
on the host
Conjugation (1) Both large and small plasmids
were found to transfer equally well
between strains
(2) Transconjugants are treated as
“non-genetically engineered” and
are, thus, subject to relatively
simple regulatory registration
(1) Plasmid incompatibility, as strains
are often limited in their capacity to
act as donors or recipients
(2) Location of cry genes on non-trans-
missible plasmids
(3) A plasmid may carry additional unde-
sirable genes
(4) Eventual segregational loss of plas-
mid in transconjugant strains
(5) Unintended transfer of plasmids from
one to another strain may occur
Transformation by electroporation Rapid, simple and effective method
of introducing plasmid DNA intro
strains of Bt
(1) The transformation depends on the
strain or the replicon used
(2) Segregational or structural instability
of some plasmids in the recombinant
strain
Genetic recombination Avoids segregational or structural
instability of plasmids in the
recombinant strain integrating
genes into resident plasmids or
into the chromosome
The low frequency of recombination
makes this approach unsatisfactory for
poorly transformable strains