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Applied and Environmental Microbiology, October 1998, p. 3910-3916, Vol. 64, No. 10
Unité des Bactéries
Entomopathogènes, Institut Pasteur, 75724 Paris Cedex 15, France1 and
CIB Biological Control Unit,
Medellin, Columbia2
Received 30 March 1998/Accepted 29 July 1998
The fragment containing the gene encoding the cytolytic Cyt1Ab1
protein from Bacillus thuringiensis subsp.
medellin and its flanking sequences (I. Thiery, A. Delécluse, M. C. Tamayo, and S. Orduz, Appl. Environ.
Microbiol. 63:468-473, 1997) was introduced into Bacillus
sphaericus toxic strains 2362, 2297, and Iab872 by
electroporation with the shuttle vector pMK3. Only small amounts of the
protein were produced in recombinant strains 2362 and Iab872. The
protein was detected in these strains only by Western blotting and
immunodetection with antibody raised against Cyt1Ab1 protein. Large
amounts of Cyt1Ab1 protein were produced in B. sphaericus recombinant strain 2297, and there was an
additional crystal, other than that of the binary toxin, within the
exosporium. The production of the Cyt1Ab1 protein in addition to the
binary toxin did not increase the larvicidal activity of the
B. sphaericus recombinant strain against
susceptible mosquito populations of Culex pipiens or
Aedes aegypti. However, it partially restored (10 to 20 times) susceptibility of the resistant mosquito populations of C. pipiens (SPHAE) and Culex quinquefasciatus (GeoR) to
the binary toxin. The Cyt1Ab1 protein produced in recombinant
B. thuringiensis SPL407(pcyt1Ab1) was
synthesized in two types of crystal
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
The Introduction into Bacillus sphaericus of
the Bacillus thuringiensis subsp. medellin
cyt1Ab1 Gene Results in Higher Susceptibility of Resistant
Mosquito Larva Populations to B. sphaericus
one round and with various dense
areas, surrounded by an envelope, and the other a regular cuboid
crystal, very similar to that found in the B. sphaericus recombinant strain.
*
Corresponding author. Mailing address: Unité des
Bactéries Entomopathogènes, Institut Pasteur, 25 rue du
Docteur Roux, 75724 Paris Cedex 15, France. Phone: (33) 01 40 61 31 83. Fax: (33) 01 40 61 30 44. E-mail: ithiery{at}pasteur.fr.
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