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M M Lecadet

Publications and source records attributed to M M Lecadet.

At least 37 records · Page 2Linked to original sources
PubMed1985

Recent aspects of genetic manipulation in Bacillus thuringiensis.

The conjugative plasmid pAM beta 1 was transferred from Streptococcus faecalis to several strains of Bacillus thuringiensis by a filter-mating process. From a transconjugant clone of B. thuringiensis a hybrid plasmid resulting from an in vivo insertion into pAM beta 1 of a 3 Md DNA sequence was isolated. This 3 Md DNA molecule (Th sequence) is related to several host plasmids found in different serotypes of B. thuringiensis. A reciprocal conjugation-like process involving the transfer of pAM beta 1 from B. thuringiensis to S. faecalis was also demonstrated. The comparison of the restriction maps of the crystal genes from plasmid and chromosomal origins of different serotypes, six of which having been cloned in E. coli, revealed the existence of two classes of genes which are very similar in the map corresponding to the N-terminal part of the protein, and which differ essentially in the 3' region. The presence of the transposon-like Th sequence was found in several cases associated with the crystal gene in the same host plasmid, and a model for their structural organization is proposed.

Bacillus thuringiensis↗
PubMed1984

A transposon-like structure related to the delta-endotoxin gene of Bacillus thuringiensis.

A DNA segment (Th-sequence) has been found in several strains of Bacillus thuringiensis. This Th-sequence [3 megadaltons (Md)] induces adjacent deletions when it is located in the pAM beta 1 plasmid derived from Streptococcus faecalis. Electron microscopic examination of reannealed single strands of one plasmid (pMT9) carrying such a deletion revealed that the Th-sequence corresponds to a single-stranded loop (2.8 Md) bounded by a short double-stranded stem (less than 0.2 Md). Southern blotting experiments established that in B. thuringiensis the Th-sequence was generally located on the large plasmid which also harbours the gene coding for the delta-endotoxin (crystal protein). Hybridization and heteroduplex analysis of the extrachromosomal DNA from the berliner 1715 strain demonstrated that the crystal gene and the Th-sequence are located in close vicinity on a 42-Md plasmid and that they are separated by a 1.3-Md DNA segment. This DNA segment is repeated in inverted orientation, once immediately adjacent to the Th-sequence and once 1.8 Md beyond the crystal gene. A model for the organization of these DNA sequences inside a transposon-like structure is proposed.

Bacillus thuringiensis↗
PubMed1983

Isolation of a DNA sequence related to several plasmids from Bacillus thuringiensis after a mating involving the Streptococcus faecalis plasmid pAM beta 1.

The transmissible plasmid pAM beta 1, which codes for resistance to erythromycin and lincomycin, was transferred from Streptococcus faecalis to several strains of Bacillus thuringiensis by a filter-mating process. Introduction of pAM beta 1 into the Emr transconjugant strains of B. thuringiensis was confirmed by Southern hybridisation using the 32P-labelled pAM beta 1 as a probe. In the B. thuringiensis transconjugant strains, used as donors, the beta plasmid conserved its ability to be transferred during intraspecific mating, with a frequency of 10(-4) per recipient cell. In addition, the transconjugant clones acted as donors of the erythromycin resistance marker and permitted the transfer of cryptic plasmids present in the B. thuringiensis (beta) strains used as donors. From a transconjugant clone of B. thuringiensis a hybrid plasmid resulting from an in vivo insertion into pAM beta 1 of a 3 Md DNA sequence was isolated. This 3 Md DNA molecule originated from a 54 Md plasmid of a kurstaki strain and is related to several plasmids found in different serotypes of B. thuringiensis.

Bacillus thuringiensis↗
PubMed1982

Molecular relationships among plasmids of Bacillus thuringiensis: conserved sequences through 11 crystalliferous strains.

Screening for the plasmid content of 11 strains belonging to nine different serotypes of B. thuringiensis was carried out by electron microscopic examination and electrophoresis in agarose gels. All the strains contained at lest two covalently closed, circular (CCC) DNA species. In one strain (berliner 1715), 17 extrachromosomal elements could be distinguished with regard to their size, ranging from 3.9 to 180 Mdal. Southern hybridisation experiments showed that most of these plasmids fell into two categories (inferior to 15 Mdal and superior to 15 Mdal) which have no homology between them. Within these two size groups there is partial conservation of DNa sequences through various serotypes. Further relationships among the plasmids were investigated by a two dimensional version of the Southern's blotting technique. Possible homology between plasmids and the chromosomal DNA was studied. It was shown that the smaller plasmids from the berliner 1715 and kurstaki HD1 strains contained no sequence related to chromosomal DNA, whereas among the larger plasmids a few showed homologous sequences.

Bacillus thuringiensis↗
PubMed1980

Generalized transduction in Bacillus thuringiensis var. berliner 1715 using bacteriophage CP-54Ber.

A phage isolated from lysates of phage CP-54 grown on Bacillus cereus 569 and selected on the basis of its ability to infect Bacillus thuringiensis var. berliner 1715 (serotype I) was designated CP-54Ber. Phages CP-54Ber and CP-54 were similar in size, morphology, cryosensitivity and stabilization by dimethyl sulphoxide. They showed significant differences with regard to inactivation by specific antiserum, adsorption to the berliner strains and host range. Phage CP-54Ber was able to mediate generalized transduction in the host strain berliner 1715 with frequencies ranging between 1 x 10(-5) and 1 x 10(-6). Cotransduction of markers was demonstrated. Cross-transduction occurred between strains belonging to serotype I whereas it was more difficult to observe when lysates were prepared on strains from other serotypes.

Bacillus thuringiensis↗
PubMed1976

[Biochemical determination of B. thuringiensis thermostabile, exotoxin, using the inhibition of bacterial RNA polymerases].

This method can determine amounts of exotoxin near 1 mug. Used on the autoclaved filtrates of cultures of B. thuringiensis var. thuringiensis (serotype 1 type-strain), it shows an excretion rate of 250 to 300 mug per millilitre. The results on different exotoxin-producer strains give a perfect parallelism with the results obtained by bio-assays on Insects, but the biochemical method is more accurate and reproducible. This biochemical technique allows us, for the first time, to place the exotoxin excretion during the sporulation stage and not during the exponential growth.

Bacillus thuringiensis↗