Characterization and properties of a novel plasmid vector for Bacillus thuringiensis displaying compatibility with host plasmids.

A novel plasmid vector, composed of a 1.7-kb Bacillus thuringiensis (B.t.) replicon, a multiple cloning site, and an erythromycin-resistance marker gene from Bacillus subtilis, was constructed for use in B.t. Unlike other vectors which have been reported to be acceptable for B.t., this new B.t. vector was stably maintained in the absence of Er and did not displace host plasmids, some of which carry crystal protein-encoding genes (cry genes). The compatibility of this B.t. vector with native plasmids is highly desirable when introducing new cry genes into a wild-type B.t. strain. When a cryIIIA gene of B.t. tenebrionis was cloned in this vector and introduced into B.t. kurstaki (kur) HD119, cryIIIA was highly expressed without affecting the level of expression of native cry genes. The stability of this vector and its compatibility with native B.t. plasmids were achieved by subcloning only nucleotide sequences required for the vector to replicate in B.t. The origin of replication was first cloned on a 9.6-kb Bg/II fragment from a 75-kb plasmid of B.t. kur HD73 and then localized to a 2.4-kb region within the 9.6-kb fragment. Sequencing of the 2.4-kb region revealed the presence of an open reading frame (ORF), encoding a putative 312-amino acid (aa) protein. The deduced aa sequence of the ORF showed no homology to any published aa sequences. Deletion analysis indicated that the B.t. vector required at least the ORF and up to 300 bp surrounding the ORF, in order to replicate.

[Swiss agriculture at the threshold of the year 2000]. / L'agriculture Suisse au seuil de l'an 2000.

The technical and biological progress together with improved educational programs for farmers have strongly influenced the development of Swiss agriculture after World War II. In spite of a decreasing number of farms and employees agricultural production has clearly increased resulting in some market problems as well as in a higher impact on the environment. Therefore, the goal of agricultural politics is to unify the sometimes divergent interests by means of offer regulation, income guarantee and environmental protection. In order to successfully meet the requirements of the 21st century, Swiss agriculture needs responsible and dynamic farmers.