| Popis: |
This chapter focuses on the Enterococcus faecalis element Tn917, which is the most extensively used transposon in Bacillus subtilis. Numerous derivatives of Tn917 have been developed to facilitate the cloning and functional analysis of regulated genes identified by insertional mutations, and delivery vectors for obtaining Tn917 insertions function effectively in several other gram-positive species. This chapter also describes a new family of insertion elements based on derivatives of the Escherichia coli transposon Tn10 that were specifically engineered for use in B. subtilis. The insertional mutagenesis systems now available for Streptomyces spp. are discussed briefly, primarily as a model for the establishment of such systems in gram-positive species in which barriers to the use of nonindigenous elements exist. Of particular importance for understanding the origins and properties of most of the Tn917 derivatives is the fact that the interval between erm and the nearest terminal inverted repeat consists of nonessential DNA that may be modified without interfering with transposition. Although transposons indigenous to other gram-positive bacteria, such as Tn551 and Tn4001 of S. aureus, have been utilized effectively for insertional mutagenesis, only in the case of Streptomyce insertion elements have efforts been made to alter natural transposons to produce derivatives more useful for genetic analysis. |
