Identification of insertion sequence element IS427 in pTiT37 plasmid DNA of an Agrobacterium tumefaciens T37 isolate

Isolation and characterization of IS1416 from Pseudomonas glumae, a new member of the IS3 family

Isolation and characterization of four different insertion sequence (IS) elements from Pseudomonas glumae MAFF 302744 through transposition into the entrapment vector pSHI1063 are described. One of the elements, IS1416, was further characterized. IS1416 is 1322 bp long and carries 29-bp terminal inverted repeats flanked by a 3-bp direct duplication. IS1416 contains three open reading frames (ORFs), which are designated ORFA1, ORFA2, and ORFB, on one strand. Both DNA sequence of IS1416 and the deduced amino acid sequences of its ORFs strongly suggest that IS1416 is a member of the IS3 family, and is closely related to IS401 from Pseudomonas cepacia and IS51 from Pseudomonas syringae. To our knowledge, IS1416 is the first IS element isolated from P. glumae. The gene organization and possible regulation of transposition functions of IS1416 are also discussed.

Isolation and characterization of insertion sequence elements from gram-negative bacteria by using new broad-host-range, positive selection vectors

On the basis of an RSF1010-derived broad-host-range vector, three different systems which enable positive detection and isolation of insertion sequence (IS) elements from gram-negative bacteria were constructed. Vectors pSUP104-pheS, pSUP104-rpsL, and pSUP104-sac were used successfully in a number of Rhizobium strains and in Xanthomonas campestris. More than 20 different IS elements were isolated and characterized. The 16 IS elements from Rhizobium meliloti were further used to characterize various R. meliloti strains by hybridization. The resulting hybridization patterns were different for every strain and gave a clear and definite IS fingerprint of each strain. These IS fingerprints can be used to identify and characterize R. meliloti strains rapidly and unequivocally, as they proved to be relatively stable. Some of the IS elements were found to be identical when the IS fingerprints from a given strain were compared. This method of IS fingerprinting can also establish whether IS elements are the same, related, or different.

Isolation and genetic structure of IS112, an insertion sequence responsible for the inactivation of the SalI restriction-modification system of Streptomyces albus G

IS112 is a transposable element identified in Streptomyces albus G by its frequent mutagenic insertion into the genes for the SalI restriction-modification system. IS112 is present in several copies in the genome of S. albus G. Homologous sequences were detected in other Streptomyces strains. Sequence analysis revealed that IS112 has a length of 883 bp with a GC content of 67.4%. The copy that was isolated contained imperfect inverted repeats (16/20 match) at its ends and was flanked by a 2 bp duplication at the target site, which was located within the gene (salIR) for the SalI endonuclease. A long open reading frame (ORF) encoding a putative polypeptide of 256-253 amino acids spans almost the entire sequence. Significant homology was detected between this polypeptide and that corresponding to ORFB of IS493, an insertion sequence recently isolated from Streptomyces lividans 66.

Nucleotide sequence analysis of IS427 and its target sites in Agrobacterium tumefaciens T37

We have determined the nucleotide sequence of IS427, an insertion sequence from Agrobacterium tumefaciens T37, IS427 is 1271 bp long, contains 16-bp imperfect terminal inverted repeats, and generates a 2-bp target sequence duplication. It is present at three sites in the pTiT37 plasmid and is absent from the chromosome of A. tumefaciens T37. Each of the IS427 elements sequenced was near a site with sequence homology to integration host factor (IHF)-binding sites which suggested that IHF may be involved in IS427 transposition.