We have physically and genetically characterized 20 symbiotic and 20 auxotrophic mutants of Rhizobium meliloti, the nitrogen-fixing symbiont of alfalfa (Medicago sativa), isolated by transposon Tn5 mutagenesis. A "suicide plasmid" mutagenesis procedure was used to generate TN-5-induced mutants, and both auxotrophic and symbiotic mutants were found at a frequency of 0.3% among strains containing...

A low resolution Not I physical map of Escherichia coli was recently constructed. In this report we demonstrated that this map can be used to map Tn5 and F insertions physically. The transposon, Tn5, contains Not I recognition sequences in its IS50 sequences. F plasmid contains an unmapped Not I site. Hence, the location of Tn5 and F in the chromosome can be mapped by identifying the location o...

Transposon Tn5 was introduced into Legionella pneumophila on plasmid pRK340, which is temperature sensitive for plasmid maintenance. The presence of plasmid DNA was confirmed by agarose gel electrophoresis and by conjugal transfer of the plasmid to Escherichia coli. Tn5 insertions were obtained by culturing L. pneumophila at the nonpermissive temperature (43 degrees C) on buffered charcoal-yeas...

Transposition of Tn5 in Escherichia coli strains containing one or multiple copies of the transposable element was investigated. It was found that the overall frequency of transposition within a cell remained constant regardless of the number of copies of Tn5 present in that cell. Experiments measuring the transposition frequency of differentially marked Tn5s confirmed that the frequency of tra...

This communication reports the development of an efficient in vitro transposition system for Tn5. A key component of this system was the use of hyperactive mutant transposase. The inactivity of wild type transposase is likely to be related to the low frequency of in vivo transposition. The in vitro experiments demonstrate the following: the only required macromolecules for most of the steps in ...

Methylation by Ava methylases in Escherichia coli increases the efficiency to transfer of Tn5 in pBR322bla:: Tn5 from E. coli to Anabaena sp. strain PCC 7120 by conjugation. Following conjugation, Tn5 but not pBR322 sequences were found at many different positions in the Anabaena chromosome. This procedure was used to mutagenize, tag, and clone a previously unrecognized gene required for nitrog...

In Escherichia coli, the frequencies of IS50 and Tn5 transposition are greater in Dam- cells than in isogenic Dam+ cells. IS50 transposition is increased approximately 1,000-fold and Tn5 transposition frequencies are increased about 5- to 10-fold in the absence of Dam methylation. However, in cells that are deficient for both integration host factor (IHF) and Dam methylase, the transposition fr...

Transposases mediate transposition first by binding specific DNA end sequences that define a transposable element and then by organizing protein and DNA into a highly structured and stable nucleoprotein 'synaptic' complex. Synaptic complex assembly is a central checkpoint in many transposition mechanisms. The Tn5 synaptic complex contains two Tn5 transposase subunits and two Tn5 transposon end ...

<i>Ralstonia solanacearum</i> species complex (RSSC) is a soil borne plant pathogen causing bacterial wilt on various important crops, including Solanaceae plants. The pathogens within the RSSC produce exopolysaccharide (EPS), highly complicated nitrogen-containing heteropolymeric polysaccharide, as major virulence factor. However, biosynthetic pathway of EPS in has not been fully c...

We have confirmed that the 28,000-molecular-weight (28K) protein encoded by the virA gene of the 90-kilobase Salmonella typhimurium virulence plasmid is a virulence factor. It was previously shown that a Tn5 insertion, vir-22::Tn5, located in the virulence plasmid greatly attenuated virulence for mice and inhibited the production of a 28K protein (P.A. Gulig and R. Curtiss III, Infect. Immun. 5...