August Van Gool

Cloning and expression of a Clostridium acetobutylicum α-amylase gene in Escherichia coli

A gene library of Clostridium acetobutylicum ATCC824 was constructed in the plasmid vector pEcoR251. The library was tested for the presence of starch hydrolyzin clones. One clone in which the recombinant plasmid, pVP101, conferred α-amylase activity to the Escherichia coli host cell, was detected. The gene is carried on a 3.45-kbp BglII restriction fragment. A detailed physical map of pVP101 is presented.

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.

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

The isolation and characterization of an insertion sequence (IS) element, IS427, from Agrobacterium tumefaciens T37 is described. IS427 is present in three nonidentical copies on the pTiT37 plasmid. The copy that was isolated through transposition on the entrapment vector pUCD800 contains at its ends a 16-bp imperfect inverted repeat and generates a 2-bp duplication of the target DNA. IS427 does not show homology with previously characterized IS elements of A. tumefaciens, based on hybridization experiments and/or sequence comparison.

Cloning of DNA Sequences from Azospirillum Brasilense, Homologous to Rhizobium Nod Genes and Agrobacterium Vir Genes

Bacteria of the genus Azospirillum (Tarrand et al 1978) are. free-living diazotrophs that can readily be isolated from the rhizosphere and roots of grasses. Little is known about the genetics of these bacteria or the molecular biology of their association with plants (for reviews, see Elmerich, 1984; Okon 1985).

Cloning and expression of a Clostridium acetobutylicumα‐amylase gene in Escherichia coli

A gene library of Clostridium acetobutylicum ATCC824 was constructed in the plasmid vector pEcoR251. The library was tested for the presence of starch hydrolyzin clones. One clone in which the recombinant plasmid, pVP101, conferred α-amylase activity to the Escherichia coli host cell, was detected. The gene is carried on a 3.45-kbp BglII restriction fragment. A detailed physical map of pVP101 is presented.

Azospirillum-Cereals: An Intriguing Partnership

Azospirillum is probably the best studied example of beneficial plant rhizosphere bacteria. Studies in our laboratory focus on the identification of bacterial genes and gene products that are of importance in the physical and metabolic interaction of Azospirillum brasilense with plant roots. Here we report for Azospirillum brasilense, flagellation, motility, the physical interaction with plant roots, the synthesis of indole-3-acetic acid, the expression of nif genes in plant-root associated bacteria, and the induction of gene expression with plant root exudates.

Cloning and expression of a Clostridium acetobutylicumα-amylase gene in Escherichia coli

A gene library of Clostridium acetobutylicum ATCC824 was constructed in the plasmid vector pEcoR251. The library was tested for the presence of starch hydrolyzin clones. One clone in which the recombinant plasmid, pVP101, conferred α-amylase activity to the Escherichia coli host cell, was detected. The gene is carried on a 3.45-kbp BglII restriction fragment. A detailed physical map of pVP101 is presented.

Developments in the Genetic Analysis of Azospirillum

Bacteria of the genus Azospirillum (1) are free-living diazotrophs that can readily be isolated from the rhizosphere and roots of grasses (2). No differentiated structures are formed following colonization of the root zone. Bacteria are thightly attached to the root surface and pictures of root hair deformation were reported (for review, see (3) Numerous field experiments, carried out since 1975, have demonstrated that Azospirillum inoculations can promote crop yield under certain environmental and soil conditions. Biochemical and physiological studies on Azospirillum in laboratory conditions suggest that processes like biological nitrogen fixation and plant hormones production might contribute to plant growth responses upon inoculation (3, 4) Until now little is known about the genetics of these bacteria or the molecular biology of their association with plants (5). Most progress has been made in the biochemistry and molecular genetics of nitrogen fixation (6, 7, 8). Recently, efforts to develop tools for the genetic analysis of Azospirillum were reinforced, and research programs to identify bacterial genes in the Azospirillum-plant interaction process were initiated.

Azospirillum Brasilense Genes that Correct Fix- Mutants of Rhizobium Meliloti Rm1021

Bacteria of the genus Azospirillum are diazotrophs associated with the root zone of grasses (for review see Dobereiner and Pedrosa 1987). The molecular genetic analysis of Azospirillum plant interaction is hampered by the lack of plant root differentiation at the site of interaction. The identification of bacterial genes possibly involved in Azospirillum rhizocoenoses has therefore been approached either by molecular hybridization with cloned genes from other rhizosphere bacteria (Fogher et al 1985; Waelkens et al 1987) or by genetic complementation of characterized mutants of Rhizobium meliloti with gene libraries of A. brasilense (Michiels et al 1988). By genetic complementation we initially isolated two A. brasilense Sp7 DNA fragments that correct R. meliloti exoB and exoC mutants respectively. These fragments are located on the p90 plasmid DNA of A. brasilense Sp7 (Michiels et al 1989b). In this paper we report a more extensive inventory of A. brasilense loci that are involved in exopolysaccharide synthesis. Furthermore we describe some experiments to study the nature and regulation of these genes, and finally we focus on the genetic map of the p90 plasmid of A. brasilense strain Sp7.