The plant pathogen Agrobacterium tumefaciens carries a virulence gene system that is required for the initiation of crown gall tumors on susceptible plants. Expression of the vir genes is activated by the VirA/VirG two component regulatory system. VirA is a histidine kinase which signals the presence of certain chemicals found at the site of a plant wound. The receiver domain located at its car...

Inducible virulence (vir) genes of the Agrobacterium tumefaciens tumor-inducing (Ti) plasmid are under control of a two-component regulatory system. In response to environmental factors (phenolic compounds, sugars, pH) VirA protein phosphorylates VirG, which in turn interacts with the promoters of other vir genes, causing induction. A mutation of virG, virGN54D (which codes for a Asn-54-->Asp a...

The vir region of Agrobacterium tumefaciens spans at least six transcriptional loci required for crown gall tumorigenesis. The transcriptional induction of two of these vir loci in response to cocultivation with tobacco suspension cells was measured by using bacteria containing mutations in each of the six vir loci located on the Ti plasmid. Induction of these vir genes occurred only in bacteri...

The ability to utilize Escherichia coli as a heterologous system in which to study the regulation of Agrobacterium tumefaciens virulence genes and the mechanism of transfer DNA (T-DNA) transfer would provide an important tool to our understanding and manipulation of these processes. We have previously reported that the rpoA gene encoding the alpha subunit of RNA polymerase is required for the e...

The effect of olive oils on lipid metabolism and antioxidant activity was investigated on 60 male Wistar rats adapted to cholesterol-free or 1% cholesterol diets. The rats were divided into six diet groups of 10. The control group (control) consumed the basal diet (BD) only, which contained wheat starch, casein, cellulose, and mineral and vitamin mixtures. To the BD were added 10 g/100 g virgin...

WRSd1 is a Shigella dysenteriae 1 vaccine containing deletions of the virG(icsA) gene required for intercellular spreading and a 20-kb chromosomal region encompassing the Shiga toxin genes (stxAB). WRSd1 was constructed from S. dysenteriae 1 strain 1617 that was originally isolated during the 1968 to 1969 epidemic of Shiga dysentery in Guatemala. The virG(icsA) deletion was constructed from a s...

BACKGROUND The emergence and spread of antibiotic resistance in pathogens have led to a restriction on the use of antibiotic growth promoters (AGPs) in animal feed in some countries. The potential negative after-effects of a ban on AGPs could be mitigated by improving animal intestinal health with prebiotic dietary fibers such as xylo-oligosaccharides (XOS). However, the mechanism(s) by which a...

Two-component systems (TCS) regulate pathogenic commitment in many interactions and provide an opportunity for unique therapeutic intervention. The VirA/VirG TCS of Agrobacterium tumefaciens mediates inter-kingdom gene transfer in the development of host tumors and sets in motion the events that underlie the great success of this multi-host plant pathogen. Significant proof for the feasibility ...

BACKGROUND Salmonella causes acute systemic inflammation by using its virulence factors to invade the intestinal epithelium. But, prolonged inflammation may provoke severe body catabolism and immunological diseases. Salmonella has become more life-threatening due to emergence of multiple-antibiotic resistant strains. Mannose-rich oligosaccharides (MOS) from cells walls of Saccharomyces cerevisi...